B. Babür et al. / Dyes and Pigments 103 (2014) 62e70
63
X
NH2
1.X=H
N
NaNO2
HCl
2.X=CH3
3.X=OCH3
4.X=Cl
N
CH3
N
CH3
CH3
X
N
5.X=CN
CH3
Fig. 1. Synthetic pathway and structure of compounds.
2. Experimental
1H, J1 ¼ 7.37 Hz, J2 ¼ 1.05 Hz), 3.74 (s, 3H, eNCH3), 2.82 (s, 3H, e
CH3), HRMS (Mþ) calcd for C16H16N3 250.1344; found, 250.1343.
2.1. Material and methods
2.2.2. Preparation of (E)-3-(4-Methylphenyldiazenyl)-1,2-dimethyl-
1H-indole (2)
The chemicals used in the syntheses of all compounds were
from the Aldrich Chemical Company and used without further
purification. The solvents were used of spectroscopic grade. IR
spectra were recorded on a Mattson 1000 FT-IR spectrophotometer
The dye was obtained from p-toluidine and 1,2-dimethylindole
as orange crystals (0.465 g, 88% yield; m.p: 145 ꢁC) FT-IR (KBr)
max: 3024 (aromatic CeH), 2918 (aliphatic CeH), 1598, 1535, 1472,
in KBr (
Spectrospin Avance DPX 300 Ultra-Shield in DMSO-d6. Chemical
shifts are expressed in units (ppm). Ultravioletevisible (UVevis)
n
, are in cmꢀ1). H NMR spectra were recorded on a Bruker-
1448 (C]C), 1385 (N]N) cmꢀ1; 1H NMR (DMSO-d6):
d
8.40 (d, 1H,
J1 ¼ 8.04 Hz), 7.78 (d, 2H, J1 ¼ 8.87 Hz), 7.55 (d, 1H, J1 ¼ 7.90 Hz),
7.30e7.20 (m, 2H), 7.05 (d, 2H, J1 ¼ 8.89 Hz), 3.70 (s, 3H, eNCH3),
2.60 (s, 3H, eCH3), 2.38 (s, 3H, eCH3), HRMS (Mþ) calcd for
d
absorption spectra were recorded on Analytik Jena Specord 200
spectrophotometer at the wavelength of maximum absorption
C17H18N3 264.1501; found, 264.1507.
(lmax, in nm) in the solvents specified. Mass spectra were recorded
on a Waters-LCT-Premier-XE-LTOF (TOF-MS) instruments; in m/z
(rel. %). The X-ray data were recorded in the Department of
Chemistry, Atatürk University, Erzurum, Turkey.
2.2.3. Preparation of (E)-3-(4-Methoxyphenyldiazenyl)-1,2-
dimethyl-1H-indole (3)
The dye was obtained from p-anisidine and 1,2-dimethylindole
as yellow crystals (0.504 g, 90% yield; m.p: 105 ꢁC) FT-IR (KBr) ٧
max
:
3050 (aromatic CeH), 2932e2833 (aliphatic CeH), 1598, 1577, 1537,
2.2. Preparation of dyes (1e5)
1495, 1455 (C]C), 1387 (N]N), 1245 (CeO) cmꢀ1; 1H NMR (DMSO-
d6):
d
8.40 (d, 1H, J1 ¼7.25 Hz), 7.70 (d, 2H, J1 ¼ 8.21 Hz), 7.56 (d, 1H,
Various carbocyclic amines can be diazotized with HCl and
NaNO2. A typical procedure of diazotizing and coupling is described
below using aniline and 1,2-dimethylindole; all other compounds
were prepared in a similar manner. The yields of the dyes are in the
range of 76e90%. The obtained compounds were purified by crys-
tallization using ethanol by slow evaporation in several days, and
then analyzed.
J1 ¼7.85 Hz), 7.35 (d, 2H, J1 ¼8.18 Hz), 7.30e7.20 (m, 2H), 3.85 (s, 3H,
eOCH3), 3.78 (s, 3H, eNCH3), 2.80 (s, 3H, eCH3), HRMS (Mþ) calcd
for C17H18N3O 280.1455; found, 280.1453.
