Hybrid Tuning in NHC Ligands: Synergistic Effects of BIAN π -Conjugation and Aryl σ -Modulation in Gold(I) Complexes
In this study, we explore extended design of metal–NHC complexes that relies on dual strategies for tuning ligand properties: (i) electronic modulation through ?-extended frameworks such as bis(imino)acenaphthene (BIAN), and (ii) systematic aryl substitution to influence ?-donor strength and steric environment. We report the first integrated exploration of these two strategies on a unified ligand platform. A series of Au(I)/BIAN–NHCX complexes were synthesized by introducing electron-withdrawing substituents (X = F, Cl, Br, CF?) at the ortho-, meta-, and para-positions of the N-aryl groups. This hybrid tuning approach allowed us to probe the synergistic and antagonistic effects arising from ?–? interplay across multiple dimensions. Each complex was thoroughly characterized with respect to synthetic yield, structural features (including X-ray structure and dynamics in solution), photophysical properties (UV-Vis and luminescence), catalytic performance in hydroamination of phenylacetylene, and cytotoxicity in HEK293T cells. Structure–property correlations revealed distinct cooperative and counteractive regimes depending on the substituent type and position. These findings demonstrate that combining orthogonal electronic control elements enables a more predictive and fine-grained design of NHC-based metal complexes, with future implications for catalysis, materials science, and biomedical applications.
Reference: Chem. Eur. J., 2025, e202501647.
