A concise DFT and TD-DFT study is presented to elucidate the effect of replacing boron with aluminium in 4,4 ' disubstituted BODIPY frameworks. Structural, electronic, and photophysical descriptors including bond parameters, HOMO-LUMO energy gaps, dipole moments, Gibbs free energies, and vertical excitation energies are systematically compared. CAM-B3LYP is employed to describe reliably long-range charge-transfer excitations. ALDIPYs exhibit larger band gaps, higher dipole moments, and blue-shifted absorption, suggesting greater thermodynamic stability than BODIPYs. Frontier orbital, MEP, NBO and conceptual DFT analyses collectively rationalize the observed electronic delocalization and photophysical trends.

Sixteen donor-pi-acceptor (D-pi-A) type sensitizers, which consist of pyrene as the donor unit coupled to various spacers and acceptor units, are investigated using density functional theory (DFT) and time dependent DFT (TDDFT) techniques. The effects of substituting an ester group for carboxylic acid as acceptor on the system are investigated. The addition of ester causes the destabilization of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the sensitizers. In carboxylic acid acceptor-based sensitizers, the frontier molecular orbital (FMO) also illustrates an efficient intramolecular charge transfer (ICT) from the donor unit to the acceptor unit. Additionally, it is observed that ester acceptor-based sensitizers have higher computed open circuit voltage (Voc) values. According to the TD-DFT investigation, the acid acceptor-based sensitizers exhibit red-shifted vertical excitation. A positive solvatochromism is seen for all the sensitizers in TD-DFT calculations. The excited state dipole moment of acid acceptor-based sensitizer, calculated using Suppan's equation, is found to be more than the ester acceptor-based sensitizers. For the furan spacer based sensitizers with double bond between donor and spacer the following result is obtained- dipole moment moment in Debye (8.2: acid and 6.4: ester), HOMO-LUMO energy gap in eV (2.5: acid and 2.6: ester), electrophilicity index in eV (6.8: acid and 6.3: ester), hyperhardness in eV (1.7: acid and 1.8: ester) and absorption maxima in THF in nm (583: acid and 572: ester) in B3LYP functional.

The work highlights the key findings and properties of two tautomeric forms of the 2-nitroso-1-naphthol (NAN). The single crystal structure of NAN has been identified as an enol-nitroso form with an orthorhombic point group and P 21 21 21 space group. The presence of the keto-oxime tautomer was confirmed in the solution phase using 13C NMR in DMSO-d6 and CDCl3, with characteristic carbonyl carbon peaks at 180.9 ppm and 182.7 ppm. The intriguing photochemical behavior observed under prolonged UV irradiation and its electron acceptor potential indicated by low-lying LUMO values from DFT study and cyclic voltammetry are outlined. The compound's effectiveness in polyester dyeing, resulting in a greenish khaki shade with 2-nitroso-1-naphthol, is also mentioned. It also emphasizes NAN's efficient UV protection, as indicated by its UV protection factor (UPF) values (50+ UPF value; excellent) and their linear increase with shade percentage. Finally, NAN's promising nonlinear optical properties, specifically its first-order hyperpolarizability (beta 0; 7.421 x 10-30 esu), are highlighted as a material for nonlinear optics. It has shown a six-fold increment compared to alpha-naphthol) and improved compared to 4-chloro-(-naphthol, 4-metoxy-(-naphthol), and other CHO and OCOMe derivatives mentioned.

Thiophene fused acenaphthene derivatives based on the D-It-A framework were synthesized to study the effect of amino and amido groups on geometrical, thermal, spectral, linear, and non-linear optical properties. These molecules exhibit absorption- 300-520 nm and emission- 450-620 nm range in toluene, CHCl3, EA, THF, MeOH, and DMSO. Moreover, these molecules exhibit- 1.20-5.67 fold increased emission intensity in the toluene-paraffin and EtOH-PEG-400 system. DFT study at B3LYP/6-311++G(d,p) revealed that these molecules are electron-rich systems with a planar geometry. TD-DFT results show a reasonable agreement with the experimental absorption maxima. Thiophene fused acenaphthene derivatives are thermal stable (- 220-250 degrees C) and display relatively higher static polarizability and hyperpolarizability in comparison to p-nitroaniline.

