This study aims at the structural and spectral analysis of 2-amino-4, 6-dimethylpyrimidine, 2 aminobenzoic acid, along with the substitution of hydroxyl (-OH), amino (-NH2), methyl (-CH3) and methoxy (-OCH3) groups. The calculations were done using DFT with B3LYP/6-311G (d, p) level of theory. The natural bond orbital analysis was carried out to identify the delocalisation of charges that is taking place due to intramolecular interactions. The electronic properties, such as molecular electrostatic potential and Frontier molecular orbital analysis, were executed to identify the reactive site and charge transfer within the molecule. The potential energy scan was performed to identify the most stable conformer. The topological analysis, namely interaction region indicator, reduced density gradient, electron localisation function and localised orbital locator were carried out to determine the intermolecular hydrogen bonding. ELF and LOL have shown an illustrative proof of intra - and intermolecular charge transfer interaction; this raises the molecule's NLO activity. To show the non-linear optical active nature of the material, hyperpolarisability calculations were carried out. The second order hyperpolarisability of 2-amino-4,6 dimethylpyrimidine - 2,6-diamino benzoic acid was estimated to be 1087.127 e.s.u, proving the potential NLO application.

The main objective of the work is to analyze the structural, vibrational, and nonlinear optical properties of three chalcones, including 2,3-dibromo-3-(4-chlorophenyl)-1-(2-hydroxyphenyl)propan-1-one utilizing DFT calculation. Geometry optimization was performed at B3LYP/6-311G(d,p) and B3LYP/6-311++G(d,p) levels. Vibrational distributions were analyzed using VEDA software. NBO analysis revealed intramolecular interactions. TD-DFT UV calculation provide insights into molecular absorption and electronic transitions. Frontier molecular orbitals were analyzed to reveal charge transfer. The PES analysis was used to determine the most stable conformer. Chalcone undergoes local excitation and charge transfer excitation which was forecasted by hole-electron analysis. NLO calculations were used to determine the hyperpolarizability of chalcones.

The novel organic single crystal 4-Bromoaniline hydrogen malonate (4-BRMAL) was grown using methanol with slow evaporation method. The crystal was analysed using UV-Vis, FT-IR, FT-Raman spectra and single-crystal diffraction. Theoretical calculations were performed using density functional theory (DFT) with the B3LYP/ 6-31G(d, p) basis set. These studies were aimed to investigate the molecular structure and vibrational frequencies of 4-BRMAL. Natural bond orbital (NBO) and natural charge analysis (NCA) have provided a detailed evaluation of the compound's stability by confirming the presence of both intra and intermolecular interactions. UV-visible spectroscopy revealed electronic transitions with a lower cut-off wavelength of 263 nm, while fluorescence spectroscopy demonstrated yellow and an orange emission spectra at 591 nm, indicating its potential for NLO applications. TG/DTA showed thermal stability up to 149.80 degrees C with significant weight loss of 4-BRMAL. Hirshfeld surface analysis and two-dimensional fingerprint plots identified key atomic interactions in the crystal packing. The frontier molecular analysis showed a 4.78 eV energy gap indicating significant charge transfer characteristics. Electron-hole distribution, interatomic interaction (IRI) and atoms in molecule (AIM) analysis revealed strong hydrogen bonding and electron delocalization confirming the compound's favorable electronic structure. Density of states (DOS) analysis further highlighted the potential for non-linear optical (NLO) applications. Theoretical NLO calculations indicated a second-order hyperpolarizability of 561.33 x 10-30 e.s.u, demonstrating 4-BRMAL's suitability for optoelectronic device applications. Z-scan analysis confirmed that 4-BRMAL is a promising potential candidate for NLO activity with a third-order hyperpolarizability of 6.05 x 10-6 e.s.u. These analyses suggest that the title compound 4-BRMAL is a promising candidate for optoelectronics and NLO devices.

