μ-1,3-Acetamide or acetate bridged, symmetric and asymmetric dicopper(II) complexes viz [Cu2(P1-O-)(NHAc-)](ClO4)2 (1), [Cu2(P2-O-)(OAc-)](ClO4)2 (2) and [Cu2(P2′-O-)(OAc-)(H2O)](ClO4)2 (3) were synthesized by employing classic dinucleating ligands; P1-OH, P2-OH (symmetric), and P2′-OH (asymmetric) having trivial differences in their ligand frame work. Solid state structures of these complexes were determined by X-ray crystallography. In solution, they were also characterized by various spectroscopic techniques, which includes ESI-MS, FT-IR, optical, solution magnetic moment, paramagnetic 1H NMR and EPR. The solution magnetic moment of these complexes at room temperature suggests a weak magnetic interaction between the two Cu(II) centers.

Narasimha N. Murthy

Department Of Chemistry

Gnana Sutha Siluvai

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Polyhedron

1H-NMR spectral properties of two paramagnetic binuclear copper(II) complexes 1 and 2, which are weakly antiferro- and ferromagnetically coupled, respectively, in the solid state, have been studied in solution; corresponding parameters are compared to a mononuclear copper(II) analogue 1a. Compound 1 exhibits unusually sharp and hyperfine shifted ligand signals (+230 to -14 ppm) that are about 100 times sharper than corresponding signals that could be detected for 1a (+20.4 to -13 ppm). Complex 2 also displays moderately sharp signals, shifted even to a greater magnitude (+272 to 0 ppm). These observations are in contrast with other moderately antiferromagnetically coupled binuclear copper(II) systems where much broader signals are observed in addition to reduced hyperfine chemical shifts. A complete assignment of signals for 1 and 2 was accomplished by a combination of proton relaxation data and two-dimensional correlated spectroscopy (COSY) measurements, while for 1a only partial analysis could be performed because of broadness of its signals. An analysis of the relaxation data and a quantitative comparison among 1a, 1, and 2 show that the unusual spectral features observed for the weakly coupled binuclear copper(II) (S = 1/4 ) centers is caused by a two orders of magnitude decrease in the electron relaxation (τ(s) = 10-11 s) as compared to τ(s) = 10-9 s for the mononuclear copper(II) species, 1a. Shortening of τ(s) for homobinuclear compounds is not otherwise predicted, and possible mechanisms for the results are discussed. The present findings are significant with respect to the factors determining electronic relaxation in magnetically coupled systems and to the understanding of proton NMR when applicable to binuclear copper(II) metalloproteins.

Journal of the American Chemical Society

NMR and electronic relaxation in paramagnetic dicopper(II) compounds

Stryer Biochemie

Inorganic Chemistry

Ferromagnetic vs Antiferromagnetic Coupling in Bis(μ-phenoxo)dicopper(II) Complexes. Tuning of the Nature of Exchange Coupling by Remote Ligand Substituents†

Inorganica Chimica Acta

A new tyrosinase model with 1,3-bis[(2-dimethylaminoethyl)iminomethyl]benzene: Binuclear copper(I) and phenoxo/hydroxo-bridged dicopper(II) complexes

Dinuclear Copper(II) Complexes with {Cu2(μ-hydroxo)bis(μ-carboxylato)}+Cores and Their Reactions with Sugar Phosphate Esters: A Substrate Binding Model of Fructose-1,6-bisphosphatase

X-ray structure and spectroscopic characterization of doubly-bridged binuclear copper(II) complexes in symmetric and asymmetric coordination environments

Journal	Polyhedron
ISSN	02775387
Open Access	No