Self-assembly supramolecular architectures of chromium(III) complexes using croconate as building block

SALIDU M;ARTIZZU, FLAVIA;DEPLANO, PAOLA;MERCURI, MARIA LAURA;PILIA, LUCA;SERPE, ANGELA;MARCHIÒ L;CONCAS, GIORGIO;CONGIU, FRANCESCO

2009-01-01

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Abstract

The synthesis, X-ray structure and magnetic properties of polynuclear Cr(III) complexes with the croconate ligand (C5O5(2-)) are reported: [Cr(mu-C5O5)(micro-OH)(OH2)2]2 x 6H2O (, orthorombic, space group Cmca, a = 6.741(7) A, b = 18.841(9) A, c = 16.886(9) A, V = 2145(3) A3) shows a dinuclear structure with two mu-OH hydroxo group and two ligand molecules that are bridging two metal centers with vicinal C[double bond, length as m-dash]O groups (micro-kappa2O,O coordination mode), the octahedral geometry of the Cr atoms being completed by the coordination of the O atom of the water molecule and [Cr(micro-C5O5)(micro-OH)(OH2)2]2[K5(C5O5)2.5] x 7H2O (, monoclinic, space group Cc, a = 15.216(9) A, b = 14.895(8) A, c = 18.503(9) A, beta = 96.77(5) degrees and V = 4164(4) A3), a polymer showing various coordination geometries of the K(I) cations. Magnetic susceptibility measurements, performed on , in the 5-400 K temperature range, show antiferromagnetic interactions with J1/k = -50.2 +/- 0.1 K and J2/k approximately -3 K with J1 and J2 the intradimer and interdimer interaction constants, respectively. DFT calculations, performed to gain insight into the coupling between the two metal centers and characterize their spin and charge distribution in the hydroxo-bridged dinuclear entities, are in good agreement with experimental findings.