Crystal and Molecular Structures of Three Co-crystals from 1,3-Dimethyl-3,7-dihydro-1H-purine-2,6-dione and Carboxylic Acids

The preparation, X-ray crystal structure, Fourier Transform infrared (FTIR) spectroscopy, and elemental analysis of the three complexes (1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione): (2,6-dichlorobenzoic acid)2: H2O [(tp)center dot (Hbza)2 center dot H2O, Hdcba = 2,6-dichlorobenzoic acid] (1) (1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione): (2-pyrazinecarboxylic acid) [(tp) center dot (Hpyca), Hpyca = 2-pyrazinecarboxylic acid] (2) and (1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione): (3-nitrophthalic acid) [(tp) center dot (Hntpa)] (3) based on 1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione, 2,6-dichlorobenzoic acid 2-pyrazinecarboxylic acid, and 3-nitrophthalic acid are reported. XRD and FTIR analysis indicated that they are all co-crystal. 1 crystallizes in the monoclinic, space group P21/n, with a = 7.1019(7) angstrom, b = 12.9494(12) angstrom, c = 26.253(3) angstrom, beta = 93.536(3)degrees, V = 2409.8(4) angstrom 3, Z = 4. 2 crystallizes in the monoclinic, space group P21/c, with a = 6.9863(7) angstrom, b = 25.437(3) angstrom, c = 7.3987(7) angstrom, beta = 95.152(2)degrees, V = 1309.5(2) angstrom 3, Z = 4. 3 crystallizes in the monoclinic, space group P21/n, with a = 14.2133(15) angstrom, b = 8.2333(9) angstrom, c = 15.3860(17) angstrom, beta = 117.236(5)o, V = 1600.9(3) angstrom 3, Z = 4. The imidazole-carboxylic acid synthon of the CO2H center dot center dot center dot N type is observed in all the co-crystal. The imidazole H-N also donated the N-H center dot center dot center dot O hydrogen bonds in all cases. Apart from the classical hydrogen bonds, the auxiliary expanding interactions as CH center dot center dot center dot O, CH3 center dot center dot center dot O, CH center dot center dot center dot Cl, O center dot center dot center dot O, Cl center dot center dot center dot O, Cl center dot center dot center dot Cl, Cl center dot center dot center dot pi, O center dot center dot center dot pi, and pi center dot center dot center dot pi also play important roles in the structure extension. For the coexistence of the various weak interactions these structures adopted the most common R22(7) supramolecular synthon. In conclusion, we have shown that 2D-3D connections can be constructed by the collective non-covalent interactions.Graphical AbstractIn the three prepared supramolecular assemblies there are plenty of weak nonbonding interactions such as directional hydrogen bonds of O-H center dot center dot center dot N, N-H center dot center dot center dot O, O-H center dot center dot center dot O, intra- and interchain CH center dot center dot center dot O, CH3 center dot center dot center dot O, CH center dot center dot center dot Cl, O center dot center dot center dot O, Cl center dot center dot center dot O, Cl center dot center dot center dot Cl, Cl center dot center dot center dot pi, O center dot center dot center dot pi, and pi center dot center dot center dot pi interactions, on account of these collective weak interactions, these compounds displayed the 2D-3D framework structures.