CRYSTALS OF PHOSPHOLIPID ANALOGS AS PLAUSIBLE MATERIAL FOR MOLECULAR ELECTRONICS .1. SYNTHESIS AND INVESTIGATION OF THE STRUCTURE AND PHYSICAL-PROPERTIES OF 2 HALOGEN HYDRIDE DERIVATIVES OF ISOBUTYL-2-AMINOETHYL PHOSPHATE-PHOSPHATIDYLETHANOLAMINE ANALOGS

Synthesis and investigation of the structure and electrophysical prope rties of two halogen hydride derivatives of isobutyl analogues of phos phatidylethanol amine (IPE), namely IPE-HCl and IPE-HBr, were performe d to offer a new material for 'molecular wires' according to the model of molecular electronics developed earlier by Karasev et al. (Adv. Ma ter. Opt. Electron., 1994, 4, pp. 203-218). X-ray analysis showed that isostructural crystals of the synthesised compounds are monoclinic wi th the space symmetry group 12/a (C2/c). They have very similar lattic e cell parameters, namely a = 21.892(8), b = 4.7747(2), c = 44.63(2) A ngstrom, beta = 91.83(3)degrees, Z = 16 for IPE-HCI and a = 22.115(14) , b = 4.808(3), c = 44.83(2) Angstrom, beta = 91.74(5)degrees, Z = 16 for IPE-HBr. It was found that the structure of IPE-HCI contains two s ymmetrically unrelated molecules of IPE. They form two bilayers within the elementary cell each of which includes three zones of hydrogen bo nds. The central zone is formed by NH, groups belonging to IPE and by chloride ions. The other two zones are quasi-one-dimensional systems o f HO-P=O groups generated by translationally related IPE molecules and can be considered as prospective 'molecular wires'. These two tones a re located symmetrically with respect to the central zone. Electrophys ical parameters (contuctance gamma and complex dielectric permittivity components epsilon' and epsilon '') were determined for polycrystalli ne samples of IPE-HCl and IPE-HBr in the temperature range from -20 to 70 degrees C. The permittivity epsilon' was found to assume abnormall y high values (about 10(6)) at low frequency and to decrease monotonic ally with increasing temperature in the frequency range from 50 Hz to 10 MHz. Possible mechanisms of polarisation of the synthesised IPE der ivatives are analysed. The conductance of the crystals was shown to ha ve an activation character with the activation energy equal to 0.7-1.3 eV for IPE-HCl and 0.4-0.6 eV for IPE-HBr. A hopping mechanism was pr oposed to explain charge transfer along the systems of HO-P=O groups i nvolving Cl- and Br- ions.