Yuri V. Il'ichev,a,e Rigoberto Hernandez,b Michael G. Kuzmina a Department ..... S4 Noam Agmon, Dan Huppert, Asnat Masad, and Ehud Pines. J. Phys. Chem ...
Kinetics of intra- and intermolecular Excited-State Proton Transfer of -(2hydroxynaphthyl-1)-decanoic acid in homogeneous and micellar solutions Kyril M. Solntsev,a,b,c,* Alexander V. Popov,b Vera A. Solovieva,a Sami Abou Al-Ainain,a,d Yuri V. Il’ichev,a,e Rigoberto Hernandez,b Michael G. Kuzmina a
Department of Chemistry, Moscow M. V. Lomonosov University, Sparrow Hills, Moscow, 119991, Russia
b
Present addresses: School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA 30332-0400, United States
and c
Olis Inc, 130 Conway Drive, Bogart, GA 30622, United States
d
Permanent address: Department of Chemistry, Faculty of Science, Tishreen University, Latakia, Syria
e
Present address: Unilife Corporation, 250 Cross Farm Lane, York, PA 17406, United States
SUPPORTING INFORMATION
Materials and methods Materials and Synthetic Techniques All reagents and solvents were obtained from commercial sources (Sigma-Aldrich, Fisher Scientific and VWR) and used without further purification.
Analytical Techniques Thin Layer Chromatography (TLC): TLC was performed on 2000 μm silica gel plates (Analtech, TLC Uniplates). The bands were visualized with UV light or solutions of ammonium molybdate/H2O and KMnO4/Na2CO3/H2O. Flash chromatography was performed on Merck Kieselgel 60 (230-400 mesh) silica.
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Liquid Chromatography - Mass Spectrometry (LC-MS): LC-MS analyses were performed on an Agilent 1260 HPLC instrument equipped with an Agilent 6130 single-quadrupole MSD. Chromatographic separation was achieved on an Epic C18 column, 1.8 μm/120 Å, 3 cm x 2.1 mm (ES Industries, West Berlin, NJ; Cat.# 582A91-EC18). Analyses were performed in isocratic mode (70% MeCN: 30% H2O, 0.05% TFA v/v) with a solvent flow of 0.4 ml/min. The sample injection volume was 1 μl. The column was termostatted at 25 °C. The MSD spray chamber parameters were as follows: drying gas (N2) flow 12.0 l/min, nebulizer pressure setpoint 11 psig, drying gas temperature setpoint 350 C. Data analysis was performed using LC/MSD ChemStation software from Agilent.
High Resolution Mass Spectrometry (HRMS): HRMS analyses were performed at Analytical Core Lab, 4700 King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
Nuclear Magnetic Resonance Spectroscopy (NMR): 1
H,
13
C spectra for routine characterization of molecules was recorded at room
temperature on a Bruker Avance-III 400 MHz (1H) NMR spectrometer equipped with a Z-axis gradient BBO probe; Bruker AVANCE-III 600 MHz (1H) NMR instrument and Bruker AVANCE-III 500 MHz (1H) NMR instrument, equipped with a 5mm Z-axis gradient TCI cryoprobe. NMR chemical shifts are reported as δ (ppm) and are calibrated against residual solvent signals of CDCl3 (δ 7.26, 77.16) and DMSO-d6 (δ 2.50, 39.52). Coupling constants are reported as (J) in Hz. Bruker Topspin 3.0 and iNMR 4.1.0 were used as the processing software.
