Frontier Molecular Orbital Analysis Research Articles

Structural analysis, reactivity descriptors (HOMO-LUMO, ELF, NBO), effect of polar (DMSO, EtOH, H2O) solvation, and libido-enhancing potential of resveratrol by molecular docking

The profound impact of health challenges related to libido, encompassing sexual dysfunction, hormonal imbalances, relationship difficulties, stress, anxiety, depression, and the effects of certain medical conditions or medications, calls for urgent mitigative measures. As a result, this study meticulously explores the compound Resveratrol (Res) to uncover its substantial properties concerning libido enhancement. The compound was optimized using the DFT/ωB97XD/6–311G++(d, p) basis set in different solvents, namely DMSO (dimethyl sulfoxide), ethanol, and water. Notably, the geometry investigation reveals that the structural bond variations can be attributed to factors such as solvent polarity, screening effects, hydrogen bonding, solvation energy, and conformational preferences. Substantially, the Frontier Molecular Orbital (FMO) analysis explored the HOMO values of the compound in different solvents, resulting in 7.59198 eV, 7.5514 eV, and 7.59687 eV for RES_DMSO, RES_EtOH, and RES_H2O, respectively. Correspondingly, their LUMO values were found to be 7.5955 eV, 7.5648 eV, and 7.5982 eV, leading to respective band gaps of 0.0035 eV, 0.0133 eV, and 0.0014eV Remarkably, RES_H2O displayed the smallest energy gap (0.0014 eV) among the interacting compounds, indicating increased conductivity and sensitivity. Furthermore, the natural bond orbital analysis revealed that RES_H2O had the highest permutation energy among the three complexes (376.5 kcal/mol for RES_DMSO, 371.79 kcal/mol for RES_EtOH, and 378.77 kcal/mol for RES_H2O), indicating a stronger interaction between the donor and acceptor orbitals. Finally, the molecular docking studies unveiled a notable difference in binding affinity, with RES exhibiting a greater affinity for 1UDT at -8.1 kcal/mol compared to 1UDU, which demonstrated a binding affinity of -6.6 kcal/mol. Thus, RES has the potential to reverse erectile dysfunction and improve libido by inhibiting the activities of phosphodiesterase (1UDT and 1UDU), ultimately promoting vasodilatory signals from cGMP to the smooth muscles of the penis, leading to enhanced erection. These groundbreaking findings offer promising prospects for the development of new and effective drugs to combat various medical conditions.

Role of Delocalization, Asymmetric Distribution of π-Electrons and Elongated Conjugation System for Enhancement of NLO Response of Open Form of Spiropyran-Based Thermochromes.

Switchable nonlinear optical (NLO) materials have widespread applications in electronics and optoelectronics. Thermo-switches generate many times higher NLO responses as compared to photo-switches. Herein, we have investigated the geometric, electronic, and nonlinear optical properties of spiropyranes thermochromes via DFT methods. The stabilities of close and open isomers of selected spiropyranes are investigated through relative energies. Electronic properties are studied through frontier molecular orbitals (FMOs) analysis. The lower HOMO-LUMO energy gap and lower excitation energy are observed for open isomers of spiropyranes, which imparts the large first hyperpolarizability value. The delocalization of π-electrons, asymmetric distribution and elongated conjugation system are dominant factors for high hyperpolarizability values of open isomers. For deep understanding, we also analyzed the frequency-dependent hyperpolarizability and refractive index of considered thermochromes. The NLO response increased significantly with increasing frequency. Among all those compounds, the highest refractive index value is observed for the open isomer of the spiropyran 1 (1.99 × 10-17 cm2/W). Molecular absorption analysis confirmed the electronic excitation in the open isomers compared to closed isomers. The results show that reversible thermochromic compounds act as excellent NLO molecular switches and can be used to design advanced electronics.

