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The trans-[CoIII(acacen)(ta)2]ClO4 (1) and trans-[CoIII((BA)2en)(ta)2]PF6 (2) complexes, where H2acacen = bis(acetylacetone)ethylenediimine, H2(BA)2en = bis(benzoylacetone)ethylenediimine, and ta = thioacetamide, have been synthesized by a solid-state method, and characterized by elemental analyses, IR, UV–vis, and 1H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography. Both compounds crystallize in the monoclinic space group P2/n. The ClO4 and PF6 ions are both disordered, ClO4 on a twofold axis in 1 and PF6 on an inversion center in 2. Also bridging N-CH2-CH2-N is disordered in both compounds. The octahedral coordination of Co(III) is slightly distorted in both cases. The thioacetamide ligands are S-bonded and occupy the axial position. The IR, UV–vis, and 1H NMR spectra of the two complexes and their solvatochromic properties are also discussed. The longest wavelength absorption that appears at 517 nm for 1 and at 528 nm for 2 in chloroform is solvent dependent, and is assigned as a metal-mediated ligand-to-ligand charge transfer (LLCT).Key words: solid-state synthesis, thioactamide, Co(III) (Schiff base), crystal structure, solvatochromism, metal-mediated LLCT.

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Synthesis, spectroscopy, and crystal structures of [Cu(ca 2 en) 2 ]ClO 4 (1) and [Cu(ca 2 en)(PPh 3 ) 2 ]ClO 4 (2) (ca 2 en N,N'-bis(trans-cinnamaldehyde)ethylenediimine) are reported. Compound 1 crystallizes in the orthorhombic space group Pbca, with a 12.5647 (7), b 21.8203(11), c 27.992(2) ä, V 7674.3(7) ä 3 , Z 8. Compound 2 crystallizes in the triclinic space group P1 ≈ , with a 13.0540(11), b 14.2935(13), c 14.9863(13) ä, a 84.130(2), b 69.761(2), g 87.749(2)8, V 2609.8(4) ä 3 , Z 2. The coordination polyhedron about the Cu I center in the two complexes is best described as a distorted tetrahedron. The 1 H-NMR and electronic spectra of these complexes are also reported and discussed. The cyclic voltammetry of the complexes indicate a quasireversible redox behavior for complex 1 (E 1/2 0.51 V). However, complex 2 displays an irreversible oxidation wave at 0.91 V. A weak emission is observed for complex 2 in CHCl 3 at room temperature.