Effect of the transition metal on the structure and order-disorder phase transition in layered hybrid metal halides (CH sub(3)CH sub(2)NH sub(3)) sub(2)[MCl sub(4)] (M = Mn and Co)

Abstract

Layered hybrid organic-inorganic metal halides (CH sub(3)CH sub(2)NH sub(3)) sub(2)[MnCl sub(4)] and (CH sub(3)CH sub(2)NH sub(3)) sub(2)[CoCl sub(4)] were synthesized by the slow evaporation method to understand the relationship between the cryst sub(a)l st sub(r)ucture and order-disorder phase transition. C lorimetric data and crystal structure determination across the phase transition temperature establish the order-disorder phase transition. (CH sub(3)CH sub(2)NH sub(3)) sub(2)[MnCl sub(4)] undergoes the reversible structural phase transition from tetragonal I4/mmm to orthorhombic Pbca at 212/222 K (cooling/heating), whereas (CH sub(3)CH sub(2)NH sub(3)) sub(2)CoCl sub(4) demonstrates the phase transition at 220/239 K from orthorhombic Pnma to orthorhombic P2 sub(1)2 sub(1)2 sub(1). Both compounds are characterized by disordered ethyl ammonium cations in the structure above the phase transition temperature, whereas they become ordered cations at temperatures below the phase transition. Dielectric results further support the observed structural phase transitions. Additionally, magnetic measurements show canted antiferromagnetic characteristics for (CH sub(3)CH sub(2)NH sub(3)) sub(2)[MnCl sub(4)] and paramagnetic behaviour is observed for (CH sub(3)CH sub(2)NH sub(3)) sub(2)[CoCl sub(4)]. The structural differences, the role of intermolecular interactions and the effect of transition metals on the phase transition were evaluated using Hirshfeld surface analysis and the topological properties of electron density distributions. An accurate description of the structure and intermolecular interactions is crucial for understanding the physical properties and designing multifunctional hybrid organic-inorganic metal halide perovskites.