6533b856fe1ef96bd12b3134

RESEARCH PRODUCT

An "S"-shaped pentanuclear CuII cluster derived from the metal-assisted hydrolysis of pyCOpyCOpy: structural, magnetic and spectroscopic studies.

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Reaction of [Cu2(O2CMe)4(H2O)2] with 2,6-di-(2-pyridylcarbonyl)-pyridine (pyCOpyCOpy or dpcp) in MeCN–H2O 10 : 1, led to the pentanuclear copper(II) complex [Cu5(O2CMe)6{pyC(O)(OH)pyC(O)(OH)py}2] (1) which crystallizes in the triclinic P space group. The copper(II) atoms are arranged in an “S”-shaped configuration, and are bridged by the doubly deprotonated bis(gem-diol) form of the ligand, pyC(O)(OH)pyC(O)(OH)py2−. Magnetic susceptibility data indicate the interplay of both ferro- and antiferromagnetic intramolecular interactions stabilizing an S = 3/2 ground state. Fitting of the data according to a next-nearest-neighbour model {Ĥ = −[J1(Ŝ1Ŝ2 + Ŝ1′Ŝ2′) + J2(Ŝ2Ŝ3 + Ŝ3′Ŝ2′) + J3(Ŝ1Ŝ3 + Ŝ3′Ŝ1′) + J4(Ŝ2Ŝ2′)]} yields exchange coupling constants J1 = +39.7 cm−1, J2 = −15.9 cm−1, J3 = −8.3 cm−1 and J4 = +4.3 cm−1, leading to an S = 3/2 ground state. X-Band EPR spectroscopy indicates a zero-field splitting of the ground state with |D3/2| = 0.38 cm−1.