An'S'-shaped pentanuclear Cu~(II)cluster derived from the metal-assisted hydrolysis of pyCOpyCOpy:structural,magnetic and spectroscopic studies

摘要

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 P1 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)py~(2-).Magnetic susceptibility data indicate the interplay of both ferro-and antiferromagnetic intramolecular interactions stabilizing anS=3/2 ground state.Fitting of the data according to a next-nearest-neighbour model{H=-[J1(S1S2+S_(1')S_(2'))+J2(S2S3+S_(3')S_(2'))+J3(S1S3+S_(3')S_(1'))+J4(S2S_(2'))]}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| D_(3/2)|=0.38 cm~(-1).