Out with Acetonitrile: Water-Assisted Accelerated-Aging Synthesis of CuI-Pyrazine Hybrid Materials

CuI and pyrazine form three hybrid materials, [(CuI)2(pyrazine)] (Yellow), [(CuI)2(pyrazine)2] (Orange), and [(CuI)(pyrazine)] (Red). In this work, Red was prepared using a green synthetic method, water-assisted accelerated-aging synthesis, for the first time. The syntheses were performed under ambient conditions with only water and no organic solvents. Depending on the reaction conditions, the other two hybrid materials can be formed as well: Orange was formed immediately after dry grinding CuI and pyrazine, while Yellow can be formed from Red and an excess amount of CuI at mildly elevated temperatures. The impacts of temperature and types and amounts of liquid added to the aging mixture on the accelerated-aging synthesis were studied, and mechanisms of the synthesis and interconversions between the three CuI-pyrazine hybrid materials were proposed. This technique presents a potentially viable technique for inexpensive, large-scale production of these materials, and these insights may be valuable in the green synthesis of other hybrid materials.