Predicting benzodithiophene based donor materials with enhanced 19.09% PCE, open-circuit voltage and optoelectronic attributes for solar cell applications: Photochemical insights from DFT

Seven benzo[1,2-b:4,5-b′]dithiophene (BDT) based novel donor (D1-D7) molecules with A-π-D-π-A configuration are investigated by DFT and TD-DFT methods and a power conversion efficiency (PCE) of 19.09% is predicted for organic solar cells (OSCs). The fundamental core of these novel compounds is the BDT molecule (R), with other significant acceptors substituted on the outer borders. To study the geometrical, photovoltaic, and optoelectronic properties of the newly designed sensitizers (D1-D7), the CAM-B3LYP/6-31G(d,p) method was employed for computational analysis and comparison with BDT (R) Evaluations were conducted on open circuit voltage (Voc), power conversion efficiency (PCE), fill factor (FF), absorption spectra, the distribution pattern of electron density, charge mobility, electron, and hole reorganizational energy, the density of state (DOS), frontier molecular orbital (FMO), and transition density matrices (TDM)of the investigated compounds. In comparison to the reference compound (R), D2, D3, and D4 have better optical and chemical characteristics. The DOS plots and the FMOs analysis showed that the addition of acceptor groups finely improved the charge distribution in the molecules under study. The optoelectronic characteristics of the proposed structure D2 in chloroform solvent were the most improved, with a lower band gap (3.87 eV), higher maximum absorbance (533 nm), and lower binding energy (1.55 eV) than others investigated. The TDM graphs revealed the reliability of the charge transfer capability. In several molecules, the mobilities of charge transfer in designed compounds were equivalent to the reference R while the D2 was the lowest among all implying that the charge carriers would be more maneuverable. For all donors, the Voc was calculated with PC71BM. Voc is high for D2, D3, and D4, compared to R. All investigated compounds were predicted to have remarkable PCEs with high FF values. Especially, D2 has the higher Voc (2.422 V) and FF (94.12), which leads to the highest PCE of 19.09%. Hence, all calculated characteristics are very favorable to the potential of our designed molecules in photovoltaic applications.

Microwave assisted green synthesis, Single crystal XRD, DFT, Hirshfeld surface analysis, Antibiofilm, Anti-inflammatory activity and Molecular docking study of 4-(4-Fluorophenyl)-5-methyl-1,3-thiazole-2-amine

The title compound 4-(4-Fluorophenyl)-5-methyl-1,3-thiazole-2-amine was synthesized by the green microwave irradiation method and the structure was confirmed by spectroscopic techniques. Single crystal X-ray diffraction study was performed to investigate the crystal structure of the title compound. Further, the molecular structure was optimized by density functional theory (DFT) calculations using the B3LYP/6-311G++ (d, p) basic set and compared with X-ray diffraction data. DFT optimized structure, geometrical parameters and IR spectra of the title compound showed excellent correlations with the experimental results. The chemical reactivity and stability of the title compound were studied by molecular electrostatic potential (MEP) and Frontier molecular orbitals (FMOs) analysis. Intermolecular interactions of the title compound were analyzed by Hirschfeld surfaces and 2D-fingerprint plots. In vitro, antibiofilm activity against C. albicans, suggests a potential biofilm inhibitor (MIC 12.5 μg/ml). A molecular docking study of the title compound with the active sights of the target protein (PDB:5TZ1) justifies the results of the antibiofilm activity whereas a drug-likeness pharmacokinetic study is used to analyze the safety and efficiency of the drug. Furthermore, the Anti-inflammatory activity study of the title compound indicates significant (82.63%) inhibition of protein denaturation.

Probing the catalytic activity of first-row transition metal doped C20 fullerene as remarkable HER electrocatalysts: A DFT study

Hydrogen evolution reaction (HER) has captivated the interest of researchers due to ever increasing demand for future sources of energy. With the advancement in renewable energy resources, electrocatalytic production of hydrogen has been considered as the most suitable way for hydrogen production for fuel cells and combustion engines. Herein, we studied HER activity of transition metal doped C20 fullerene (M@C20) by means of adsorption energy, Gibbs free energy and electronic density calculations. Ni@C20 and Cu@C20 complexes provide the best HER activity with Gibbs free energy of −0.09 eV for each. Furthermore, electronic properties such as the density of states (DOS) and frontier molecular orbital analyses are performed which indicate that transition metal doping significantly alters the electronic properties of studied M@C20 complexes. Whereas the adsorption of hydrogen does not affect the electronic parameters much. The basic understanding of hydrogen adsorption mechanism together with analyses of electronic parameters is crucial for the synthesis of highly efficient electrocatalysts for hydrogen energy applications. The critical findings of this study declares that both Ni@C20 and Cu@C20 complexes can act as promising electrocatalysts for hydrogen evolution reaction with low overpotential.

