J. Jayabharathi et al. / Spectrochimica Acta Part A 79 (2011) 6–16
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methoxy-benzylidene)benzenamine(SB3), (0E,4E)-4-(2-phenyl-
2.6. General procedure for the synthesis of Schiff bases (1–6)
diazenyl)-N-(m-hydroxybenzylidene)benzenamine(SB4), (0E,4E)-
4-(2-phenyldiazenyl)-N-(o-hydroxy-m-bromobenzylidene)ben-
zenamine (SB5) and (0E,4E)-4-(2-phenyldiazenyl)-N-(p-hydroxy-
m-methoxybenzylidene)benzenamine (SB6) are reported, their
structures were confirmed by elemental, mass, IR and NMR anal-
–6) were carried out and discussed in detail. The Schiff base (SB5)
was developed as a possible Cu(II)-selective fluorescence sensor.
Theoretical calculations were carried out using Gaussian-03
program [20,21] to supplement the experimental results.
The Schiff bases (1–6) were synthesized according to the
procedure reported in the literature [23]. solution of p-
aminoazobenzene (1 mmol) and the corresponding substituted
benzaldehydes (1.5 mmol) in 20 ml absolute ethanol was refluxed
for 2 h. The resulting precipitate was filtered off and purified by
column chromatography.
A
2.6.1. (0E,4E)-4-(2-phenyldiazenyl)-N-benzylidenebenzenamine
(SB1)
Yield: 76%, m.p.: 127 ◦C. Anal. calcd. for C19
H15N3: C, 82.41; H,
6.92; N, 10.68. Found: C, 82.02; H, 6.69; N, 10.70. MS: m/z 262.00,
calcd. 262.35. 160.24. 1H NMR: 8.70 (s) CH N, 6.75 (d) H(2), 7.94
(d) H(3), 7.47 (d) H(5), 6.75 (d) H(6), 8.00 (d) H(42), 7.47(d) H(46),
7.55–7.51 (m) H(44), 7.55–7.51 (m) H(43), 7.55–7.51 (m) H(45),
7.92 (d) H(12), 7.37 (d) H(16), 7.83 (t) H(14), 7.83 (t) H(13), 7.83
(t) H(15). 13C NMR: 161.00 CH N, 121.53 C(2), 124.01 C(3), 125.02
C(5), 114.53 C(6), 122.24 C(42), 122.71 C(46), 130.76 C(44), 128.94,
128.89, 128.78 C(43), 128.94, 128.89, 128.78 C(45), 129.00 C(12),
129.72 C(16), 131.71 C(14), 128.94, 128.89, 128.78 C(13), 128.94,
128.89, 128.78 C(15), 150.62 C(1), 149.47 C(4), 145.45 C(11), 152.84
C(41).
2. Experimental
2.1. Materials and methods
Aniline (Sigma–Aldrich Ltd.), p-methoxybenzaldehyde, p-
bromo-o-hydroxybenzaldehyde,
hyde, vanillin and m-hydroxybenzaldehyde (S.D. fine) and all other
reagents were used without further purification.
N,N-dimethylaminobenzalde-
2.2. Optical measurements and composition analysis
NMR spectra were recorded for Schiff bases (1–6) on a Bruker
400 MHz. The ultraviolet–visible (UV–Vis) spectra were measured
on a UV–Vis spectrophotometer (Perkin Elmer, Lambda 35) and
corrected for background due to solvent absorption. Photolumi-
nescence (PL) spectra were recorded on a (Perkin Elmer LS55)
fluorescence spectrometer. MS spectra were recorded on a Varian
Saturn 2200 GCMS spectrometer.
2.6.2. (0E,4E)-4-(2-phenyldiazenyl)-N-(p-N,N-
dimethylaminobenzylidene)benzenamine
(SB2)
