Molecular knot with nine crossings: Structure and electronic properties from density functional theory computation

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Materials Science

Background:

• Complex molecular knots present unique electronic and structural properties.
• The ability of molecular cages to capture anions is of significant interest for chemical applications.
• Understanding molecular stability and reactivity is crucial for designing new materials.

Purpose of the Study:

• To investigate the electronic structure and properties of a nine-crossing composite knot molecule (9_7^3 link, complex-1).
• To evaluate the molecule's capability to capture anions, specifically chlorine ions.
• To analyze the stability, chemical reactivity, and semiconductor behavior of the complex and its chlorine adduct.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to study the electronic structure.
• Theoretical methods including chemical hardness and chemical potential were used to assess stability and reactivity.
• Infrared (IR) spectra simulations, Quantum Theory of Atoms in Molecules (QTAIM), Natural Bonding Orbital (NBO) analysis, and Hirshfeld charge analysis were performed.

Main Results:

• The electronic structure and frontier molecular orbitals of complex-1 were analyzed.
• The molecule demonstrated a characteristic IR signal between 1000-1600 cm⁻¹.
• The study confirmed complex-1's ability to capture a chlorine ion, with detailed analysis of bonding and electron transfer.

Conclusions:

• Complex-1 exhibits semiconductor behavior, as do its chlorine complexes.
• The theoretical analysis provides insights into the molecular properties and anion-binding capabilities of complex knot molecules.
• These findings contribute to the understanding of complex molecular systems for potential applications in materials science.