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Ten new hybrid coordination compounds containing the octahedral tris(2,2′-bipyridine)ruthenium(II) cation and structurally diverse metal chloride anions were synthesized and characterized by single-crystal X-ray diffraction. The inorganic components exhibit remarkable structural diversity; the formation of discrete tetrahedral anions [CoCl4]2–, [CdCl4]2–, oligomeric units [Zn2Cl6]2–, [Cu2Cl6]2–, [Cd4Cl12]4–, [Fe2Cl6O]2–, [Bi4Cl16]4– and polymeric chains [Sb6Cl22]n4n–, [SbIII6SbVCl27]n4n– and [Pb7Cl22DMF]n8n– is observed. The metal chloride anions display a wide range of coordination environments, including tetrahedral, trigonal-bipyramidal, square-pyramidal, and octahedral geometries, often with substantial distortions and pronounced differences in metal–chloride bond lengths. These coordination polyhedra are connected through edge- and corner-sharing to form diverse inorganic architectures, with particularly complex arrangements observed for antimony- and lead-containing compounds. In several structures, the inorganic substructures are further distinguished by mixed oxygen/chlorine coordination, coordinated solvent molecules, or additional interpolyhedral contacts.
The optical and photocatalytic properties of two selected compounds containing cobalt(II) and cadmium(II) chloride species were investigated. Both compounds exhibit similar visible-light absorption dominated by the common ruthenium-based chromophore. However, differences in their emission characteristics indicate that the inorganic component influences the relaxation of photoexcited states.
The photocatalytic activity of both compounds was evaluated by monitoring the degradation of 2-mercaptobenzothiazole under visible-light irradiation. Both materials promoted degradation, whereas negligible changes were observed in control experiments conducted without either illumination or catalyst. The cobalt-containing compound exhibited substantially higher photocatalytic activity than its cadmium-containing analogue, achieving complete disappearance of the characteristic absorption band of the organic substrate within the investigated irradiation period. This difference suggests that the inorganic component plays an important role in determining photocatalytic performance. The accessible redox chemistry of cobalt(II) may contribute to electron-transfer processes following excitation of the ruthenium-based chromophore, whereas cadmium(II) is more likely to influence the reaction through structural, electrostatic, or adsorption-related effects.
These results demonstrate that combining the same molecular photosensitizing component with different metal chloride species provides an effective strategy for generating hybrid materials with diverse crystal architectures and tunable optical and photocatalytic properties. The findings highlight the importance of inorganic substructure design in establishing relationships between crystal structure, photophysical behaviour, and photocatalytic performance.
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