Shedding light into the biological activity of aminopterin, via molecular structural, docking, and molecular dynamics analyses

In this study, the structural and anticancer properties of aminopterin, as well as its antiviral characteristics, were elucidated. The preferred conformations of the title molecule were investigated with semiempirical AM1 method, and the obtained the lowest energy conformer was then optimized by using density functional (DFT/B3LYP) method with 6-311++G(d,p) as basis set. The vibrational frequencies of the optimized structure were calculated by the same level of theory and were compared with the experimental values. The vibrational assignments were performed based on the computed potential energy distribution (PED) of the vibrational modes. The molecular electrostatic potential (MEP) and frontier molecular orbitals (HOMO, LUMO) analyses were carried out for the optimized structure and the chemical reactivity has been scrutinized. To enlighten the biological activity of aminopterin as anticancer and anti-COVID-19 agents, aminopterin was docked into DNA, αIIBβ3 and α5β1integrins, human dihydrofolate reductase, main protease (Mpro) of SARS-CoV-2 and SARS-CoV-2/ACE2 complex receptor. The binding mechanisms of aminopterin with the receptors were clarified. The molecular docking results revealed the strong interaction of the aminopterin with DNA (−8.2 kcal/mol), αIIBβ3 and α5β1 integrins (−9.0 and −10.8 kcal/mol, respectively), human dihydrofolate reductase (−9.7 kcal/mol), Mpro of SARS-CoV-2 (−6.7 kcal/mol), and SARS-CoV-2/ACE2 complex receptor (−8.1 kcal/mol). Moreover, after molecular docking calculations, top-scoring ligand-receptor complexes of the aminopterin with SARS-CoV-2 enzymes (6M03 and 6M0J) were subjected to 50 ns all-atom MD simulations to investigate the ligand-receptor interactions in more detail, and to determine the binding free energies accurately. The predicted results indicate that the aminopterin may significantly inhibit SARS-CoV-2 infection. Thus, in this study, as both anticancer and anti-COVID-19 agents, the versatility of the biological activity of aminopterin was shown. Communicated by Ramaswamy H. Sarma

Synthesis and characterization of tetradentate benzophenone derivative Schiff base and properties in different lyotropic media

A new Schiff base ligand of 6,6′-(1Z,1′Z)-(butane-1,4-diylbis(azanylyidene))bis (phenylmethanylylidene))bis(3-octyloxy) phenol) was synthesized and characterized using XRD and different spectroscopic analyses (FTIR, 1H NMR, 13C NMR, and UV–Vis.) DFT/B3LYP/6-31G(d,p) level of theory was applied successfully to the present compound. Theoretically calculated parameters of the synthesized compound were compared with the experimentally obtained results. The optimized structure has been investigated using the same level of theory for various studies, including frontier molecular orbital analysis, molecular electrostatic potential, chemical reactivity indexes, natural bond orbital analysis, electrostatic potential, and the electrophilicity-based charge transfer with DNA bases.

