Synthesis, crystal structure, and photocatalytic degradation of rhodamine B by chiral silver(I) complexes based on chiral bidentate chelating ligands.

The photocatalytic degradation of dyes using silver complexes fundamentally relies on semiconductor principles. The practical performance of these silver-based materials heavily depends on their electron-hole recombination rates, optical absorption ranges, and structural stability. To develop robust photocatalysts, we synthesized and thoroughly characterized a series of binuclear chiral silver(I) complexes, specifically the enantiomeric pairs Ag2(R-BINAP)2X2 (X = Cl, Br, I) (1-3) and Ag2(S-BINAP)2X2 (X = Cl, Br, I) (4-6), consisting of three pairs of enantiomers. Single-crystal X-ray diffraction verifies that the BINAP ligands bind to the silver centers via bidentate phosphorus chelation, establishing a stable chiral coordination environment. Upon UV irradiation, these chiral silver complexes display high photocatalytic activity for rhodamine B (RhB) degradation and reveal distinct structure-activity relationships. The degradation efficiency follows a strict halide anion sequence of I- > Br- > Cl-, with the R-configured complexes consistently outperforming their S-configured isomers. Complex 3 (Ag2(R-BINAP)2I2) and complex 2 (Ag2(R-BINAP)2Br2) exhibited the most impressive catalytic performance. This enhanced activity is driven by the synergistic effect of the 2D network directed by the R-configuration and the optimized coordination sphere induced by the larger I- and Br- anions. As a result, they achieve remarkable RhB degradation rates of 97.6% and 93.3% within 120 minutes, respectively, reaching complete removal after extended illumination. Finally, the specific degradation pathways were systematically identified using reactive species trapping experiments and electron paramagnetic resonance (EPR) spectroscopy. This research establishes a practical framework and solid theoretical basis for designing highly efficient metal-organic photocatalysts via the synergistic tuning of chiral ligands and anions.