Structural and spectroscopic studies of a metacyclophane and its binuclearCu2+ complex

In a new chelating metacyclophane, 2,9,18,25-tetraoxo-4,7,20,23-tetrakis(ca rboxymethyl)-1,4,7,10,17,20,23,26-octaaza[10.10]metacyclophane, the amino n itrogen atoms have a higher basicity than that of the corresponding paracyc lophane, although the local electron densities on the donor atoms are ident ical in the two isomers. The molecular structure of a binuclear Cu2+ comple x with the metacyclophane has been studied by X-ray crystal analysis: the c oordination geometry around each metal ion is described by a compressed tri gonal bipyramid. The solution electronic spectra of the Cu2+ complex change with pH as a result of the conversion of the coordination sites of the ami de groups. (C) 2001 Elsevier Science B.V. All rights reserved.