Solid–Liquid Transitions in 1D Metal–Organic Chalcogenolates

A lack of melt processability is noted for emerging hybrid material systems like metal–organic frameworks, lead-halide perovskites, and metal–organic chalcogenolates (MOChas). Here, we report reversible solid-to-liquid phase transitions ranging from 67 to 184 °C in silver secondary-alkanethiolate 1-dimensional (1D) MOChas. These MOChas were synthesized using five different secondary alkanethiols: 2-propanethiol, 2-butanethiol, 2-pentanethiol, 3-hexanethiol, and 4-heptanethiol. Structural characterization using small-molecule serial femtosecond crystallography (smSFX) reveals a 1D wire crystal motif. These 1D wire lattices exhibit green-yellow photoluminescence that disappears upon melting. The low melting temperature is attributed to the conformational flexibility of the secondary alkanethiol ligands, providing entropic benefits for the amorphous state. Furthermore, the transition from a nonmolecular, infinite covalent (Ag-SR)∞ network in the solid state to oligomolecular species (Ag-SR)x in the molten state contributes to a higher enthalpy of fusion. Large crystallites are observed to evolve from the liquid near the phase transition temperature. Notably, unmixing of chiral domains occurs in the racemic crystals while the inorganic network remains unchanged.