Nonlinear optical properties of dicyanomethylene-derived heteroaromatic dyes: Semiempirical molecular orbital calculations and experimental investigations
✍ Scribed by Michael C. Zerner; Walter M. F. Fabian; Renate Dworczak; Dietmar W. Kieslinger; Gert Kroner; Hans Junek; Max E. Lippitsch
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 248 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
The effect of conformation (E/Z isomerism), nature (donor/acceptor) of substituents, and endgroups (indandione, pyrazolone, pyrazoledione) on the molecular hyperpolarizability β vec of dicyanomethylene (hetero)aromatic dyes is investigated by means of semiempirical (AM1, ZINDO) molecular orbital calculations. Unless Z isomers are stabilized by intramolecular hydrogen bonding, generally E conformers have larger β vec 's. Replacement of one nitrile group of the dicyanomethylene moiety by p-aminoaryl rather than p-R-arylamino (R = NMe 2 , MeO, H, NO 2 ) is found to be advantageous. Increasing the acceptor strength of 29 by successively replacing the carbonyl with dicyanovinyl groups leads to a maximum of β vec for the derivative with one rather than two C(CN) 2 groups. With respect to endgroups, the indandione moiety generally is the least active group. Solvent effects are treated within the framework of the self-consistent reaction field approximation. In most cases gas-phase tendencies are either parallel or even reinforced if solvent effects are taken into account. The calculated results are compared with electric field induced second harmonic generation (EFISH) measurements.