Dye with carbazole-based donors, such as furan, thiophene, and phenyl-spacer with ethyl cyanoacrylate acceptor, was designed and synthesized to investigate the effects of donor and it-spacer on both linear and nonlinear optical (NLO) properties. This study employed density functional theory (DFT), solvent polarity maps, and time-dependent DFT. For furan, phenyl, and thiophene-based carbazole dyes, the maximum absorption and emission were seen in the range of 475-477, 429-437, and 476-484, and in the range of 552-615, 524-610, and 553-619 nm, respectively. Thiophene and phenyl spacer dye displayed the greatest red-shifted and blue-shifted absorption and emission properties, respectively. Significant viscosity sensitivity was demonstrated by all dyes in both non-polar (paraffin: toluene) and polar (PEG: methanol) mediums. Furthermore, above 350 degrees C, the title dyes demonstrated good thermal stability. Furthermore, the theoretical research showed that dyes with thiophene-spacer had better CT (as measured by FMO, MEP, BLA, BOA, and QC calculations), which results in superior linear and NLO properties in solvent phases.

Trans form of tryptanthrin exhibits greater stability than the cis form of quinozolinedione, supported by its smaller energy gap, longer vertical excitation, and higher first-order hyperpolarizability. The reduced highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap in tryptanthrin promotes enhanced charge transfer. Compared to tryptanthrin (3.64 eV in B3LYP, 6.20 eV in CAM-B3LYP), quinozolinedione shows slightly higher energy gaps (3.92 and 6.47 eV, respectively). Among the derivatives, nitro (NO2) substitutions significantly lower energy gaps. The 3-NO2-8-N(CH3)2 tryptanthrin (SD36) stands out with the smallest energy gap, highest dipole moment, and exceptional hyperpolarizability, alongside vertical excitation above 600 nm. In the quinozolinedione group, 7-NO2 quinozolinedione (SD79) is the most active. Other 8-N(CH3)2 tryptanthrin derivatives also show vertical excitations above 600 nm. Overall, NO2-substituted derivatives from both families display excellent density functional theory (DFT)-based properties, making them strong candidates for NLO applications. Future efforts will focus on synthesizing these derivatives and evaluating their potential in real-world photonic and optoelectronic devices.

We report the synthesis of dual-state emissive benzothiazole-functionalized bis-benzimidazole-benzothiazole molecules, focusing on their applications in viscosity sensing and in-silico nonlinear optics (NLO). These compounds exhibited weak emission in solution but strong emission in the solid state, highlighting their potential for aggregation-induced emission (AIE) properties and viscosity sensing application. Viscosity sensing studies revealed that the methyl-substituted derivative demonstrated the highest sensitivity, with a 16-fold increase in viscosity response (from 0.59 cP to 14.75 cP) in paraffin oil. At the same time, the methoxy‑substituted variant showed the lowest sensitivity (8-fold increase). The sensitivity behavior was quantitatively analyzed using the Förster-Hoffmann equation. In addition, we explored the nonlinear optical properties of these molecules through an assessment of intramolecular charge transfer (ICT) using natural bond orbital (NBO) analysis, frontier molecular orbital (FMO) analysis, and reactivity descriptors (ω, η, Ґ). Notably, the methoxy substituted compound exhibited maximum first-order hyperpolarizability (β₀) of 68.17 × 10−30 esu and second-order hyperpolarizability (γ) of 505.58 × 10−36 esu. Compared to the urea and p-nitro aniline, a maximum of 87.40 and 14.26 fold increments is achieved for the methoxy derivative. These findings underscore the significant potential of these functionalized molecules in sensing applications and nonlinear optics.

A comprehensive computational study was conducted on the nonlinear optical (NLO) properties, intramolecular charge transfer (ICT), electronic structure, electrostatic potential, Mulliken charge distribution, and frontier molecular orbital energies of thiophene‐based heterocyclic azo dyes using density functional theory (DFT). The dye D6 exhibited a red‐shift in its vertical excitation energy, in agreement with experimental data, indicating effective ICT characteristics. The incorporation of a nitro group significantly decreased the HOMO–LUMO energy gap, which contributed to enhanced polarizability (α) and both first‐order (β) and second‐order (γ) hyperpolarizabilities. All computed NLO values were within the fundamental theoretical limits, ensuring structural stability and practical applicability. Furthermore, the NLO responses evaluated at laser frequencies and EFISH (electric field‐induced second harmonic generation) frequencies showed a marked enhancement, suggesting strong frequency‐dependent optical activity. Comparative analysis revealed that the thiophene‐based azo dyes demonstrated more than a twofold increase in NLO response relative to previously reported analogues. Among them, nitro‐substituted derivatives (D4–D6) displayed superior performance across all evaluated parameters, highlighting the influence of electron‐withdrawing substituents in tuning NLO behavior. These findings position nitro‐substituted thiophene‐based azo dyes as promising materials for advanced nonlinear optical applications such as photonic switches, optical data storage, and frequency conversion technologies.

