Effect of solvent, temperature and pressure on the stability of chiral and perovskite metal formate frameworks of [NHNH][M(HCOO)] (M = Mn, Fe, Zn).

We report the synthesis, crystal structure, and thermal, Raman, infrared and magnetic properties of [NHNH][M(HCOO)] (HyM) compounds (M = Mn, Zn, Fe). Our results show that synthesis from methanol solution leads to perovskite polymorphs while that from 1-methyl-2-pyrrolidinone or its mixture with methanol allows obtaining chiral polymorphs. Perovskite HyFe, chiral HyFe and chiral HyMn undergo phase transitions at 347, 336 and 296 K, respectively, with symmetry changes from Pnma to Pna2, P6 to P222 and P6 to P2.