A novel organic single crystal 2,4,6-triaminopyrimidine-1,3-diium cyanoacetate monohydrate (TAPCM) was grown effectively by the slow evaporation technique and analysed using FTIR, FT-Raman and UV-Vis spectral analysis. Single crystal XRD revealed the cell parameters and confirmed that TAPCM was crystallized in the monoclinic, centrosymmetric C2/c space group. Quantum chemical computations were conducted by applying the density functional theory (DFT) with B3LYP/6-311G(d,p) and B3LYP/6-311++G(d,p) basis sets. The stability and intermolecular interactions of the TAPCM were examined using the natural bond orbital (NBO) analysis. FT-IR and FT-Raman spectral analyses confirmed the functional groups in TAPCM. The frontier molecular orbital and molecular electrostatic potential (MEP) analyses were employed to illustrate the charge distribution in the TAPCM molecule. UV-Vis spectral analysis was carried out to analyse the optical quality and related characteristics. The intermolecular hydrogen bonding interactions were investigated using topological analysis techniques such as atoms in molecules (AIM) analysis, reduced density gradient (RDG), interaction region indicator (IRI) analyses and electron localization function. Hole-electron analysis was performed to identify the nature of electronic excitations. Fluorescence studies revealed red emission from the TAPCM single crystal at 671 nm. Thermogravimetric and differential thermal analysis (TG-DTA) was utilised to determine the thermal stability of the single crystal. The surface morphology of TAPCM was determined using scanning electron microscopy (SEM). The NLO properties were investigated both experimentally and theoretically using Z-scan and DFT methods. The research findings discovered novel optical limiting behaviour and a high laser damage threshold in the TAPCM.

The slow evaporation method was employed to synthesize the organic nonlinear optical single crystal 2-amino-4,6-dimethoxypyrimidinium salicylate, which was subsequently examined by FTIR, UV-visible and FT-Raman spectroscopy. The quantum chemical calculations were performed using the density functional theory (DFT) method on the B3LYP/6-31G (d, p) basis set. The information regarding the 2DASA’s stability and intermolecular interactions has been made available by the NBO study. The occurrence of several functional groups in the 2ADSA molecule was verified via FT-IR and FT-Raman spectral analyses. Frontier molecular (FMO) and natural population (NPA) analysis was deployed to graphically depict the charge distribution of the 2ADSA molecule. Using MEP analysis, the feasible locations for the electrophilic and nucleophilic sites were identified. The Hirshfeld surface analysis was used to investigate the interaction between the molecules. The O-H…O and N-H…O intermolecular interactions within the 2ADSA molecule were investigated using the atoms in molecule (AIM), interaction region indicator (IRI), and reduced density gradient (RDG) studies. The hole-electron analysis was utilized to illustrate the charge transfer throughout the molecule. To ascertain the optical properties and bandgap energy of the 2ADSA, the UV-Vis optical spectrum was employed. Using fluorescence spectrum analysis, the emission spectra at 625 nm was beneficial for the creation of red light-emitting devices. Both theoretical and experimental analysis of the NLO activity of the 2ADSA molecule was conducted through the DFT and Z-scan methodologies. When comparing the outcomes of FMO, NLO, UV-visible, and Z-scan with those of other pyrimidinium-based compounds, the 2ADSA molecule exhibits high NLO activity.

A novel organic non-linear optical (NLO) single crystal of 2,6-diaminopyridinium p-chlorophenoxyacetate (DAPPCA) was synthesized and structurally characterized using single crystal X-ray diffraction (SCXRD) technique, UV–Vis, FTIR and FT-Raman spectra. This study presents investigation of a novel organic salt focusing on its structural, electronic, vibrational and nonlinear optical (NLO) properties through both experimental and theoretical methodologies. Density functional theory (DFT) was employed to analyse the optimized geometry and electronic structure while natural bond orbital (NBO) analysis provided insight into charge transfer interactions within the molecule. Vibrational characteristics were examined through both theoretical calculations and experimental FTIR and Raman spectroscopy to validate molecular vibration modes. The strong N27–H2…O17 intermolecular hydrogen bonding interaction further stabilizes the crystal lattice. The HOMO–LUMO shows energy gap of about 4.007 eV which highlighted the compound’s NLO property. UV–visible spectroscopy confirmed high optical transparency with 254 nm low cutoff wavelength. Fluorescence spectroscopy revealed a distinct emission band of 403, nm which shows violet emission. The thermal stability was established at 180 °C via thermogravimetric (TG) and differential thermal analysis (DTA). The molecular electrostatic potential (MEP) map was used to identify electrophilic and nucleophilic reactive regions and the nature of non-covalent interactions were explored using interaction region indicator (IRI) and independent gradient model (IGM) analyses. Z-scan experiment demonstrated the third-order NLO response of 3.91E-07 in DAPPCA confirming its suitability for optical limiting applications. The enhanced NLO activity is attributed to strong hydrogen bonding π-electron delocalization and efficient charge transfer within the crystal structure. These results show that DAPPCA as a promising material for photonic and optoelectronic device applications.

