Linear and Nonlinear Optical Responses of Nitrobenzofurazan-Sulfide Derivatives: DFT-QTAIM Investigation on Twisted Intramolecular Charge Transfer

Abstract

In this study, we report on the green fluorescence exhibited by nitrobenzofurazan-sulfide derivatives (NBD-S i , i = 1–4). The optical responses of these studied compounds in a polar methanol solvent were simulated by the use of time-dependent density functional theory (TD-DFT) employing the Becke-3-Parameter-Lee–Yang–Parr (B3LYP) functional along with the 6-31G­(d,p) basis set. The computed energy and oscillator strength (f) results complement the experimental results. The band gap was calculated as the difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Additionally, the density of states (DOS) was computed, providing a comprehensive understanding of the fundamental properties of these materials and further corroborating the experimental data. When the experimental data derived from ultraviolet/visible (UV/visible) and fluorescence spectroscopic techniques and those from simulated spectra are analyzed, the extracted values match up adequately. In addition, the NBD-sulfide compounds exhibit a large Stokes shift up to 85 nm in a polar methanol solvent. They are hypothesized to represent a novel paradigm of excited-state intramolecular charge transfer (ICT). To understand the intrinsic optical properties of NBD-S i materials, an ICT was identified, and its direction within the molecule was evaluated using the ratio of βvect and βtotal, values extracted from the computed nonlinear optical (NLO) properties. Moreover, the reduced density gradient (RDG)-based noncovalent interactions (NCIs) were employed to characterize the strength and type of NBD-Si interactions. Furthermore, noncovalent interactions were identified and categorized using the Quantum Theory of Atoms in Molecules (QTAIM) analysis. Ultimately, the combination of Hirshfeld surface analysis and DFT calculations was utilized to enhance the characterization and rationalization of these NCIs.

DFT-Computational Modeling and TiberCAD Frameworks for Photovoltaic Performance Investigation of Copper-Based 2D Hybrid Perovskite Solar Absorbers

“…Using Bader’s quantum theory of atoms in molecules (QTAIM), the characteristics of the intramolecular bonds present in (C 6 H 10 N 2 )­[CuCl 4 ] have been examined, along with the topological parameters within the selected BCPs. − The QTAIM-NCI graphs and the RDG isosurface are provided in Figure . The calculated values of ρ­( r ), ∇ 2 ρ­( r ), G ( r ), V ( r ), ε­( r ) parameters, and the E int energies are compiled in Table .…”

Synthesis, characterization, crystal structure, and fabrication of photosensitive Schottky device of a binuclear Cu(ii)-Salen complex: a DFT investigations

“…[54][55][56][57][58] Electronic plots, including Density of States (DOS), partial density of plots (PDOS), and Frontier Molecular Orbitals (FMO), were calculated using TD-DFT theory. 59,60 Multiwfn package 61 generated LOL and ELF. QTAIM topological analyses revealed that a series of electrostatic interactions stabilize the complex.…”

A theoretical and electrochemical impedance spectroscopy study of the adsorption and sensing of selected metal ions by 4-morpholino-7-nitrobenzofuran

“…In addition, various global reactivity parameters were determined based on the frontier molecular orbitals (FMOs). The HOMO and LUMO energy levels, the electronic gap energy (Eg), chemical potential (μ), global hardness (η), and global softness (σ) are determined and expressed through the subsequent formulas [ [48] , [49] , [50] ]: …”