Classification of hydrogen-bond motives in crystals of NH-pyrazoles: A mixed empirical and theoretical approach

Abstract

A search in the Cambridge Structural Database for NH-pyrazoles lacking other hydrogen-bond donor and acceptor sites, has identified 49 compounds that crystallize in 47 structures forming dimers (16), tetramers (13), trimers (8), hexamers (1) and catemers (10) using N-H⋯N hydrogen bonds. These structures have been classified in two classes (dimers and tetramers vs. trimers and catemers) using the accessible surface to an atom with good results. The method has been extended to new pyrazoles by means of theoretical calculations (B3LYP/6-31G*) of the geometry of the monomers. Aspects like the conformation of phenyl substituents, the additivity of substituent effects and the buttressing effect have been approached theoretically. ©ARKAT.