Single Crystal XRD, Hirshfeld Surface, Quantum Chemical and Molecular Docking Studies on Diethyl1-(4-Nitrobenzyl)-4-(4-Nitrophenyl)-2,2-Dioxooctahydro-2-Pyrrolo[2,1-c]1,2Thiazine-1,3-Dicarboxylate: a Novel HIV-1Inhibitor

The single crystal of the title compound Diethyl 1-(4-nitrobenzyl)-4-(4-nitrophenyl)-2,2-dioxooctahydro-2-pyrrolo[2,1-c]1,4thiazine-1,3-dicarboxylate was grown and characterized by single crystal X-ray diffraction technique. Further, Hirshfeld surface, quantum chemical, and molecular docking analyses of the compound were carried out. The title compound was crystallized in a triclinic crystal system with a centrosymmetric space group of P-1 and has one molecule in the asymmetric unit. The stability of the grown crystal structure was confirmed by the C-H…O and π…π interactions. The hydrogen bonding features were analyzed and the prominent intermolecular interactions present in the structure were investigated using Hirshfeld surface analysis. The interaction energy between pairs of the molecule was obtained from Energy Framework analysis. The molecular structure of the title compound was optimized using density functional theory calculation in the ground state and the calculated structural parameters of the compound were compared with the experimental XRD data. Mulliken atomic charge distribution and frontier molecular orbitals analyses were also carried out to validate the reactivity of the title molecule. Molecular docking studies confirm that the title compound has potent inhibitory nature against the human mutant HIV-1 reverse transcriptase protein. Thus, the present study paves the way for the development of a novel HIV-1 drug.

Influence of anionic species on the molecular structure, nature of bonding, reactivity, and stability of ionic liquids-based on 1-butyl-3-methylimidazolium

The unique physicochemical properties of ionic liquids (ILs) have positioned them as a significant class of solvents, making them a subject of considerable interest. In this investigation, the experimental analysis involved solvothermal reflux techniques, while theoretical approaches utilized density functional theory (DFT) with the def2-SVP/ωB97XD computational approach to explore the electronic properties, reactivity, stability, and structural aspects of ILs based on the combinations of [BMIM]+ cation with [MeSO3]-, [BF4]-, [PF6]-, and [C2H3O2]- anions. The experimental and theoretical data exhibited good agreement, demonstrating that the choice of cation and anion greatly influences the stability of ILs. By employing Frontier molecular orbital analysis, the reactivity and stability of the studied ionic species were observed to follow the order of [BMIM]+[MeSO3]- > [BMIM]+[BF4]- > BMIM > [BMIM]+[PF6]- > [BMIM]+[C2H3O2]-, with corresponding energy gaps of 4.8474 > 3.1971 > 2.013 > 1.8830 and 1.3276 eV, respectively. The Natural Bond Orbital (NBO) analysis, encompassing second-order perturbation energy, revealed the strength of interactions within the investigated systems in the following order: [BMIM]+[PF6]- < [BMIM]+[MeSO3]- < [BMIM]+[BF4]- < [BMIM]+[C2H3O2]-. Topology analysis indicated a higher electron density (ρ(r)) value of 0.8966 a.u., indicating a denser distribution of electrons. Furthermore, the nature of bonding in the studied ion pairs displayed the following order: [BMIM]+[MeSO3]- > [BMIM]+[BF4]- > [BMIM]+[PF6]- > [BMIM]+[C2H3O2]-, signifying that [BMIM]+[MeSO3]- exhibited stronger interactions compared to the other combinations. The vibrational spectra and UV–vis results of the investigated ILs underscored the sensitivity of characteristic peaks in frequency and intensity to the specific cation–anion combination. These findings have the potential to guide experimental researchers in exploring the applications of the studied ionic species in diverse areas such as energy storage and catalysis.

Novel Zn- and Cd-Schiff base complexes as the potent anticancer agents: Synthesis, spectral characterization and theoretical study

