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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Dalton Trans., 2009, 9759 - 9769, DOI: 10.1039/b905463d

Molecular squares of NiII and CuII: ferromagnetic exchange interaction mediated by syn–anti carboxylate-bridging

Himanshu Arora, Francesc Lloret and Rabindranath Mukherjee

The synthesis of four discrete tetranuclear complexes {[NiII(L2)][ClO4]}4·MeCN ( 1), {[CuII(L1)(O3SCF3)]}4·H2O ( 2), {[CuII(L3)(OClO3)]}4·MeCN ( 3) and {[CuII(L4)][ClO4]}4·3MeCN·4H2O ( 4), supported by a closely similar group of carboxylate–appended (2–pyridyl)alkylamine ligands [L1(-): 3-[N-methyl-{2-(pyridin-2-yl)ethyl}amino]propionate; L2(-): 3-[(2-(pyridin-2-yl)ethyl){2-(pyridin-2-yl)methyl}amino]propionate; L3(-): 3-[N-isopropyl-{2-(pyridin-2-yl)methyl}amino]propionate and L4(2-): 3-[N-{2-(pyridin-2-yl)methyl}amino]-bis(propionate)] is described. Structural characterization reveals that each NiII centre in 1 has square-pyramidal NiIIN3O2 coordination and each CuII centre in 2–4 has distorted square-pyramidal CuIIN2O3 coordination, utilizing three N and one carboxylate O in 1 and two N and carboxylate O (one in 2 and 3; two in 4) of the ligand and the fifth/fourth coordination is provided by an oxygen atom belonging to the carboxylate group of an adjacent molecule. A CF3SO3- or a ClO4- ion provides an O coordination in 2 and 3, respectively. Temperature-dependent magnetic studies reveal the existence of ferromagnetic exchange interaction in each case, due to the presence of equatorial–equatorial syn–anti carboxylate bridge between MII centres.

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