Spectral and photophysical properties of 1,6-naphthyridine derivatives: a new class of compounds for nonlinear optics.

1,6-Naphthyridines are a class of compounds that exhibit second harmonic generation on excitation with a Nd-YAG laser (1064 nm). Solvatochromism has been used to estimate enhancement in the dipole moments on excitation and the values of first-order hyperpolarizability, beta. Photophysical studies on the title compounds show that they have a fluorescence lifetime of about 10 ns and fluorescence quantum yield of approximately 0.05-0.1 in different solvents. Kurtz powder method has been used to find the NLO efficiency of the compounds with reference to urea.

3-amino-4'-methyl-5-ethylbiphenyl-2,4-dicarbonitrile and 3-amino-4'-(n,n-diethylamino)-5-ethylbiphenyl-2,4-dicarbonitrile.

In the title compounds, C17H15N3 and C20H22N4, the methyl derivative crystallizes with two molecules in the asymmetric unit, while the N,N-diethylamino derivative crystallizes with one molecule per asymmetric unit. The biphenyl twist angle for both molecular structures is approximately 45 degrees. The molecular packing is stabilized by N-H...N hydrogen bonds.