Synergistic impact of organic and inorganic features in carborane hybrids for nonlinear optics and solvent-tunable properties

Abstract

Carborane-based systems, renowned for their distinctive electronic structure, have recently attracted significant attention in the design of organic–inorganic hybrid materials. This study employs a quantum chemical approach to investigate the nonlinear optical (NLO) properties of novel V-shaped hybrid systems, especially derivatives of 1,2-diaryl-o-carborane as CB-1 to CB-6. Systematic donor group substitutions led to increased polarization and charge transfer. CB-6 displayed the highest isotropic and anisotropic polarizabilities (107.1 × 10⁻²⁴ esu and 34.05 × 10⁻²⁴ esu) and the highest second hyperpolarizability (334.7 × 10⁻³⁶ esu), supported by TD-DFT simulations with the lowest transition energy of 3.928 eV. Analysis through unit sphere representation for CB-1 and CB-6 highlights the comparative dipole induced by replacing strong donor groups. Solvation studies for selected systems (CB-1, CB-4, and CB-6) reveal 〈γ〉 values ∼2–3 higher in implicit solvents compared to the gas phase, with explicit solvent results aligning closely. The results were more reliable in the explicit medium, where the 〈γ〉 for CB-6 was 374.7 × 10⁻³⁶ esu, demonstrating consistency and correlation with the gas phase. To confirm its practical relevance, dynamic hyperpolarizability was evaluated over a broad frequency range (1947–510 nm) for CB-6. Furthermore, the charge transfer and reactivity of these systems were studied using frontier molecular orbitals (FMOs), and electrostatic potential maps were obtained, confirming efficient intramolecular charge transfer (ICT) from the donor groups toward the acceptor central borane cage. The excited-state charge transfer properties were studied based on hole–electron analysis, with higher reported values for the D-index ranging from 0.575 Å to 8.424 Å, indicating clear charge separation in these hybrid systems. All hybrids exhibited superior absorption compared to CB-1, with CB-6 peaking at 245 nm. Our findings pave the way for carborane-based hybrids to emerge as game-changers in the ever-evolving realm of laser technology.