Effect of Different Carboxylates on a Series of Ag(I) Coordination Compounds with Benzoguanamine Ligand

The ultrasonic reactions of Ag2O with benzoguanamine and ancillary carboxylate ligands under the ammoniacal condition gave eight new coordination compounds (CCs), namely, [Ag4(bga)6(mal)2] (1), [Ag4(bga)6(mlc)2] (2), [Ag(bga)2(tpa)0.5]n (3), {[Ag(bga)(suc)0.5]·C2H5OH}n (4), {[Ag(bga)(pta)0.5]·CH3OH}n (5), {[Ag(bga)(ox)0.5]·C2H5OH·H2O}n (6), {[Ag2(bga)2(dnb)2]·DMF}n (7), and [Ag2(bga)2(pma)0.5(H2O)]n (8) (bga = benzoguanamine, H2mal = malonic acid, H2mlc = maleic acid, H2tpa = terephthalic acid, H2suc = succinic acid, H2pta = phthalic acid, H2ox = oxalic acid, Hdnb = 3,5-dinitrobenzoic acid, H4pma = pyromellitic acid, and DMF = N,N′-dimethylformamide). All CCs have been characterized by elemental analyses, IR spectra, and single-crystal X-ray diffraction. Compounds 1 and 2 are 0D discrete molecules and contain centrosymmetric [Ag2(mal)]2 and [Ag2(mlc)]2 units, respectively, which are extended to 1D supramolecular chains through intermolecule N–H···N complementary hydrogen bonds. Compounds 3 and 4 contain similar 1D [Ag2(tpa)]n and [Ag2(suc)]n infinite chains incorporating monodentate bga ligand as an ornament. It is noteworthy that the Ag···Ag interaction was exclusively observed in the 1D chain of compound 4, which may be caused by different coordination environments of the Ag(I) center between 3 and 4. The Ag···π interactions further extend the 1D chains into 2D sheet in 4. In 5 and 6, the μ2-bga ligands link Ag(I) ions to form 1D helical chains, which are further extended by μ2-dicarboxylate to 2D 63-hcb net incorporating different dimensions of hexagonal grids. Compound 7 is a 1D chain containing [Ag2(dnb)2] subunits, to which the monodentate and bidentate bga ligands as well as DMF coordinate. Compound 8 is a 2D sheet structure incorporating μ6-η1:η1:η1:η1:η1:η0:η1:η0 pma, monodentate and bidentate bga ligands. The results show that the structural diversity (0D–2D) of the CCs is mainly attributed to the usage of diverse ancillary carboxylate ligands as well as diverse coordination modes of bga ligand. Moreover, the photoluminescence properties of the CCs 1–6 were also investigated in the solid state at room temperature.