Crystal and molecular structure of the discogen bis[1,3-di(p-n- Decylphenyl)propane-1,3-dionato]paliadium(ll)

The transition metal containing discogen, bis[1,3-di(p-n-decylphenyl)propane-1 ,3-dionato ]paliadium(II)crystallizes in the triclinic space group pI with one molecule in a unit cell of dimensions a = 10.260(2), b = 12.961(2), c = 13.403(2)A., ex= 110.54(1), f3= 101.75(1) and 'I = 98.44(lt. The crystal structure was solved by direct methods and refined using full matrix least squares procedure. The palladium atom is lying on an inversion center. The decyl chains are fully extended in an all trans conformation. In the crystal structure, the molecules form a tilted columnar arrangement. The angle between the normal to the core and the column axis is 68xB0;. Each column is surrounded by six others. Along the13; column axis, adjacent palladium atoms are separated by 10.26A

Observing the emergence of phase biaxiality in a polar smectic A system via polarised Raman spectroscopy

We report polarised Raman spectroscopy, optical and dielectric properties of an asymmetric bent-core compound derived from 3-hydroxybenzoic acid with a long terminal chain at one end and a nitro group at the other. Earlier X-ray scattering experiments on the compound suggested a partial bilayer smectic A phase (SmA_d) and a partial bilayer biaxial antiferroelectric smectic A phase (SmA_d P_A) in the material. The dielectric behaviour, the microscopic textures and conoscopy experiments all explicitly show that the compound exhibits two different phases, with the lower temperature phase biaxial in nature. Raman spectroscopy was used to determine the temperature evolution of the uniaxial order parameters 〈P_2 〉 and 〈P_4 〉, deduced from analysis of the depolarisation ratio, informed by modelling the bent-core structure. Anomalously low values were measured (less than 0.5 and 0.15 respectively) which could suggest that the smectic A phase may be de Vries like in nature, rather than a partial bilayer structure. Raman spectroscopy was also used to investigate the biaxial nature of the SmA_d P_A phase. The effect that the biaxial order parameters 〈P_220 〉,〈P_420 〉 and 〈P_440 〉 has have on the depolarisation ratio is calculated. By making the assumption of an approximately continuous increase in the 〈P_2 〉 and 〈P_4 〉 order parameters, it was possible to deduce the behaviour of the biaxial order parameters in the biaxial SmA_d P_A phase; the emergence of biaxial order in the system is clearly demonstrated as all of the biaxial order parameters increase in magnitude as the temperature decreases in the (SmA_d P_A) phase. The dielectric studies show that the perpendicular component of the dielectric permittivity increases from 10 to 70 in the SmA_d phase and decreases from 70 to 45 in the SmA_d P_A phase. A strongly temperature dependent relaxation frequency with a large value ~400 kHz is observed in the SmA_d phase. On the other, the SmA_d P_A phase exhibits a weakly temperature dependent relaxation frequency at ~100 kH

Crystal and Molecular Structure of the Discogen bis[1,3-d(p-n-octylphenyl)propane-1,3-dionato ]copper(II)

The transition metal containing diswgen bis[1,3-di(p-n-octylphenyl)propane-l ,3-dionato ]copper(II)13; crystallizes in the triclinic space group Pl. The copper atom lies on an inversion centre and is surrounded13; by four oxygen atoms in a square planar arrangement. The octyl chains are fully extended in an alltrans13; conformation. The molecules form a tilted columnar arrangement, the angle of tilt between the13; disc normal and the column axis being 122xB0;. The column axis coincides with the crystallographic a-axis.13; In the crystal structure, each column is surrounded by six others. Along the column axis, adjacent13; copper atoms are separated by 5.821(3)A.

Crystaland Molecular Structures of Isomorphous Bis[1,3-di(p-n-.octylphenyl)propane-1 ,3-dionato]Paliadium(lI)and Bis[1,3-di(p-noctylphenyl) propane-1,3-dionato]Nickel(ll)

Crystal structures of the transition metal complexes bis(I,3-di(p-n-octylphenyl)propane-l,3-dionato]palladium(II) and bis(I,3-di(p-n-octylphenyl)propane-l,3-dionato] nickel(II) have been solved and refined to R = 0.051 and 0.064 respectively, using diffractometer collected X-ray data. The palladium and the nickel complexes are found to be isomorphous with the P-form of the copper complex bis[1,3-13; di(p-n-octylphenyl propane-l ,3-dionato] copper(II). Despite the unambiguous structural isomorphism, only the palladium and the copper complexes are mesogenic; the nickel complex is reportedly nonmesogenic.In the crystal structures, the metal atoms are surrounded by four oxygen atoms in a square planar arrangement. The octyl chains are fully extended in an all-trans conformation. The crystal13; structures are characterized by both layer-like and columnar arrangement of molecules

X ray investigations on the conformation and molecular arrangement of discotic bis[ 1,3-di(p-n-octyloxyphenyl) propane-1,3-dionato] copper (II)

Since the discovery of the discotic mesophase in 1977, a large number of x ray investigations on the mesophase of discogens has been reported and their structural characteristics have been analysed. However, the solid phase of discogens has not received much attention till now. Crystal structure of no discogen seems to have been accurately determined by conventional crystallographic13; procedures. In this letter, we report the results obtained from the first detailed x ray analysis of the crystal structure of a discogen using single crystals and three dimensional intensity data. Only the details concerning the conformation and molecular arrangement of discotic bis[1,3-di(p-n-octyloxyphenyl)propane-1,3-dionato]copper(II), (a), are presented in this preliminary communication