Columnar metallomesogens: vanadyl complexes derived from beta,delta-triketones

Two series of vanadyl complexes derived from bis(o-hydroxybenzoyl)methane w ere reported. The mesomorphic properties of the compounds 1 and 2 were stud ied by differential scanning calorimetry (DSC) and polarizing optical micro scopy. Formation of the columnar mesophases was found to be dependent on th e sidechain density around the mesogenic core. All the compounds 2 with six alkoxy sidechains exhibited columnar hexagonal (Col(h)) phases, however, c ompounds 1 with two alkoxy sidechains formed crystalline phases. Studies of variable-temperature IR spectra for compounds 2 indicated that linear poly meric structures were observed both in the mesophase and crystalline phase. The crystal and molecular structure of 1 (n = 8) were determined by means of X-ray single crystal analysis. It crystallizes in the monoclinic space g roup P2(1)/c, with a = 14.6581 (1) Angstrom, b = 14.5933 (2) Angstrom, c = 21.7985 (1) Angstrom, alpha = 90 degrees, beta = 100.320 (1)degrees, gamma = 90 degrees, and Z = 4. The vanadyl center is bonded in a typical five-coo rdinate fashion with a solvated tetrahydrofuran molecule sixth-coordinated opposite the axial oxygen. The EPR spectra measured at variable temperature s were also studied.