Abrupt change from moderate positive to colossal negative thermal expansion caused by imidazolate composite formation.

ABSTRACT: This work describes temperature-induced crystallization processes and reaction mechanisms occurring in the borohydride-imidazolate system. In the course of thermal evolution, crystal structures of two novel bimetallic imidazolates AMnIm₃ (A = Na, K) were solved using synchrotron radiation powder diffraction data. Both the alkali metal cation and the Mn cations exhibit distorted octahedral coordination while each imidazolate is surrounded by two alkali metal and two manganese atoms. Extensive study of the thermal expansion behaviour revealed that the expansion of the bimetallic imidazolates does not proceed uniformly over the entire temperature range but rather abruptly changes from a colossal negative to a moderate positive volume expansion. Such behaviour is caused by the coher

SUBMITTER: Burazer S 

PROVIDER: S-EPMC9246808 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature