Positron annihilation studies of some charge transfer molecular complexes

Positron annihilation lifetimes were measured for some solid charge transfe r (CT) molecular complexes of quinoline compounds (2,6-dimethylquinoline, 6 -methoxyquinoline, quinoline, 6-methylquinoline, 3-bromoquinoline and 2-chl oro-4-methylquinoline) as electron donor and picric acid as an electron acc eptor. The infrared spectra (IR) of the solid complexes clearly indicated t he formation of the hydrogen-bonding CT-complexes. The annihilation spectra were analyzed into two lifetime components using P ATFIT program. The values of the average and bulk lifetimes divide the comp lexes into two groups according to the non-bonding ionization potential of the donor (electron donating power) and the molecular weight of the complex es. Also, it is found that the ionization potential of the donors and molec ular weight of the complexes have a conspicuous effect on the average and b ulk lifetime values. The bulk lifetime values of the complexes are consiste nt with the formation of stable hydrogen-bonding CT-complexes as inferred f rom the IR-spectral data. (C) 2000 Elsevier Science Ltd. All rights reserve d.