Heterocyclic disperse azo dyes was synthesized through the incorporation of molecules derived from a thiophene and 2,5-dimethoxyaniline core and characterized all with analytical techniques. All the azo dyes exhibit a broad range of light absorption, including near-UV, visible, and deep red wavelengths, with Dye D6 notably surpassing 600 nm in absorption. Dyes D1-D9 were utilized on nylon and polyester materials, showing good saturation confirmed on fabrics by the color coordinate measurements and a high percent of dye exhaustion. Dye D6 demonstrates higher thermal stability at temperature 370 °C, while all dyes displayed remarkable photostability. Each of the dyes demonstrates significant fastness properties, encompassing light, wash, rub, and sublimation fastness for both fabric types. Additionally, UV protection studies demonstrated that all the dyes effectively block harmful UV-A and UV-B radiation, with nylon fabrics showing outstanding UPF results compared to polyester. All the dyes exhibited antibacterial activity against S. aureus (Gram-positive) and E. coli (Gram-negative), with D6 showing particularly strong efficacy against E. coli (MIC = 62.5 ppm). Overall, these heterocyclic azo dyes possess biological significance, enhancing their multifunctional properties.

The current research involves a computational examination of the anthrapyrazoles, anthraisoxazoles, and proposed anthraisothiazoles using density functional theory (DFT). Through this analysis, it was found that the heterocyclic cores exhibit significant chemical reactivity, serving as electron donor spots and active sites for potential electrophilic attacks. Various quantum chemical parameters, such as chemical potential, hardness, softness, electronegativity, and electrophilicity index, were determined to better understand the molecular behavior. The molecular structure was optimized, and its electronic nature was quantified using quantitative molecular electrostatic potential (QMEP) plots. Nonlinear optical (NLO) properties, including polarizability, first-order hyperpolarizability, and second-order hyperpolarizability of proposed anthraisothiazoles (P15-P19), lie in between the anthrapyrazoles and anthraisoxazoles. In a molecular docking study, the inhibitory potential against topoisomerase II alpha bound to DNA (PDB ID: 6ZY6) binding proteins was observed that the oxygen and nitrogen atom combinational anthraisoxazoles (P6-P14) played a crucial role in the binding interactions.

Dyes were synthesized via Knoevenagel condensation using various aldehydes of julolidine, n-hexylcarbazole, n-hexylphenothiazine, triphenylamine, and 7-N, N-diethylaminocoumarin named as MB1, MB2, MB3, MB4, and MB5. The dyes were characterized using FT-IR, 1H NMR, 13C NMR, and HRMS, which provided detailed structural information. Significant absorption, emission, and Stokes shift properties were observed through spectroscopic analysis. Notably, MB2, MB3, and MB4 exhibited solid-state and aggregation-induced emission (AIE) properties. MB1, MB3, and MB4 showed high viscosity sensitivity in polar solvents. Dyes containing nitrogen donors (MB1, MB2, and MB3) demonstrated acidochromism, responding to trifluoroacetic acid, while MB4 and MB5 remained neutral. Solvatochromic analysis indicated enhanced hyperpolarizabilities (αCT, βCT and γCT) in polar solvents, with MB1 exhibiting the highest linear and second-order hyperpolarizability, making it ideal for non-linear optical (NLO) applications. MB5 also showed a notable solvent polarity response. Computational studies using B3LYP and CAM-B3LYP functionals confirmed increased hyperpolarizabilities in polar environments. All dyes displayed solvatochromism and promising NLO properties, with MB3 and MB5 showing lower band gaps and higher dipole moments in polar solvents, indicating their potential for photonics, bioimaging, and sensors.

Acenaphthenone-derived methine derivatives are synthesized by oxidation of acenaphthene to acenaphthenone (I) followed by Knoevenagel condensation using malononitrile, benzothiazole acetonitrile, benzimidazole acetonitrile. The resulting molecules- I-1, I-2, and I-3 show absorption- 300-600 nm and emission- 360-500 nm range, respectively, in THF, MeOH, DMF, and DMSO. I-1, I-2, and I-3 also displayed solid-state emission at 515 nm, 517 nm, and 574 nm, respectively. Further, these derivatives were found sensitive toward viscous, acidic, and basic environments. I-1 and I-2 displayed aggregation-induced emission in THF:distilled water system. They show thermal stability- 250 degrees C. DFT studies revealed that these molecules are an electron-rich system with a planar geometry. The electron density is evenly distributed throughout the skeleton in both HOMO and LUMO. TD-B3LYP/6-311++G(d,p), TD-CAM-B3LYP/6-311++G(d,p), and experimental absorption maxima showed the same trend in THF. Vertical excitation is mainly assigned to HOMO -> LUMO transition with % orbital contribution- 94-98 % and oscillator strength in the 0.09-0.93 range. These molecules can show linear properties exclusively.

