The odd–even effect in n-carboxyalkylammonium-containing organic–inorganic hybrids of Mn(ii) halides: structural and magnetic characterisation

Abstract

The understanding of magnetic properties of hybrid compounds is important for the design of magnetic devices. In this contribution a prominent odd–even effect in both the structural characteristics and magnetic properties of four new hybrid compounds comprised of n-carboxyalkylammonium cations and perchloridomanganate anions is reported. When the n-carboxyalkylammonium cations contain an even number of carbon atoms, compounds of the formula (NH₃(CH₂)_nCOOH)₂[MnCl₄], with n = 3 and 5, are formed, which display the two-dimensional (2D) hybrid halide perovskite structure in which bridging chlorido ligands link Mn²⁺ ions. Compounds containing n-carboxyalkylammonium cations with an odd number of carbon atoms have the formula (NH₃(CH₂)_nCOOH)₂[MnCl₄(H₂O)₂], with n = 2 and 4, and display a zero-dimensional (0D) structure with hydrogen bonding interactions linking neighbouring [MnCl₄(H₂O)₂]²⁻ anions. The odd–even effect is also evident in the magnetic properties of the compounds, which are linked to the structural differences observed in these compounds. Compounds containing an even number of carbon atoms show antiferromagnetic (AFM) interactions and spin canting at temperature T_N, with 2J_K = −8.28(5) K and T_N = 45.0(5) K when n = 3 and 2J_K = −7.72(4) K and T_N = 43(1) K when n = 5. Much weaker AFM interactions and no spin canting is observed in compounds containing an odd number of carbon atoms, with 2J_K = −0.14(2) K when n = 2 and 2J_K = −0.14(2) K when n = 4.