Coordination Versatility of Thiazolidinone-Based Ligands toward Ag + : Structural and Photophysical Insights

The reaction of the thiazolidinone-based ligands HAm4DHotaz, Am4Motaz, and Am4Eotaz with AgClO4 in a 1: 1 molar ratio yields complexes of varying nuclearities depending on the Nthiazolidinone R-substituent. The unsubstituted HAm4DHotaz (R = H) affords the coordination polymer Ag (HAm4DHotaz) (ClO4) n (1) whereas Am4Motaz (R = Me) and Am4Eotaz (R = Et) lead to the discrete mononuclear complexes Ag (Am4Motaz) 2 (ClO4) (2) and Ag (Am4Eotaz) 2 (ClO4) ] (3), respectively, as the main products. From the corresponding mother liquors, small amounts of the coordination polymers Ag (Am4Motaz) (ClO4) n (4) and Ag2 (Am4Eotaz) 2 (H2O) (ClO4) (ClO4) ·H2On (5·H2O) were also obtained. In addition, the reaction of AgNO3 with Am4Eotaz in 1: 1 or 0. 5: 1 molar ratio leads to Ag (Am4Motaz) 2 (NO3) ·H2O (6·H2O), while the mother liquors of the 0. 5: 1 experiment produced small amounts of the coordination polymer Ag2 (Am4Motaz) 3 (NO3) 2·H2On (7·H2O). X-ray diffraction analyses of all the complexes highlight the remarkable coordination versatility of these ligands, revealing five distinct binding modes, including the unprecedented tridentate μ2-κ2NN′: κ1N″ and μ2-κ1N: κ2N′S bridging motifs, as well as the two rarely reported modes μ2-κ2NN′: κ1S and μ2-κ3NN′S: κ1. In addition, photophysical studies also highlight a pronounced dependence of the emission properties on the Nthiazolidinone R-substituent. Notably, although Ag+ coordination quenches ligand-centered emission in all cases, Ag (Am4Eotaz) 2 (ClO4) ] (3) stands out as the only complex that remains emissive.