Aerobic Melt-Quenching and Glass Formation in One-Dimensional Metal–Organic Hybrids

Abstract

Crystalline hybrid organic–inorganic structures from the coordination polymer (CP)/metal–organic framework (MOF) family have recently emerged as materials which liquify upon heating to high temperature and then transform into glass upon cooling to room temperature. This melt-quench process of this material family generally requires an anaerobic atmosphere to avoid oxidation of organic component at high temperature. Anaerobicity here brings in an extra cost and makes melt-quench setup robust. Besides, these hybrid liquids often show intriguing thermal behaviour such as exothermic recrystallization (on cooling), cold crystallization (on reheating), etc. which again limits the typical melt-quench process of glass fabrication and processability. Here we turn to hybrid organic–inorganic structures of one-dimensional (1-D) family and design five 1-D (PrPh3P)2[M(dca)4] (PrPh3P = propyltriphenylphosphonium; M = Mn, Fe, Co, Ni, Cu; dca = dicyanamide) compounds which overcome above hurdles and were successfully vitrified upon direct in-situ melt-quenching on laboratory time scales under aerobic conditions. The combined spectroscopic and X-ray total scattering studies reveal successful structural characterization of these glasses that largely retain the coordination bonding of the crystalline phase and show valuable physical properties such as low liquid fragility (m), large ‘glass-crystal network density deficit’ (Δρ/ρg)network, high glass-forming ability (GFA) and polymer-like mechanical hardness (H).