Co2+, Ni2+, Cu2+, Zn2+, Hg2+ and Cd2+ were added as their perchlorate for the different UV-vis.
spectroscopic experiments.
2.2 Synthetic procedures
2.2.1 Synthesis of 2-(1H-Benzoimidazol-2-yl)-phenol (1)
o-Phenylene diamine (250 mg, 5 mmol) and salicylaldehyde (395 mg, 5 mmol) were taken in a
50 mL round bottom flask and irradiated under 640 watt for 10 minutes with an interval of 2
minutes between the two halves of the total duration [37]. After completion of reaction (TLC
monitoring), the crude product was recrystallized to yield light colored product 1. Brown Solid,
Mp (oC) 149 (Mp litr 152 0C), Yield (%) 82; FT-IR (cm-1): 3318 (νO-H str.), 3232 (νN-H str.),
3055.06 (νC-H str., aromatic), 2867.09 (ν =C-H str.), 1629.35 (νC=N str.), 1319.75 (νC-O str.), 1129.90 (νC-N
str.); 1H NMR (DMSO, 400 MHz) δ (ppm): 6.96 (dd, J1= 11.8, J2 = 6.0 Hz, 2H, Ar-H), 7.24 (dd,
J1 = 5.16, J2 = 2.88 Hz, 2H, Ar-H), 7.32 (t, J = 5.85 Hz, Ar-H), 7.60 (s, 2H, Ar-H), 7.98 (d, J =
13
5.88 Hz, 1H, Ar-H), 13.11 (s, 2H, -OH phenolic ring, -NH- benzimidazole ring ); C NMR
(DMSO, 100 MHz) δ (ppm): 158.02, 151.62, 131.40, 125.94, 123.08, 118.83, 117.02, 112.49;
ESI-MS: m/z (relative abundance (%), assignment) = 211 [100, (M+1)+].
2.2.2 Synthesis of 2-(Benzimidazol-2-yl-4-phenylazo)phenol (2)
In a 100 mL round bottom flask, aniline (0.094 g, 1mmol) was suspended in 30.0 mL of distilled
water at the temperature of 0-5 oC. Then 1.0 mL of HCl solution was added to the mixture. After
15 min, aqueous solution of sodium nitrite (0.076 g, 1.1 mmol) was added, followed by THF
solution of 1 (0.227g, 1 mmol), then pH was adjusted to 8-9 with NaOH solution. After stirring
for 4h, the solution was neutralized with HCl solution. The produced precipitate was filtered and
washed several times with water and dried at vacuum. Column chromatography was performed
in hexane-ethyl acetate solvent system to obtain pure azo compound 2 in a yield of 60%. Solid,
Mp (oC) 183, Yield (%) 65; IR (cm-1) 3342 (νNH str.), 3064 (νAr-OH str.), 1632 (νC=N), 1586 (νC-N);
1H NMR (DMSO, 400 MHz) δ (ppm): 7.24 (d, 1H, J = 8.0 Hz, Ar-H), 7.33 (dd, 2H, J1 = 8.0 Hz,
J2 = 4.0 Hz, Ar-H), 7.56 (t, 1H, J1, J2 = 8.0 Hz, Ar-H), 7.63 (t, 2H, J1, J2 = 8.0 Hz, Ar-H), 7.72
(brs, 2H, Ar-H), 7.91 (d, 2H, J1, J2 = 8.0 Hz, Ar-H), 7.99 (d, 1H, J = 8.0 Hz, Ar-H), 8.78 (s, 1H,
Ar-H), 13.8 (brs, 2H, -OH phenolic ring, -NH- benzimidazole ring); 13C NMR (DMSO, 100
MHz) δ (ppm): 161.0, 152.0, 150.9, 144.9, 130.9, 129.5, 125.4, 122.4, 122.2, 118.3, 113.0; ESI-
MS: m/z (relative abundance (%), assignment) = 315.0781 [100, (M+1)+].
2.2.3 Synthesis of 2-(Benzimidazol-2-yl-4-(4-methoxyphenyl)azo)phenol (3)