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

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Abstract
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)·H2O} n (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·H2O} n (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.
Funding Information
  • Agencia Estatal de Investigación (PID2024-155748NB-I00)
  • European Regional Development Fund (PID2024-155748NB-I00)
  • Xunta de Galicia (ED481D-2025/006)
  • European Cooperation in Science and Technology (CA22131)
  • Universidade de Santiago de Compostela (2025-PU019)

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