Yield: 76%, m.p.: 127 ◦C. Anal. calcd. for C21H20N4: C, 76.80; H,
6.14; N, 17.06. Found: C, 76.02; H, 6.02; N, 16.92. MS: m/z 328.17,
calcd. 328.00. 1H NMR: 7.37 (d) CH N, 8.00 (d) H(2), 7.37 (d) H(3),
6.41 (d) H(5), 8.00 (d) H(6), 8.00 (d) H(42), 7.83 (t) H(44), 7.49–7.39
(m) H(43), 7.49–7.39 (m) H(45), 7.93(d) H(16), 8.27 (d) H(13),
7.49–7.39 (m) H(15), 2.75 (s) CH3. 13C NMR: CH N 158.00, 121.23
C(2), 122.76C(3), 124.52 C(5), 115.04 C(6), 122.76 C(42), 124.52
C(46), 131.31 C(44), 129.37 C(43), 129.15 C(45), 122.23 C(12),
130.47 C(16), 132.92 C(14), 130.47 C(13), 127.61 C(15), 154.53 C(1),
151.44 C(4), 153.17 C(41), 40.2 CH3.
2.3. Non-linear optical measurements
Its second harmonic generation efficiency was assessed by Kurtz
powder technique [22] at IISc., Bangalore, India. It is a well estab-
lished tool to evaluate the conversion efficiency of nonlinear optical
materials. A Q-switched Nd:YAG laser operating at the fundamental
wavelength of 1064 nm, generating about 4.1 mJ and pulse width
of 8 ns was used for the present experimental study. The input laser
beam was passed through an IR reflector and then incident on the
powder form of the Schiff bases (1–6), which was packed in a glass
capillary tube. The output energy was detected by a photodiode
detector integrated with oscilloscope assembly.
2.6.3. (0E,4E)-4-(2-phenyldiazenyl)-N-(o-
methoxybenzylidene)benzenamine
(SB3)
Yield: 85%, m.p.: 113 ◦C. Anal. calcd. for C20H17N3O: C, 76.17;
H, 5.43; N, 13.32. Found: C, 76.02; H, 6.59; N, 13.12. MS: m/z
315.37, calcd. 315.02. 1H NMR: 8.45 (s) CH N, 6.75 (d) H(2), 7.89
(d) H(3), 7.32 (d) H(5), 6.71 (d) H(6), 7.98 (d) H(42), 7.83 (t)
H(44), 7.55–7.41 (m) H(43), 7.55–7.41 (m) H(45), 7.92 (d) H(12),
7.55–7.41 (d) H(16), 7.01 (d) H(13), 7.01 (d) H(15), 3.83 (OCH3).
13C NMR: 160.24 CH N, 121.53 C(2), 124.00 C(3), 125.02 C(5),
114.53 C(6), 122.24 C(42), 122.67 C(46), 129.72 C(44), 128.89 C(43),
128.89 C(45), 129.10 C(12), 130.72 C(16), 162.46 C(14), 114.53
C(13), 114.19 C(15), 154.70 C(1), 149.47 C(4), 152.84 C(41), 55.39
(OCH3).
2.4. Cyclic voltametry
Cyclic voltammetry (CV) analysis was performed using CHI
604C electrochemical analyzer, working electrode is glassy carbon
electrode (GCE) diameter: 1 mm, length: 9 cm; reference elec-
trode: silver/silver chloride (Ag/AgCl) diameter: 1 mm, length:
9 cm; counter electrode: 1.5 cm platinum wire fused in glass diam-
eter: 1 mm, length: 9 cm. The electrochemical cell has an inner
diameter of 2.5 cm, an outer diameter of 3.2 cm and a height of 4 cm.
The scan rate of 100 mV/s was applied with current sensitivity as
0.01 A.
2.6.4. (0E,4E)-4-(2-phenyldiazenyl)-N-(m-
hydroxybenzylidene)benzenamine
(SB4)
Yield: 85%, m.p.: 113 ◦C. Anal. calcd. for C19H15N3O: C, 75.73; H,
5.02; N, 13.94. Found: C, 75.42; H, 4.69; N, 13.21. MS: m/z 301.12,
calcd. 301.00. 1H NMR: 8.46 (s) CH N, 7.28 (d) H(2), 7.98 (d) H(3),
7.92 (d) H(5), 7.28 (d) H(6), 7.85–7.76 (m) H(42), 7.85–7.76 (m)
H(46), 7.85–7.76 (m) H(44), 7.51–7.31 (m) H(43), 7.51–7.31 (m)
H(45), 7.48–7.27 (m) H(16), 6.78–6.73 (m) H(14), 7.48–7.27 (m)
H(15), 4.48 (OH). 13C NMR: CH N 152.87, 122.28 C(2), 122.28 C(3),
124.05 C(5), 121.58 C(6), 122.12 C(42), 125.06 C(46), 129.77 C(44),
129.06 C(43), 128.93 C(45), 114.59 C(12), 129.77 C(16), 128.93
2.5. Computational details
optimized geometry, NLO, NBO, HOMO–LUMO and TD-DFT with
Guassian-03 program using the Becke3–Lee–Yang–Parr (B3LYP)
functional supplemented with the standard 6-31G(d,p) basis set
[20,21].