Size effects in large cyclo[26]carbon: a theoretical study.

Area of Science:

• Materials Science
• Theoretical Chemistry
• Nanotechnology

Background:

• Cyclo[n]carbons are novel carbon allotropes with size-dependent properties.
• Cyclo[26]carbon, an even-numbered ring (n>20), is underexplored.
• Understanding its electronic and structural characteristics is crucial for potential applications.

Purpose of the Study:

• To systematically investigate the bonding, electron delocalization, vibrational modes, and aromaticity of cyclo[26]carbon.
• To explore its stability, electronic excitations, and nonlinear optical properties.
• To provide a theoretical foundation for cyclo[26]carbon and its derivatives.

Main Methods:

• Density Functional Theory (DFT) calculations for electronic structure and properties.
• Ab initio molecular dynamics (AIMD) for stability analysis.
• Analysis of bond length alternation (BLA), electrostatic potential (ESP), and average local ionization energy (ALIE).

Main Results:

• Pronounced BLA observed, with shorter C-C bonds showing stronger π interactions and electron delocalization.
• Cyclo[26]carbon exhibits dual aromaticity with weak overall aromatic strength.
• Electrophilic properties identified on shorter C-C bonds; molecule shows stability under vacuum at low to moderate temperatures.
• Calculated mean second-order hyperpolarizability is 4.5-5.0 times higher than that of cyclo[18]carbon.

Conclusions:

• Cyclo[26]carbon possesses unique electronic and structural features, including dual aromaticity and electrophilicity.
• The molecule demonstrates promising nonlinear optical properties, exceeding those of cyclo[18]carbon.
• This study enhances the theoretical understanding of cyclo[26]carbon, paving the way for future research and material design.