Self-assembly synthesis of two new cocrystals of 1,5 bis(3-pyridyl)-3,4-diaza-2,4-hexadiene: an experimental and theoretical study

Abstract

 In this paper, we report the synthesis, characterization and theoretical studies of two new cocrystals of 1,5 bis(3-pyridyl)-3,4-diaza-2,4-hexadiene (3-bpdh) with two simple organic acids; oxalic and succinic with 1:1 stoichiometric ratio. These cocrystals, [(3-bpdh)(oxalic acid)] (1) and [(3-bpdh)(succinic acid)] (2), have been prepared by slow evaporation of saturated solutions and characterized by elemental and thermal analysis, FTIR, ¹H NMR spectroscopy, and single X-ray crystallography. X-ray crystal analyses show that these structures have been crystallized in triclinic and monoclinic space groups of ${\mathrm{P}}_{\overline{1}}$ and P2₁/n, respectively. Also, the thermal behavior of compounds was investigated in an atmosphere of static air with thermal gravimetric analysis (TGA), differential thermal analysis (DTA).

These structures have been studied theoretically using RB3LYP hybrid density functional method with 6–31G(d) basis set. DFT calculations have been used to predict the geometry of the cocrystal structures. Furthermore, molecular electrostatic potential (MESP) maps of the compounds have been generated. Theoretical results show good agreement with the experimental data and these data show hydrogen bonding has played an important role in supramolecular structure formation. The cocrystal design was done based on the perfect selection of two distinct hydrogen donor and acceptor molecules.