Aldehyde Substituted Phthalocyanines: Synthesis

J Fluoresc DOI 10.1007/s10895-016-1852-x

ORIGINAL ARTICLE

Aldehyde Substituted Phthalocyanines: Synthesis, Characterization and Investigation of Photophysical and Photochemical Properties Pinar Sen 1 & S. Zeki Yildiz 1 & Ali Erdoğmuş 2 & Necmi Dege 3 & Yusuf Atalay 4

Received: 2 March 2016 / Accepted: 30 May 2016 # Springer Science+Business Media New York 2016

Abstract The new free and nickel phthalocyanine derivatives, tetrakis [(2-formylphenoxy)-phthalocyanine (4), tetrakis [(2-formylphenoxy)-phthalocyaninato]nickel(II) (5) have been synthesized via de-protection of tetra acetal-substituted phthalocyanines in acetic acid/FeCl3 system. The starting phthalocyanines, tetrakis [(2-(1,3-dioxolan-2-yl)phenoxy)phthalocyanine (2) and tetrakis [(2-(1,3-dioxolan-2yl)phenoxy)-phthalocyaninato]nickel (3), were prepared by the tetramerization of 4-(2-(1,3-dioxolan-2-yl) phenoxy) phthalonitrile (1). The new compounds have been characterized by the combination of FT-IR, 1H NMR, UV–Vis, Mass spectra and elemental analysis. Compound 1 crystallizes in the Orthorhombic, space group Pbca with a = 9.2542 (4) Å, b = 13.3299 (5) Å, c = 23.2333 (11) Å, and Z = 8. Compound 1 is built up from two planar groups (phthalonitrile and phenoxy), with a dihedral angle of 69.693(36)° between them and non-planar dioxolane group. We report a combined experimental and theoretical study on molecule 1, as well. Geometric, spectroscopic and electronic properties of compound 1 has been calculated using B3LYP method and 6– 311++G(dp) basis set. Fluorescence spectroscopy was applied

* S. Zeki Yildiz [email protected]

1

Department of Chemistry, Faculty of Arts and Sciences, Sakarya University, 54187 Sakarya, Turkey

2

Department of Chemistry, Yildiz Technical University, 34210 Esenler, Istanbul, Turkey

3

Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Samsun, Turkey

4

Department of Physics, Faculty of Arts and Sciences, Sakarya University, 54187, Serdivan, Sakarya, Turkey

to record the photoluminescence spectra of the prepared phthalocyanines and the photophysical and photochemical properties were examined in DMSO.

Keywords Synthesis . Single crystal . X-ray structure . Theoretical calculation . Phthalocyanine . Fluorescence property . Singlet oxygen . Photodegradation

Introduction Phthalocyanine (Pc) and its metal complexes (metallophthalocyanines, MPcs) are known as excellent functional materials due to their unique optical, physicochemical, electronic, catalytic and structural properties [1, 2]. Their high thermal, chemical and photochemical stabilities led them to be used in material science and technology such as non-linear optical applications [3], sensitizers for photodynamic therapy (PDT) of cancer [4], information storage [5] and chemical sensors [6]. Phthalocyanine derivatives exhibit a very wide choice of molecular properties by altering the type of metal and/or nature of the substituents [7]. However, many Pc compounds are practically insoluble in common organic solvents and this problem can be overcome by the introduction of appropriate substituents such as alkyl, alkoxyl and aryl groups to the periphery position of Pc ring [8]. Functional group substituted phthalocyanines are also great of importance for the development of new molecular materials [9, 10]. Phthalocyanines containing reactive functional groups, such as amino carboxyl or hydroxyl have been interesting target for researchers for further chemical reactions on Pc macrocyclic rings [11–13].

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Aldehyde substituted Pcs have been synthesized as desired compounds in derivatization from the reactive aldehyde functionalities to the further substituted phthalocyanines. However, self-condensation of the phthalonitrile derivatives containing aldehyde group does not occur properly because of the interference of aldehyde groups in the cyclotetramerization reaction. To solve this problem, the conversion of the aldehyde group to the O/O-acetal was employed in the first place to obtain the acetal substituted Pc, than it was converted to the desired aldehyde substituted derivative [14]. Applying this way, we have recently described the synthesis and aggregation properties of tetra (2-formylphenoxy) substituted Zn-Pc and its four Schiff’s base units bearing Zncomplex substituted derivative. In the present paper, we report on the preparation, characterization, photophysical and photochemical properties of two members of tetra substituted (H2Pc and NiPc) phthalocyanines (2–5). Metal free derivatives showed more good photophysical and photochemical properties than nickel derivatives. Insertion of paramagnetic nickel ion into phthalocyanines cavity caused decreasing of photophysical and photochemical properties synthesized molecules [15, 16]. This study also explores the effects of ring substitutions on the fluorescence and singlet oxygen generation properties of nickel and metal-free phthalocyanines using the similar literature [17].

spectrofluorometer using 1 cm pathlength cuvettes at room temperature. Infrared spectra were recorded on a Perkin Elmer Spectrum-Two FT-IR spectrophotometer equipped with Perkin Elmer UATR-TWO diamond ATR and corrected by applying the atr-correction function of Perkin Elmer Spectrum software. 1H-NMR spectra were recorded on a Bruker 400 spectrometer in Ataturk University, Erzurum. The experiments were carried out using a Bruker micrOTOF (Germany) in Gebze Technical University for Maldi-TOF spectra. The compounds were ionized by the positive electro-spray ionization ion source (ESI+) in the mass-spectrometer. The elemental compositions of the samples were analyzed by an element analyzer (Flash 2000, Thermo Scientific). Photo-irradiations were carried out using a General Electric quartz line lamp (300 W). A 600 nm glass cut off filter (Schott) and a water filter were used to filter off ultraviolet and infrared radiations respectively. An interference filter (Intor, 700 nm with a band width of 40 nm) was additionally placed in the light path before the sample. Fluorescence spectra was recorded on Varian Eclipse spectrofluoremeter. Synthesis 4-(2-(1,3-Dioxolan-2-Yl) Phenoxy) Phthalonitrile (1) The preparation of 1 has been performed in our earlier studies and reported [19].