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Organic Synthesis and Compound Characterization
10-(2-hydroxynaphthalen-1-yl)-10-oxodecanoic acid: Suspension of 2-naphthol (1.45 g, 0.01 mol), sebacic acid (2.02 g, 0.01 mol) and boron trifuoride diethyl etherate (2 mL 48% solution in diethyl ether) in carbon tetrachloride 5 mL was sealed in the pressure flask under nitrogen and vigorously stirred at 80 oC for 2 days. The reaction mixture was allowed to cool to room temperature; excess of sebacic acid was filtered off. Filtrate was poured to 15% aq. NaOH (40 mL), acidified to pH 11 and extracted with ethyl acetate (4 x 15 mL), organic layer containing unreacted naphthol-2 was discarded. Water layer was acidified to pH 7 and extracted with ethyl acetate (4 x 15 mL); combined organic layers were washed with brine (1 x 10 mL) and dried over magnesium sulfate. Solvent was evaporated under reduced pressure to provide off-white solid 10-(2-hydroxynaphthalen-1-yl)-10-oxodecanoic acid pure enough for further transformation (0.95 g, 29%, purity 90%). 1H-NMR (400 MHz; CDCl3): δ 12.97 (s, 1H), 8.03 (d, J = 8.6 Hz, 1H), 7.87 (d, J = 9.0 Hz, 1H), 7.78 (t, J = 7.1 Hz, 1H), 7.56 (td, J = 7.8, 1.4 Hz, 1H), 7.39 (t, J = 7.4 Hz, 1H), 7.14 (d, J = 8.9 Hz, 1H), 3.16 (t, J = 7.5 Hz, 2H), 2.34 (t, J = 7.5 Hz, 2H), 1.82 (quintet, J = 7.2 Hz, 2H), 1.61 (q, J = 7.2 Hz, 2H), 1.37-1.26 (m, 9H). 13C NMR (101 MHz; CDCl3): δ 208.2, 179.5, 162.9, 137.0, 129.6, 128.1, 124.7, 123.9, 120.0, 117.9, 115.7, 109.6, 44.1, 34.0, 29.34, 29.31, 29.16, 29.07, 25.7, 24.7 MS (ESI+) calculated [C20H25O4]+: 329.17, found: 329.2. HRMS (ESI-) calculated [C20H23O4]−: 327.15909, found: 327.15967.
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10-(2-Hydroxynaphthalen-1-yl)decanoic acid (1S2N, -(2-hydroxynaphthyl-1)decanoic acid): To the suspension of zinc powder (2.14 g) and mercury chloride (0.22 g) in 2.75 mL of water conc. HCl (0.2 mL) was added. Mixture was stirred at room temperature for 15 min; then water layer was discharged. To the residue in the flask 10-(2hydroxynaphthalen-1-yl)-10-oxodecanoic acid (0.95 g), water (1.35 mL) and toluene (1.8 mL) were added followed by dropvice addition of conc. HCl (0.33 mL). Flask was closed with reflux condenser and reaction mixture was refluxed overnight. While refluxing more conc. HCl (0.5 mL) was added portion vice. Reaction mixture was allowed to cool to room temperature and decanted from amalgam. Reaction mixture was diluted with 50 mL of water, extracted 4 x 15 mL of ethyl acetate. Organic layer washed with brine and dried under magnesium sulfate. Solvent was removed under reduced pressure; residue was purified by chromatography (toluene/ethyl acetate 95:5) to provide off white powder of 10-(2-hydroxynaphthalen-1-yl)decanoic acid (0.88 g; 95%).
1
H-NMR (400 MHz;
CDCl3): δ 7.92 (d, J = 8.6 Hz, 1H), 7.77 (d, J = 8.1 Hz, 1H), 7.62 (d, J = 8.8 Hz, 1H), 7.48 (ddd, J = 8.4, 6.9, 1.4 Hz, 1H), 7.32 (t, J = 7.0 Hz, 1H), 7.06 (d, J = 8.8 Hz, 1H), 5.88 (s, 2H), 3.02 (t, J = 7.9 Hz, 2H), 2.35 (t, J = 7.5 Hz, 2H), 1.70-1.60 (m, 4H), 1.46 (dt, J = 14.8, 7.2 Hz, 2H), 1.32 (d, J = 16.3 Hz, 8H). 13-C NMR (101 MHz; CDCl3): δ 179.63, 150.44, 133.32, 129.56, 128.72, 127.65, 126.40, 123.16, 123.11, 120.50, 117.77, 34.06, 29.97, 29.88, 29.53, 29.38, 29.23, 29.09, 25.19, 24.75. MS (ESI+) calculated [C20H27O3]+: 315.19, found: 315.2. HRMS (ESI-) calculated [C20H25O3]−: 313.17982, found: 313.18046.
