679400-85-2Relevant academic research and scientific papers
Silver and Gold Trinuclear Complexes Based on 3-Substituted or 3,5-Disubstituted Pyrazolato Ligands. X-Ray Crystal Structure of cyclo-Tris{μ-[3,5-bis(4-phenoxyphenyl)-1H-pyrazolato-κN 1:κN2]}trigold Dichloromethane ([Au(μ-pz pp2)]3·CH2Cl2)
Torralba, M. Carmen,Ovejero, Paloma,Mayoral, M. Jose,Cano, Mercedes,Campo, Jose A.,Heras, Jose V.,Pinilla, Elena,Torres, M. Rosario
, p. 250 - 263 (2007/10/03)
Ten new silver and gold trimeric complexes of the type [M 3(μ-pz′)3] (M = Au, Ag), where pz′ indicate pyrazolato ligands derived from mesogenic 3,5-disubstituted 1H-pyrazoles HpzR2 or non-mesogenic 3-substituted 1H-pyrazoles HpzR (R = C6H4OCnH2n+1), were synthesized and characterized. The gold and silver complexes 7, 8, 10, and 11 containing symmetric pyrazolato ligands as bridging groups (pzR2; R = C6H4OCnH2n+1, n = 4 (pz bp2) and 8 (pzop2)) exhibited a trigonal symmetric structure. The same results were obtained for the related silver derivatives 16-18 with 3-substituted pyrazolato ligands (pzR; R = C 6H4OCnH2n+1, n = 4 (pz bp), 12 (pzddp), and 18 (pzodp)). By contrast the 3-substituted pyrazolato-gold compounds 13-15 adopted an asymmetric molecular structure related to the position of the substituents on the trinuclear core. The thermal behavior of these complexes was investigated by differential scanning calorimetry and polarized-light microscopy. The mesomorphism of the parent 3,5-disubstituted pyrazoles is avoided in their corresponding trinuclear complexes 7, 8, 10, and 11. However, the metal derivatives 14 and 17 containing the asymmetric 3-[4-(dodecyloxy)phenyl]pyrazolato ligand were found to have liquid-crystal properties. These compounds exhibited monotropic behavior with columnar mesophases that could be related to the disc-like shape of the molecular core and the appropriate length of the alkyloxy chain. For comparative purposes, the X-ray structure of the related gold complex [Au3(μ-pz pp2)3] (9) having phenoxyphenyl substituents at the 3- and 5-positions of the pyrazolato ligand is also described. The molecular structure is formed by a non-planar (Au-N-N)3 core, containing three Au-atoms bridged by three pyrazolato ligands. The molecular packing is described as a columnar organization, the shortest Au ... Au distance being 4.639(1) A between consecutive trimers.