Experimental Tetrakis [(2-(1,3-Dioxolan-2-Yl)Phenoxy)-Phthalocyanine (2) Chemicals and Instruments The deuterated dimethyl sulfoxide (DMSO-d6) for NMR spectroscopy and the following chemicals were obtained from Sigma-Aldrich; hexane, MeOH, N,N-dimethylaminoethanol (DMAE), 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU), THF, Dimethylacetamide (DMAc), DMF, DMSO, AcOH, CH2Cl2, n-pentanol and FeCl3.6H2O. All other reagents and solvents were reagent grade quality and obtained from commercial suppliers. All solvents were stored over molecular sieves (3 A°) after they dried and purified as described by Perrin and Armarego [18]. NiCl2 were dried at 120 °C and used as anhydrous. Oxygen free inert atmosphere was supplied by argon through dual-bank vacuum-gas manifold system. Thin-Layer chromatography (TLC) was performed using silica gel 60-HF254 as an adsorbent. Column chromatography was performed with silica gel (Merck grade 60) and the size exclusion chromatography with Bio-beads gel (SX-1).) Melting points (mp.) were determined using a BarnstadElectrotermel 9200 apparatus and are uncorrected. Electronic spectra were recorded on a Shimadzu UV-2600 Pc-spectrophotometer with quartz cell of 1 cm. Fluorescence excitation and emission spectra were recorded on a Varian Eclipse

4-(2-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (1) (100 mg, 0.362 mmol) was dispersed in n-pentanol (2 mL) in a standard schlenk tube. To the slurry was added a couple drops of DBU and purged by argon. The reaction mixture was heated up to the reflux temperature and maintained for 18 h. After completion of the reaction the reaction mixture was cooled to room temperature, and the reaction mixture was precipitated by adding of methanol (15 ml). The precipitate was collected by centrifugation, washed with methanol several times to dissolve any unwanted organic impurity and dried in vacuum. Further purification of the phthalocyanine was performed by size exclusion chromatography columns on Bio-beads gel (SX-1) eluting with CH2Cl2. The collected column phases was concentrated on a rotary evaporator and re-precipitated with methanol to obtain pure metal free phthalocyanine (2) in 42.0 % yield (44 mg) as a green solid, m.p > 250 °C, FT-IR (UATR-TWO™) ν max/cm−1: 3288 (N-H), 3067–3024 (Ar, C-H) , 2920–2886 (Aliph., C-H), 1604 (C = N), 1587 (Ar, C = C), 1491–1396 (Aliph., C-C), 1230 (Ar-O-Ar), 1070 (−C-O-C-). UV–Vis (DMAc): λmax (nm) (log ε) 701 (5.09), 668 (5.06), 640 (4.64), 609 (4.47), 344 (4.82). (MALDITOF): m/z 1171 [M + H]+. 1H-NMR (DMSO-d6) δ (ppm):

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9.50–9.11 (m, 4H, ArH), 8.64–8.51 (d, 4H, ArH), 7.77–7.56 (m, 16H, ArH), 7.38–7.29 (m, 4H, ArH), 6.30 (br, 1H, AlipH), 4.16–3.99 (m, 4H, AlipH), −3.75 (br, 2H, NH). Found (%): C, 69.47; H, 4.22; N, 9.62. Calc. (%) for C68H50N8O12: C, 69.74; H, 4.30; N, 9.57. Tetrakis [(2-(1,3-Dioxolan-2-Yl)Phenoxy)-Phthalocyaninato] Nickel(II) (3) 4-(2-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (1) (100 mg, 0.362 mmol) was dissolved in DMAE (2 mL) in a standard schlenk tube. To the solution was added anhydrous NiCl2 salt (11.73 mg, 0.0905 mmol) and catalytic amount of DBU. The reaction mixture was purged by argon at room temperature and heated up to 155 °C for 18 h. After cooling to room temperature, the reaction mixture was precipitated by adding methanol (15 ml). The precipitate was collected by centrifugation, washed several times with methanol to dissolve any unwanted organic impurity and dried in vacuum. Size exclusion chromatography on Bio-beads gel (SX-1) using CH2Cl2 as the eluent was applied for further purification of the phthalocyanine. The collected column phases were combined and concentrated on a rotary evaporator and re-precipitated with methanol to obtain pure phthalocyanine Ni(II) (3) in 46.2 % yield (48 mg) as a green solid. m.p > 250 °C. FT-IR (UATRTWO™) ν max/cm−1: 3062 (Ar, C-H), 2949–2881 (Aliph., C-H), 1606 (C = N), 1587–1534 (Ar, C = C), 1470–1331 (Aliph., C-C), 1228 (Ar-O-Ar), 1072 (−C-O-C-). UV–Vis (DMAc): λmax (nm) (log ε) 672 (5.02), 644 (4.62), 609 (4.49), 334 (4.61).MS (MALDI-TOF): m/z 1227 [M + H]+. Found (%): C, 66.32; H, 3.89; N, 9.01. Calc. (%) for C68H48N8NiO12: C, 66.52; H, 3.94; N, 9.13. General Procedure for Cleavage Reactions of 2 and 3 The cleavage reaction of 2 and 3 was performed in acetic acid ( 5 mL) / FeCl3 (catalytic amount) system using THF (5 mL) to solve the phthalocyanine before adding to the cleavage regents. The reaction solution was stirred at 75 °C for 3 days and at room temperature for another 3 days. The resulting mixture was diluted with water (20 ml), and the precipitate was collected by centrifugation. The crude product was washed several times with ethanol and water to remove any inorganic, organic impurity and acidic residue and then it was dried under vacuum. Further purification of the obtained phthalocyanines (4, 5) was performed by size exclusion chromatography on Bio-beads gel (SX-1) using CH2Cl2 as the eluent. The desired phthalocyanines were obtained by the re-precipitation with methanol of the collected organic eluent phases which were concentrated by rotary evaporation.

Tetrakis [(2-Formylphenoxy)-Phthalocyanine (4) Tetrakis [(2-(1,3-dioxolan-2-yl)phenoxy)-phthalocyanine (2) (32 mg, 0.0272 mmol) was treated to obtain blue-green product in (22 mg) (80 % yield), m.p > 250 °C. FT-IR (UATRTWO™) ν max/cm−1: 3286 (N-H), 3059–3024 (Ar, C-H), 2922–2752 (O = C-H), 1691 (C = O), 1598(C = N), 1579 (C = C), 1472–1393 (C-C), 1224 (Ar-O-Ar). UV–Vis (DMAc): λmax (nm) (log ε) 699 (4.71), 666 (4.70), 637 (4.44), 617 (4.30), 340 (4.61). MS (MALDI-TOF): m/z 995 [M + 1]+. Found (%): C, 72.24; H, 3.36; N,11.02. Calc. (%) for C60H34N8O8: C, 72.43; H, 3.44; N,11.26. Tetrakis [(2-Formylphenoxy)-Phthalocyaninato]Nickel (5) Te t r a k i s [ ( 2 - ( 1 , 3 - d i o x o l a n - 2 - y l ) p h e n o x y ) phthalocyaninato]nickel (3) (30 mg, 0.0245 mmol) was reacted and blue-green product was obtained in (21 mg) (84 % yield), m.p > 250 °C. FT-IR (PIKE MIRacle™ ATR) ν max/cm−1: 3064–3027 (Ar, C-H), 2852–2754 (O = C-H), 1689 (C = O), 1597(C = N), 1583 (C = C), 1467–1395 (C-C), 1228 (Ar-O-Ar). UV–Vis (DMAc): λmax (nm) (log ε) 670 (4.24), 636 (4.17), 334 (4.23). MS (MALDI-TOF): m/z 1051 [M + H]+. Found (%): C, 68.25; H, 3.03; N, 10.41. Calc. (%) for C60H32N8NiO8: C, 68.53; H, 3.07; N, 10.66. X-Ray Crystal Structure Determination A colorless single crystal with dimensions (0.73 × 0.62 × 0.52) mm3 was chosen and mounted on a glass fiber then carefully mounted on goniometer of a STOE IPDS II [20] diffractometer and used for the structure determination for the crystallographic study. All diffraction measurements were collected on a Stoe IPDS II diffractometer up to (2θ) max. of 50.0° with graphite monochromatized Mo Kα radiation (λ = 0.71073 Å) using the ω scan method. A total of 2980 independent reflections were collected, among which 2004 reflections were considered as observed [I > 2σ(I)] and used for the structure refinement. Usual Integration X-RED absorption corrections were applied. For 4-(2-(1,3-dioxolan-2-yl) phenoxy) phthalonitrile (1) data collection: X-AREA; cell refinement: X-AREA; data reduction: X-RED32 [20]. The structure was solved by direct methods followed by Fourier synthesis using SHELXS-2014 [21] and refined on F2 by full-matrix least-squares methods using SHELXL-2014 [21] and molecular figures: ORTEP-3 for Windows version 2014.1 implemented in WinGX 2014 [22–24] program suit. The general-purpose crystallographic tool PLATON [25] was used for the structure analysis. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were generated geometrically and allowed to ride on their parent carbon and oxygen atoms. H atoms bonded to C atoms were located in a difference Fourier map and refined

