Second Harmonic Generation from a Homologous Series of Molecular Crystals: Impact of Supramolecular Interactions

Abstract

Optical second harmonic generation (SHG) from molecular crystals is largely controlled by the molecular hyperpolarizability and the relative disposition of the molecules in the crystal lattice. Even though it is known that intermolecular interactions can modify the bulk SHG, strong and direct influence of such effects in crystals has not been widely demonstrated. We present a new family of crystals based on the achiral remote functionalized nonlinear optical (NLO) chromophore, N-(2-aminoethyl)-4-nitroaniline, combined with a homologous series of carboxylic acids, in which the overwhelming impact of supramolecular interactions on the solid-state SHG is clearly manifested. Crystallographic investigations reveal a systematic variation in the superstructure formation of the NLO-phore unit across the series, and the intensities of the SHG from microcrystalline samples are found to correlate with the assembly pattern. Failure of simple additive models in explaining the SHG trend is analyzed using quantum chemical computations of the hyperpolarizability of molecular clusters which establishes the dominant influence of noncovalent intermolecular interactions. The present study illustrates the feasibility of exploiting supramolecular structural features to enhance the NLO response of molecular materials.

Isosorbide based chiral polyurethanes: optical and thermal studies

“…The amido diols were characterized by elemental analysis, 1 H NMR, 13 A series of polyurethanes were synthesized [12] by the polyaddition reaction between chromophores (CED, CBD and CHD) and chiral diols, IS with the diisocyanate, toluene diisocyanate (TDI) in dimethyl acetamide solvent medium. The scheme of polymer synthesis are shown in Scheme 2.…”

“…The effective second order susceptibility was evaluated using Kurtz-Perry powder technique [13], which is considered to be a valuable technique for initial screening of materials for second harmonic generation. Particles were graded using standard sieves; sizes ranging from 40 to 300 lm were studied.…”

Theoretical and experimental studies of chiral polyurethanes

“…The second harmonic generation efficiency of the polymers were analysed in the powder form by Kurtz Perry technique [28]. The well powdered sample was filled in a capillary tube of 0.8 mm thickness.…”

Influence of Spiral Framework on Nonlinear Optical Materials

“…[18][19][20][21][22][23][24] An organic molecule with an electron donor (D) linked to an electron acceptor (A) through a p-conjugated bridge [25][26][27][28][29] (i.e. Among all the D-p-A frameworks, 4-nitroaniline [30][31][32] composed of a p-conjugated organic bridge (benzene) with an electron-donor amino (NH 2 ) group and an electron-acceptor nitryl (NO 2 ) group is well known in NLO research. Among all the D-p-A frameworks, 4-nitroaniline [30][31][32] composed of a p-conjugated organic bridge (benzene) with an electron-donor amino (NH 2 ) group and an electron-acceptor nitryl (NO 2 ) group is well known in NLO research.…”

“…D-p-A) is a classical class of NLO materials that exhibit large first hyperpolarizability. Among all the D-p-A frameworks, 4-nitroaniline [30][31][32] composed of a p-conjugated organic bridge (benzene) with an electron-donor amino (NH 2 ) group and an electron-acceptor nitryl (NO 2 ) group is well known in NLO research. In contrast, 4-nitrophenyldiphenylamine can be obtained not only by replacing the H atom at the 4-position of triphenylamine with a NO 2 group, but it can also be obtained by replacing the two H atoms of the NH 2 group in 4-nitroaniline with two phenyl groups.…”