The nonlinear organic single-crystal 2-amino-4,6-dimethylpyrimidinium cyanoacetate (2AMPCA) was grown using slow evaporation method. Using single-crystal X-ray diffraction (SXRD), the grown 2AMPCA was assigned to the triclinic with centrosymmetric space group P-1. FT-IR and FT-Raman spectral analysis were used to confirm the functional groups of the 2AMPCA crystal. In order to determine the theoretical electron density boundary surface between the molecules in a grown crystal, the Hirshfeld surface analysis was performed. All theoretical computations were accomplished using density functional theory (DFT) B3LYP method with 6-311G (d, p) basis set. Natural bond orbital analysis, HOMO–LUMO and molecular electrostatic potential surface analysis were performed for determining various intermolecular interactions of the molecule. The estimation of the transmittance and the optical band gap energy of the title compound have been performed using UV–visible spectral analysis, and the energy gap was found to be 5.46 eV. The emission behaviour of 2AMPCA single crystal has been scrutinized using fluorescence spectral analysis and green colour emission is evidenced at 542 nm. Using the thermal analysis, it was determined that the stability of 2AMPCA was at 1340C. The laser damage threshold value of 2AMPCA was estimated as 4.83Gw/cm2 using Nd:YAG laser. The NLO activity of the title compound was investigated both experimentally and theoretically using Z-scan and DFT techniques.

A novel organic nonlinear optical (NLO) crystal of creatininium 4-aminobenzenesulfonate (CABS) is obtained through the slow evaporation technique and the molecular structure is detected by the single crystal X-ray diffraction method. The density functional theory (DFT) method with B3LYP/6-311G (d, p) basis set is used to optimize the structure and to determine the structural parameters. The FT-IR and FT-Raman spectral analysis is carried out to identify the functional groups present in the molecule. The molecular elucidation of CABS is done with the aid of 13C and 1H NMR spectroscopic studies. The stability of the molecule, intermolecular hydrogen bonding and hyperconjugative interaction of CABS are determined by making use of natural bond orbital (NBO) analysis. Molecular electrostatic potential (MEP) is utilized for discerning the reactive sites for electrophilic and nucleophilic attacks. Topological analyses are performed to investigate the intra and intermolecular interactions especially the characteristics of N–H...O hydrogen bonds. To discern the contribution of intermolecular interactions, Hirshfield surface analysis and fingerprint plot are carried out. The UV–visible analysis reveals that the synthesized CABS crystal exhibits good optical activity and the minimum Urbach energy indicates that the crystal possesses well-defined crystalline quality. The nonlinear optical (NLO) parameters are theoretically evaluated by the same DFT theory. The capability of the crystal to withstand laser power is investigated using laser damage threshold (LDT) studies. The third-order nonlinear optical parameters of the CABS compound are determined by the Z-scan technique and are found to be higher than other related compounds. The obtained result shows that the CABS crystal is a good candidate for nonlinear optical applications.