2.2.4. Preparation of (E)-3-(4-Chlorophenyldiazenyl)-1,2-dimethyl-
1H-indole (4)
The dye was obtained from p-chloroaniline and 1,2-
dimethylindole as yellow crystals (0.436 g, 82% yield; m.p:
137 ꢁC) FT-IR (KBr) ٧
max: 3047 (aromatic CeH), 2931 (aliphatic Ce
2.2.1. Preparation of (E)-3-phenyldiazenyl-1,2-dimethyl-1H-indole
(1)
H), 1531, 1473, 1451, 1404 (C]C), 1380 (N]N) cmꢀ1 1H NMR
;
Aniline (0.18 mL, 2.0 mmol) was dissolved in concentrated HCl
(1.5 mL, % 36 w/w) and water (4.0 mL). The solution was cooled in
an ice-salt bath and a cold solution of NaNO2 (0.15 g, 2 mmol) in
water (3.0 mL) was added dropwise with stirring. The mixture was
stirred for an additional 1 h at 273 K. Excess nitrous acid was
destroyed by the addition of urea. The resulting diazonium salt was
cooled in a salt/ice mixture. 1,2-dimethylindole (0.29 g, 2.0 mmol)
was dissolved in a mixture of acetic acid and propionic acid solution
(3.0 : 1.8 mL) and cooled in an ice bath. Then, cold diazonium so-
lution was added to this cooled solution by stirring in a dropwise
manner. The solution was stirred at 273e278 K for 1 h. The pH of
the reaction mixture was maintained at 4e6 by the simultaneous
addition of saturated sodium carbonate solution. The mixture was
stirred for a further 1 h at room temperature. The resulting solid
was filtered, washed with cold water, and then dried. Recrystalli-
zation from ethanol gave yellow crystals (0.425 g, 85% yield; m.p:
125 ꢁC) FT-IR (KBr) ٧
max: 3055 (aromatic CeH), 2915 (aliphatic Ce
H), 1534, 1476,1446 (C]C), 1387 (N]N) cmꢀ1; 1H NMR (DMSO-d6):
(DMSO-d6):
d
8.45 (d,1H, J1 ¼7.18 Hz), 7.89 (d, 2H, J1 ¼8.68 Hz), 7.64
(d, 1H, J1 ¼ 8.90 Hz), 7.62 (d, 2H, J1 ¼ 8.71 Hz), 7.37e7.28 (m, 2H),
3.85 (s, 3H, eNCH3), 2.82 (s, 3H, eCH3), HRMS (Mþ) calcd for
C16H15N3CI 284.0955; found, 284.0955.
2.2.5. Preparation of (E)-3-(4-Cyanophenyldiazenyl)-1,2-dimethyl-
1H-indole (5)
The dye was obtained from p-aminobenzonitrile and 1,2-
dimethylindole as brown crystals (0.418 g, 76% yield; m.p: 152 ꢁC)
FT-IR (KBr) ٧
max: 3050 (aromatic CeH), 2910 (aliphatic CeH), 2224
(C^N), 1596, 1529, 1474, 1409 (C]C), 1394 (N]N) cmꢀ1 1H NMR
;
(DMSO-d6):
d
8.41 (dd, 1H, J1 ¼ 8.13 Hz, J2 ¼ 1.59 Hz), 7.94 (m, 4H),
7.60 (d, 1H, J1 ¼7.45 Hz), 7.35 (td, 1H, J1 ¼7.26 Hz, J2 ¼ 1.42 Hz), 7.25
(td, 1H, J1 ¼7.25 Hz, J2 ¼ 1.12 Hz), 3.70 (s, 3H, eNCH3), 2.60 (s, 3H, e
CH3), HRMS (Mþ) calcd for C17H15N4 275.1297; found, 275.1295.
2.3. Computational study
d
8.39 (dd, 1H, J1 ¼ 7.80 Hz, J2 ¼ 1.11 Hz), 7.82 (dd, 2H, J1 ¼ 8.10 Hz,
J2 ¼ 1.13 Hz), 7.58 (d, 1H, J1 ¼ 7.59 Hz), 7.51 (t, 2H, J1 ¼ 8.01 Hz), 7.38
(t, 1H, J1 ¼ 7.28 Hz), 7.29 (td, 1H, J1 ¼ 7.25 Hz, J2 ¼ 1.33 Hz), 7.25 (td,
The geometries of all the compounds (dyes 1e5) has been fully
optimized in the ground state at the B3LYP/6-311þG(p,d)