Metal complexes of thionine, azure C and azure A with copper(II) chloride were prepared using two easy steps as dissolving and then slow evaporation in acetonitrile. Cl⁻ anion in the chloride salt of PTZ dyes was formed [CuCl₃]⁻ with CuCl₂ in the solvent environment, producing its own ionic character (PTZ⁺[CuCl₃]⁻). ThCu, ACCu and AACu complexes were characterized with theoretical computations, thermal, spectral, electrochemical and fluorescence techniques. Such PTZ⁺[Metal Sult]⁻ complexes can be useful for the applications in optoelectronics with their interesting ionic characters.

Structures held together by secondary interactions such as intramolecular or intermolecular hydrogen bonding, electrostatic and π–π interaction without covalent bonds can exhibit new properties such as high orientation, optoelectronics, biocompatibility and reversibility (self-renewal). Recently, interest has been growing surrounding novel molecules fashioned through non-covalent interactions. These molecules have garnered attention due to their significant roles in both physical and chemical applications. However, the formation of complexes between cationic phenothiazine derivative dyes, commonly employed in electrochemical studies, and diverse metal groups presents a challenge. Therefore, the existing literature contains only a scant number of studies concerning the formation of phenothiazine complexes with metal salts. In this study, metal complexes of thionine, azure C and azure A with copper(II) chloride were prepared using two steps: dissolving and then slow evaporation of dyes-copper(II) chloride in acetonitrile. Besides the theoretical computations, thermal, spectral, electrochemical and fluorescence techniques were performed to determine the characteristics of the monoclinic crystals of Cu–dyes complexes. Cl⁻ ion in the dyes and copper(II) chloride conjugated to form [CuCl₃]⁻, then this anion electrostatically bound to cationic phenothiazine ring bond to be phenothiazine⁺[CuCl₃]⁻. Cu–dye complexes showed interestingly high electron transportation. In addition, prepared Cu–dye complexes have a great potential to be used in optical and spectral applications with extraordinary behaviour of their spectral and fluorescence features.