0000000000805650
AUTHOR
Franz Effenberger
Enhanced nonlinear optical properties and thermal stability of donor-acceptor substituted oligothiophenes
Abstract Linear and nonlinear optical properties of a series of novel donor-acceptor substituted α-oligothiophenes were investigated by means of electrooptical absorption measurements (EOAM) and electric field induced second harmonic generation (EFISH). The second-order polarizabilities β(−2ω; ω, ω) were related to dipole changes Δμ ag and transition dipoles μ ag associated with low-lying charge-transfer (CT) excitations by using the perturbational two-level approximation. Systematic variation of the donor and acceptor groups led to compounds with exceptional nonlinearity and thermal stability. Too strong donor/acceptor pairs, however, yielded structures in the charge-resonance (CR) limit w…
Raman and theoretical study of the solvent effects on the sizable intramolecular charge transfer in the push-pull 5-(dimethylamino)-5'-nitro-2,2'-bithiophene.
In this paper, we analyze the degree of intramolecular charge transfer in a push-pull π-conjugated system, 5-(dimethylamino)-5'-nitro-2,2'-bithiophene, from changes in frequencies and relative intensities of its strongestRaman scatterings in a bunch of solvents with different polarities. Density functional theory (DFT) was used as a support of the experimental study. Solvent effects on the molecular and electronic structures and on the vibrational properties were estimated by performing B3LYP/6-31G** calculations within the framework of the polarized continuum model (PCM) developed by Tomasi. Calculations reveal that the molecule is highly polarized in the ground state and behaves as a very…
Donor-acceptor substituted polyenes : orientation in mono- and multilayers
Large molecules containing different chemical units whose interactions within the molecule result in new macroscopically observable effects, have become increasingly important.The organization of molecules of this type in ordered structures leads to functional molecular materials.Their use in molecular electronics requires that the units exhibit specific electronic properties. Recently, we reported on the intramolecular energy transfer through terminally substituted conjugated polyenes. An intramolecular electron transfer within donor-acceptor substituted polyenes can be achieved by introducing suitable terminal groups.
Properties of amphiphilic terminally substituted conjugated nonaene- and 2-docosylnonaene carboxylic acids in monolayers at the air-water interface
was a lo-' M Co(NO,), + lo-' M CH,COONa solution, with pH 7.5; the counter electrode was a Pt sheet, conveniently located in the electrochemical cell. After deposition, the electrochemical/electrochromic properties of the films were analyzed in degassed lo-' M KOH electrolyte, in a three electrode cell (Pt wire counter electrode, saturated calomel reference electrode) with optical windows. A PAR 173 potentiostat-galvanostat associated with a PAR 175 function generator was used in the electrochemical experiments. Data were recorded in a analogical X-Y (X-T) recorder. Monochromatic transmission (He-Ne laser, A = 632.8 nm) was recorded in situ, by means of a versatile optical bench; spectral t…