UV-VIS SPECTROSCOPIC CHARACTERIZATION OF A ONE-DIMENSIONAL CADMIUM(II) ISONICOTINATE COORDINATION POLYMER

Abstract

Coordination polymers based on pyridine-carboxylate ligands have attracted considerable attention due to their structural diversity and potential applications in catalysis, adsorption, luminescent materials, and crystal engineering. In the present study, a cadmium(II)-based coordination polymer incorporating the isonicotinate ligand was synthesized and characterized by UV-Vis spectroscopy. Single-crystal structural analysis revealed the formation of a one-dimensional coordination polymer formulated as catena-poly[(μ₂-isonicotinato-κ²O,O′:κN)(κ²-O,O′-nitrato)(diaqua)cadmium(II)]·(N,N-dimethylamine), with the general composition [Cd(μ-INA)(NO₃)(H₂O)₂]_n. The isonicotinate ligand acts as a bridging linker through both carboxylate oxygen and pyridyl nitrogen donor atoms, connecting adjacent Cd(II) centers into infinite one-dimensional chains. According to the accepted nomenclature for coordination polymers, the compound is therefore classified as a catena-poly structure.

The electronic absorption spectrum exhibits an intense absorption maximum at 295 nm, which is assigned to ligand-centered π→π electronic transitions associated with the conjugated aromatic pyridine-carboxylate framework. A weak and broad absorption feature observed within the 320-360 nm region may be attributed to n→π transitions of the coordinated carboxylate groups and possible ligand-to-metal charge-transfer interactions. No significant absorption bands were detected in the visible region, which is consistent with the d¹⁰ electronic configuration of Cd(II) and the absence of d–d transitions. The observed spectroscopic behavior confirms the successful coordination of the isonicotinate ligand to the cadmium centers and supports the formation of a stable one-dimensional coordination polymer. These findings contribute to the understanding of the electronic properties of cadmium-based coordination polymers and provide a basis for future investigations of their functional applications.