Acknowledgement: Salim Sioud for help with registration of HRMS spectra.
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(CH2 )9COOH O
-
-
ArO -(CH2)9-COOH
ArO -(CH2)9-COO
IV
III
(CH2 )9COOH OH
pKa
ArOH-(CH2)9-COOH I
GROUND STATE
pKa
C
A
ArOH-(CH2)9-COO
-
(CH2 )9COO O
-
II
(CH2 )9COO OH
Scheme S1. Protolytic reactions of 1S2N in the ground state showing the structures of the acidbase forms.
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Brij-35
CTAB 0 1.0
4
8
12
4
8
12 1.0
1.0
0.8
I'/Io'
0.5
0.4
A1/(A1+A2)
0.6
0.8 1.0
0.4 0.5
0.0
0.2
0.2
0.0
0.0
12
2
2
i, ns
0.6
0.0 12
8
8
1
4 0
4
1 4
8
12
4
8
12
pH Figure S1. (Top row) The relative fluorescence intensities yield of anionic species (Iʹ/Iʹ0, open blue lozenges) and the relative amplitude of the shortest decay time in the fluorescence kinetics of *ArOH (A1/(A1 + A2), solid red circled) plotted against pH for 1S2N in CTAB solutions. Note the different Y-scales for these plots. (Bottom row) Plot of *ArOH fluorescence decay times vs. pH. CTAB micellar solution – left column, Brij35 micellar solution – right column.
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1.0 I
Ai
III
II
0.5 0.0 3
6
9
12
pH Figure S2. Magnified portion of Figure 4 showing the pH dependence of the ground-state population 1S2N acid-base forms in EtOH/H2O from Scheme 1. Circles are experimental data points. Lines are the fits to the following equations (see also Eq. (13) in the main text): I(pH)
1
1 exp 2.3· pH pKaC
II(pH)
1 I (pH)
1 exp 2.3· pH pKaA
III(pH) 1
QC (pH) 1 PC (pH)
QA (pH)PC (pH)
1
1 exp 2.3· pH pKaA
PA (pH) 1 QA (pH)
(S1)
(S2)
(S3)
All analogous data for other solvents was treated in the same way.
S7
20
CTAB
o (III*), '1(IV*)
15
i / ns
2 (II*)
10 2 (IV*)
5 1 (II*)
3
6
9
12
pH Figure S3. Magnified portion of Figure 4 showing the pH dependence of the 1S2N fluorescence lifetimes from Table 3 measured in CTAB micellar solutions. Symbols are experimental data points. Lines are the fits to the following equations:
2 (IV*)(pH) F8 (pH) F13 (pH) F9 (pH) F16 (pH) 1 F8 (pH) F9 (pH) F26 (pH) , (S4) where
F8 (pH) 1 exp 2.3· pH pKa
1
(S5)
F9 (pH) 1 F8 (pH) QC (pH)
(S6)
F16 (pH) F12 (pH) F13 (pH) F14 (pH)·F11 (pH) F15 (pH) 2
F12 (pH) F13 (pH) F14 (pH)·F11 (pH) F15 (pH)
2
4 F12 (pH)·F14 (pH)·F11 (pH)
(S7)
F11 (pH) H3O exp 2.3·pH
(S8)
F12 k1
(S9)
F13 1 0
(S10)
F14 k1
(S11)
F15 1 0
(S12)
F26 (pH) F12 (pH) F13 (pH) F24 (pH)·F11 (pH) F15 (pH) 2
F12 (pH) F13 (pH) F24 (pH)·F11 (pH) F15 (pH) F24 (pH) F212 (pH) 1 F21 (pH) F15 (pH)
2
4 F12 (pH)·F24 (pH)·F11 (pH)
(S13)
(S14)
S8
F21 I I 0 at neutral pH
(S15)
2 (II*)(pH) F8 (pH) F13 (pH) F9 (pH) F10 (pH) F20 (pH) F16 (pH) ,
(S16)
where
F10 (pH) PC (pH)F8 (pH)
(S17)
F20 (pH) PA (pH)
(S18)
Synthesis and spectroscopic studies of -(6-hydroxynaphthyl-2)-decanoic acid (6S2N) and -(1-hydroxynaphthyl-2)-decanoic acid (2S1N): -(1-hydroxynaphthyl-2)-decanoic acid (2S1N) was synthesized identically to 1S2N, only 1naphthol was used instead of 2-naphthol as a starting material. Final product was purified by chromatography on silicagel (Chemapol) with toluene-ethylacetate (5/1 v/v) as eluent. Thin layer chromatography on silicagel (Kavalier, same eluent) gives Rf - 0.29. -(6-hydroxynaphthyl-2)-decanoic acid (6S2N) was synthesized using the acylation of protected naphthol with the mixed anhydride of silicic and sebacic acids as described in Ref. S1. This method avoids the formation of diketons, which are common products of acylation with dicarboxylic acids derivatives. The acylation was a two-step reaction. First, SiCl4 was added to the solution of sebacic acid in nitrobenzene upon heating.