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isotropically. Details of the data collection conditions and the parameters of refinement process are given in Table 1. CCDC 1032888 contains the supplementary crystallographic data for this structure. This data can be obtained from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336,033; or e mail: [email protected] or www.ccdc.cam.ac.uk).

Fluorescence Quantum Quantum Yields Fluorescence quantum yields (ΦF) were determined by comparative method [29] Eq. (1):

ΦF ¼ ΦFðStdÞ

Computational Details The molecular structure of 4-(4-formylphenoxy)phthalonitrile in the ground state (in vacuo) is computed by performing the density functional theory (DFT) by a hydrid functional B3LYP functional (Becke’s three parameter hybrid functional using the LYP correlation functional) methods [26] at 6– 311++G(d,p) level. The optimized geometrical structure, IR spectra, 1 H and 13 C NMR chemical shifts of 4-(4formylphenoxy)phthalonitrile in this study are carried out by using Gaussian 09 W program package [27] and Gauss-View molecular visualization program [28]. Additionally, harmonic vibrational frequencies for the title compound are calculated with these methods and then scaled by 0.9608 [27] and these results were compared with the experimental data. Table 1

Photophysical and Photochemical Studies

Crystal data and structure refinement for the title compound

Chemical Formula Color/shape

C17H12N2O3 Colorless/plate

Crystal system Space group Temperature

Orthorhombic Pbca 296 K

Unit cell dimensions

Volume Z Density (calculated) Wavelength Reflections collected Independent reflections Absorption correction Δρmax, Δρmin (e Å−3) S

a = 9.2542 (4) Å b = 13.3299 (5) Å c = 23.2333 (11) Å α = 90° β = 90° γ = 90° 2866.0 (2) Å3 8 1.355 Mg m−3 0.71073 Å Mo Kα 17008 2980 Integration X-RED 0.10,−0.14 1.02

Rint θ range for data collection (˚) Absorbtion coefficient (μ) Final R indices [I > 2r(I)] h/k/l

0.079 1.5≤θ≤28.9 0.19 mm−1 R1= 0.037, wR2= 0.094 −11/10, −16/16, −29/29

F:AStd :n2 FStd:A :n2Std

where F and FStd are the areas under the fluorescence curves of the MPc derivatives and the reference, respectively. A and AStd are the absorbances of the sample and reference at the excitation wavelength, and n2and n2Std are the refractive indices of solvents used for the sample and standard, respectively. Unsubstituted ZnPc was used as a standard; ΦF = 0.20 in DMSO [30].

Singlet Oxygen Quantum Yields The theoretical information are given about quantum yields of singlet oxygen photo-generation were determined in air (no oxygen bubbled) using similar literatures [31–35]. Eq. (2): ΦΔ ¼ ΦStd Δ

R :IStd abs RStd :Iabs

whereΦStd Δ is the singlet oxygen quantum yield for the unsubstituted ZnPc standard; ΦStd Δ = 0.67 in DMSO [36]. R and RStd are the DPBF photo bleaching rates in the presence of the respective sample and standard, respectively. Iabs andIStd abs are the rates of light absorption by the sample and standard, respectively. The concentration of quencher, DPBF was lowered to ~3 x 10−5 mol dm−3 to avoid chain reactions induced by DPBF in the presence of singlet oxygen. Solutions, that contain DPBF, were prepared in the dark and irradiated in the Q band region. The degradation of DPBF at 417 nm was monitored after each 5 s irradiation. The light intensity of 7.05 x 1015 photons s−1 cm−2was used for ΦΔ determinations.,

Photodegradation Quantum Yields Photodegradation quantum yield (Φd) determinations were carried out using the experimental set-up described in similar literature [31–35] Eq.(3): where BC0^ and BCt^ are the sample concentrations before and after irradiation respectively, BV″ is the reaction volume, BNA^ is the Avogadro’s constant, BS″ is the irradiated cell area, Bt^ is the irradiation time, BIabs^ is the overlap integral of the radiation source light intensity and the absorption of the

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sample. A light intensity of 2.42x1016 photons s−1 cm−2 was employed for Φd determinations.

Results and Discussion Synthesis and Spectroscopic Characterization Scheme 1 shows the synthetic route of the target symmetrical phthalocyanines 2–5. The acetal substituted Pc derivatives 2 and 3 were prepared from the cyclotetramerization reaction of phthalonitrile derivative 1. To obtain metal-free Pc 2, reaction was performed in pentanol in the presence of DBU. The corresponding anhydrous metal salt NiCl2 was used in the similar reaction condition presence of DMAE and DBU as a strong base to obtain metallophthalocyanine 3. The purification of the prepared phthalocyanines (2, 3) was performed by size exclusion chromatography on Bio-beads gel (SX-1) by eluting dichloromethane after the crude products refined simply washing with water and ethanol several times in order to reduce unwanted organic and inorganic impurity. The synthesis of the aldehyde substituted phthalocyanines was improved on yield by applying acetal protection method [14]. The acetal groups at the peripheral position on phthalocyanine 2 and 3 were de-protected in acetic acid / FeCl3 system in order to achieve the synthesis of 4 and 5, containing aldehyde functional groups, in desired yield. This cleavage reaction was applied at 75 °C by dissolving of the