In this work bis (2-amino-3-methylpyridinium) 5-sulfosalicylate monohydrate (2AM5SSA), a new organic NLO active compound was synthesized by slow evaporation technique and subsequently analyzed using X-ray crystallography, UV-Vis, FTIR and FT-Raman spectral analysis. The 2AM5SSA comes under the centrosymmetric space group P-1 of the triclinic crystal system as verified by single crystal X-ray (SXRD) diffraction. Density functional theory (DFT) with B3LYP/6-31 G (d, p) basis set was deployed to execute the quantum chemical computation. Both FTIR and FT-Raman spectral analysis, authenticate the existence of several functional groups and vibrational modes. NBO study has provided information about the stability and intermolecular interactions of the 2AM5SSA. The charge distribution of the title molecule is graphically visualized using the natural population analysis (NPA) and frontier molecular (FMO) analysis. Through reduced density gradient (RDG) and interaction region indicator (IRI) analyses, the molecule's steric effect and van der Waals interaction were determined. To determine the potential sites for nucleophilic and electrophilic attack, the Fukui analysis was performed. To examine the intermolecular interactions, the Hirshfeld surface analysis was executed. The optical features and band gap energy of 2AM5SSA were ascertained using the UV-Vis optical spectrum. TG/DTA analysis was used to determine the thermal stability of the grown crystal. Scanning electron (SEM) microscopy was employed to determine the grown crystal's surface morphology. Through fluorescence spectral analysis, the green emission of the 2AM5SSA single crystal at 544 nm was detected. Both experimental and theoretical analysis of the NLO property of the 2AM5SSA molecule was performed via z-scan and DFT techniques. Z-scan, NLO, UV-Vis and HOMO-LUMO values were compared with other related 5-sulfosalicylic acid based NLO active compounds that have previously been investigated.

A novel organic single crystal bis(2-amino-4,6-dimethoxypyrimidinium) 5-sulfosalicylate (B2AD5SSA) was synthesized and examined through the FT-Raman, UV–Vis, single crystal X-ray diffraction and FT-IR investigations. The B2AD5SSA crystal affiliated to the triclinic with centrosymmetric space group P-1 was validated through single crystal X-ray diffraction (SXRD). The B3LYP/LANL2DZ basis set was employed in the density functional theory (DFT) for the quantum chemical calculations. The natural bond orbital (NBO) analysis provides a detailed study of the intermolecular interactions and stability of the B2AD5SSA molecule. To highlight the existence of different functional groups in the B2AD5SSA molecule, the FT-Raman and FT-IR spectral analysis were carried out. A graphical representation of the B2AD5SSA molecule’s charge distribution was provided by the frontier molecular orbital (FMO) and molecular electrostatic potential (MEP). The energy gap of B2AD5SSA was determined to be 5.33 eV. Reduced density gradient (RDG), interaction region indicator (IRI) and atoms in molecule (AIM) analyses were used to explore the N–H…O and O–H…O interaction within the B2AD5SSA molecule. Using UV–visible spectral analysis, the transmittance spectra and band gap energy of the title compound were measured and examined. Fluorescence spectral analysis has been used to examine the emission spectra at 407 nm, which was advantageous for the development of violet light-emitting devices. By employing TG–DTA analysis, the thermal stability of the B2AD5SSA crystal was calculated to be 192 °C. The hole-electron analysis was performed to demonstrate charge transfer within the molecule. Hirshfeld surface analysis and a two-dimensional fingerprint plot were used to examine the molecular surface contours and intermolecular interactions. The NLO activity of the B2AD5SSA molecule was investigated both theoretically and experimentally using the DFT and Z-scan techniques. The first-order hyperpolarizability (β) and third order susceptibility (χ(3)) of the B2AD5SSA was found to be 70.51*10–30 esu and 6.58*10–6 esu. While comparing the results of UV–visible, NLO, FMO and Z-scan with 5-sulfosalicylate based compounds, the compound B2AD5SSA shows strong NLO activity.

An organic complex derived from 2,6-diaminopyridinium hydrogen malonate (DAPMAL) was studied for its crystal growth, structure and properties including its non-linear optical (NLO) behavior. Single-crystal X-ray diffraction (SXRD) confirmed a monoclinic crystalline structure with a C2/c (15) space group. Density functional theory (DFT) calculations using the B3LYP/6311G(d, p) approach revealed significant hyperpolarizability indicative of strong NLO behavior. The natural bond orbital analysis is performed to identify hydrogen bonding and charge transfer interaction. A combined experimental and theoretical quantum chemical calculation has been accomplished to examine the molecule’s geometry, vibrational wavenumber, electronic transition, and NLO activity. Molecular electrostatic potential and are carried out to identify chemical reactivity and charge transfer interaction. The HOMO–LUMO energy gap for DAPMAL was calculated to be 5.926 eV at the B3LYP/6-311G(d,p) level of theory. The hole–electron analysis was performed to determine the type of excitation. Reduced density gradient is performed to identify the hydrogen bonding, steric, and van der Waals interactions. Thermal analysis (TG–DTA) shows thermal stability at 185 ℃ and decomposition patterns, while SEM–EDX is used to find the material’s purity and crystalline nature. UV–visible spectroscopy demonstrated transparency with a lower cutoff wavelength of 210 nm and fluorescence spectroscopy revealed 628 nm shows red emission. The Z-scan technique further validated 3.49E-06 the compound’s NLO potential for DAPMAL.

