A mu(1,1)- or mu(1,3)-carboxylate bridge makes the difference in the magnetic properties of dinuclear Mn-II compounds

作者：Gomez Veronica^*; Corbella Montserrat; Font Bardia Merce; Calvet Teresa

来源：Dalton Transactions, 2010, 39(48): 11664-11674.

DOI：10.1039/c0dt00902d

Six new dinuclear Mn-II compounds with carboxylate bridges have been synthesized and characterized by X-ray diffraction: [{Mn(phen)(2)}(2)(mu-RC6H4COO)(2)](ClO4)(2) with R = 2-Cl (1), 2-CH3 (2), 3-Cl (3), 3-CH3 (4), 4-Cl (5) and 4-CH3 (6). Compounds 1 and 2 show two mu(1,3)-carboxylate bridges in a syn-anti mode while compounds 3-6 present a very uncommon coordination mode of the carboxylate ligand: the mu(1,1)-bridge. The magnetic properties of these compounds are very sensitive to the bridging mode of the carboxylate ligands. While compounds 1 and 2 (mu(1,3)-bridge) display antiferromagnetic interactions, with J values of -1.41 and -1.66 cm(-1), respectively, compounds 3-6 (mu(1,1)-bridge) show ferromagnetic interactions, with J values of 1.01, 0.98, 1.04 and 1.06 cm(-1), respectively. It is worth noting that compounds 3-6 are the first of their class to be magnetically characterized. The EPR spectra at 4 K for compounds with antiferromagnetic coupling (1 and 2) are more complex than those for compounds with a ferromagnetic interaction (3-6). Quite good simulations can be obtained with the ZFS parameters of the Mn-II ion D-Mn similar to 0.095 cm(-1) and E-Mn similar to 0.025 cm(-1) for compounds 1 and 2 and D-Mn similar to 0.060 cm(-1) and E-Mn similar to 0.004 cm(-1) for compounds 3-6.

• 出版日期2010