Unveiling the Influence of Organic Chain Length on the Physical Properties of Two-Dimensional Cobalt-Based Hybrid Perovskites

Recent interest in two-dimensional (2D) lead-free hybrid organic–inorganic perovskites (HOIPs) has driven significant progress in the development of magnetic and electronic materials. Herein, we systematically compare a series of low-temperature growth of 2D cobalt-based HOIPs (Co-HOIPs) by varying the methylene chain length (n) of n = 1, 2, 3, and 4, for the first time. The Co-HOIP crystal structure with a single carbon chain displays a monoclinic arrangement with a space group of P21/c, while those with two, three, and four methylene chain lengths manifest triclinic crystal structures with a space group of P1. The optical measurements exhibit apparent odd–even effects as a function of the length of the organic ligand. The first-order phase transitions of BA2CoCl4 are distinctly observed at temperatures of 12.46 and 139.77 °C compared to the shorter EA2CoCl4 counterparts. Notably, this particular compound exhibits the highest magnetic saturation and coercive fields with Ms = 0.160 emu/g and Hc = 19.416 T, respectively. Furthermore, BA2CoCl4 demonstrates superior dielectric properties, as evidenced by the shortest diameter of the equivalent circuit in EIS. These findings underscore the potential of BA2CoCl4 for diverse applications in magnetic and electronic devices, highlighting its promising role in advanced technological applications.