Crystal chemical and IR spectroscopic studies of intermolecular interactions in potentially prototropic organic crystals of N-substituted benz(isonicotine) hydrazides

From crystal chemical analysis of potentially prototropic N-furfurylidene ( thienylidene) benzhydrazides, it was found that increasing the benzhydrazid e molecular volume by S --> O replacement in the five-membered ring causes the formation of crystals with space group of lower symmetry (Pbca --> P2(1 )/b). The presence of two proton acceptor centres in N-furfurylidene (thien ylidene) isonicotinehydrazide (IH) molecules (N-Py and C=O) leads to the oc currence of one of two types of intermolecular hydrogen bond (IB) ( > C=O.. .HN < and > N-Py...HN <) depending on the crystallization conditions. The p rocess of IH crystallization was studied by a crystal chemical approach. An alysis of the N-H valence vibration intensity for IH showed that specific C H...O and S...O intermolecular interactions play an important role in coope rative interactions of > N-Py...HN < IB. (C) 1998 Elsevier Science B.V. All rights reserved.