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

摘要

The synthesis, X-ray structure and magnetic properties of polynuclear Cr(III) complexes with the croconate ligand (C5O52-) are reported: [Cr(mu-C5O5)(mu-OH)(OH2)(2)](2) center dot 6H(2)O (1, orthorombic, space group C-mca, a = 6.741(7) angstrom, b = 18.841(9) angstrom, c = 16.886(9) angstrom, V = 2145(3) angstrom (3)) shows a dinuclear structure with two mu-OH hydroxo group and two ligand molecules that are bridging two metal centers with vicinal C=O groups (mu-kappa O-2, 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(mu-C5O5)(mu-OH)(OH2)(2)](2)[ K-5(C5O5)(2.5)] center dot 7H(2)O (2, monoclinic, space group Cc, a = 15.216(9) angstrom, b = 14.895(8) angstrom, c = 18.503(9) angstrom, beta = 96.77(5). and V = 4164(4) angstrom (3)), a polymer showing various coordination geometries of the K(I) cations. Magnetic susceptibility measurements, performed on 1, in the 5-400 K temperature range, show antiferromagnetic interactions with J(1)/k =-50.2 +/- 0.1 K and J(2)/k similar to-3 K with J(1) and J(2) 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.