Harnessing the Crystal Structures of Perfluoroiodoarenes (PFIArs) for the Design of Halogen-Bond Donor Catalysts

This study investigates the use of perfluoroiodoarenes (PFIArs) as halogen-bond (X-bond) donors in anion-binding catalysis, focusing on the design and effectiveness of two-point X-bond donor catalysts. A comprehensive analysis was carried out, including crystal structure determination, density functional theory (DFT) calculations, and binding constant (K) measurements, to assess catalyst performance. While structural parameters, such as dihedral angles and C–I bond lengths, demonstrated strong correlations between the crystal structures and computed models, their relationship with K values and reaction yields was weaker. Correlation analysis demonstrated that the Gibbs free energy (ΔG) values of the chloride (Cl–) complexes were more strongly correlated with the K values (r = +0.74) and moderately correlated with the yields (r = +0.52), compared to atomic distances. The two-point X-bond design, exemplified by catalysts such as 1a-syn, exhibited superior Cl–-binding ability, with a K value of 9.3 × 103 M–1, a 40-fold increase compared to C6F5I. The findings highlight that, while structural information can be deduced from both crystal and computational data, precise conformational control, as indicated by ΔG values, is a more reliable predictor of catalytic performance. These results provide important quantitative insights for the development of efficient X-bond-driven organocatalysts, underscoring the critical role of ΔG values in designing high-performance catalysts.