Supramolecular structures and fluorescence properties of three transition-metal complexes

Three mononuclear transition-metal(II) compounds [Co(imidazole)6]CO3 · 5H2O (1), [Co(nicotinate)2(H2O)4] (2) and [Mn(isonicotinate)2(H2O)4] (3) ware obtained under the hydrothermal conditions. It deserves to note that they all exhibit interesting supramolecular topologies: in a crystal host of 1 three crystallographically unique free H2O molecules form a two-dimensional (2-D) water network based on the cyclic dodecamers with the occluded CO32- anions; both 2 and 3 possess 3-D network structures formed through the π–π stacking interactions of the pyridine rings and multi-types of O⋯Ow hydrogen-bonded interactions. All of these compounds show the strong fluorescence emissions with the peaks at 389, 650 and 390–420 nm (broad band) when excited at 220, 360 and 254 nm, respectively, which can be assigned to the charge transfer between the metal and the ligand.

Graphical abstractIn a crystal host of [Co(imidazole)6]CO3 · 5H2O (1), three crystallographically unique free H2O molecules form a 2-D water network based on the cyclic dodecamers with a L12(6) pattern.Figure optionsDownload full-size imageDownload as PowerPoint slide