Supporting Information
Sensitive Fluorescent Detection and Lewis Basicity of Aliphatic Amines
Ivan Pietro Oliveri and Santo Di Bella* Dipartimento di Scienze Chimiche, Università di Catania, I-95125 Catania, Italy E-mail:
[email protected]
Contents I.
Job’s plot analysis ……..…………...……….…………………………………….…. S2
II.
ESI Mass spectrometry………………………………………………………………. S3
III.
1
IV.
Spectrophotometric and fluorimetric titrations ……………………………………... S5
V.
Calculation of the binding constants..…………………………………...…..……… S7
VI.
Calculation of the limits of detection……………………………………………….. S8
VII.
Competitive experiments……………………………………………………………. S9
VIII.
Preliminary studies in DCM/H2O …………………………………………………… S10
H NMR analysis ……………………………………………………………………. S4
S1
I. Job’s plot analysis To determine the binding stoichiometry between the complex 1 and the amines 2-15, the continuous variation method with fluorescence data was used. As representative example, the case of propylamine is presented. Job’s plot analysis clearly indicates the formation of a 1:1 adduct (Figure S1).
1.0
λexc = 467 nm F = F-[F0(1-χ)]
0.8
0.6
0.4
0.2
0.0 0.0
0.2
0.4
0.6
0.8
1.0
χpropylamine Figure S1. Job’s plot for the binding of 1 with propylamine in DCM. The total concentration of 1 and propylamine is 10 μM. F and F0 (the initial fluorescence intensity of 1) are the fluorescence intensities at 600 nm.
S2
II. ESI Mass spectrometry Formation of 1·amine adducts was investigated by ESI mass spectrometry. As representative example, the ESI mass spectrum of the 1·propylamine adduct is reported (Figure S2).
[M + H]+
Figure S2. ESI mass spectrum of the 1·propylamine adduct.
S3
III. 1H NMR analysis The axial coordination of amines to the ZnII ion of 1 was further established by 1H NMR studies. For example, the addition of an equimolar amount of diethylamine to a CD2Cl2 solution of 1 (5.0 × 10-4 M) results in a down-field shift of H1, H3 and the OCH2- signals, according to the deaggregation of the complex.11 Moreover, the observed up-field shift of the hydrogens of the diethylamine clearly indicates its axial coordination to the complex (Figure S3). NC
CN
N
N
H4
H1
Zn O H2C
O
H2 H3
CH (CH2)9 O
O H5
H4
H1
H2
(CH2)8
CH
CH2
H5
H5
H3
Hb
Ha
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
δ / ppm Figure S3.
1
H NMR spectra of 1 (5.0 × 10-4 M; 27 °C) in CD2Cl2 (top), and upon addition an
equimolar amount of diethylamine (middle). The 1H NMR spectrum of diethylamine in CD2Cl2 (bottom) is reported as reference.
S4
IV. Spectrophotometric and fluorimetric titrations As further representative examples, the titrations of 1 with a secondary (diethylamine, Figure S4) and a tertiary (tris(2-ethylhexyl)amine, Figure S5) amine, are reported.
Absorbance
0.4
18 μ M
0.3
0.0
0.2
0.1
0.0
300
400
500
600
Wavelength / nm R2 = 0.997
6.0
18 μ M
5.0 0.0
4.0
Intensity / a.u.
Fluorescence Intensity / a.u.
7.0 6 4 2 0
3.0
0
5
10
15
20
[diethylammine] / μ Μ
2.0 1.0 0.0 500
600
700
800
Wavelength / nm
Figure S4. UV/vis absorption (top) and fluorescence (bottom) (λexc = 468 nm) titration curves of 1 (10 µM solution in DCM) with addition of diethylamine, 7. The concentration of diethylamine added varied from 0 to 18.0 µM. Inset: variation of fluorescence intensity at 600 nm as a function of the concentration of diethylamine added. The solid line represents the curve fitting analysis with eq. 1. S5
0.5 5 mM
Absorbance
0.4 0.0
0.3
0.2
0.1
0.0
300
400
500
600
Wavelength / nm
R2 = 0.995
6
5 mM
5.0
0.0
4.0
Intensity / a.u.
Fluorescence Intensity / a.u.
6.0
4 2 0
3.0
0
2
4
[tris(2-ethylhexyl)amine] / mΜ
2.0 1.0 0.0 500
550
600
650
700
750
800
Wavelength / nm
Figure S5. UV/vis absorption (top) and fluorescence (bottom) (λexc = 467 nm) titration curves of 1 (10 µM solution in DCM) with addition of tris(2-ethylhexyl)amine, 14. The concentration of tris(2ethylhexyl)amine added varied from 0 to 5.0 mM. Inset: variation of fluorescence intensity at 602 nm as a function of the concentration of tris(2-ethylhexyl)amine added. The solid line represents the curve fitting analysis with eq. 1.
S6
V. Calculation of the binding constants As representative example, the calculation of the binding constant for propylamine (using eq. 1) is reported (Figure S6).
7
Intensity / a.u.
1.6x10
7
1.2x10
6
7.9x10
Data: propylamine Model: eq.1
6
4.0x10
0.0
R^2
= 0.9995
Flim
20349323 ± 969588
K
0
1206508 ± 673584
4 8 12 [propylammine] / μ Μ
Figure S6. Variation of fluorescence intensity of 1 (10 µM solution in DCM) at 600 nm as a function of the concentration of propylamine added. The solid line represents the curve fitting analysis with eq. 1. For replicate titrations, we have: Replicate 1 2 3
log K 6.08 5.90 6.32
which allows the calculation of a log K = 6.1 ± 0.2.
S7
R2 0.9995 0.9975 0.9892
VI. Calculation of the limits of detection For example, in the case of propylamine, from the linear best fit data of Figure S7, a LOD of 0.17 µM is calculated.
7
Fluorescence Intensity / a.u.
1.2x10
Linear Regression for Propylamine: Y=A+B*X Weight given by Data error bars.
6
9.0x10
Value Error -----------------------------------------------------------6 A 2.01124 * 10 46852.68887 12 10 B 1.23529 * 10 1.55087 * 10 ------------------------------------------------------------
6
6.0x10
SD N P R -----------------------------------------------------------0.99971 0.73286 13
