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

A search for potential non-linear optical (NLO) compounds has been performe d using the Cambridge Structural Database and molecular modeling. We have s tudied a series of monosubstituted derivatives of dicyanovinylbenzene as th e NLO proper ties 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 alo ng with results of molecular mechanics and ab initio quantum chemical calcu lations. The influence of crystal packing on the molecular planarity has be en revealed. Two new compounds from the series studied were found to be act ive in the second harmonic generation (SHG) in the powder state. The measur ements 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, re spectively. The peculiarities of crystal structure formation in the framewo rk of balance between the van der Waals and electrostatic interactions have been discussed. The crystal morphology of DIVA and two new SHG-active comp ounds have been calculated on the basis of the known crystal structures. (C ) 2000 Elsevier Science B.V. All rights reserved.