Rhodium(I) and iridium(I) complexes containing β-diketonate or pyrazole ligands.: Liquid crystal and nonlinear optical properties

Square-planar rhodium or iridium "n-decyloxy-beta-diketonate" complexes of the general formula [M(beta-diketonate)(CO)(2)] (M = Ph (1-3) or Ir (4-6)) and pyrazole-rhodium derivatives of the type [RhCl(CO)(2)(pyrazole)] (7-9) have been prepared and their liquid-crystalline properties studied. Compounds 1 and 4 show monotropic smectic A phases, and complex 7 shows a monotropic nematic phase. The behavior of the melting points seems to be related to the X group directly bonded at the 3-position of the beta-diketonate ligand (1-6) or at the 4-position of the pyrazole ring (7-9). When X = OOC higher melting points are obtained. Two different polymorphs, red (M Ph) or blue (M = Ir) and yellow (M = Ph, Ir), have been obtained for complexes 1, 4, and 6. The yellow form for compound 4 (C31H35IrO9. CH3OH, monoclinic system, space group P2(1)/c (No. 14) with a = 26.991(6) Angstrom, b = 4.0093(8) Angstrom, c = 31.169(6) Angstrom, beta = 104.950(13)degrees, and Z = 4) has also been characterized by an X-ray single-crystal diffraction experiment in order to explain the influence of the packing arrangement in the formation of different polymorphs. Additionally, measurements of the first-order optical hyperpolarizability (beta) of the rhodium compounds and some of the precursor ligands using the EFISH technique have also been performed.