Solution based studies of tetranuclear (mu(4)-oxo)-copper(II) complexes

The solution based behavior of a series of tetranuclear based Cu(II) complexes of the form (mu4-O)Cu4Cl6(Ligand) 4 has been characterized by using a combination of conductivity, infra red, visible absorption, EPR and NMR spectroscopy.; The unique properties of these spin-spin coupled tetramers have been utilized to establish the integrity of these complexes in a variety of solvents: if the tetramer remains intact in any given solvent then NMR can be used to probe the structure of each related terminal ligand and its corresponding spin distribution. In the case of piperidine and morpholine the analysis indicates that spin transfer is sensitive to the conformation of the respective ligand. In addition, the identity of the bridging halide appears to modify exchange coupling between each center in such a way that the distribution of positive and negative spin within each apical ligand is changed systematically.; This analysis becomes possible because ligand mediated exchange interactions enhance the rate of electronic relaxation within the spin manifold of the tetramer. This in turn effectively modulates the hyperfine interaction in such a way that proton NMR analysis becomes feasible. Relaxation measurements and correlation time calculations have been performed and these confirm the general rule that electronic relaxation rates must be enhanced by a factor of ∼100 if paramagnetic NMR is to be used as a viable tool in the study of Cu(II) based compounds.; The stability of these compounds is shown to be dependent upon the solvating power (or donor number) of the solvent in question. Previous claims concerning the stability of these compounds (and their electrochemical behavior) in DMSO and other aprotic solvents have been shown to be incorrect as a consequence of these measurements.; Based upon theoretical considerations of charge transfer in polynuclear complexes it is also argued that heteronuclear polymetallic compounds cannot be utilized as precursors in the electrodeposition of alloys. A tentative interpretation of the previous electrochemical data, based upon the behavior of CuCl2 in DMSO, is subsequently proposed.