Scheme 1 Synthesis route: (I) Method I: n-pentanol, DBU, Method, II: DMAE, NiCl2, DBU (vi). THF, acetic acid, FeCl3.6H2O

corresponding phthalocyanines (2, 3) in THF before adding. All phthalocyanines (2–5) were obtained in moderate yield and characterized by a combination of methods including FT-IR, 1H-NMR, melting point, UV/Vis, Mass spectroscopy and elemental analysis. All the spectral data are in accordance with the proposed structures. Formation of acetal substituted Pc compounds (2, 3) starting from the corresponding phthalonitrile 1 derivative was confirmed by the disappearance of the C ≡ N stretching vibration band at 2225 cm−1, this band is calculated at; 2241–2247 cm −1 using B3LYP method and 6–311++G(dp) basis set in each case, theoretically. The similar characteristics were observed in the FT-IR spectra of metal-free (2) and metallophthalocyanine (3), except the peak appeared at 3288 cm−1 attributed to NH groups in the inner core which is the diagnostic feature for metal-free 2. The typical aliphatic C-H vibrational bands at 2920–2886 cm−1 and 2949–2881 cm−1 were assigned to the acetal C–H group of Pcs (2, 3), respectively. Aza group, Ar-O-Ar, C-O-C and C-N vibrations of the pyrrole, benzene and isoindol rings of the Pc assemblies were detected on their corresponding bands in the range of 1606–1072 cm−1. The sharp peaks at 1689 and 1691 cm−1 in the FT- IR spectra of 4 and 5 belong to the C = O stretching vibrations are indicative for the achievement of cleavage reaction of 2 and 3 to the desired aldehyde substituted Pcs. Furthermore, the peaks in the range of 2922–2752 cm−1 for O = C-H group show characteristic Fermi resonance and prove the aldehyde formation. The other sharp peaks at around 1070 cm−1 for -CO-C- originating from acetal group were disappeared in the spectra of 4 and 5. 1 H-NMR spectra of the free-base ligand 2 in DMSO gave characteristic resonances due to the peripheral protons of the phthalocyanine ring (Fig. 1). The aromatic protons appeared at 9.50–7.29 ppm. The aliphatic protons belonging to the – CHO2- moieties and -OCH2CH2O- protons of the acetal groups of 2 exhibited at 6.30 ppm as the broad band and 4.16–3.99 ppm as the multiplet due to the mixture of isomers, respectively. 1H-NMR spectrum of 4 was not able to record due to high aggregation tendency and low molecular solubility, and the 1H-NMR spectra of 3 and 5 could not be taken due to paramagnetic nature of the central metal ion, as well. 13CNMR spectroscopy technique gives also good opportunity to clarify and characterize the molecular structure. However, peripherally substituted phthalocyanines (2–5) were prepared as a statistical mixture of four regioisomers owing to the various possible positions of the substituents. The four possible isomers can be obtained as D4h, C4h, C2v and Cs. Because of that, it is difficult to obtain satisfactory spectroscopic results and the 13C-NMR spectra contain more peaks than the expected ones for the designed molecules. So that, in our study, The 13 C-NMR spectra of the prepared phthalocyanines were not

J Fluoresc Fig. 1 1H-NMR Spectrum of compound 2

attempted to record due to the above mentioned difficulty and the low solubility properties. The Mass spectrum of 2–5 was obtained by the MALDITOF Mass spectrometer confirming the proposed structure. Many different MALDI matrices were tried to find an intense molecular ion peak and low fragmentation under the MALDIMS conditions for this Pcs. The best matrice for all Pc compounds was found to be 2,5-dihydroxybenzoic acid (DHB). Mainly molecular ion peak of all Pcs were observed at high intensity and easily identified at m/z: 1172 [M + 1]+ for 2, 1228 [M + 1]+ and 1382 [M + DHB]+ for 3, 994 [M]+ for 4 and 1074 [M + Na]+ for 5 which exactly overlapped with the calculated molecular ion peaks of all compounds as seen in Fig. 2. The ground-state electronic absorption spectroscopy is one of the most useful methods for determination of the structural properties and aggregation characteristics of phthalocyanines. The absorption spectra of phthalocyanines give information about the symmetry of HOMO and LUMO orbitals and aggregation type of the molecules. Generally, phthalocyanine compounds display two intense absorption bands in the ground-state electronic spectra. One of them is observed in the visible region of spectrum at around 600–700 nm (Qband), and the other one is in the UV region of spectrum at around 300–350 nm (B-band), both correlated to π–π* transitions. Q and B bands are assigned to the electronic transition between the HOMO and LUMO orbitals and deeper level to L U M O o r b i t a l s , r e s p e c t i v e l y. S y m m e t r y o f t h e metallophthalocyanine is D4h. In case of metal free phthalocyanine, LUMO orbital splits to two energy levels called

LUMO and LUMO +1 due to the absence of the central metal. This splitting results in the formation of two sharp and intense bands (Qx, Qy) in the absorption spectrum and symmetry reduces to D2h [37]. Phthalocyanine compounds also exhibit vibronic bands on the left of the Q-bands in the visible region of spectra, correlating to n–π* transitions [38]. The electronic spectra of the prepared phthalocyanines were recorded in three different solvents such as DMAc, DMF and DMSO to observe the relation between polarity and basicity of the solvents and the aggregation tendency. When the basicity of the solvent increased, the solubility of the compounds (2–5) increased and the aggregation of the molecules decreased (Fig. 3). The absorption intensities in the electronic spectra of the prepared phthalocyanines are remarkably different due to having unique solution properties individually. So that, the UV–vis spectra for 2–5 were supplied as their characteristic to show the spectral details clearly. For the metal-free phthalocyanine complexes, the split Qbands were observed at 701–668 nm for 2, 699–666 nm for 4 in DMAc, vibronic bands of compounds 2 and 4 at 640– 609 nm and 637–617 nm, respectively (Fig. 3a, 3c). It was observed the similar UV/vis spectrum for compound 2 in the studied other solvents in terms of appearance of the splitted Q bands as expected for the metal-free phthalocyanines with non-degenerate D2h symmetry [37]. However for compound 4, the Q band did not split in DMF because of increase of the symmetry [39], and more broadened in DMSO, probably due to aggregation or some unresolved splitting. It is well known that the nature of solvent has a great influence on the aggregation behavior of Pcs [40]. As shown in Fig. 3c, the UV–vis

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Fig. 2 MALDI-TOF MS spectra of (a) 2, (b) 3, (c) 4, (d) 5

spectra of metal-free Pc 4 in DMAc is remarkably different from that in DMSO and DMF. Thus, the aggregation of 4 was inhibited by using DMAc as the solvent, and shows the split nature of the Q band. Dilution of DMF solution of 4 from 1x10−5 M to the 1x10−6 M disaggregates the molecules as expected (Fig. 3c, embedded graph.). Intense Q band absorptions indicate clearly the presence of monomeric species in DMAc. High aggregation tendency in DMSO is evidenced from both the broadening in Q band absorption and the appearance of a broad shoulder at its blue side. Metallated phthalocyanine complex 3 showed intense Qabsorption band around 672 nm with no splitting on the Qband which assigned that it was metallophthalocyanine with the D4h symmetry as expected [41]. Vibronic bands of compounds 3 were observed at about 640 nm as seen in Fig. 3b. DMSO, which is a strong coordinating solvent with a high donor number that is able to coordinate to most central metals

of porphyrins and phthalocyanines through either the sulfur or the oxygen atoms, normally prevents aggregation [42]. Thus aggregation should be more diminished in DMSO. However, this is not the case in this work. The aggregation tendency in DMF is positioned between those in DMAc and DMSO. High aggregation tendency of phthalocyanine compounds due to the interactions between their 18 π-electron systems often cause weak solubility or insolubility in many solvents. It also affects seriously their spectroscopic, photophysical, photochemical and electrochemical properties [43, 44]. Phthalocyanine compounds form aggregates (dimer and high order oligomers) both in solution and in solid state due to ππ* stacking, hydrogen bonding, ligand–metal coordination and donor-acceptor interactions [45–47]. Pcs have two types of aggregations which effect to the electronic and optical properties of these compounds. One of them namely face to face H-aggregation and another one is side to side J-aggregation. In

