Transition-Metal Supramolecular Complexes with 2-Phenylacetate and a Bent Dipyridyl Ligand: In Situ Hydrothermal Syntheses, Crystal Structures, and Photoluminescent Properties

This work presents seven CoII, CdII, ZnII, MnII, and NiII supramolecular complexes synthesised by hydrothermal reactions from a bent dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) and 2-phenylmalonic acid (2-phmalH2). Interestingly, the in situ generation of 2-phenylacetic acid (Hpa) by decarboxylation of the 2-phenylmalonic acid precursor is observed in all the complexes. Single-crystal X-ray diffraction reveals that these complexes display a variety of 1D (for 2–7) and monomeric (for 1) coordination motifs, which are further extended into polymeric supramolecular architectures by multiple secondary interactions, such as hydrogen bonding and aromatic stacking. The results evidently demonstrate that the structures of 1–7 are significantly affected by the metal centres and the counter anions of inorganic salts. The photoluminescence properties of complexes 1–7 have also been investigated and discussed.