DUGi

Design of dinuclear copper species with carboranylcarboxylate ligands: study of their steric and electronic effects

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@2072@@296998

A series of new mononuclear and carboranylcarboxylate-bridged dinuclear copper(II) compounds containing the 1-CH3-2-CO2H-1,2- closo-C2B10H10 carborane ligand (LH) has been synthesized. Reaction of different copper salts with LH at room temperature leads to dinuclear compounds of the general formula [Cu2(μ-L) 4(Lt)2] (Lt=thf (1), L t=H2O (1′)). The reaction of 1 and 1′ with different terminal pyridyl (py) ligands leads to the formation of a series of structurally analogous complexes by substitution of the terminal ligand thf or H2O (Lt=py (2), p-CF3-py (3), p-CH 3-py (4), pz (6), and 4,4′-bpy (7)), which maintain the structural Cu2(μ-O2CR)4 core in the majority of the cases except for o-(CH3)2-py, where a mononuclear compound (5) is exclusively obtained. These compounds have been characterized through analytical, spectroscopic (NMR, IR, UV-visible, ESI-MS) and magnetic techniques. X-ray structural analysis revealed a paddle-wheel structure for the dinuclear compounds, with a square-pyramidal geometry around each copper ion and the carboranylcarboxylate ions bridging two copper atoms in syn-syn mode. The mononuclear complex obtained with the o-(CH3)2-py ligand presents a square-planar structure, in which the carboranylcarboxylate ligand adopts a monodentate coordination mode. The magnetic properties of the dinuclear compounds 1, 3, 4, and 6 show a strong antiferromagnetic coupling in all cases (J=-261 (1), -255 (3), -241 (4), -249 cm-1 (6)). Computational studies based on hybrid density functional methods have been used to study the magnetic properties of the complexes and also to evaluate their relative stability on the basis of the strength of the bond between each CuII and the terminal ligand

This research has been financed by MEC of Spain through projects CTQ2010-21532-C02-01 and CTQ2010-16237 and Generalitat de Catalunya (2009/SGR/00279). M.F. thanks Generalitat de Catalunya for an FI predoctoral grant and A.R.P. to the Spanish Ministry of Education for the FPU grant. The access to the computational facilities of High Performance Computing Centre of CSIC and Centre de Supercomputaci de Catalunya (CESCA) is gratefully acknowledged. Serveis T cnics de Recerca (STR) from UdG are also acknowledged for technical support. N.A.-A. thanks the Spanish Ministerio de Ciencia e Innovaci n (CTQ2009-06959) and ICREA (Instituci Catalana de Recerca i Estudis Avançats). E.R. thanks to the Ministerio de Ciencia e Innovaci n and the Direcci General de Recerca for the grants CTQ2008-06670-C02-01 and 2009SGR-1459 as well as to the Centre de Supercomputaci de Catalunya (CESCA) for providing computational resources

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