Using the slow evaporation method, 2-amino-5-methyl pyridinium oxalate (2A5MPOXA), a novel organic single crystal, was grown. The crystal was characterized by fluorescence analysis, UV–Vis spectral analysis, FT-IR, FT-Raman and single crystal x-ray diffraction. Density functional theory was applied to theoretical studies utilizing the B3LYP/6-311G(d,p) basis set. Natural bond orbital analysis was employed to ascertain the intermolecular hydrogen bonding of 2A5MPOXA. Different functional groups in 2A5MPOXA were identified using FT-IR and FT-Raman spectrum analysis. HOMO–LUMO, charge analysis and molecular electrostatic potential were used to assess a molecule's chemical stability. Intermolecular interactions and molecular surface contours were investigated utilizing Hirshfeld and two-dimensional fingerprint plot analysis. The topological study of reduced density gradient, atoms in molecules, localized orbitals and electron localization was examined. Light harvesting efficiency has been used to determine the grown crystal's light efficiency. The fluorescence analysis has determined the emission spectra of the grown crystal. The UV–visible transmittance spectral analysis was utilized to measure and examine the optical transmittance and band gap energy of the 2A5MPOXA single crystal. The molecule's charge transfer was demonstrated using hole-electron analysis. The DFT and Z-scan approaches were used to both theoretically and experimentally determine the molecule's NLO activity.

The optimized structural parameters of the benzenedimethanol (BDM) were computationally obtained at the DFT/B3LYP level. Using NBO analysis, the molecule’s stability, intra- and intermolecular hydrogen bonding, and the hyperconjugative interaction of BDM and its water complexes were also examined. Molecular electrostatic potential analysis has identified the chemical reactivity locations. The intermolecular interactions in the BDM were confirmed by Hirshfeld surface analysis. The molecule’s chemical stability is indicated by the calculated HOMO and LUMO energies. The stable conformation of BDM has been identified by potential energy surface scan analysis. The orange-red color emission was observed by fluorescence study. Vibrational frequencies were computed and compared with FT-IR and FT-Raman spectrum data from experiments. The compound’s UV–visible spectrum was captured and examined. The first order hyperpolarisability (β) and related properties (α0, ∆α, γ) of BDM and its water complexes were calculated. The Z-scan approach was utilized to determine the third-order NLO parameter of the BDM molecule.

The compound N,N'-Diphenylthiourea acetone monosolvate was synthesized using slow evapouration technique and characterized by FT-IR, FT-Raman, UV-visible spectra. The optimized molecular geometry (bondlength, bondangle and dihedral angle), the complete vibrational frequency were calculated by using density functional theory (DFT) B3LYP method with the help of 6-31 G(d,p) basis set. The protonated N-H horizontal ellipsis O intermolecular interaction liable for the NLO activity was deliberated using DFT method along with experimental spectroscopic techniques. The inter and intramolecular interactions accountable for the stabilization of the material was done via NBO and AIM analysis. In addition, the molecular electrostatic potential, frontier molecular orbital, global reactivity descriptors, Hirshfeld surface and 2D-fingerprint was analyzed to acquire a greater understanding of the molecular effect. UV-Vis spectrum of DPTA crystal exhibits good optical transmittance in the spectral analysis. By using spectroflurometer technique the green band region was observed in fluorescence emission spectrum. The dipole moment, polarizability, first-order hyperpolarizability (& alpha;0), related properties (& beta;, & alpha;0 and & UDelta;& alpha;) and second-order hyperpolarizabilties were calculated for the identification of non-linear optical activity of the molecule. The molecular docking studies were performed to investigate the binding affinity of legend with target receptor.