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Fig. 3 Absorption spectra of the compound 2–5 in DMAc, DMF and DMSO. Concentration 1x10−5 mol.L−1

general, the blue shifted aggregate peak is because of the cooperative interaction between transition dipole moments on the molecule. This event causes a decrease in intensity and broadening the Q bands with respect to the monomer peaks. Shifting to the lower wavelengths indicates to H-type aggregation among the phthalocyanine molecules. Since the all Pc compounds show more good solubility in DMAc, they were dissolved for obtaining quantitative concentration data or to observe the solvatochromic/chemical effect and for the molar absorption coefficient studies. Also, aggregation behavior of 3 were examined by UV–vis spectroscopy at different concentrations in DMAc. The phthalocyanine derivative 3 did not show aggregation in this solvent at a certain concentration. The Beer–Lambert law was obeyed for compound 3 for concentrations ranging from 1x10−5 to 1x10−6 M (Fig. 4). As illustrated in Fig. 4, the appearance of the Q-band absorption maxima remained unchanged as the concentration increases and no new bands were observed. Molar extinction coefficient of 3 remains almost constant indicating purely monomeric

form which obeyed the Beer–Lambert law in the outlined range of concentration [48]. Beside solvent types and their concentration, the central metal species have also a great influence on the

Fig. 4 Aggregation behaviour of 3 in DMAc at different concentrations. (Inset: plot of log ε versus concentration)

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aggregation behavior of the molecules [49]. NiPc complex (5) showed rather broad absorbance in UV/vis spectrum as different from the others in view of intramolecular and inter-molecular interaction and their aggregation types (Fig. 2d). These inter-molecular interactions include the typical π- π interactions between the macrocycle cores as well as possible hydrogen bonding interactions due to the aldehyde units [50]. This might be because of the higher planarity structure of the molecule and lower tendency of the solvents to axial coordination [51]. Another potential mode of interaction is through axial coordination of aldehyde unit to the Ni(II) center of the phthalocyanine. As a result of the propensity of Ni to form octahedral complexes with metal– ligand interaction, it was seen intense self-assemble at about 10−5 M concentration in the spectrum of 5 [52]. In case of convenient substituents, this tendency can be observed for all type phthalocyanines, as well. When compared the λmax values of B-bands in the electronic spectra of the prepared Pc compounds (2–5), no significant shift was observed as the substituents were altered on the substituted phthalocyanines. However, aldehyde group substituted phthalocyanines (4, 5) have lower absorption maxima as shown in Fig. 5.

Description of the Crystal Structure The molecular structure, an ORTEP 3 [23] and the theoretical geometry views of which are shown Fig. 6, crystallizes in the Orthorhombic space group Pbca with eight molecules in the unit cell (Fig. 7). The crystal structure analysis shows that the title molecule (1) contain a phenoxy unite combined to a phthalonitrile molecule and a dioxolane molecule in the asymmetric unit.

Figure 6 shows the molecular structure of the compound 1 with the atomic numbering scheme. The compound (1) contains two phenyl rings (ring A: C1/C2/C3/ C4/C5/C6) and (ring B: C7/C8/C9/C10/C11/C12) with two acetonitrile group (C13/N1 and C14/N2) substituted at C9, C10 in ring B, respectively and one dioxolane ring (ring C: O2/C15/C16/O3/C17). One of the phenyl rings substituted at C1 and C6 with dioxolane ring and phthalonitrile group, respectively. Phenyl rings are essentially planar but dioxolane ring is non planar. The three rings are not coplanar. The maximum deviation of the dioxolane ring and the phenyl rings from planarity are −0.1978 Å for atom C15 and 0.0116 Å for atom C1 and −0.0101 Å for atom C9 at C and A and B rings, respectively. The plane of the dioxolane ring makes dihedral angles of 61.225 (0.0641) and 49.217 (0.0732)° with the planes of rings A and B, respectively. Two phenyl rings between dihedral angles is 69.693 (0.036)°. In the molecular structure of the compound 1, there are no intra molecular interactions and intermolecular hydrogen bonds. The phthalonitrile group exhibits normal geometry and is planar. The cyano groups deviate from this plane by −0.0566(11) and 0.0346(11) Å at atoms N1 and N2, r e s p e c t i v e l y. T h e C ≡ N b o n d l e n g t h s [N1 ≡ C13 = 1.140 (2) Å and N2 ≡ C14 = 1.140 (2) Å], and the bonds show N ≡ C triple bond character and are in good agreement with the literature compare values reported in the literature [53–57] and those bond lengths are calculated at; 1.15 Å. As expected, the N— C—C angles [N1—C13—C9 = 177.98 (18)° and N2— C14—C10 = 178.97 (18)°] are almost linear and in a good agreement with previously reported values by [19, 58–60] and these angles are calculated at; 178.13 and 178.58° as theoretical. Some selected optimized geometric parameters (bond lengths, bond angles and dihedral angles) of the compound 1 are listed in Table 2. For the proposed molecular structure of the obtained crystal, the theoretical calculations have yielded some valuable results. The highest occupied molecular orbital (HOMO, −5.197 eV) and the lowest unoccupied molecular orbital (LUMO, −5.711 eV) are the main orbital taking part in chemical reaction. The HOMO energy characterizes the ability of electron-giving, the LUMO characterizes the ability of electron accepting, and the gap between HOMO and LUMO characterizes the molecular chemical stability [61]. The energy gap (ΔE = 0.514 eV) is calculated as seen Fig. 8. Fluorescence Spectra and Quantum Yields

Fig. 5 Absorption spectra of the compound 2–5 in DMAc. Concentration 1x10−5 mol.L−1

Fluorescence properties of metal free (2 and 4) and nickel (3 and 5) phthalocyanines were investigated in DMSO. The result of absorption, fluorescence excitation

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Fig. 6 Experimental and theoretical X-ray structure of compound 1

and emission spectra of the complexes 3 and 5 in DMSO are shown in Fig. 9 as examples. However, fluorescence emission intensities were observed at 681 nm for 2, 705 nm for 3, 692 nm for 4 and 681 nm for 5. The shape of the excitation spectra (λEx = 712 nm for 2, 682 nm for 3, 682 nm for 4 and 680 nm for 5) of studied compounds was similar to their absorption spectra. The excitation spectrum is narrower than the absorption spectrum due to the effects of some aggregation tendency of nickel Pcs (3, 5). The splitting in the Q band of excitation was observed for

