Rationalization of the structural, electronic and photophysical properties of silver(i) halide n-picolylamine hybrid coordination polymers

Abstract

Hybrid coordination polimers based on AgX (with X = Cl, Br) and 2-, 3-, 4-picolylamine ligands, obtained by means of solvent-free methods, show peculiar luminescence properties that are strongly influenced by their structural motif, which in turn is defined by the adopted isomer of the ligand. A comprehensive study, combining photophysical methods and DFT calculations, allowed to rationalize the emissive behaviour of such hybrid coordination polymers in relation to their crystal structures and electronic properties. By means of luminescence measurements at variable temperatures, the nature of the emissive excited states and their deactivation dynamics was interpreted, revealing XMLCT transitions in the [(AgX)(2-pica)]_n compounds, a TADF behaviour in the case of 3-pica derivatives, and a dual emission at room temperature for the [(AgX)(4-pica)]_n family. The presence of low energy CC states, permitted by argentophilic interactions, is also considered in [(AgX)(2-pica)]_n, whose structures are characterized by single/double inorganic chains, and in [(AgX)(4-pica)]_n, where discrete dimeric Ag₂X₂ units are present. These findings open new avenues for the design and application of luminescent AgX-based hybrid materials.