Structures and magnetic properties of ionic hybrids of metal halides and carboxyalkylamines.

Abstract

Organic-inorganic hybrid materials combine an organic- and inorganic component at the molecular scale. The resulting hybrid material retains the properties of each component, allowing for the design of a material with specific properties through the selection of the components. This study investigated the structural characteristics and magnetic properties of ionic hybrid compounds prepared from metal halides and n-aminoalkanoic acids, HOOC(CH2)nNH2. In the presence of an acid, the organic component is protonated to form an n-carboxyalkylammonium cation, HOOC(CH2)nNH3+, while the inorganic component forms a perhalidometallate anion, [MaXb]z-, where M is a metal ion and X a halido ligand. Three families of compounds were investigated, namely compounds obtained through the combination of n-aminoalkanoic acids with CuCl2, CuBr2, or MnCl2, in an acidic medium. The metal ions Cu2+ and Mn2+ were chosen to impart magnetic properties to the materials. n-Aminoalkanoic acids of different chain lengths were selected to investigate the effect cation chain length on the structures and magnetic properties. The cations (HOOC(CH2)nNH3+), with n = 2, 3, 4, 5 and 10, were selected. A family of bis(n-carboxyalkylammonium) tetrachloridocuprates, (HOOC(CH2)nNH3)2[CuCl4], was obtained through the combination of the n-aminoalkanoic acids with CuCl2. These compounds exhibit two-dimensional hybrid halide perovskite structures in which bilayers of organic cations alternate with inorganic layers consisting of corner-sharing [CuCl6]4-¬ polyhedra. The compounds with n = 3 and 5 undergo phase transitions to incommensurate phases. Ferromagnetic intralayer interactions, occurring at temperature TC, are observed in these compounds. The ferromagnetic intralayer exchange interactions, JK¬, fall in the range of 13.3(1) K to 15.1(8) K, while TC ranged from 7.9 K to 13.4 K. Weak, interlayer antiferromagnetic interactions were observed for some of the compounds. The combination of the n-aminoalkanoic acids with CuBr2 gave bis(n-carboxyalkylammonium) tetrabromidocuprates, (HOOC(CH2)nNH3)2[CuBr4], and the compounds exhibit two-dimensional hybrid halide perovskite structures. Ferromagnetic intralayer interactions are present, with JK observed between 20.4(1) K to 23.7(3) K, while TC ranged between 10.5 K to 13.4 K. Weak, interlayer antiferromagnetic interactions were identified in all the members of this family. An interesting odd-even effect is observed for the compounds obtained from the combination of the n-aminoalkanoic acids with MnCl2. When the number of carbon atoms in the cation is even, bis(n-carboxyalkylammonium) tetrachloridomanganates, (HOOC(CH2)nNH3)2[MnCl4], are formed, which display two-dimensional hybrid halide perovskite structures. Antiferromagnetic intralayer interactions are present, occurring at temperature TN, with 2JK¬ ranging from -7.72(4) K to -8.28(5) K, and TN¬ ranging from 43 K to 45 K. When the number of carbon atoms in the cation is odd, bis(n-carboxyalkylammonium) diaquatetrachloridomanganates, (HOOC(CH2)nNH3)2[MnCl4(H2O)2], are formed. These compounds have layered structures containing [MnCl4(H2O)2]2- anions. Weak antiferromagnetic intralayer interactions are present, with 2JK = -0.14(2) K when n = 2 and 4. The study showed that the compounds' magnetic properties can be tailored by selecting different components. Magneto-structural correlations were identified in these families of compounds and in related compounds reported in the literature. Identifying these relationships contributes to the fundamental understanding of the magnetic behaviour of these materials.