Fig. 7 A view of the packing of the title compound

complex bearing formyl group (5). This could be changing of the symmetry of molecules than the former. The fluorescence quantum yields (ФF) of complexes 2–5 were calculated in DMSO. The introduction of dioxalan and formyl groups on the phthalocyanine ring results in high quantum yield [14] for metal free phthalocyanines (0,4289 for 2 and 0.2236 for 4). Low values of ФF were observed due the paramagnetic nature of central metal atom effect for Nickel Pcs (0.0024 for 3 and 0. 0807 for 5). When we compare the ΦF values of the complexes, the highest ΦF value is 0.4289 for 4 and the

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3

Table 2 Some experimental and theoretical bond distances and angles of the compound 1 (Å. °)

B3LYP/6311++G(d.p)

Experimental

C7—O1

1.357

1.3637

C6—O1 C3—C4

1.399 1.395

1.4062 1.373

C13—N1

1.155

1.140

C14—N2 C9—C13

1.155 1.433

1.140 1.438

C10—C14 C1—C17

1.427 1.525

1.434 1.499

C17—O2

1.399

1.3985

C17—O3

1.401

1.3999

O2—C15 O3—C16 Bond Angles

1.440 1.440

1.411 1.410

C6—O1—C7

120.26

119.60

O1—C7—C8 O1—C5—C6 O3—C17—C1

122.01 119.76 111.81

123.75 120.29 112.84

O2—C17—C1 O1—C6—C1 O1—C7—C12 C2—C1—C17

108.26 117.63 114.28 121.43

108.78 117.18 115.97 121.22

N1-C13-C9 N2-C14-C10

178.13 178.58

177.98 178.97

lowest Φ F value is 0.0024 for 3 in DMSO. The paramagnetic properties due to unpaired electron on the central metal ion of the phthalocyanine ring, fluorescence is expected to be weak [62, 63]. When investigated group effects on the fluorescence quantum yield of phthalocyanines, we obtained higher ΦF values for formyl group derivatives than carrying dioxolane g r o up s i n D M S O . W h i l e t he Φ F va lu e o f th e substituted metal free phthalocyanines both are higher than unsubstituted ZnPc, nickel derivatives is lower than ZnPc in solvents used.

Fig. 8 The HOMO and LUMO orbitals of the compound 1

0,8

Emission Excitation Absorption

0,6 0,4 0,2 0 550

600

650

700

750

800

750

800

Wavelength (nm)

a 5 1 Absorbance

Bond Distances

Absorbance

1

Atoms

Emission Excitation

0,8 Absorption

0,6 0,4 0,2 0 550

600

650

700

Wavelength (nm)

b Fig. 9 Absorption, excitation and emission spectra for compound 3 (a) and 5 (b) (Excitation wavelength = 620 nm) in DMSO

Photochemical Properties Singlet Oxygen Quantum Yields Singlet oxygen quantum yields of the synthesizes phthalocyanines were calculated in DMSO. The Pcs obtained have lower singlet oxygen quantum yield than standard ZnPc because of the metal free properties and open shell orbital metal ion (nickel) in the Pc core. The dioxolane substituted phthalocyanines has lower singlet oxygen quantum yields than formyl substituted Pcs. Compare to singlet oxygen generation properties, metal free derivatives (2 and 4) have higher singlet oxygen quantum yields than nickel phthalocyanine derivatives (3 and 5). Insertion of paramagnetic metal ion in to Pc ring caused decreasing of singlet oxygen generation. The highest quantum yield ΦΔ (0.15) was obtained for 4, and then it is followed by 2 (0.12). The complexes 3 (0.04) and 5 (0.09) exhibit low yield in DMSO. Figure 10 indicates the typical changes on the UV–vis spectra for the determination of singlet oxygen quantum yield in DMSO. Singlet oxygen quantum yield value of employed the substituted metal free and nickel

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Fig. 10 A typical spectrum for the determination of singlet oxygen quantum yield. These determinations were compounds 3 (a) and 5 (b) in DMSO. (Inset: plot of DPBF absorbance versus time)

3 0 sec 0,27

5 sec

0,265

0,25 DPBF Abs.

0,26

0,25

15 sec

0,245 0,24

20 sec

0,235

0,2

Absorbance

10 sec

0,255

0,23

25 sec

0,225 0

5

10

15

20

25

30

35

40

45

50

55

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35 sec

0,15

40 sec 45 sec 0,1

0,05 340

50 sec

390

440

490

540

590

640

690

740

Wavelength (nm)

a 0.3

5

0 sec

0,29

5 sec

0,28

0.25 BPBF Abs.

0,27

15 sec

0,25 0,24

20 sec

0,23

0.2

Absorbance

10 sec

0,26

25 sec

0,22 0,21 0

10

20

30

40

50

30 sec

60

Time (Sec)

0.15

35 sec 40 sec 45 sec

0.1

50 sec 55 sec 60 sec

0.05

0

340

390

440

490

540

590

640

690

740

Wavelength (nm)

b phthalocyanine complexes are lower compared to unsubstituted zinc phthalocyanine and some derivatives in literature [31–35]. Photodegradation (Photobleaching) Quantum Yields Photo-degradation quantum yield (Φd) is a measure of the stability of a molecule under photo irradiation. This progress was determined in DMSO by monitoring the decrease in the intensity of the Q band under irradiation with increasing time and the quantum yields. The new complexes (2 to 5) are moderate resistant to photochemical degradation. They have almost same stability (Φd: 3.15.23x10−4 for 4 and 2.23x10−4 for 5 ) compare to unsubstituted ZnPc (Φd: 2.61x10−4) with

Φd of the order of 10−4. The lowest photo-degradation stability is observed for complex 2 (Φd: 6.23x10−4) in DMSO among Pc molecules studied. Photo-degradation quantum yield (Φd) value of Pc 3 showed highest stability (Φd: 1.99x10−4) compare to unsubstituted ZnPc in DMSO [64–66].

Conclusion In the present work, the synthesis, spectral and photophysicochemical properties of new peripherally tetrasubstituted phthalocyanine compounds (2–5) carrying reactive functional groups was discussed. The phthalocyanine molecules have been studied as colorful macromolecules

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having unique photophysical and photochemical properties for many decades. However, there are very few work dealing with the future reaction via these molecules to reach the new functional materials. Recently, our group started to investigate the preparing aldehyde substituted pthalocyanines as the functional macromolecular starting materials to improve and add dimension to the phthalocyanine chemistry. The photophysical and photochemical properties of phthalocyanine complexes (2 to 5) were investigated in DMSO. Phthalocyanines bearing formyl group showed better photophysicochemical results than dioxolane group. The introduction of a formyl group into the macrocycle allows various structural modulations [67] and could represent a useful building block to obtain a new type of compounds via substituents of Pc ring. Acknowledgments This work was supported by Ministry of Science, Industry and Technology of Turkey (SANTEZ project no. 0182.STZ.2013-1) and Research Fund of Sakarya University (project no. 2014-02-04 007).

12.

13.

14.

15.

16.

17.

18. 19.

References 20. 1.

