ISSN:
1057-9257
Schlagwort(e):
phospholipid analogue crystals
;
synthesis
;
molecular structure
;
X-ray analysis
;
electrophysical properties
;
conjugated ionic-hydrogen bond systems
;
molecular wires
;
molecular electronics
;
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Elektrotechnik, Elektronik, Nachrichtentechnik
,
Physik
Notizen:
Synthesis and investigation of the structure and electrophysical properties of two halogen hydride derivatives of isobutyl analogues of phosphatidylethanol amine (IPE), namely IPE-HCl and IPE-HBr, were performed to offer a new material for ‘molecular wires’ according to the model of molecular electronics developed earlier by Karasev et al. (Adv. Mater. Opt. Electron., 1994, 4, pp. 203-218). X-ray analysis showed that isostructural crystals of the synthesised compounds are monoclinic with the space symmetry group I2/a (C2/c). They have very similar lattice cell parameters, namely a = 21.892(8), b = 4.7747(2), c = 44.63(2) Å, β = 91.83(3)°, Z = 16 for IPE-HCl and a = 22.115(14), b = 4.808(3), c = 44.83(2) Å, β = 91,74(5)°, Z = 16 for IPE-HBr. It was found that the structure of IPE-HCl contains two symmetrically unrelated molecules of IPE. They form two bilayers within the elementary cell each of which includes three zones of hydrogen bonds. The central zone is formed by NH3 groups belonging to IPE and by chloride ions. The other two zones are quasi-one-dimensional systems of HO(SINGLE BOND)P(DOUBLE BOND)O groups generated by translationally related IPE molecules and can be considered as prospective ‘molecular wires’. These two zones are located symmetrically with respect to the central zone. Electrophysical parameters (contuctance γ and complex dielectric permittivity components ε′ and ε″) were determined for polycrystalline samples of IPE-HCl and IPE-HBr in the temperature range from -20 to 70°C. The permittivity ε′ was found to assume abnormally high values (about 106) at low frequency and to decrease monotonically with increasing temperature in the frequency range from 50 Hz to 10 MHz. Possible mechanisms of polarisation of the synthesised IPE derivatives are analysed. The conductance of the crystals was shown to have 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 proposed to explain charge transfer along the systems of HO(SINGLE BOND)P(DOUBLE BOND)O groups involving Cl- and Br- ions.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
Permalink
