Theoretical study of the boron-nitrogen (B-N) effects on electronic, optoelectronic, linear, and nonlinear optical properties of cyclo[2N]carbon series

This work focuses on the electronic, optoelectronic, and nonlinear optical properties of the cyclo[2N]carbon series (C₁₀, C₁₂, C₁₄, C₁₆, C₁₈, C₂₀, C₂₂, and C₂₄), and their derivative systems (C₈BN, C₁₀BN, C₁₂BN, C₁₄BN, C₁₆BN, C₁₈BN, C₂₀BN, and C₂₂BN) obtained by functionalizing each molecule of the series with the boron–nitrogen (B–N) binomial. The results were obtained from density functional theory and time-dependent density functional theory at the B3LYP-D3, CAM-B3LYP-D3, and ωB97XD/6–31 + G(d) levels of theory. The study found that the cumulative B–N effects on the molecules studied break the centrosymmetry of these molecules while, lowering the energy gap (from 3.11 eV for C₁₈ to 2.80 eV for its derivative C₁₆BN) making these molecules good materials for electronics. The C_2N molecules (2N = 4n), namely C₁₂, C₁₆, C₂₀, and C₂₄, and their derivatives C₁₀BN, C₁₄BN, C₁₈BN, and C₂₂BN, are found to have high chemical softness (s), electronegativity (η), and electrophilic index (ω), making them useful materials in optoelectronics. An impressive impact of the B–N cumulative effect on the cyclo[2N]carbon’s series is that it significantly generates the first-order hyperpolarizability values. Like C₂₄ of which β = 0.00 a.u. and its derivative C₂₂BN of which β = 8812.77 a.u., value 8 times higher than that of paranitroaniline (β = 1072.44 a.u.), which is the reference compound in nonlinear optics, rendering these molecules interesting for linear and non-linear optical applications.