Structural studies of new co-crystal compound including pyridine–2,6– dicarboxilic acid and pyridine–2–carbocxamide: Synthesis and DFT calculations


  • Mohammad Chahkandi, Behzad Chahkandi


Co-crystal ligand; 2,6–pydc(py–2–cm)2; DFT; Charge transfer; Hydrogen bonding


The proton transfer compounds (PTCs) by transferring of one or more protons from a donor group to an acceptor one are prepared .PTCs can coordinate to transition metals to form coordination complexes. In this study, colorless crystals of a new co-crystal named 2,6–pydc(py–2–cm)2 through the reaction of pyridine–2,6– dicarboxilic acid (2,6–pydc) and pyridine–2–carbocxamide (py–2–cm) were prepared and characterized by FTIR, UV–Vis, and CHNS analysis. DFT calculations including geometry optimization, frequency calculations, time dependence (TD), and NBO analysis of 2,6–pydc, py–2–cm, and the proposed structure of 2,6–pydc(py–2–
cm)2 at B3LYP/6–311+G(d,p) level of theory using Gaussian 09 program were performed. The comparison of FTIR spectra of the synthesized 2,6–pydc(py–2–cm)2 with the vibrational peaks of donor and acceptor groups confirm the inter–molecular hydrogen bond (HB) formation. The calculated UV−Vis spectrum is consistent with the experimental spectrum depicting four major electron–transition bands derived from n (p) → π* and π → π* Intra–Ligand Charge Transfer (ILCT) transitions. Moreover, the calculated stabilization energy of the prepared-1
–1 co-crystal that made by O−H···N O-H and N−H···O HBs measured as – 161.92 kcal mol