Two cadmium(II) complexes with polymeric 2D layer and discrete mononuclear motifs: Syntheses, crystal structures, and fluorescent properties

Abstract

Two new 1,3-bi(4-pyridyl)propane-based cadmium(II) complexes, [Cd(Bpp)₂(Nas)₂]_n (I) and [Cd(Bpp)₂(Na)₂(H₂O)₂] (II) (Bpp = 1,3-bi(4-pyridyl)propane, Nas^– = 2-aminonaphthalene-1-sulfonate, and Na^– = 1-naphthoate) (CIF files CCDC nos. 1429589 (I), 1429590 (II)) have been hydrothermally synthesized by varying carboxylate- or sulfonate-containing coligands. Structural analyses reveal that, complex I with monodentate Nas^– ligands exhibits a two-dimensional (2D) layered motif extended by equatorial Bpp connectors. By contrast, complex II modified by monodentate Na^– ligands exhibit discrete mononuclear structure. Althouth the Nas^–/Na^– coligands showed the same monodentate binding modes, the Bpp ligand exhibits bridging or terminal binding modes in I and II, respectively. So it is obvious that the competitive coordination in the present mixed-ligands system is responsible for the aggregation or dissociation of mononuclear structural units. Furthermore, both of the two compounds are linked to 3D supramolecular architecture by intermolecular C–H···O hydrogen bonding or C–H···π stacking interactions, exhibiting strong fluorescent emissions resulting from the ligand-to-metal or Na^‒-based intraligand charge transfer at room temperature, which can be hopefully used as fluorescent materials.