Polarization Upends Convention: Halogen Bonding Propensities of Main Group Halides

Area of Science:

• * Inorganic Chemistry
• * Computational Chemistry
• * Materials Science

Background:

• * Halogen bonding, a non-covalent interaction, is crucial in supramolecular chemistry and materials science.
• * Previous research primarily focused on halogen bonding involving period 2 elements.
• * Systematic investigation of sigma hole bonding in heavier main group elements is lacking.

Purpose of the Study:

• * To systematically analyze the propensity for sigma hole bonding in main group compounds (H to At) using iodine as the reference halogen.
• * To probe the viability of halogen bonding in heavy main group R_M-I compounds.
• * To identify novel interactions and understand factors influencing sigma hole characteristics.

Main Methods:

• * Computational analysis of electronic structure and bonding in iodine-substituted main group compounds.
• * Examination of complexes formed with sigma-donating bases (ammonia, trimethylamine).
• * Calculation of electrostatic potentials to characterize sigma hole properties.

Main Results:

• * Demonstrated anomalous trends in halogen bonding propensities for F_M-I systems as M increases in atomic number.
• * Identified polarization-induced escalation of electrostatic potential on iodine in certain cases.
• * Found cases where the sigma hole potential on iodine is weaker than on central or geminal atoms.
• * Discovered previously unexplored strong halogen bonding in fluoroiodides of heavy group 13 elements.

Conclusions:

• * Halogen bonding capabilities of heavy main group elements exhibit complex, non-monotonic behavior.
• * Electrostatic potential modulation by the central atom significantly impacts halogen bond strength.
• * Heavy group 13 fluoroiodides represent a promising new class of halogen bonding agents.