The metal salts used in this investigation were of an analytical grade. Potassium chromate (K2CrO4, 99% Aldrich), Zinc chloride anhydrous (ZnCl2, 99.9% PURE), aluminum chloride (AlCl3, 99.9% Merck), mercuric chloride (HgCl2, 99.9% VEB BERLIN-CHEME), nickel chloride hexahydrate (NiCl2·6H2O, 99% PURE), Manganese chloride hydrate (MnCl2·4H2O, 99% BDH), and tin chloride dihydrate (SnCl2·H2O, 99% Laboratory Rusayan). The solvent used with high purity, N,N-Dimethylformamide (DMF, 99.8% Sigma-Aldrich), Ammonium hydroxide solution (NH4OH, 30% Sigma-Aldrich).
Synthesis of 1-(5-Methyl-1aryl-1H-1,2,3-triazol-4-yl)-3-(naphthalen-2-yl)prop-2-en-1-ones 3a,b
Compounds 1a or 1b (5 mmol) were added to an ethanolic sodium hydroxide [sodium hydroxide (0.4 g, 10 mmol) in water (10 mL) and ethanol (30 mL)] was stirred at room temperature for 30 min. Then add 2-naphthaldehyde (0.78 g, 5 mmol) and the stirring was continued for an additional 3.5 h. Pour the resulting solution into ice water and complete the stirring for 30 min. Filter the solid product and wash with water and dry then crystallize from ethanol.
Synthesis of 1-(5-Methyl-1-phenyl-1H-1,2,3-triazol-4-yl)-3-(naphthalen-2-yl)prop-2-en-1-one 3a
Compound 3a was obtained as colorless solid (95%); mp 180–182 °C. 1H NMR (500 MHz, DMSO): δ = 2.65 (s, 3 H, CH3), 7.46 (d, 1H, CH, J = 8.6 Hz), 7.48, 7.49 (2s, 2H, Ar-H), 7.53 (d, 1H, CH, J = 8.6 Hz), 7.55–8.20 (m, 12H, Ar-H); 13 C NMR (125.7 MHz, DMSO): 10.45, 123.34, 124.29, 125.38, 126.21, 126.74, 127.39, 127.89, 128.76, 129.75, 130.10, 130.82, 132.63, 133.47, 134.52, 135.53,138.60, 143.76, 144.15, 184.35.
Synthesis of 1-(1-(4-Fluorophenyl)-5-methyl-1H-1,2,3-triazol-4-yl)-3-(naphthalen-2-yl)prop-2-en-1-one 3b
Compound 3b was obtained as colorless solid (93%); mp 160–161 °C. 1H NMR (500 MHz, DMSO): δ = 2.66 (s, 3H, CH3), 7.27 (d, 1H, CH, J = 9.2 Hz), 7.48, 7.51 (2d, 2H, J = 8.5 Hz Ar-H) 7.86 (d, 1H, CH, J = 9.2 Hz), 7.87–8.18 (m, 9H, Ar-H); 13C NMR (125.7 MHz, DMSO): 10.36, 116.80 (d, JC−F = 23.85 Hz), 116.99, 123.19, 124.26, 126.75, 127.40, 127.47, 127.89 (d, JC−F = 52.46 Hz), 128.76, 130.87, 131.60, 132.57, 133.47, 134.58, 143.94, 144.15 (d, JC−F = 26.22 Hz), 162.31, 164.30 (d, JC−F = 48.60 Hz), 184.31.
Synthesis of 4-(1-(2-(2,4-Dinitrophenyl)hydrazineylidene)-3-(naphthalen-2-yl)allyl)-5-methyl-1-aryl-1H
-1,2,3-triazoles 4a,b
To a solution of appropriate chalcones 3a or 3b (3 mmol) in ethanol (25 mL) and Conc. HCl (0.5 mL), 2,4-dinitrophenylhydrazine (3 mmol) was added. The reaction mixture was refluxed for 3 h. The formed solid was filtered and washed with ethanol and crystallized from DMF.
