Designing Glass and Crystalline Phases of Metal-Bis(acetamide) Networks to Promote High Optical Contrast

Owing to their high tunability and predictable structures, metal-organic materials offer a powerful platform to study glass formation and crystallization processes and to design glasses with unique properties. Here, we report a novel series of glass-forming metal-ethylenebis(acetamide) networks that under -go reversible glass and crystallization transitions below 200 degrees C. The glass-transition temperatures, crystallization kinetics, and glass stability of these materials are readily tunable, either by synthetic modification or by liquid-phase blending, to form binary glasses. Pair distribution function (PDF) analysis reveals extended structural correlations in both single and binary metal-bis-(acetamide) glasses and highlights the important role of metal- metal correlations during structural evolution across glass-crystal transitions. Notably, the glass and crystalline phases of a Co- ethylenebis(acetamide) binary network feature a large reflectivity contrast ratio of 4.8 that results from changes in the local coordination environment around Co centers. These results provide new insights into glass-crystal transitions in metal-organic materials and have exciting implications for optical switching, rewritable data storage, and functional glass ceramics.

Automated summary

Metal-organic materials with high tunability and predictable structures are powerful for studying glass formation and crystallization processes. In this study, a novel series of metal-ethylenebis(acetamide) networks that exhibit reversible glass and crystallization transitions below 200 degrees C are reported. The properties of these materials, including glass-transition temperatures, crystallization kinetics, and glass stability, can be easily tuned through synthetic modification or liquid-phase blending. Pair distribution function (PDF) analysis reveals structural correlations in both single and binary metal-bis-(acetamide) glasses and emphasizes the role of metal-metal correlations in glass-crystal transitions. Notably, a binary network of Co-ethylenebis(acetamide) shows a large reflectivity contrast ratio resulting from changes in Co center's local coordination environment. These findings provide insights into glass-crystal transitions in metal-organic materials and have potential implications for optical switching, rewritable data storage, and functional glass ceramics.