I. THE SYNTHESES, SOLUTION BEHAVIOR, CRYSTAL STRUCTURES AND MAGNETIC PROPERTIES OF SOME IMIDAZOLATE BRIDGED COPPER(II) COMPLEXES. II. THE CRYSTAL STRUCTURE AND MAGNETIC PROPERTIES OF A TRICOPPER(II) CLUSTER CONTAINING A TRIPLY BRIDGING CARBONATE GROUP

Part I of this thesis comprises the syntheses and characterization of the first discrete, water soluble, imidazolate (im) bridged copper(II) clusters.; Dinuclear imidazolate bridged complexes were crystallized from basic aqueous or methanolic solutions of Cu(PIP)('2+) (PIP = 2-{lcub}2-(2-pyridyl)-ethyliminomethylpyridine) or Cu(PMDTA)('2+) (PMDTA = 1,1,4,7,7-pentamethyl-diethylenetriamine) and variously substituted imidazoles. Crystallographic studies of the imidazolate, 2-methylimidazolate and benzimidazolate bridged complexes reveal that the imidazolate rings lie nearly perpendicular to the equatorial copper coordination planes and the angles made by the two Cu-(im)N vectors fall in the range of 127 to 141 degrees. The Cu-Cu distances vary from 5.662(2) to 5.930(6) (ANGSTROM).; The condensation of imidazole-4,5-dialdehyde with Cu(2-(2-amino-ethyl)pyridine)('2+) affords the Cu(,2)bpim('3+) cluster. Addition of imidazole and sodium hydroxide to aqueous solutions of Cu(,2)bpim('3+) yields the tetranuclear complex {lcub}Cu(,2)bpim(.)im{rcub}(,2)(NO(,3))(,4)(.)4H(,2)O. Crystallographic studies of this complex show that the {lcub}Cu(,2)bpim(.)im{rcub}(,2)('4+) cluster is composed of two Cu(,2)bpim('3+) clusters linked together by two imidazolate groups coordinated to the fourth equatorial coordination sites of the copper atoms of the Cu(,2)bpim('3+) cluster. The imidazolate ring of the Cu(,2)bpim('3+) cluster is constrained to be coplanar with the copper coordination planes, the Cu-(im)N vectors are nearly colinear and the Cu-Cu distance is 6.214(2) (ANGSTROM). The structural details of the two inter-(Cu(,2)bpim('3+)) Cu-im-Cu fragments are similar to those found in the imidazolate bridged Cu(PIP)('2+) complex above.; Variable temperature magnetic susceptibility studies reveal that the imidazolate group can mediate a moderately strong (J = -26.90(2) cm('-1)) antiferromagnetic interaction. The coupling constants for a series of Cu(PIP)('2+) and Cu(PMDTA)('2+) complexes in which the bridging ligands are substituted imidazolates parallel the values for the first pK(,a) of the respective bridging ligand suggesting that exchange interactions between the cupric ions are mediated via the sigma-type orbitals of the imidazolate ring. The coupling constant for the Cu(,2)bpim('3+) cluster (-81.8(5) cm-('1)) is larger than the basicity of the imidazolate ring would suggest and a possible relationship between the exchange interactions and the structure of this cluster is discussed. Two coupling constants (-87.27(7) and -32.5(7) cm-('1)) are required to fit the data for the {lcub}Cu(,2)bpim(.)im{rcub}(,2)('4+) cluster. The assignment of the coupling constants to the appropriate bridging imidazolate rings was made by comparison to the J values obtained for Cu(,2)bpim('3+) and {lcub}Cu(PIP){rcub}(,2)(im)('3+). These magnetic studies verify the existence of an imidazolate bridged center in a form of bovine erythrocyte superoxide dismutase in which cupric ion replaces Zn(II) but casts into doubt the presence of an imidazolate bridged heme iron-copper(II) unit in cytochrome c oxidase.; Part II of this thesis comprises a discussion of the crystal structure and variable temperature magnetic susceptibility behavior of a unique tricopper(II)-carbonate cluster which was originally obtained from basic solutions of Cu(PIP)('2+) and imidazole by hydration of dissolved CO(,2). Crystallographic studies of the nitrate salt reveal that the cluster has (TURN)C(,3) symmetry and consists of three Cu(PIP)(H(,2)O)('2+) moieties coordinated to a single carbonate group. The three cupric ions of the cluster are ferromagnetically coupled (J = 4.6(2) cm-('1)); Weak intercluster (zJ' = -0.08 cm-('1)) coupling is also observed in both the nitrate and perchlorate salts. Both salts of the cluster are examples of order-disorder structures and an attempt has been made to describe the partial ordering in the nitrate complex.