Unexpected chalcogen bonds in tetravalent sulfur compounds

Area of Science:

• Chemistry
• Crystallography
• Computational Chemistry

Background:

• Chalcogen bonds are non-covalent interactions crucial in molecular recognition and crystal engineering.
• The strength of chalcogen bonds typically increases with decreasing electronegativity of the chalcogen atom (S < Se < Te) and with electron-withdrawing substituents.
• Understanding factors governing chalcogen bond directionality and strength is essential for predicting and designing molecular assemblies.

Purpose of the Study:

• To investigate the role of polarizability in chalcogen bonding interactions.
• To determine if polarizability can override the effect of electron-withdrawing groups in directing chalcogen bond formation.
• To provide experimental and theoretical evidence for the factors influencing chalcogen bond acceptor preferences.

Main Methods:

• Utilized Cambridge Structural Database (CSD) analysis for experimental data.
• Performed theoretical calculations using the RI-MP2/def2-TZVP level of theory.
• Employed Natural Bond Orbital (NBO) and Bader's Atoms-in-Molecules (AIM) theory for detailed electronic structure analysis.

Main Results:

• Demonstrated that polarizability plays a significant role in chalcogen bonding.
• Observed instances where the chalcogen bond acceptor preferentially interacts with the more polarizable region of the chalcogen donor, rather than the electron-withdrawing substituent.
• Computational analyses confirmed these preferences, highlighting the interplay between polarizability and electronic effects.

Conclusions:

• Polarizability is a critical factor in determining the geometry and strength of chalcogen bonds.
• The distribution of polarizability within the chalcogen donor can influence the regioselectivity of chalcogen bond formation.
• This finding offers new insights into the nuanced nature of chalcogen bonding and its implications in various chemical systems.