High-pressure effects in the solvothermal syntheses and precipitation of [M(HIm)6]2+ (M = Ni, Co) complexes and novel dense dia-Co(Im)2.

The effects of high pressure involved in solvothermal synthesis and crystallisation have been explored for Zn(II), Ni(II) and Co(II) imidazolium systems. Different synthetic protocols - including compression up to 3 GPa of solid oxides (ZnO and nano-ZnO) and salts Zn(NO3)2, Ni(NO3)2 and Co(NO3)2 together with imidazole and its derivatives, with or without the addition of a small amount of solvent, with or without heating; as well as the isochoric dissolution of the salts Zn(NO3)2, Ni(NO3)2 and Co(NO3)2 mixed with a stoichiometric amount of imidazole in water, with and without the addition of NH4OH - were designed to recognize the effect of pressure and temperature on the reaction outcome. An unprecedented high-density dia-Co(Im)2 with the structure composed of two interwoven 3-dimensional diamondoid networks, a new hydrate of 0-dimensional complex Co(HIm)6·2NO3·2H2O, and Ni(HIm)6·2NO3 have been obtained as single crystals at high pressure. Their specific features of highly compact packing testify to the systematic effects of pressure under solvothermal conditions.