The resulting
acylsiloxane was then used as an acylating agent in a Friedel-Crafts reaction using AlCl3 as a catalyst. Deethylation was then carried on in boiling AcOH/HBr. The resulting ketone was then reduced using the Clemmensen method as described earlier for 1S2N. Final product 6S2N was purified by chromatography on silicagel (Chemapol) with toluene-ethylacetate (1/1 v/v) as eluent. Thin layer chromatography on silicagel (Kavalier, same eluent) gives Rf – 0.47.
S1
Yyurev, Y. K.; Elyakov, G. B.; Belyakova, Z. V. Zh. Obsh. Khim. 1954, 24, 1568-1571.
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OC2H5
1) HOOC(CH2)8COOH SiCl4, PhNO 2, 2) AlCl3, P
hNO2
OC2H5
HOOC(CH2) 8CO AcOH / HBr 10 hrs, OH
OH Zn/Hg in HCl(aq)/PhCH3 30 hrs,
HOOC(CH2) 9
HOOC(CH2) 8CO
6S2N OH (CH2) 9COOH
2S1N Scheme S2. Synthesis of 6S2N and molecular structure of 2S1N. 1H
NMR (200 MHz, Acetone-d6, ref to the solvent at 2.07 ppm)
6S2N. 7.66 (1H – arom of ArOH, d, J = 8.6 Hz), 7.57 (1H – arom of ArOH, d, J = 8.5 Hz), 7.54 (1H - arom of ArOH, s), 7.26 (1H – arom of ArOH, dd, J = 8.6 and 1.8 Hz), 7.13 (1H – arom of ArOH, s), 7.07 (1H – arom of ArOH, dd, J = 9.2 and 2.4 Hz), 2.70 (2H - CH2-Ar , t, J = 7.9 and 7.3 Hz), 2.25 (2H - CH2-COOH , t, J = 7.3 Hz), 1.66 (2H - CH2-CH2Ar, m), 1.56 (2H CH2-CH2COOH, m), 1.1-1.5 with max. at 1.30 (10H - H of methylene chain, m).
2S1N. 8.26 (1H - 8 arom. Of ArOH, dd, J = 6.1 Hz and 2.4 Hz), 7.80 (1H - 5 of ArOH, dd, J = 6.1 Hz and 2.4 Hz), 7.36 - 7.51 (2H - 6 and 7 arom. ArOH, complex.), 7.40 (1H - 3 arom. ArOH, d, J = 8.5 Hz), 7.31 (1H - 4 arom. ArOH, d, J = 8.5 Hz), 2.87 (2H - CH2-Ar, t, J = 7.4 and 7.9 Hz), 2.29 (2H - CH2-COOH, t, J = 7.3 and 7.4 Hz), 1.70 (2H - CH2-CH2Ar, m), 1.61 (2H - CH2-CH2-Ar, m), 1.1-1.5 with max. at 1.34 (10H - H of methylene chain, m).
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Excited-state proton transfer reactions of 6S2N. It is known that 1- and 6-alkylsusbituted 2-naphthols have comparable pKa values both in the ground and in the excited states.S2 Therefore, we expected that the acid-base properties of 1S2N and 6S2N will be similar.