A novel unsymmetrical bidentate Schiff base ligand and its complexes, with the common formula of MLX2 (M(II) = Zn(II) and Cd(II); X− = Cl−, Br− and I−), using a reaction between 1,2-diaminobenzene and (E)-3-(4-(Dimethylamino) phenyl) acrylaldehyde were successfully synthesized. The structure of all the as-made compounds was identified by techniques including 1H NMR,13C NMR, ESI-mass, FT-IR, UV–Vis, melting point and molar conductivity. The analytical and spectral data confirmed the metal to ligand ratio of 1:1 in the Zn(II) and Cd(II) complexes. The anticancer activity of the compounds on cancer cells was investigated on HCT116 cell line, where the MTT method was used to screen cytotoxicity effects. The flow cytometry method also was used to determine the mechanism of cell death. Our data reveal that CdLCl2 can block the cell cycle and induction apoptosis. In addition, using Gaussian 16 program, the structure of the samples was optimized, and some important properties such as enthalpy change, entropy change and total energy were extracted. The molecular electrostatic potential, nonlinear optical properties, natural bond orbital and frontier molecular orbitals analysis were calculated for all compounds. Further, the electrophilic and nucleophilic sites, energy gap, ionization potential, electron affinity, natural population analysis and natural atomic orbitals were studied.

Exploring the Crystal Structure Landscape of Sulfasalazine through Various Multicomponent Crystals.

Sulfasalazine is used as an anti-inflammatory drug to treat large intestine diseases and atrophic arthritis. In the solid state, two tautomers are known: an amide tautomer (triclinic polymorph) and an imide tautomer (monoclinic polymorph). Crystallization of six new multicomponent solids of sulfasalazine with three cocrystal formers and three salt formers has been achieved by slurry, liquid-assisted grinding and slow evaporation methods. All of the solid forms are characterized by X-ray diffraction techniques, thermal analysis, and Fourier transform infrared spectroscopy. The crystal structural analysis reveals that two sulfasalazine molecules or anions arrange in a head-to-head fashion involving their pyridyl, amide, and sulfonyl groups in an R22(7):R22(8):R22(7) motif. This is the key structural unit appearing in both sulfasalazine imide polymorph and all six multicomponent crystals. In addition, sulfasalazine exists in the amide form in all unsolvated multicomponent crystals obtained in this work and adopts the imide tautomer in the solvated cocrystals and salt. Hirshfeld surface analysis and the associated two-dimensional (2D) fingerprint plots demonstrate that sulfasalazine has significant hydrogen bond donor capability when cocrystallized and is a significant hydrogen bond acceptor in the salts. The frontier molecular orbital analysis indicates that sulfasalazine cocrystals are chemically more stable than the salts.

M@C78 (M = U, Th): Inherent Topological Connectivity Existed in Thermodynamically Stable Isomers and the Possibility of an Endohedral Fullerene Containing One Heptagon Ring.

The density functional theory combined with statistical thermodynamic analyses of M@C78 (M = U and Th) demonstrated that four isomers, M@D3h(24109)-C78, M@C2v(24107)-C78, M@C1(22595)-C78, and M@C1(23349)-C78, and a nonclassical isomer, M@C1(id7)-C78, containing one heptagon ring possess outstanding thermodynamic stabilities in the two M@C78 series. Especially, the M@C1(id7)-C78 isomer is the first nonclassical C78 fullerene that can exist stably. Importantly, these five fullerene cages are found to be related in the form of Stone-Wales (SW) transformations. Geometric analyses disclosed that, unlike lanthanide metals, actinide metals are more likely to bond with sumanene-type hexagonal rings when they are encapsulated in IPR C78 cages. Frontier molecular orbital analysis showed that both U and Th atoms donate four electrons to the C78 carbon cages.

Deciphering the sensing mechanism in a sarin gas surrogate, diethylchlorophosphate specific probe: Colorimetric observation and theoretical analysis

