Thermal switching of dielectric response linked with photoluminescence in DABCOnium-based hybrids involving cyclometallated dicyanidoiridate(III) and dicyanidorhodate(III) ions

This study presents the synthesis and characterization of eight novel molecular materials, incorporating cyclometallated dicyanidometallates, [MIII(CN)2(ppy)2]− (MIII = RhIII or IrIII, ppy = 2-phenylpyridine), and R-DABCOnium cations of varying alkyl chain lengths (DABCO = 1,4-diazabicyclo[2.2.2]octane, R = Me, Et, nPr, and nBu). The obtained systems were analyzed using the single-crystal X-ray diffraction (SC-XRD) method to determine their molecular structure, while UV-Vis absorption spectroscopy and photoluminescence studies provided insights into their optical properties. Dielectric spectroscopy was employed to investigate their dielectric relaxation behavior, revealing a significant influence of the alkyl chain length and metal center on the dielectric response. The Ir(III)-based materials exhibit room-temperature photoluminescence, whereas their rhodium(III)-based analogues show only the emission at low temperature. The study highlights the interplay between molecular flexibility, steric constraints, and electronic characteristics, together with the observed trends in the activation energy barrier and relaxation times. These results underline the potential of multifunctional luminescent materials for optoelectronic applications, offering a foundation for the rational design of advanced systems with tunable photophysical and dielectric properties, for their use in sensors, memory devices, and other electronic applications.