The work aims to investigate the nonlinear optical (NLO) activity of piperazine‐1,4‐diium acetate (PAA) molecule utilizing computational techniques. The computational calculations are performed using density functional theory (DFT) to explore the vibrational modes, electronic and NLO properties of PAA by comparing them with piperazine and acetic acid molecules. The natural bond orbital analysis is performed to identify hydrogen bonding and charge transfer interaction. A vibrational analysis is carried out and the assignment of fundamental modes is done using the vibrational energy distribution analysis (VEDA) program. Molecular electrostatic potential, frontier molecular orbital, electron localization function, localized orbital locator and Fukui analysis are carried out to identify chemical reactivity and charge transfer interaction. The UV–visible analysis is performed to obtain the electronic absorption spectrum. The hole–electron analysis is performed for the first five excitations to identify the type of excitation. The atoms in molecules, reduced density gradient and independent gradient model are performed to identify the hydrogen bonding, steric and van der Waals interactions. Hirshfeld analysis is performed to explore the intermolecular interactions within the PAA molecule. The NLO calculation is performed to evaluate the NLO parameters. The obtained results show that the PAA molecule is suitable for NLO applications.

Semi-organic nonlinear optical (NLO) melaminium sulfamate (MASA) single crystals were synthesized by slow evaporation method and analyzed by using X-ray diffraction, UV-vis, FT-IR and FT-Raman experiments. Single crystal X-ray diffraction (SXRD) analysis confirms that MASA crystal belongs to triclinic system with centrosymmetric space group P-1. The quantum chemical calculation were carried out using density functional theory (DFT) with B3LYP/6-31+G(d) basis set. The intermolecular interactions were deeply analyzed by NBO analysis. The molecule with intermolecular N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds show notable vibrational effect. The optical property of MASA was evaluated by UV-vis optical transmittance spectrum. Thermal stability of the grown crystal was performed by using TG-DTA analysis. The frontier molecular orbital analysis illustrates the charge transferred from sulfamate anion to melaminium cation. Hirshfeld and 2D fingerprint plot reveals the intermolecular N-H center dot center dot center dot O and N-H center dot center dot center dot N contacts of MASA molecule. The existence of various functional groups and vibrational modes are affirmed by Fourier transform infrared (FT-IR) and FT-Raman spectral analysis. Additionally, the molecular electrostatic potential (MESP) and topological analysis such as electron localization function (ELF), reduced density gradient(RDG), localized orbital locator(LOL) and atoms in molecule(AIM) have been used to predict the intermolecular interaction, especially the hydrogen bonds. The hydrogen atom from sulphamic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The outcome of SXRD, UV-visible, TG/DTA, HOMO-LUMO, NLO and Z-Scan values were compared with earlier reported compounds and amongst the analyzed compound MASA shows good NLO activity. The NLO activity of MASA was analyzed theoretically and experimentally by DFT and Z-scan method.

The main objective of the study is to analyze the structural behavior and NLO activity of 4-cumyl phenol by experimental and theoretical spectroscopic techniques. Its computational result is compared with the cumene compound. The optimized structural parameters of the title compound were computationally obtained at the B3LYP/6-31G (d, p) basis set. The fundamental modes of vibration were examined by experimental FT-IR, and FT-Raman techniques. The distribution of the vibrational bands was carried out with the help of normal coordinate analysis (NCA). The resulting harmonic wavenumbers were scaled by using NCA method. Topological analysis, such as Electron localization function (ELF), natural bond orbital analysis (NBO), reduced density gradient (RDG) and atoms in molecule (AIM) analysis, molecular electrostatic potential (MEP) have been used to evaluate the intermolecular interaction, especially the hydrogen bonds. UV-visible spectrum of the compound was recorded in the region 200-900 nm and the electronic properties and HOMO-LUMO energies were calculated by time dependent density functional theory approach.

