Insights on the Jahn-Teller distortion, hydrogen bonding and local-environment correlations in a promised...

Perovskite-type formates have recently emerged as potential candidates for multiferroics. Previous ab initio calculations have concluded that copper guanidinium formate (CuGF) is a promising multiferroic. Although ab initio design and characterisation of inorganic multiferroics is at a mature stage, this situation is not true for multiferroic metal-organic frameworks. Regardless of these limitations, such predictions have also been extended to other materials. Here, we present with deeper insights into the structural aspects based on single crystal neutron diffraction studies, questioning such predictions in CuGF. The comparative investigation of the polar CuGF and its centrosymmetric cousin, MnGF, uncovers the differences in the N-H⋯O bonds. Such differences are associated with the Jahn-Teller distortion, which balances its influence on the local-environment of the three sets of ND₂ in the guanidinium cation. Hydrogen bonds which were not dealt with in the previous ab initio studies have been carefully treated in this experimental study. Hence, providing a crucial understanding based on which an encouraging platform may be rendered for improving the ab initio calculations for hybrid perovskites catering various applications.