Synthesis, optical, electronic and magnetic studies of air-stable chiral Cu(ii) chlorides

Abstract

Chiral magnetic metal halide semiconductors (MHSs) have recently emerged as a unique platform of hybrid materials for state-of-the-art applications, where both chiroptical and magnetic properties are essential. Motivated by the scarcity of MHS compounds that feature the latter traits and the absence of relevant structure–property relationships, we present here the synthesis and the optical, electronic, and magnetic properties of two new polar 0D, Cu(II) based materials, namely (S-/R-THBTD)₂CuCl₆, where THBTD = 4,5,6,7-tetrahydro-benzothiazole-2,6-diamine. Both enantiomers exhibit direct and indirect optical bandgap characteristics based on UV-vis and density functional theory (DFT) calculations, while circular dichroism (CD) measurements confirmed their chiral character. Magnetometry measurements revealed a notable transition from a paramagnetic to a ferromagnetic-like state at around 4 K, with a low-temperature saturation magnetization value of up to 9.86 emu g⁻¹, which is among the highest reported for chiral magnetic MHSs. Notably, (S-/R-THBTD)₂CuCl₆ maintain their structural integrity and magnetic and optical properties (based on UV-vis studies) after one year of air exposure, a record stability performance among chiral magnetic MHSs. This work proves that air-stable MHSs with competitive chiroptical and magnetic properties can be acquired by properly selecting suitable templating agents, paving the way for further materials development.