The extreme toxicity of organophosphates (OPs) nerve agents poses a significant public health risk and national safety. Increasing interest in developing reliable and accurate methods for simple and fast detection of these toxic, i.e., poisonous chemicals, is necessary and urgent. In this contribution, [(E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol] (DPAP), a cinnamalimine-based chromogenic probe with high selectivity and sensitivity towards the detection of sarin mimic diethylchlorophosphate (DCP), has been introduced. The detection limit of DPAP towards the detection of DCP is in the nM region. The developed probe DPAP shows reddish pink color upon treatment with DCP and reverses to its original one by adding triethylamine (TEA); it is observed eight times reversibility by alternative addition of DCP and TEA. The detailed mechanism has been elucidated through the density functional theoretical analysis depicting the energy profile diagram and Frontier molecular orbital analysis. To establish the practical application, we have demonstrated a paper strips-based test kit to establish the capacity of DPAP for on-spot detection and quantification of DCP. A dip-stick experiment has also been performed to identify DCP in the gaseous phase within the various OPs, inorganic phosphates, and other toxic analytes to establish the probe, DPAP, as a proficient chemosensor. To detect the response capacity of probe DPAP towards the identification and quantification of DCP, a time-dependent UV–visible spectrophotometric experiment, and dip-stick method have been performed for 0–6 min. A smartphone-based readout technique has been executed for on-spot detection and quantification of DCP in remote areas. The present contribution introduced an excellent probe and technique for identifying and quantifying sarin gas in actual threatening situations. It would be helpful to monitor the environmental toxicology from exposure to these toxic nerve agents.

Molecular structure, electronic, topology and non-covalent interaction of 4-(Bis(2-chloroethyl)amino)-L-phenylalanine- Anti-blood cancer activity

In this study, it is attempted to scrutinize the global minimum energy structure of anti-blood cancer drug 4-(Bis(2-chloroethyl)amino)-L-phenylalanine (4B2CA-LPA) and functionalized density functional theory (DFT) calculations regarding their geometries, topological features of covalent, non-covalent interactions with employing Atoms in molecule (AIM) and Reduced density gradient (RDG) studies. As per the topological results, a new type of non-covalent attraction forces of hydrogen-hydrogen interaction was found in this molecule. Electrostatic potential variation as well as global reactive descriptor energy variations in the solvation phases was carried out by molecular electrostatic potential (MEP) and frontier molecular orbitals (FMOs) analysis. Moreover, the electronic excitations in liquids of 4B2CA-LPA were evaluated in UV-Vis absorptions. The local bonding electron transitions and optical properties of the compound were examined with natural bond orbital (NBO) studies. The 4B2CA-LPA molecule can serve as lead molecules for the growth of anti-blood cancer drugs. Molecular docking investigation has also been carried out to determine the ability of target molecules to bind with Hematopoietic inhibitors in blood cells.

Vibrational spectral and electronic properties, Topology studies and biological assay of a potent Anticonvulsant agent: Divalproex Sodium

In this research work, Density Functional Theory based computational analysis on the molecular structure of Divalproex Sodium was carried out in the gas phase. Comprehensive analysis of vibrational spectra, Proton and Carbon Nuclear Magnetic Resonance, and electronic absorption spectrum have been carried out and the findings were compared to those obtained using computational techniques. The electronic transport properties were studied by the Ultraviolet-Visible spectrum obtained in distinct solvents by Time Dependent-Density Functional Theory method. Also, inter and intra-molecular interactions and charge transfer activity within the system were studied by Natural Bond Orbital and Frontier Molecular Orbital analyses. For the Non-Linear Optical profile of the compound, hyperpolarizability calculations were performed. The chemical reactivity of the investigated substance has also been disclosed by reactivity descriptors. The biological assessment through drug-likeness characteristics and molecular docking studies was performed to find the compound as anticonvulsant drugs. Highlights Optimized geometrical parameters were computed Vibrational, Electronic, and NMR spectra have been analyzed. Stability and chemical reactivity were studied. Inter/intramolecular interactions have been observed. Pharmacological activities were reported.

Synthesis, single crystal structure, NBO investigations, and Hirshfeld topology analysis of new ethyl-5,8-dimethyl-6-phenyl-(1H-pyrrol-1-yl)-6,7-dihydrothieno[2,3-c]isoquinoline-2-carboxylate