Organic nonlinear optical (NLO) 2-amino-4,6-dimethoxypyrimidine-4-aminobenzoic acid (2AD4AB) single crystal was grown by slow evaporation method and characterized via single crystal X-ray diffraction (SXRD), FTIR, FT-Raman and UV–visible spectroscopy. The synthesized crystal is monoclinic with centrosymmetric space group P21/c. Using density functional theory (DFT), the quantum chemical computations were performed with a B3LYP/6-31G (d, p) basis set. Natural bond orbital analysis (NBO) was executed to analyze the hydrogen bonding interaction, stability and charge delocalization of 2AD4AB. The charge distribution of the 2AD4AB molecule can be graphically depicted by frontier molecular orbital analysis (FMO) and molecular electrostatic potential (MEP). The energy gap of 2AD4AB was estimated to be 4.96 eV. MEP analysis shows that the electrophilic attack was extended over oxygen atoms of the carboxylic group. Atoms in molecule (AIM) and reduced density gradient (RDG) analysis were carried out to investigate the O–H…N and N–H…O interactions within the 2AD4AB molecule. The presence of different functional groups and vibrational modes were validated by FT-IR and FT-Raman spectral analysis. The optical property and band gap energy of 2AD4AB were determined using the UV–Vis optical transmittance spectrum. Thermal stability of the 2AD4AB crystal was estimated to be up to 155 °C using TG–DTA analysis. The intermolecular O–H···N, N–H···O, and C–H···N interactions of the 2AD4AB molecule were revealed by Hirshfeld and 2D fingerprint plots. The potential energy scan (PES) was performed to identify the most stable conformer. To demonstrate charge transfer in the molecule, hole electron analysis was implemented. Light harvesting efficiency (LHE) of the grown crystal was 78.88

The structure of sulfathiazole-4-nitrobenzoic acid (STZBA) was characterized by X-ray diffraction (XRD). The crystal was stabilized by C–H…O, N–H…O, and S–O…S intermolecular interaction along with C–H…π and π…π interactions. The experimental FT-IR, FT-Raman, and UV-Vis spectra of STZBA were recorded and the results were compared with quantum chemical computation using the DFT method. Molecular electron density, topology, and natural bond orbital (NBO) analysis were used to explain the strength of the interaction. The molecular electrostatic potential and Fukui function of STZBA was determined to give a visual representation of charge distribution and provide information about the electrophilic and nucleophilic site of the molecule. Hirshfeld surface analysis was carried out to analyze the stability of the crystal structure. The antimicrobial activity of STZBA was determined against anticancer, bacterial strain E. coli and fungal stain Candida albicans and Sars-cov. Molecular docking analysis was performed with antimicrobial proteins to confirm the bioactivity of the molecule and drug likeness factors were calculated to comprehend the biological assets of STZBA. The molecular dynamic (MD) simulation result explains the protein stability, ligand properties, and protein-ligand interactions. The compounds were assessed for their structural, physic-chemical, pharmacokinetic, and toxicological properties.

Piperazin-1-ium 4-aminobenzoate monohydrate (PPAB) single crystals were grown by slow evaporation method. The grown crystal PPAB has been characterized by single-crystal X-ray diffraction, FTIR, FT-Raman, and UV-visible analysis. The B3LYP method and 6-311G (d, p) basis set were used to optimize the structure. The title compound was investigated theoretically and experimentally by FT-IR, FT-Raman, and UV-Vis spectral analysis. The presence of various functional groups in the structure was elucidated by FTIR and FT-Raman spectral studies. The intermolecular interactions within the crystal structure were investigated using Hirshfeld surface analysis. The crystal packing diagram reveals interesting non-covalent interactions involving C–H···O, N–H···O, and N–H···N hydrogen bonds, leading to the generation of 3D supramolecular architecture. The charge transfer within the molecule was deeply analyzed by using the NBO approach. The molecular electrostatic potential (MEP) and the local reactivity descriptors, such as Fukui function (fk+, fk−) analyses were performed to determine the reactive sites within the molecule. The HOMO and LUMO analysis was used to determine the chemical reactivity and bioactivity of the molecule. Hole-electron analysis was performed to analyze the charge transfer in an excited state. Based on the hole-electron analysis, the inter-fragment charge transfer (IFCT) analysis establishes the amount of charge transfer among different fragments. Topological analyses, such as AIM, RDG, and ELF were carried out to identify the non-covalent interaction within the molecule. The molecular docking studies of the molecule are performed to investigate the binding affinity of the ligand with the protein receptor. Drug-likeness properties, such as Lipinski’s rule of five, adsorption, distribution, metabolism, excretion, and toxicity (ADMET) have been investigated by in silico web-based tools like SwissADME and ADMETlab.