One-dimensional assembling of diiodo[phthalocyaninato(1-)] chromate(III) molecules through neutral I(2) molecules. Alternating ferro- and antiferromagnetic interactions in the metal-radical system.

Abstract

Crystals of diiodo[phthalocyaninato(1-)] chromate(III) diiodine, CrPcI(2).I(2), were grown directly in the reaction of chromium powder with 1,2-dicyanobenzene under a stream of iodine at about 250 degrees C. The CrPcI(2).I(2) complex crystallizes in the centrosymmetric space group of the triclinic system with one molecule per unit cell, with the cell dimensions a = 7.851(2) A, b = 8.402(2) A, c = 12.668(3) A, alpha = 80.32(3)(o), beta = 74.06(3)(o), gamma = 82.33(3)(o), and V = 788.7(3) A(3). The X-ray single-crystal analysis shows that each of the centrosymmetric CrPcI(2) molecules is bridged by a neutral I(2) molecule (detected also by Raman spectroscopy) and develops a polymeric one-dimensional structure. The magnetic measurements have been carried out in the temperature range 300-2 K. Temperature dependence of the effective magnetic moment, mu(eff), shows the ferro- and antiferromagnetic interactions in the system of the paramagnetic central Cr(3+) ion and surrounding pi-conjugated radical ligand Pc(1-). The conductivity measurement on a polycrystalline sample exhibits weak temperature dependence (dsigma/dT < 0). The UV-vis spectrum exhibits, besides the B- and Q-bands, one additional band assigned to the electronic transition from a deeper level to the half-occupied HOMO level in the one-electron oxidized phthalocyaninato(1-) radical ligand.