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-β-diketonate” complexes of the general formula [M(β-diketonate)(CO)2] (M = Rh (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 β-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
= Rh) or blue (M = Ir) and yellow (M = Rh, Ir), have been obtained for complexes 1, 4, and 6. The yellow form
for compound 4 (C31H35IrO9·CH3OH, monoclinic system, space group P21/c (No. 14) with a = 26.991(6) Å, b
= 4.0093(8) Å, c = 31.169(6) Å, β = 104.950(13)°, 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 (β) of the rhodium
compounds and some of the precursor ligands using the EFISH technique have also been performed.