Molecular modeling and experimental study of non-linear optical compounds: monosubstituted derivatives of dicyanovinylbenzene

Abstract

A search for potential non-linear optical (NLO) compounds has been performed using the Cambridge Structural Database and molecular modeling. We have studied a series of monosubstituted derivatives of dicyanovinylbenzene as the NLO properties of one of its derivatives ( o-methoxy-dicyanovinylbenzene, DIVA) were described earlier. The molecular geometry in the series of the compounds studied was investigated with an X-ray analysis and discussed along with results of molecular mechanics and ab initio quantum chemical calculations. The influence of crystal packing on the molecular planarity has been revealed. Two new compounds from the series studied were found to be active in the second harmonic generation (SHG) in the powder state. The measurements of the SHG efficiency have shown that the o-F-, and p-Cl-derivatives of dicyanovinylbenzene are about 10 and 20 times more active than urea, respectively. The peculiarities of crystal structure formation in the framework of balance between the van der Waals and electrostatic interactions have been discussed. The crystal morphology of DIVA and two new SHG-active compounds have been calculated on the basis of the known crystal structures.