Ethyl-5,8-dimethyl-6-phenyl-(1H-pyrrol-1-yl)-6,7-dihydrothieno[2,3-c]isoquinoline-2-carboxylate has been synthesized and single-crystal X-ray diffraction at 170 K and DFT calculations were performed to characterize the reactivity and its electronic structure. The asymmetric unit of the title molecule, C26H24N2O2S, contains two independent molecules differing primarily in the rotational orientations of the pyrrolyl substituent. The two independent molecules are connected by a C—H···O hydrogen bond and in the crystal, two asymmetric units are linked by inversion-related C—H···N hydrogen bonds. The Hirshfeld surface (HS) analysis reveals intermolecular interactions and surface reactivity in a single crystal. The highest fraction of intermolecular contact of 64% can be seen for H⋅⋅⋅H while the lowest contribution of 3.9% was observed for O⋅⋅⋅H contact in crystal packing. The interaction energies between chemical pairs in the crystal structure are investigated by energy framework analysis which indicates repulsion outweighs the coulomb energy and dispersion energy. The performed density functional theory (DFT) investigation has provided us an electronic picture the of structure and fabulous reactivity. The frontier molecular orbital (FMO) analysis reveals a narrow HOMO-LUMO gap (3.81 eV) and global reactivity descriptors also agree with molecular reactivity and remarkable electronic properties. The density of state (DOS) study shows a pictorial representation the of density of states while MESP shows reactive sites (electron-rich) of the compound for electrophilic attack.

Influence of azo-based donor modifications on nonlinear optical amplitude of D-π-A based organic chromophores: A DFT/TD-DFT exploration

Organic heterocyclic fused ring compounds possess remarkable nonlinear optical (NLO) amplitude, are potentially employed in optical computing and nano-photonics. Herein, ITTBCR1 was quantum chemically modified into a series of novel D-π-A configured NLO compounds (ITTBCD2-ITTBCD6) by substituting various efficient donor moieties. To investigate the electronic, photophysical, and NLO properties, ITTBCR1 and ITTBCD2-ITTBCD6 were subjected to density functional theory (DFT) and time-dependent DFT calculations at M06/6–311 G(d,p) level of theory. Frontier molecular orbital analysis (FMOs) illustrated that the newly designed chromophores exhibit smaller energy gaps (1.625–2.013 eV) compared to ITTBCR1 (2.384 eV). The global reactivity parameters estimated through Egap revealed higher softness (σ = 0.49–0.61 Eh) values, implying enhanced reactivity of ITTBCD2-ITTBCD6 compounds. An efficient push-pull mechanism disclosed positive charges on donors and π-spacers, while the acceptor moieties exhibited a negative charge. The presence of charge separation states and the substantial involvement of molecular orbitals in the charge transfer were explored by natural bond orbitals (NBOs), transition density matrix and density of states analyses. The UV-Vis study of the designed compounds displayed larger bathochromic shifts with wider absorption spectra. Also, a significantly large NLO behavior was found in all the novel entities (ITTBCD2-ITTBCD6), thus potentially employable as NLO materials. Inclusively, compound ITTBCD5 demonstrated highest linear polarizability (〈α〉 = 2.250 ×103a.u.), and first hyperpolarizability (βtot = 70.155 ×104a.u.), therefore proposed as the most proficient NLO material. Comparative study for NLO properties at various functional showed that at M06/6–311 G (d,p) significant NLO results could be obtained. The current investigation revealed that by controlling the type of donor motifs, numerous NLO compounds can be designed, which are equally productive in hi-tech NLO applications.

Theoretical insight into the acceptorless dehydrogenation catalyzed by the transition metal bifunctional catalysts: Mechanism and metal effect

In this paper, the density functional theory study was performed to investigate the reaction mechanism of acceptorless dehydrogenation catalyzed by bifunctional catalysts. The calculation results indicate that the catalyst bearing the Co(III) center adopts the inner-sphere stepwise dehydrogenation mechanism. The H2 formation was found to be the rate-determining step, and the proton-shuttle type transition state effectively reduces the activation energy barrier. Furthermore, the catalytic activities of the noble metals (Rh and Ir) were investigated and compared. The results suggest that the noble metals prefer the outer-sphere bifunctional transfer mechanism for the dehydrogenation reaction. Frontier molecular orbital analysis shows that the HOMO-LUMO gap of the active species increases along with the periodic number, which leads to a weakening of the coordination strength of the substrate to the metal center, resulting in the different mechanistic selectivity toward dehydrogenation reaction. In addition, based on the distortion-interaction analysis, the different activation energy barrier in the H2 formation step is illuminated. The reduced ionic radii of the Co result in lower deformation energies of the catalyst and substrate structures in the H2 formation transition state, thus lowering the activation energy barrier. Our results reveal the advantages of base metal in dehydrogenation reactions, which is expected to provide theoretical guidance for future catalyst design.

