Synthesis and characterization of copper(II) complexes of a 14-membered cis-N2S2 dibenzo macrocycle and of its bis-acetato and bis(methylpyridyl) derivatives

The synthesis and characterization of seven copper coordination compounds with the 14-membered macrocyclic cis-N2S2 dibenzo ligand 6,7,13,14,15,16,17,18-octahydrodibenzo[e,m]-[1,4,8,11]dithiadiazacyclotetradecine (L(1)) and its N,N'-bisacetato and -bis(methylpyridyl) functionalized derivatives H(2)L(2) and L(3) are described. The structures of five compounds were determined by single-crystal X-ray diffraction. The tetrahedrally distorted square-planar coordination geometry of [CuL(1)](ClO4)(2) (1) changes upon reduction of copper to a severely distorted tetrahedral geometry in [CuL(1)]Br . MeCN (2). The Cu-N bond lengths increase from 1.988(3) to 2.029(5) Angstrom; the Cu-S bond lengths decrease from 2.293(1) to 2.255(2) Angstrom. Copper(II) is hexacoordinated in [CuHL(2)]HSO4 . 2.5 H2O (5) and [CuHL(2)]ClO4 . H2O (6). Both compounds exhibit very similar overall structures in the cationic part. The macrocyclic ring of the ligand is folded along an N...S axis, the octahedral geometry is strongly Jahn-Teller distorted, with O and S donor atoms in the apical positions. Compound 5 contains one very short [2.271(3) A] and one long [2.701(3) Angstrom] Cu-S (thioether) bond. In [CuL(3)](ClO4)(2) . 2 H2O (7) one thioether group of the ligand L(3) remains uncoordinated. The coordination polyhedron is rather irregular: Cu-S 2.506(3) and Cu-N 1.960(7)-2.107(8) Angstrom. The compounds were further characterized by electronic and EPR spectroscopy and by cyclic voltammetry. Some relationships to the structural and spectroscopic properties of ''blue'' copper proteins were found.