Solvomorphism and catecholase activities of bis(μ-phenoxido)dicopper(II) complexes

• Published in: Polyhedron 2013-09, Vol.61, p.253-261
• Main Authors: Biswas, Apurba, Das, Lakshmi Kanta, Ghosh, Ashutosh
• Format: Article
• Language: English
• Subjects: Catecholase activity; Copper(II); Crystal structure; Reduced Schiff base; Solvomorphs
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2013.05.039

Three phenoxido bridged dinuclear Cu(II) complexes, [Cu2(L1)2(NCO)2] (1), [Cu2(L2)2(NCO)2]·2CH3OH (2) and [Cu2(L2)2(NCO)2] (3), obtained from the reduced Schiff base ligands show that the Cu(II) ions are penta-coordinated having the geometry intermediate between distorted square pyramid and trigonal bipyramid. The compounds 2 and 3 are pseudopolymorphs. The complexes show moderate catecholase activity. Two phenoxido bridged dinuclear Cu(II) complexes, [Cu2(L1)2(NCO)2] (1), and [Cu2(L2)2(NCO)2]·2CH3OH (2), have been synthesized using the tridentate reduced Schiff-base ligands 2-[(2-dimethylamino-ethylamino)-methyl]-phenol (HL1) and 2-[(2-diethylamino-ethylamino)-methyl]-phenol (HL2) respectively. Re-crystallization of compound 2 from dichloromethane produced desolvated complex [Cu2(L2)2(NCO)2] (3). The compounds 2 and 3 are pseudopolymorphs or solvomorphs which differ in the crystal system (orthorhombic, Pbca for 2 and monoclinic, P21/n for 3). The complexes have been characterized by X-ray structural analyses and spectroscopic methods. In all three complexes Cu(II) is penta-coordinated having the geometry intermediate between distorted square pyramid and trigonal bipyramid with Addison parameter (τ)=0.33, 0.48 and 0.53 for 1, 2 and 3 respectively. Using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate, the catecholase activity of complexes 1 and 2 has been studied in methanol solution; compound 2 shows slightly higher catecholase activity (kcat=98.4h−1) than compound 1 (kcat=64.2h−1).