Coordination polymers Nitrilotriacetate Silver Bipyridine Photoluminescence

What is it about?

Three new coordination polymers (CPs), [Ag3(nta)(azpy)3(H2O)]n·5H2O, 1, [Ag3(nta)(bpa)2.5]n·5.5H2O, 2 and [Ag6(nta)2(tmdp)5]n·17H2O, 3 (where nta=nitrilotriacetate, azpy=4,4′-azobipyridine, bpa=1,2-di(4-pyridyl) ethane and tmdp=4,4′-trimethylenedipyridine) have been synthesized and characterized by different techniques viz. elemental analysis, PXRD, IR, UV–vis and X-ray crystallography. Single crystal X-ray studies reveal that CP 1 is one-dimensional structure whereas, 2 and 3 are two-dimensional and three-dimensional structures respectively. By altering the flexibility of bipyridine ligands, different coordination behaviour of nta was observed and also dimensionality of CPs changed from 1D to 3D. A supra-molecular 3D structure of 1 was generated because of π⋯π interactions. The argentophilic interactions involved in the formation of 2D and 3D structures of 2 and 3 respectively. The photoluminescent properties of CPs 1–3 were studied in a solid state at room temperature. CPs 1 and 2 showed emission bands at 432 and 401 nm respectively because of intra-ligand charge transfer transitions. In the case of 1, the emission band is red-shifted with respect to azpy since of π-π stacking in the solid state. CP 3 showed emission in the visible region at 488 nm, is due to the promotion of the lone pair of electrons of the metal to the π* orbital of the ligand.

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