Iron(II) and nickel(II)-thiocyanato complexes of 1-alkyl-2-(arylazo)imidazole: single crystal X-ray structure of [Fe(MeaaiEt)2(NCS)2] (MeaaiEt = 1-ethyl-2(p-tolylazo)imidazole) and [Ni(MeaaiMe)(NCS)2(H2O)2] · 2DMF (MeaaiMe = 1-methyl-2(p-tolylazo)imidazol

The reaction of green vitriol (FeSO4,7H2O) with 1-alkyl-2-(arylazo)imidazoles [RaaiR′ where R = H (a), Me (b); R′ = Me (1/3/5), Et (2/4/6)] and NH4SCN in 1:2:2 mole proportion affords mononuclear bis-chelated [Fe(RaaiR′)2(SCN)2] (3, 4) complexes. Reaction of NiSO4 · 6H2O with 1-alkyl-2(arylazo)imidazole and ammonium thiocyanate (1:2:2 molar ratio) in methanol solution forms mononuclear monochelated thiocyanato complexes of the type [Ni(RaaiR′)(H2O)2(SCN)2] · 2H2O (5, 6). Slow diffusion of DMF solution of [Ni(MeaaiMe)(H2O)2(NCS)2] in methanol has isolated the X-ray quality crystals. All the complexes are characterized by elemental, UV–Vis, IR, thermal and magnetic studies. In both cases, the distorted octahedral structure was confirmed by single crystal X-ray diffraction study of [Fe(MeaaiEt)2(NCS)2] (4b) and [Ni(MeaaiMe)(H2O)2(NCS)2] · 2DMF (7). Variable temperature susceptibility measurements of [Fe(MeaaiEt)2(NCS)2] (4b) do not exhibit spin crossover property, which may be due to high structural distortion.