A QUASI-TETRAHEDRAL CU-4 CLUSTER WITH SYN-ANTI BRIDGING CARBOXYLATE GROUPS - CRYSTAL AND MOLECULAR-STRUCTURE AND MAGNETIC-PROPERTIES

The complex [Cu4(L)3(LH)(NO3)(H2O)] · 2H2O, L and LH representing the dideprotonated and the monodeprotonated forms, respectively, of 6-amino-1,3-dimethyl-5-((2-carboxyphenyl)azo)uracil, has been prepared, investigated by single-crystal X-ray analysis, and characterized through magnetic susceptibility and spectroscopic measurements. It crystallizes in the monoclinic space group P21/c with cell constants a = 12.43 (8) Å, b = 41.95 (4) Å, c = 14.77 (7) Å, β = 105.45 (5°), Z = 4, R = 0.130, and Rw= 0.113. The framework of the structure is a 16-membered (-0-C-0-Cu)4ring involving bridging carboxylate groups in the syn-anti conformation. The ring is folded in such a way that the copper atoms fall at the corners of a distorted tetrahedron. The magnetic study points to a ferromagnetic ground state. The magnitude of the magnetic interaction is discussed on the basis of structural data. © 1990, American Chemical Society. All rights reserved.