Fluorescence spectra of 6S2N in
ethanol/water mixture at various pH are presented on Figure S4. Similarly to 1S2N, 6S2N shows the appearance of the anionic emission at pH 6.5 and 9 due to intramolecular ESPT. However, the relative intensity of this band was much lower than in 1S2N. The fluorescence decay behavior was also similar to 1S2N, but the lifetimes of the*ArOH band were larger for 6S2N (Table S1). Using the equation
k2 1 1 1 0 where 0 is the *ArOH lifetime at pH 2 in ethanol/water, where all excited-state proton reactions are suppressed we obtained the k 2 values of 0.024 and 0.12 ns−1 for 6S2N and 1S2N, respectively. We propose that the decrease of ESIPT efficiency in 6S2N as compared to 1S2N is caused by the steric factors and much lower probability to reach the favorable transition state of this reaction. To model these transition states we minimized the energies of the intramolecular cyclic peroxides for 1S2N and 6S2N using the Avogadro packageS3 starting with different initial configurations (Fig. S5). One can see that while the intramolecular cyclic structure on 1S2N can be easily formed, the formation of the similar structure in 6S2N is accompanied by the (highly energetically unfavorable) bending of the naphthalene ring and deviation of the methylene chain from sp3 hybridization. The distributions (histograms) of the local energy minima are presented in Fig. S6. The corresponding cumulative distributions are shown in Fig. S7. It is easy to see that the minimal energies for 6S2N are shifted to higher values on the average by 90 kJ/mol.
Solntsev K M, Il’ichev Y V, Demyashkevich A B and Kuzmin M G J. Photochem. Photobiol. A Chem. 1994, 78, 39–48 S3 http://avogadro.openmolecules.net/ S2
S11
nm
Figure S4. Emission spectra of 6S2N in ethanol/water (1/1 vol) at various pH values: 2.0 (1), 6.5 (2), 9.2 (3).
Table S1. Parameters of the fluorescence decay curves of 6S2N in ethanol/water mixtures at various pH values. *ArOH
*ArO−
Solvent
pH
1 , ns
1 , ns
2 , ns
A2 A1
EtOH/
2.0
8.17
-
-
-
H2O (1/1)
9.2
6.86
6.42
11.0
0.91
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Figure S5. (top) Structures of the energy-minimised intramolecular peroxy derivatives of 6S2N (left) and 1S2N (right). (bottom) Different angles of view of the same structures reveal the bending deformation of 6S2N naphthalene moiety.
S13
Figure S6. The distributions of the local energy minima of intramolecular peroxy derivatives of 6S2N (top) and 1S2N (bottom). The average energies are 480±180 kJ/mol and 570±220 kJ/mol, accordingly.
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Cumulative distribution
1.0
0.8
1S2N 6S2N
0.6
0.4
0.2
0.0 200
400
600
800
1000
1200
1400
E, kJ/mol
Figure S7. The cumulative distributions of the local energy minima of intramolecular peroxy derivatives of 6S2N (red) and 1S2N (blue). The average difference between the energies is 90 kJ/mol.
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Excited-state proton transfer reactions of 2S1N It is known that 1-naphthol exhibits intermolecular ESPT to water in methanol/water mixtures down to 7 vol% of water.S4 As a result, we can conclude that the anionic emission in spectrum 1 of Fig. S8 is due to the ESPT process I*→IV* from Scheme 1 at the conditions where no ESIPT is possible. At higher pH (8.0) the additional processes II*→IV*and II*→III contribute to the photoinduced behavior of 2S1N. More detailed studies of compounds 6S2N and 2S1N will be reported in the next paper. 8
2
I 6
1 1
4
2 2
0
350
400
450
, nm , íì
500
550
600
Figure S8. Emission spectra of 2S1N in methanol/water (1/1 vol) at various pH values: 3.2 (1), 8.0 (2).
S4
Noam Agmon, Dan Huppert, Asnat Masad, and Ehud Pines. J. Phys. Chem. 1991, 95, 10407-10413.
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