Polarization and Dipole Moment Effects on Sigma‐Hole Potential in Tin(IV)‐Porphyrins

TL;DR

This paper explores how molecular polarization and dipole moments affect halogen bonding in tin(IV)-porphyrin complexes.

Contribution

The study reveals that axial fluorination has a negligible effect on sigma-hole potential due to orthogonal molecular orientation.

Findings

Increased fluorine substitution reduces dipole moments and polarizability of tin in metalloporphyrins.

Axial fluorination does not significantly impact sigma-hole potential at iodine atoms.

Orthogonal orientation suppresses resonance interactions between porphyrin core and phenyl rings.

Abstract

This study investigates how electron‐withdrawing substitution, molecular polarization, and dipole moment influence the σ‐hole potential in six‐coordinate metalloporphyrins. To evaluate halogen bonding tendencies, we synthesized a series of five Sn(IV)‐5,10,15,20‐meso‐tetrakis(4‐iodophenyl)porphyrin complexes with various fluorinated phenolate axial ligands. Single‐crystal X‐ray diffraction analysis revealed distinct halogen‐bonded supramolecular motifs, which vary depending on the degree of fluorination at the axial ligands. Our findings highlight the critical role of ligand‐induced polarization and dipole moment variations in modulating the σ‐hole characteristics of the equatorial iodine atoms. Computational modelling showed that increased fluorine substitution reduces both the atomic dipole moments of fluorine and the polarizability of the central tin ion. However, despite these changes, the axial fluorination has a negligible effect on the σ‐hole potential at the iodine atoms. This limited influence is attributed to the orthogonal orientation between the porphyrin core and the peripheral phenyl rings, which suppresses resonance interactions. Overall, this work emphasizes the importance of understanding electronic effects at the molecular level, particularly in the design and formation of halogen‐bonded supramolecular architectures.

Through this work with experimental and computational studies we have systematically investigated the role of interplay of electronic effects such as polarization, dipole moment and resonance on the sigma‐hole potential in macrocyclic system like, metalloporphyrin system. The behavior of the sigma‐hole potential of equatorial iodine atom of metalloporphyrin has been studied upon changing substituted ligands at axial position in metalloporphyrin.

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