2. 3.

4. 5.

6.

7.

8.

9.

10.

11.

Ishii K, Kobayashi N, In: Kadish KM, Smith KM, Guilard R (Eds.) (2003) The Porphyrin handbook, Academic Press/Elsevier, New Yor 16:1–40. McKeown NB (1998) Phthalocyanine materials synthesis, structure and function. Cambridge University Press, Cambridge Torre G, Vazquez P, Agullo-Lopez F, Torres T (1998) Phthalocyanines and related compounds: organic targets for nonlinear optical applications. J Mater Chem 8:1671–1683 Bonnett R (2000) Chemical aspects of photodynamic therapy. Gordon and Breach Science, Canada Struve WS (1999) Primary process of Photocarrier generation in Yform Titanyl phthalocyanine studied by electric-field-modulated picosecond time-resolved fluorescence spectroscopy. J Phys Chem B 103:6835–6838 Radhakrishnann S, Deshpande S.D (2002) Conducting polymers functionalized with phthalocyanine as nitrogen dioxide sensors. Sensors 2:185–194. Hanack M, Lang M (1994) Conducting stacked metallophthalocyanines and related compounds. Adv Mater 6: 819–833 Agar E, Sasmaz S, Akdemir N, Keskin, I (1997) Synthesis and characterization of novel phthalocyanines containing four 15membered oxadithiadiaza mixed-donor macrocycles. J Chem Soc Dalton Trans 12:2087–2090 Leclaire J, Dagiral R, Fery-Forgues S, Coppel Y, Donnadieu B, Caminade A, Majoral J (2005) Octasubstituted metal-free phthalocyanine as core of phosphorus dendrimers: a probe for the properties of the internal structure. J. Am. Chem. Soc, 127:15762–15770. Fouriaux S, Armand F, Araspin O, Ruaudel-Teixier A, Maya E. M, Vazquez P, Torres T (1996) Effect of the metal on the organization of tetraamidometallophthalocyanines in langmuir–Blodgett films. J Phys Chem 100:16984–16988. Liu.S G, Liu YQ, Xu Y, Zhu DB, Yu AC, Zhao XS (1998) Synthesis, Langmuir–Blodgett film, and second-order nonlinear optical property of a novel asymmetrically substituted metal-free phthalocyanine. Langmuir 14:690–695

21. 22. 23. 24. 25. 26. 27.

28. 29.

30.

31.

32.

33.

34.

Chen J, Chen N, Huang J, Wang J, Huang M (2006) Derivatizable phthalocyanine with single carboxyl group: synthesis and purification. Inorg Chem Commun 9:313–315 Akkurt B, Hamuryudan E (2008) Enhancement of solubility via esterification: synthesis and characterization of octakis (ester)substituted phthalocyanines. Dyes Pigments 79:153–158 Sen P, Yildiz SZ, Tuna M, Canlica M (2014) Preparation of aldehyde substituted phthalocyanines with improved yield and their use for Schiff base metal complex formation. J Organomet Chem 769: 38–45 Gümrükçü G, Karaoğlan GK, Erdoğmuş A, Gül A, Avcıata U (2012) A novel phthalocyanine conjugated with four Salicylideneimino complexes; photophysics and fluorescence quenching studies. Dyes Pigments 95:280–289 Gümrükçü G, Karaoğlan GK, Erdoğmuş A, Avcıata U, Gül A (2014) Photophysical, photochemical and BQ quenching properties of zinc phthalocyanines with fused or interrupted extended conjugation. Journal of Chemistry 2014:1–11 Öztürk C, Erdoğmuş A, Durmuş M, Uğur AL, Kılıçarslan F. A, Erden I (2012) Highly soluble 3,4-(dimetoxyphenylthio) substituted phthalocyanines: synthesis, photophysical and photochemical studies. Spectrochim Acta A Mol Biomol Spectrosc, 86: 423–431. Perrin DD, Armarego WLF, Perrin DR (1985) Purification of laboratory chemicals, second edn. Pergamon Press, New York Sen P, Yildiz SZ, Atalay Y, Dege N, Demirtas G (2014) The synthesis, characterization, crystal structure and theoretical calculations of a new meso-BOBIPY substituted phthalonitrile. J Lumin 149: 297–305 Stoe & Cie, X-AREA (Version 1.18) and X-RED32 (Version 1.04) (2002) Stoe & Cie, Darmstadt, Germany Sheldrick GM (2008) A short history of SHELX. Acta Crystallogr A 64:112–122 Farrugia LJ (1999) WinGX suite for small-molecule single-crystal crystallography. J. Appl. Cryst. 32:837–838 Farrugia L (2012) WinGX and ORTEP for windows: an update. J Appl Cryst 45:849–854 Burnett MN, Johnson CK (1996) ORTEP-III, Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA Spek AL (2009) Structure validation in chemical crystallography. Acta Cryst D65:148–155 Becke AD (1993) Density-functional thermochemistry. III The role of exact exchange J Chem Phys 98:5648–5654 Frisch M J, Trucks G W, Schlegel HB, Scuseria GE, Robb M A, Cheeseman J R, Scalmani G, Barone V, Mennucci B, Petersson GA, Nakatsuji H, et al., Gaussian, Inc., Wallingford CT, (2009). Gaussian 09, Revision A.1 Dennington R, Keith T, Millam J (2009) Semichem Inc. Shawnee Mission, KS, Gauss View Version 5 Frey-Forgues S, Lavabre D (1999) Are fluorescence quantum yields so tricky to measure? A demonstration using familiar stationery products J. Chem Educ 76:1260–1264 Ogunsipe A, Chen JY, Nyokong T (2004) Photophysical and photochemical studies of zinc(II) phthalocyanine derivatives effects of substituents and solvents. New J Chem 28:822–827 Erdoğmuş A, Nyokong T (2010) Synthesis of zinc phthalocyanine derivatives with improved photophysicochemical properties in aqueous media. J Mol Struct 977:26–38 Erdoğmuş A, Nyokong T (2010) Novel, soluble, FluXoro functional substituted zinc phthalocyanines; synthesis, characterization and photophysicochemical properties. Dyes Pigments 86:174–181 Erdoğmuş A, Nyokong T (2009) Synthesis, photophysical and photochemical properties of novel soluble tetra-4-(thiophen-3yl)phenoxy-phthalocyaninato zinc(II) and Ti(IV)O complexes. Inorg Chim Acta 362:4875–4883 Erdoğmuş A, Nyokong T (2009) New soluble methylendioxyphenoxy-substituted zinc phthalocyanine derivatives: synthesis,

J Fluoresc

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

48.

