Frontier Molecular Orbital Energies Research Articles

Synthesis, Optical Properties and DNA‐Binding Behavior of a Quinoxaline Ring‐Fused π‐Elongated Chlorin – Efforts Towards Preparation of Long Wavelength Absorbing Porphyrinoids

AbstractA porphyrinoid containing cis‐diol pyrroline subunit and fused nitro‐quinoxaline π‐elongated unit at its peripheral β,β’‐positions was prepared. The UV‐visible spectrum exhibits typical chlorin‐like sharp Qy‐band, but significantly more red‐shifted (687 nm) and more intense than for a normal diol chlorin. The precursor porphyrin exhibited weak Q‐bands slightly above 650 nm. The same porphyrin exhibited a low pH dependent ∼40 nm red‐shift in its UV‐visible spectrum. Analysis of the frontier molecular orbital energies using electrochemical techniques and theoretical analysis of the lowest energy geometry of the porphyrin confirmed the roles of non‐planar conformation and electronic charge redistribution in inducing this spectral feature. In addition, biophysical and computational analysis of DNA‐binding behavior of these porphyrinoids indicated that groove binding induced by Van der Waals contacts was the preferred mode of interaction.

Integrated bioinformatics-cheminformatics approach toward locating pseudo-potential antiviral marine alkaloids against SARS-CoV-2-Mpro.

The emergence of the severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) with the most contagious variants, alpha (B.1.1.7), beta (B.1.351), delta (B.1.617.2), and Omicron (B.1.1.529) has continuously added a higher number of morbidity and mortality, globally. The present integrated bioinformatics–cheminformatics approach was employed to locate potent antiviral marine alkaloids that could be used against SARS‐CoV‐2. Initially, 57 antiviral marine alkaloids and two repurposing drugs were selected from an extensive literature review. Then, the putative target enzyme SARS‐CoV‐2 main protease (SARS‐CoV‐2‐Mpro) was retrieved from the protein data bank and carried out a virtual screening‐cum‐molecular docking study with all candidates using PyRx 0.8 and AutoDock 4.2 software. Further, the molecular dynamics (MD) simulation of the two most potential alkaloids and a drug docking complex at 100 ns (with two ligand topology files from PRODRG and ATB server, separately), the molecular mechanics/Poisson‐Boltzmann surface area (MM/PBSA) free energy, and contributions of entropy were investigated. Then, the physicochemical‐toxicity‐pharmacokinetics‐drug‐likeness profiles, the frontier molecular orbitals energies (highest occupied molecular orbital, lowest unoccupied molecular orbital, and ΔE), and structural–activity relationship were assessed and analyzed. Based on binding energy, 8‐hydroxymanzamine (−10.5 kcal/mol) and manzamine A (−10.1 kcal/mol) from all alkaloids with darunavir (−7.9 kcal/mol) and lopinavir (−7.4 kcal/mol) against SARS‐CoV‐2‐Mpro were recorded. The MD simulation (RMSD, RMSF, Rg, H‐bond, MM/PBSA binding energy) illustrated that the 8‐hydroxymanzamine exhibits a static thermodynamic feature than the other two complexes. The predicted physicochemical, toxicity, pharmacokinetics, and drug‐likeness profiles also revealed that the 8‐hydroxymanzamine could be used as a potential lead candidate individually and/or synergistically with darunavir or lopinavir to combat SARS‐CoV‐2 infection after some pharmacological validation.

Solvent polarizability modulated the electronic state of conjugated long-chain polyene molecules by DFT

As a typical organic conjugated long-chain polyene molecule, the study of β-carotene’s molecular structure in local environments is of great significance. Quantum chemical calculations of β-carotene in different polarization fields were carried out with density functional theory (DFT). The lowest energy structure of the ground state had a centrosymmetric structure, and the bond length of β-carotene was between 1.084 and 1.549 Å. The influence of the polarization field on the electronic state of β-carotene mainly manifested in the Raman intensity, frontier molecular orbital energy, dipole moment, and polarizability. With the decrease of the solvent polarizability, the Raman intensity, dipole moment, and polarizability of β-carotene decreased. Conversely, the highest occupied molecular orbital (HOMO) – the lowest unoccupied molecular orbital (LUMO) gap increased. The difference between the infrared (IR) activity and Raman activity of β-carotene was studied by vibration analysis, and the Raman peaks that could not be distinguished during experiments were decomposed and assigned.

