Resonance-assisted intramolecular triel bonds.

Area of Science:

• Computational Chemistry
• Inorganic Chemistry

Background:

• Intramolecular triel bonds (Tr⋯S) are crucial in various chemical systems.
• Understanding factors influencing triel bond strength is essential for predicting molecular properties.

Purpose of the Study:

• To investigate the role of resonance in strengthening intramolecular triel bonds.
• To analyze the impact of substituents (R = NO2, CH3) on triel bond characteristics.
• To assess the aromaticity within the five-membered ring system.

Main Methods:

• Quantum chemical calculations were employed.
• Analysis of bond lengths, bond energies, and atomic charges.
• Nuclear Independent Chemical Shift (NICS) analysis was performed.

Main Results:

• Intramolecular triel bonds were found to be short (2.4-2.7 Å) with significant bond energy (12-21 kcal mol⁻¹).
• Resonance involving conjugated double bonds enhances triel bond strength by approximately 25%.
• Electron-withdrawing NO2 groups weaken the bond, while electron-donating CH3 groups strengthen it.

Conclusions:

• Resonance plays a key role in stabilizing intramolecular triel bonds.
• Substituent effects significantly modulate triel bond strength.
• The studied five-membered rings exhibit a degree of aromaticity.