Synthesis of 4-(1-(2-(2,4-Dinitrophenyl)hydrazineylidene)-3-(naphthalen-2-yl)allyl)-5-methyl-1-phenyl-1H-1,2,3-triazole 4a
Compound 4a was obtained as orange solid (88%); mp 225–226 °C. 1H NMR (500 MHz, DMSO): δ = 2.64 (s, 3H, CH3), 7.25 (s, 1H, ArH), 7.52 (d, 1H, J = 7.65 Hz, CH), 7.63 (d, 1H, CH, J = 7.65 Hz), 7.64–8.01 (m, 13H, Ar-H), 9.17 (s, 1H, ArH), 11.70 and 12.56 (s, 1H, NH, D2O exchangeable); 13C NMR (125.7 MHz, DMSO): 10.80, 116.92, 117.35, 117.47, 123.44, 124.23, 126.63, 127.26, 127.74, 128.22, 128.44, 128.51, 128.71, 128.76, 128.94, 129.27, 129.75, 132.42, 133.76, 135.75, 138.09, 138.38, 144.42, 145.31, 162.19, 164.16.
Synthesis of 4-(1-(2-(2,4-Dinitrophenyl)hydrazineylidene)-3-(naphthalen-2-yl)allyl)-1-(4-fluorophenyl)-5-methyl-1H-1,2,3-triazole 4b
Compound 4b was obtained as orange solid (87%); mp 238–240 °C. 1H NMR (500 MHz, DMSO): δ = 2.53 (s, 3H, CH3), 7.48 (d, 1H, J = 7.65 Hz, CH), 7.52 (s, 1H, ArH), 7.83 (d, 1H, CH, J = 7.65 Hz), 7.93–8.16 (m, 12H, Ar-H), 8.84 (s, 1H, ArH), 11.78 and 12.57 (s, 1H, NH, D2O exchangeable); 13C NMR (125.7 MHz, DMSO): 10.80, 116.81, 116.92, 117.13, 117.29, 117.47 (d, JC−F = 22.65 Hz), 124.23, 126.63, 127.26, 127.74, 128.22, 128.51, 128.71, 128.76, 128.94 (d, JC−F = 31.00 Hz),, 129.01, 129.27, 133.65, 133.76, 135.75, 136.38, 138.38, 144.42, 145.31 (d, JC−F = 112.07 Hz), 162.19, 164.16 (d, JC−F = 48.85 Hz).
Optical sensing of ammonia and chromium ions
Optical detection of hexavalent chromium, aqueous ammonia, and other heavy metal ions was evaluated through freshly prepared compound 4a,b using the UV–visible spectrophotometer Shimadzu, UV-1800 (Japan). To investigate the prepared compound 4a,b interaction with different metals like ZnCl2, AlCl3, HgCl2, NiCl2, MnCl2, SnCl2 about 20 ppm stock solution of these metal ions were prepared. For sensing of chromium, 1.5 mL of different chromium solution concentrations (0–14 ppm) was added to a 4 mL quartz cuvette. About 1.5 mL of freshly prepared compound 4a,b (20 ppm) was introduced into a cuvette. The increase in intensity and changes in absorbance peaks at 549 nm of compound 4a,b after 3 min of the addition of chromium was monitored by UV–visible spectrophotometer. The same procedure was used for sensing aqueous ammonia. Different concentrations of ammonia were used for sensing procedures, as follows: 0–20 ppm. All experiments were performed in triplicate.
Characterizations of prepared compounds
Melting points were determined using an Electrothermal (variable heater) melting point apparatus. The NMR spectra were measured with a JEOLNMR 500 MHz spectrometer. 1H (500 MHz) and 13C NMR (125 MHz) spectra were recorded in deuterated dimethyl sulfoxide (DMSO-d6) using tetramethylsilane as a standard. The chemical shift (δ) was reported in ppm and the chemical shift (J) was reported in Hz. The UV–VIS spectrum was recorded using Shimadzu Spectrophotometer.