Coexistent Ag⋯Ag and Ag⋯C interactions in three photoluminescent silver(I) coordination networks based on o-, m-, p-methylbenzoic acid

Abstract

Three new silver(I) coordination polymers (CPs) [Ag4(o-mba)4]n (1), [Ag2(m-mba)2]n (2) and [Ag2(p-mba)2]n (3) have been constructed from AgNO3 and three isomeric ligands, o-, m-, p-methylbenzoic acid (Hmba = methylbenzoic acid), and characterized by elemental analysis, infrared (IR) spectroscopy, powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. In 1, μ3–η1: η2 and μ4–η1: η3 o-mba ligands link Ag(I) ions to form a 1D chain based on a tetranuclear Ag(I) aggregation with a folded rhombus geometry. When the methyl group was moved from o- to m-position, we obtained 2 as a similar 1D chain but incorporating a parallelogram tetranuclear Ag(I) aggregation, where two crystallographically independent m-mba ligands show the identical μ3–η1: η2 coordination fashion. Using p-Hmba as ligand, complex 3 becomes a 2D (3,6) net with μ3–η1: η2 p-mba ligands. Interestingly, all CPs exhibit diverse Ag⋯Ag and Ag⋯C interactions, which are in the range of 2.7899(10)–3.3666(7) Å and 2.843(11)–3.336(10) Å, respectively. These secondary interactions cooperatively play important roles in the formation of the resulting 3D supramolecular frameworks. The structural dissimilarity can be mainly assigned to the change of relative positions of methyl and carboxyl groups. Moreover, the thermal stabilities and photoluminescence properties of 1–3 were investigated.