Four thiophene-based donor-pi-azo-acceptor dyes were designed and synthesized with benzoic and salicylic acids anchoring groups for dye-sensitized solar cells (DSSC). The results show that the orientation of the secondary donor significantly affects molecular planarity, which in turn affects the characteristics of charge transfer (CT) inside the backbones of thiophene-azo-benzoic or salicylic acids. These results have been confirmed by the time-dependent density functional theory (TD-DFT) study, which shows that the dyes' vertical absorption maximum increases as the secondary donors' providing strength increases. Photovoltaic parameters indicate an increase in DSSC performance from PG9 to PG12. Moreover, dye@TiO2 cluster investigations suggest that these dyes could combine with TiO2 to cause dye@TiO2 cluster absorbance to shift red. The synthesis of PG9 to PG12 confirms theoretical predictions, with initial absorption in dimethylformamide (DMF) and energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) following a pattern like that seen in density functional theory (DFT) investigations. According to TGA data, PG9 to PG12 have exceptional thermal stability, making them suitable for DSSCs. The built-in DSSCs had varying efficiencies; PG10 had the highest efficiency at 4.73 +/- 0.1, and PG12 had the lowest at 1.72 +/- 0.1. According to the theoretical and practical DSSC results, secondary donors are essential in defining molecular properties and device performance.

The robust nature of perylene diimide (PDI) toward thermal, optical, and redox properties makes it an ideal candidate for many applications including optoelectronic, chemo-bio sensing, liquid crystal, and photo- catalysis. The current study aimed to design and synthesize a novel PDI scaffold bearing apremilast intermediate amine. The UV-visible (vis) absorption spectroscopy investigation revealed its characteristic three absorption peaks at 523, 488, and 456 nm. In contrast, fluorescence spectroscopy investigation illustrated two prominent emission peaks at 527 and 564 nm, and one small peak at 614 nm. The computed E LUMO and E HOMO values of -4.039 and -6.031 eV align well with the experimental values of -3.156 and -5.390 eV determined through electrochemical and optical measurements. The water-dependent UV-vis absorption analysis revealed that the PDI (10 mu M) showed a minor change in absorption intensity as the water percentage in THF increased from 10% to 60%. As the proportion of water grows from 70% to 90%, the absorption intensity decreases and shifts to the red. The PDI emission spectroscopy investigation revealed that increasing the water percentage from 20% to 90% gradually reduced the emission intensity and demonstrated an aggregation-caused quenching (ACQ) effect. With increasing water percentage in THF, the PDI transformed from its monomer state to the J-aggregates of crystalline fractured angular grain morphology, which exhibit intense yellow emission.

Designing and synthesized dyes with diethylamino coumarin as fixed and diethylamino coumarin, julolidine, and pyrene-based donors with dicynovinylene acceptor, the effects of donor and pi-linker on linear and non-linear optical (NLO) properties were examined. Density functional theory (DFT) and time-dependent DFT were used for this investigation. Maximum absorption and emission were seen in the range of 500-547, 525-569, and 420-429 nm, as well as 576-653, 592-653, and 492-536 nm for diethylamino coumarin, julolidine, and pyrene-based dyes. A julolidine-based donor dye showed red-shifted absorption and emission properties compared to diethylamino and pyrene-based coumarin. All dyes in polar demonstrated significant viscosity sensitivity (PEG: methanol) solutions. Furthermore, above 250 degrees C, the title dyes demonstrated good thermal stability. Additionally, the theoretical analysis suggested that dyes based on julolidine have superior linear and NLO properties in solvent phases and better CT (as determined by FMO, MEP, BLA, and BOA calculations).

In this study, four novel 6-substituted benzothiazole-linked bis-benzimidazoles (3a-d) were synthesized and characterized using 1H NMR, 13C NMR, FTIR, and HRMS techniques. The physicochemical properties of these compounds were examined, and experimental data validated the computed values. The absorption and emission properties were also investigated using carbonate, acetate, and phosphate buffers at various pH levels. In-silico studies revealed that methoxy derivative (3c) possesses the highest docking affinity for tyrosine kinase. Pharmacokinetic studies showed that, like the marketed drug erlotinib, none of the compounds act as substrates for p-glycoprotein, and all except compound 3d do not inhibit CYP-2C9. The gastrointestinal absorption profiles, including blood-brain barrier permeability, were also studied. Drug-likeness assessments based on Lipinski's rule of five and Ghose criteria suggested favourable properties, though some compounds showed deviations in molecular weight and logP values. In-vitro anticancer study via MTT assay includes its potency against MCF-7 and MDA-MB-231 breast cancer cell lines, including 3c as the most potent against MCF-7 cells, which coincides with the In-silico study.

