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Synthesis, Characterization, Solvatochromic Behavior and Crystal Structures of Complexes [Co^III(salophen)(thioacetamide)₂]ClO₄ and [Co^III(salophen)(thiobenzamide)₂]ClO₄

M. Salehi^a, M. Amirnasr^a,* and K. Mereiter^b

^aDepartment of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Iran
^bFaculty of Chemistry, Vienna University of Technology, Getreidemarkt 9/164SC, A-1060 Vienna, Austria

Two new cobalt(III) complexes of the Schiff base N,N'-disalicylidene-1,2-phenylendiimine dianion (salophen), trans-[Co^III(salophen)(ta)₂]ClO₄, (ta = thioacetamide) (1) and trans-[Co^III(salophen)(tb)₂]ClO₄, (tb = thiobenzamide) (2) were synthesized and characterized using single-crystal X-ray diffraction and spectroscopic techniques. Both complexes show solvatochromism in a variety of solvents. Complex (1) crystallized from CHCl₃ as a solvate of orthorhombic symmetry, space group Pca2₁ with a = 17.3480(10) Å, b = 18.7522(10) Å, c = 18.8128(11) Å, a = β = γ = 90°, and Z = 8. The cobalt(III) center lies in a distorted octahedral environment. The crystal structure of (1) consists of two independent [Co^III(salophen)(ta)₂]⁺ cations and ClO₄^- anions held together essentially via hydrogen bonds and π-π stacking interactions. Complex (2), forming also a CHCl₃ solvate, crystallized in the monoclinic space group P2₁/n with a = 14.710(3) Å, b = 13.506(3) Å, c = 18.595(4) Å, β = 100.295(4)Å, and Z = 4. The geometry around cobalt(III) center is a distorted octahedron. The crystal structure of (2) contains a [Co^III(salophen)(tb)₂]⁺ complex with a remarkably twisted salophen ligand. Both complexes, (1) and (2), contain approximately one disordered CHCl₃ molecule per Co in the solid state.

Keywords: Cobalt(III) complexes, Salophen Schiff base, X-Ray crystal structure, Solvatochromism