Linking quinoline ring to 5-nitrofuran moiety via sulfonyl hydrazone bridge: Synthesis, structural characterization, DFT studies, and evaluation of antibacterial and antifungal activity

In the present work, we report the synthesis, structural characterization, and computational studies of (E)-N'-((5-nitrofuran-2-yl)methylene)quinoline-8-sulfonohydrazide (QNF) as a potential antimicrobial drug candidate. To design the target molecule, we utilized a molecular hybridization technique that connects two antimicrobial pharmacophores (quinoline and 5-nitrofuran rings) with a sulfonyl hydrazone moiety. QNF was synthesized by the condensation of quinoline-8-sulfonohydrazide with 5-nitrofuran-2-carbaldehyde, and characterized by various spectral techniques including single-crystal X-ray crystallography. QNF was extensively evaluated for its antibacterial and antifungal activity. The inhibition capacity of QNF on Candida albicans filamentation and biofilm formation was further investigated. Biofilm inhibition of QNF against C. albicans was supported by molecular docking studies in the binding site of agglutinin-like sequence 3 (Als3). Drug-like profile of QNF was confirmed by in silico calculation of its significant physicochemical properties. Additionally, the optimized geometrical structure, natural bond orbital calculations, frontier molecular orbital and molecular electrostatic potential analysis of QNF were carried out using the density functional theory method at the B3LYP with 6–31+G(d,p) basis set. The predictions of 1H and 13C NMR chemical shift values were performed using the gauge-independent atomic orbital method. Structural parameters and NMR values obtained experimentally were compared with the calculated values.

Insights into structural, spectroscopic, and hydrogen bonding interaction patterns of nicotinamide-oxalic acid (form I) salt by using experimental and theoretical approaches.

In the present work, nicotinamide-oxalic acid (NIC-OXA, form I) salt was crystallized by slow evaporation of an aqueous solution. To understand the molecular structure and spectroscopic properties of NIC after co-crystallization with OXA, experimental infrared (IR), Raman spectroscopic signatures, X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC) techniques were used to characterize and validate the salt. The density functional theory (DFT) methodology was adopted to perform all theoretical calculations by using the B3LYP/6-311++G (d, p) functional/basis set. The experimental geometrical parameters were matched in good correlation with the theoretical parameters of the dimer than the monomer, due to the fact of covering the nearest hydrogen bonding interactions present in the crystal structure of the salt. The IR and Raman spectra of the dimer showed the red (downward) shifting and broadening of bands among (N15-H16), (N38-H39), and (C13=O14) bonds of NIC and (C26=O24), (C3=O1), and (C26=O25) groups of OXA, hence involved in the formation of NIC-OXA salt. The atoms in molecules (AIM) analysis revealed that (N8-H9···O24) is the strongest (conventional) intermolecular hydrogen bonding interaction in the dimer model of salt with the maximum value of interaction energy -12.1kcal mol-1. Furthermore, the natural bond orbital (NBO) analysis of the Fock matrix showed that in the dimer model, the (N8-H9···O24) bond is responsible for the stabilization of the salt with an energy value of 13.44kcal mol-1. The frontier molecular orbitals (FMOs) analysis showed that NIC-OXA (form I) salt is more reactive and less stable than NIC, as the energy gap of NIC-OXA (form I) salt is less than that of NIC. The global and local reactivity descriptor parameters were calculated for the monomer and dimer models of the salt. The electrophilic, nucleophilic, and neutral reactive sites of NIC, OXA, monomer, and dimer models of salt were visualized by plotting the molecular electrostatic potential (MESP) surface. The study provides valuable insights into combining both experimental and theoretical results that could define the physicochemical properties of molecules.