Nonaqueous Synthesis of Low-Vacancy Chromium Hexacyanochromate

Prussian blue analogues\n(PBAs) are a highly tunable family of materials\nwith properties suitable for a wide variety of applications. Although\ntheir straightforward aqueous synthesis allows for the facile preparation\nof a diverse set of compositions, the use of water as the solvent\nhas hindered the preparation of specific compositions with highly\nsought-after properties. A typical example is Cr[Cr(CN)<sub>6</sub>]: its predicted strong magnetic interactions have motivated many\nattempts at its synthesis but with limited success. The lack of control\nover vacancies, crystallinity, and the oxidation state has prevented\nthe experimental validation of its theoretical magnetic properties.\nHere, we report the nonaqueous synthesis of vacancy-suppressed, nanocrystalline\nchromium hexacyanochromate. The control over vacancies and the oxidation\nstate leads to stronger magnetic interactions with a markedly increased\nabsolute Weiss temperature (Θ = −836(6) K) and magnetic\nordering temperature of (240 ± 10) K. Our results challenge the\nnotion of the solvent as merely reaction medium and introduce a pathway\nfor exploring moisture- and air-sensitive PBA compositions.