In this study, we report the successful growth of single crystals of 3-hydroxynaphthalene-2-carboxanilides (NAS) with a monoclinic structure in the P21/c space group and space group number of 14 for the first time. We have developed a yield and time-effective modified synthetic procedure using a synthetic reactor by replacing the traditional microwave method. Additionally, acylated derivatives of NAS, including novel acryloyl derivative (NAS AC), are synthesized with a modified procedure, replacing pyridine with triethylamine.We investigate the structural, photophysical, and quantum chemical properties of N-(4-acetylphenyl)-2-oxo-2H-chromene-3-carboxamide (NAS) and its acylated derivatives (NAS AC, NAS ACT, NAS BZ). Photophysical studies reveal significant Stokes shifts observed in different solvents, including time-enhanced fluorescence in DMSO, attributed to solvent relaxation processes. Natural bond orbital (NBO) analysis, molecular electrostatic potential (MEP) maps, and frontier molecular orbital (FMO) provide insights into electronic interactions and asymmetric charge distribution. Low-lying LUMO values of these compounds (-2.31 eV to-1.95 eV) support candidature for the electron acceptor applications. Nonlinear optical properties were thoroughly investigated, with NAS displaying the highest static first-order hyperpolarizability (17.89 x 10-30 esu) and NAS BZ exhibiting the highest second- order hyperpolarizability (113.09 x 10-36 esu), indicating significant nonlinear optical responses. Thermal stability (TGA and DTA) highlights the significant range of temperatures for the NLO applications.

Unsymmetrical xanthene dyes are a hybrid structure of two symmetrical xanthene dyes. Therefore, are the structural, spectral, electronic, linear, and non-linear optical (NLO) properties of unsymmetrical xanthene dyes comparable to, distinct from, or better than those of their parent symmetrical xanthene dyes? This study provides a detailed analysis of unsymmetrical and symmetrical xanthene dyes using the Density Functional Theory (DFT) and Time-dependent (TD)-DFT methods. DFT study demonstrated that symmetrical xanthene dyes are energetically more stable and exhibit BLA values lower than unsymmetrical xanthene dyes. Moreover, symmetrical xanthene dyes show destabilized energy of HOMO, LUMO, and lower LUMO-HOMO energy gap than unsymmetrical xanthene dyes. Vertical excitation calculated from the TD-DFT method shows reasonable agreement with experimental absorption. However, unsymmetrical xanthene dyes with higher dipole moments and hyperpolarizability show superior NLO properties.

The core E, obtained on replacing one -NH- with -S- demonstrates the lowest energy gap among observed cores, with values of 3.26 eV in B3LYP and 5.63 eV in CAM-B3LYP. This small energy gap between the HOMO and LUMO facilitates enhanced charge transfer. Among cores A, B, and C, N(CH3)2-substituted thioepindolidiones (core B) shows the highest vertical excitation, while the N(CH3)2-substituted thiazaepindolidione (core E) ranks highest among the cores D, E and F. Core B exhibits the greatest linear polarizability (alpha), while core E has the highest first-order hyperpolarizability, making them the suitable candidates for nonlinear optical (NLO) applications. Cores A, B, and C, with their symmetric structures, have zero dipole moment, effectively cancelling out each other's dipoles. Oxoepindolidione shows excellent stability, demonstrated by higher ionization potential (IP), hardness (eta), hyperharness (Gamma), and energy gap. NO2 substitution generally provides the best performance across most density functional theory (DFT) descriptors.

This study investigates the optical properties and first-order hyperpolarizability of Violerythrin (SV) and quinoid carotenoid isorenieratene-3,3′-dione (IRD) structures, prominent natural nonlinear materials, using DFT and TD-DFT methods. Employing B3LYP and CAM-B3LYP functionals with a 6–311++G (d, p) basis set, calculations are conducted in both gas and acetone environments. Results show IRD's preference due to its closer alignment with experimental values and its red-shifted absorption compared to SV. In acetone, reductions in HOMO-LUMO energy gaps and increases in electrophilicity index suggest potential electron transfer with low band gap molecules. Higher dipole moments in acetone indicate increased charge transfer due to solvation. IRD exhibits superior nonlinear optical characteristics compared to SV in both acetone and gas phases, highlighting avenues for further experimental exploration.