The pattern of bifurcated hydrogen bonds in thiourea cocrystals with diazine derivatives: experimental and quantum theoretical studies

Abstract

Cocrystals of thiourea with pyrazine N-oxide as thiourea–pyrazine N-oxide (2/1), C4H4N2O·2CH4N2S, (I), and with phenazine as thiourea–phenazine (6/7), 7C12H8N2·6CH4N2S, (II), both crystallize in the monoclinic space group P21/c. In the crystalline state, molecules of both components are linked by N—H...N hydrogen bonds. In addition, there are R 2 2(8) hydrogen-bond synthons between thiourea molecules in both crystal structures. Furthermore, bifurcated hydrogen bonds between the –NH groups in the thiourea molecule and the N and O atoms in the N-oxide ring [in (I)], as well as the N atom in the central phenazine ring [in (II)], play a significant role in both structures. This emerging motif was thoroughly examined using quantum chemistry methods.