[DMA]2ZnCl4, [DMA]2CoCl4 and [DMA]2ZnBr4 crystallized in the monoclinic system, in the P21/n, P21/n and P21/c space groups, respectively.

Monoclinic crystals of [(CH3)2NH2]2CoCl4 are of the space group P21/n. Unit cell dimensions are as follows: a = 8.5393 Å, b = 11.3905 Å, c = 13.4069 Å and β = 91.02°. This compound undergoes several phase transitions. The optical properties were measured by means of UV–visible absorption spectroscopy in the range 200–800 nm. Analysis of the data revealed the existence of direct allowed optical transition mechanisms with bandgap energy equal to 3.84 eV. The electrical conductivity of [(CH3)2NH2]2CoCl4 was studied in the frequency range 10−1–106 Hz and in the temperature range 411–449 K by means of impedance spectroscopy. Impedance and modulus analyses indicated temperature‐independent distribution of relaxation times and non‐Debye behavior in this material. A super‐linear power law was observed for the AC conductivity, which was analyzed based on the jump relaxation model σac = σdc + A1ωs1 + A2ωs2. Accordingly, the first AC term A1ωs1 corresponds to translational hopping motion and the second term A2ωs2 to well‐localized hopping and/or reorientational motion. Conduction takes place via correlated barrier hopping in phases I and II.