Deciphering cation-driven structure-property correlations in 0D hybrid ruthenium halide perovskites

Hybrid organic-inorganic halides have emerged as a structurally tunable class of materials that allow simultaneous modulation of optical properties and magnetic interactions. By varying the A-site cation with organic amines of different carbon chain lengths, a series of zero-dimensional (0D) hybrid ruthenium halide perovskites, (EDA)₂RuCl₆·Cl·H₂O (1), (PDA)₂RuCl₆·2Cl·3H₂O·(H₃O) (2) and (BDA)₂RuCl₆·2Cl·H₂O·(H₃O) (3) (where EDA = ethylenediamine, PDA = 1,3-diaminopropane and BDA = 1,4-diaminobutane) with absorption edges (1.95-1.92 eV), have been assembled. Thermogravimetric analysis of compounds 1-3 reveals that the choice of organic diamine cations and lattice water content enable tuning of thermal stability in hybrid ruthenium halides, linking the amine structure to decomposition temperature. Low temperature magnetization behaviours of compounds 1 and 2 demonstrate typical J = 1/2 paramagnetism, while all compounds 1-3 exhibit broad deep-blue emission spectra, owing to the isolated single ion [RuCl₆]^3- octahedra. These findings establish structure-property correlations, highlighting the interplay of the A-site cation in structural modulation, photophysical properties and magnetic behaviour in a new family of 0D hybrid ruthenium halides.