49.

photophysical and photochemical studies. Polyhedron 28:2855– 2862 Erdoğmuş A, Ogunsipe A, Nyokong T (2009) Synthesis, photophysics and photochemistry of novel tetra(quinoxalinyl)phthalocyaninato zinc(II) complexes. J Photochem Photobiol A Chem 205:12–18 Kuznetsova N, Gretsova N, Kalmykova E, Makarova E, Dashkevich S, Negrimovskii V, Kaliya O, Luk’yanets E (2000) Relationship between the photochemicl properties and structure of pophyris and related compounds. J Russ Gen Chem 70:133–138 Sen P, Dumludag F, Salih B, Ozkaya AR, Bekaroglu O (2011) Synthesis and electrochemical, electrochromic and electrical properties of novel s-triazine bridged trinuclear Zn(II), Cu(II) and Lu(III) and a tris double-decker Lu(III) phthalocyanines. Synth Met 161:1245–1254 Arıcan D, Arıcı M, Uğur AL, Erdoğmuş A, Koca A (2013) Effects of peripheral and nonperipheral substitution to the spectroscopic, electrochemical and spectroelectrochemical properties of metallophthalocyanines. Electrochim Acta 106:541–555 Ogunsipe A, Maree D, Nyokong T (2003) Solvent effects on the photochemical and fluorescence properties of zinc phthalocyanine derivatives. J Mol Struct 650:131–140 Stillman MJ, Nyokong T, Leznoff CC (1989) A.B.P. Lever (Eds.), Phthalocyanines: Properties and Applications, vol. 1, VCH, New York. Yildiz SZ, Kucukislamoglu M, Tuna M (2009) Synthesis and characterization of novel flavonoid-substituted phthalocyanines using (±)naringenin. J Organomet Chem 694:4152–4161 Tau P, and Nyokong T (2006) Synthesis, electrochemical and photophysical properties of phthalocyaninato oxotitanium(IV) complexes tetra-substituted at the α and β positions with arylthio groups. J Chem Soc Dalton Trans 37:4482–4490 Schutte WJ, Rehbach MS, Sluyters JH (1993) Aggregation of an octasubstituted phthalocyanine in dodecane solution. J Phys Chem 97:6069–6073 Yang YC, Ward JR, Seiders RP (1985) Dimerization of cobalt(II) Tetrasulfonated phthalocyanine in water and aqueous alcoholic solutions. Inorg Chem 24:1765–1769 Escosura A, Martinez-Diaz MV, Thordarson P, Rowan A.E, Nolte R.J.M, Torres T (2003) Donor-acceptor phthalocyanine Nanoaggregates. J Am Chem Soc, 125: 12300–12308. Martinez-Diaz MV, Rodriguez-Morgade MS, Feiters MC, Kan PJM, Nolte RJM, Stoddart JF, Torres T (2000) Supramolecular phthalocyanine dimers based on the secondary Dialkylammonium Cation/ Dibenzo-24-crown-8 recognition motif. Org Lett 2:1057– 1060 Yang ZY, Gan LH, Lei SB, Wan LJ, Wang C, Jiang J.Z (2005) Selfassembly of PcOC8 and its sandwich lanthanide complex Pr(PcOC8)2 with Oligo(Phenylene-ethynylene) molecules. J Phys Chem B, 109:19859–19865. Tran-Thi T-H (1997) Assemblies of phthalocyanines with porphyrins and porphyrazines: ground and excited state optical properties. Coord Chem Rev 160:53–91 Palewska K, Sworakowski J, Lipinski J (2012) Molecular aggregation in soluble phthalocyanines – chemical interactions vs. π-stacking. Opt Mater 34:1717–1724

50.

51.

52.

53.

54. 55.

56. 57.

58. 59. 60. 61. 62.

63.

64.

65.

66.

67.

Sessler JL, Jayawickramarajah J, Gouloumis A, Dan Pantos G, Torres T, Guldi DM (2006) Guanosine and fullerene derived deaggregation of a new phthalocyanine-linked cytidine derivative. Tetrahedron 62:2123–2131 Adebayo AI, Nyokong T (2009) Synthesis, spectroscopic and electrochemical properties of manganese, nickel and iron octakis-(2diethylaminoethanethiol)-phthalocyanine. Polyhedron 28:2831 Li X-Y, Ng DKP (2001) Synthesis and spectroscopic properties of the first phthalocyanine–nucleobase conjugates. Tetrahedron Lett 42:305–309 Akbal T, Akdemir N, Ozil M, Agar E, Erdonmez A (2005) 4,5-bis(3-methoxyphenylsulfanyl)phthalonitrile. Acta Cryst E61:1121–1122 Dinçer M, Agar A, Akdemir N, Ağar E, Özdemir N (2004) 4(Benzyloxy)phthalonitrile. Acta Crystallogr E 60(79–80):34 Tereci H, Askeroğlu I, Akdemir N, Uçar I, Büyükgüngör O (2012) Combined experimental and theoretical approaches to the molecular structure. Spectrochim Acta A Mol Biomol Spectrosc 96:569–577 İskeleli NO (2007) 4-(m-Tolyloxy)phthalonitrile. Acta Crystallogr E 63(997–998):37 Mei C, Lia K, Zhang P (2008) Poly[[tetraaquabis(1H-imidazoleκN3)bis[2-(oxaloamino)benzoato(3–)]dicopper(II)barium(II)] dihydrate]. Acta Cryst E 64:356–356 Işık Ş, Köysal Y (2006) 4-(4-Heptyloxyphenoxy)phthalonitrile. Acta Crystallogr E 62:671–672 Köysal Y, Işık Ş, Akdemir N, Ağar E, McKee V (2003) 4-(8Quinolinoxy)phthalonitrile. Acta Crystallogr E 59:1423–1424 Tanak, H., Köysal, Y., Işık, Ş.,Yaman, H., Ahsen, V. (2011). Bull. Korean Chem. Soc., 32, 2: 673–680. Öner N, Tamer Ö, Avcı D, Atalay Y (2014) Spectrochim Acta 133: 542–549 Yarasir MN, Kandaz M, Güney O, Salih B (2012) Synthesis and photophysical properties of metallophthalocyanines substituted with a benzofuran based fluoroprobe. Spectrochim Acta A Mol Biomol Spectrosc 93:379–383 Sanusi K, Khene S, Nyokong T (2014) Enhanced optical limiting performance in phthalocyanine-quantum dot nanocomposites by free-carrier absorption mechanism. Opt Mater 37:572–582 Çoşut B, Yeşilot S, Durmuş M, Kılıç A, Ahsen V (2010) Synthesis and properties of axially-phenoxycyclotriphosphazenyl substituted silicon phthalocyanine. Polyhedron 29:675–682 Yaşa G, Erdoğmuş A, Uğur AL, Şener MK, Avcıata U, Nyokong T (2012) Photophysical and photochemical properties of novel phthalocyanines bearing non-peripherally substituted mercaptoquinoline moiety. J. Porphyrins Phthalocyanines 16:845–854 Kırbaç E, AtmacaYaşa G, Erdoğmuş A (2014) Novel highly soluble fluoro, chloro, bromo-phenoxy-phenoxy substituted zinc phthalocyanines; synthesis, characterization and photophysicochemical properties. J Organomet Chem 752: 115–122 Schweikart KH, Hanack M (2000) Synthesis of nickel phthalocyanines with one aldehyde group and preparation of a BisvinylenePhenylene-bridged Bisphthalocyanine. Eur J Org Chem 2551-2556