The reactions of N-(O-hydoxyphenyl)-N'-phenylthiourea (L) derived from with Cu +, Cu 2+, Co 2+ and Co 3+ chloride and/or iodide afford new metal complexes. The isolated complexes were synthesized by two different techniques (chemical and tribochemical methods). Two complexes were synthesized by the direct chemical reactions of N-(O-hydoxyphenyl)-N'-phenylthiourea (L) with MCl 2·XH 2O (M = Co 2+ and Cu 2+; X = 6 in case of Co 2+ and X = 2 in case of Cu 2+) in absolute EtOH. The general formulae of the two complexes derived by the chemical method are [Cu(L) 2(EtOH) 2]Cl 2 and [Co(L) 2Cl 2]Cl. These complexes were used to synthesize another two complexes using tribochemical reaction by grinding the previous chloride complexes with excess KI in agate mortar in the solid state. The isolated complexes have the general formulae, [Cu(L)I·H 2O]·1/2H 2O and [Co(L)I 3(Et- OH)]·3EtOH. The results indicate the substitution of the chloride by iodide ions during grinding and extraction of the complexes by solvents. The IR spectra of the complexes suggest that L acts in a bidentate manner towards the metal ions. Moreover, the results of electronic spectra and magnetic measurements for the chloride complexes suggest distorted-octahedral structure for Cu 2+ and low-spin octahedral structures around the Co II and Cu 2+ ions, respectively. On the other hand the data suggest that the iodide complexes have square-planer and low-spin for the Cu + and Co 3+ ions, respectively. The results of mass spectra confirm the formulae proposed for the isolated complexes. The mechanisms of reduction of Cu II and oxidation of Co II for the metal complexes were elucidated.
Thiourea is the analogue compound to urea and has a considerably wide range of applications. The properties of urea and thiourea differ significantly because of the difference in electronegativity between sulfur and oxygen [
N-(O-hydoxyphenyl)-N'-phenylthiourea (L) was synthesized by refluxing equivalent amounts of 2-aminophenol (10.9 g) dissolved in EtOH and phenyl isothiocyanate (12 ml) on hot plate for 2 h. The white product (m.p.; 138˚C; yield: 93%) was obtained by cooling and characterized by chemical and spectral methods. The ligand (L) is insoluble in most organic solvents but easily soluble in DMF and DMSO.
Two complexes derived from Cu2+ and Co2+ ions with the general formulae, [Cu(L)2(EtOH2)]Cl2 and [Co(L)2- Cl2]Cl, were synthesized by the direct reaction of CuCl2・2H2O (1.7 g, 0.01 mol) and/or CoCl2・6H2O (2.8 g, 0.01 mol) dissolved in EtOH (50 ml) with N-(O-hydoxyphenyl)-N'-phenylthiourea (4.8 g, 0.01 mol) dissolved in absolute EtOH (25 ml). The reaction mixtures were refluxed on a water bath for ~3 h. The two complexes were filtered off, washed several times with absolute EtOH followed by dry diethyl ether and finally dried in a vacuum desiccator over anhydrous CaCl2. The results of elemental analyses and some physical properties are shown in
The contents of copper and cobalt were carried using complexometric titration and xylenol orange as an indicator [
Compound; Empirical formula | (F. Wt) | Color | M.p. (˚C) | % Found (Calcd.) | A+m (DMSO) | Yield (%) | |||
---|---|---|---|---|---|---|---|---|---|
C | H | N | S | ||||||
L; C13H12N2OS | 244.321 | White | 137 - 139 | 63.7 (63.9) | 5.0 (5.0) | 11.3 (11.5) | 13 (13.1) | - | 94 |
[Cu(L)EtOH)2]Cl2; C30H36CuN4O2Cl3 | 715.228 | Yellowish-green | 171 | 50.4 (50.4) | 4.2 (5.1) | 7.2 (7.8) | 9.6 (9.9) | 66.3 | 83 |
[Co(L)2Cl2]Cl; C26H24CoN4O2Cl3 | 653.931 | Brown | 146 | 47.8 (47.8) | 3.6 (3.7) | 9.2 (8.6) | 8.8 (9.8) | 49 | 80 |
[Cu(L)I.H2O]・1/2H2O; C13H15CuN2O2.5I | 461.795 | Pale yellow | 260 | 33.3 (33.8) | 2.9 (3.3) | 6.8 (6.1) | 6.2 (6.9) | 10.2 | 74 |
[Co(L)I3EtOH]・3EtOH; C\21H36CoN2O5I3 | 868.261 | Yellowish-brown | 154 | 28.1 (29.1) | 4.3 (4.2) | 3.4 (3.2) | 3.6 (3.8) | 6.7 | 71 |
UV2. 1H-NMR spectra of the free ligand and some of its metal complexes (Cu+ and Co3+) were recorded on Jeol-90Q Fourier transform (200 MHz) in CDCl3 and 1H-NMR Spectrometer (400 MHz) in d6-DMSO at King Saud University at Riyadh, Saudi Arabia. Magnetic moments were determined using a Sherwood balance at room temperature (25˚C) with Hg[Co(NSC)4] as a calibrate. The diamagnetic corrections for the ligand and the metal atoms were computed using Pascal’s constants [
The results of the isolated solid complexes are listed in
The IR spectrum of L in KBr (
The 1H-NMR spectrum of L in d6-DMSO (
A comparison of the IR spectra of L with Cu2+ and Co2+ complexes allows us to determine the mode of bonding. The IR spectra of the two complexes obtained by chemical method with the general formulae, [Cu(L)- EtOH)2]Cl2 (
The electronic spectra of the complexes of the Cu2+ and Co3+ with the general formulae, [Cu(L)(EtOH)2]Cl2 (
19,840 and 21,740 - 28,900 cm−1 regions attributed to the 1A1g → 3T2g, 1A1g → 1T1g and 1A1g → 1T2g transitions, respectively, in a low-spin Co3+ system. The observation of these three bands may also suggest that the complexes have trans-configuration [
The Cu+ and Co3+ complexes synthesized by tribochemical reaction are diamagnetic in nature. Also, the absent of any d-d transition bands in case of the Cu+ complex synthesized is taken as evidence for the reduction of Cu2+ to Cu+.
reduction of Cu2+ to Cu+ as well as the substitution of chloride by iodide ions during grinding and extraction by solvent is reported in our earlier work [
The IR spectrum of the Co3+ complex with the general formula, [Co(L)I3(EtOH)]・3EtOH (
The 1H-NMR spectra of the Cu+ and Co3+ complexes in d6-DMSO (
In continuation of our earlier work on tribochemical reactions and the role of metal ions as well as the ligand used in reduction of Cu2+and oxidation of Co2+, we extend our work to include N-(O-hydoxyphenyl)-N'-phe- nylthiourea (L) with Cu+, Cu2+, Co2+ and Co3+ by chemical and tribochemical reactions. The ligand coordinates
in a bidentate manner towards the metal ions. The results indicate that the substitution of the chloride by iodide ions has occurred in Cu2+ and Co2+ complexes. Also, the reduction of Cu2+ to Cu+ and the oxidation of Co2+ to Co3+ have occurred and been confirmed by chemical, spectral and magnetic measurements.
Sawsan Mohamed Al-Ashqar, (2016) Comparative Studies between Chemical and Tribochemical Reactions of Some Metal Complexes Derived from N-(O-Hydoxyphenyl)-N'-phenylthiourea (L). Open Journal of Inorganic Chemistry,06,195-204. doi: 10.4236/ojic.2016.63015