Investigations on spectroscopic, ADMET properties and drug-likeness, molecular docking, chemical properties of (2E)-3-(biphenyl-4-yl)-1-(2,4-dichlorophenyl)-prop-2-en-1-one by combined density-functional theory

The title compound, (2E)-3-(Biphenyl-4-yl)-1-(2,4-dichlorophenyl)-prop-2-en-1-one (BPDC) has been derived from the compounds namely biphenyl-4-carbaldehyde and 2,4-dichloroacetophenone to perform 3D-Potential energy conformations for molecular stability by DFT calculation of B3LYP/6-311++G(d,p). The geometrical optimization and atoms vibrational spectral data observed FT-IR and FT-Raman spectra values were compared with theoretical values (B3LYP, CAM-B3LYP). The molecule was characterized by absorbed infrared radiation, scattered Raman techniques with the attention on important functional groups (Cl, O, N). Electro negativity difference has been discussed and their biochemical and biomedical properties have been examined. The chemical reactivity of the compound was characterized by MEP-map, NHO, NLMO, and NBO analyses. The frontier molecular orbital (HOMO–LUMO) energy gap, vertical electron truncation of UV–Visible spectrum, and their λ-max value have been compared with CAM-B3LYP and M062X/6-311++G(d,p) approach data. The orbitals arrangements were studied by the density of states (DOS) and the partial density of states (PDOS). BPDC is investigated by Hirshfeld surface analysis that employs three-dimensional contours and two-dimension fingerprint area for intermolecular interactions quantitatively. The biological investigations like drug-likeness and toxicity properties of BPDC molecule were conformed to Lipinski's rule of five and ADMET properties, respectively. The title molecule exhibits a good bioactive score and less toxicity. Antibacterial and also antifungal activities of BPDC were done by docking analysis.

Synthesis, crystal structures, α-glucosidase and α-amylase inhibition, DFT and molecular docking investigations of two thiazolidine-2,4-dione derivatives

In this work, two thiazolidine-2,4-dione derivatives 3 and 4 have been synthesized and characterized through infrared (IR), nuclear magnetic resonance (1H/13C NMR), mass spectrometry (ESI-MS) and single-crystal X-ray diffraction (XRD). The optimized geometries, the vibrational frequencies, the frontier molecular orbital (HOMO-LUMO) energies and thermodynamic properties of the two molecules 3 and 4 were investigated using Density Functional Theory (DFT) calculation at the B3LYP/6-31++G(d,p) level of theory. Further, 3 and 4 were tested in vitro for their anti-diabetic activity through the inhibition of α-glucosidase and α-amylase enzymes. Binding interactions of 3 and 4 with α-glucosidase and α-amylase binding sites were emphasized by the analysis of molecular docking outputs. The results showed that the two compounds have low binding energies and good affinity toward the active site residues. Thus, they may be considered as good inhibitors of α-glucosidase and α-amylase enzymes.

Rational design of phenothiazine-based hole transport material with fluorene-containing asymmetric peripheral donor group for perovskite solar cells

Developing low-cost and highly efficient hole transport materials (HTMs) is extremely important to promote the industrial application of perovskite solar cells (PSCs). Phenothiazine (PTZ) is validated as promising building block to construct low-cost and highly efficient HTM for PSCs. In this work, by using PTZ as core unit, we reported two HTMs, termed PTZT-MPF and PTZT-FF, through substituting the peripheral methoxybenzene group with fluorene. The asymmetric fluorene substituted donor provides the corresponding HTM PTZT-MPF with higher hole mobility, suitable frontier molecular orbital energy levels and smoother film morphology. As a result, the PTZT-MPF based PSCs exhibits a promising PCE of 20.15% with an enhanced open-circuit (Voc) of 1.13 V, even higher than well-known Spiro-OMeTAD. Meanwhile, with the fluorene substitution, the hydrophobicity of HTM is promoted with improved, and guarantee improved long-term stability for PTZT-MPF based PSCs.

DFT analysis of valproic acid adsorption onto Al12/B12-N12/P12 nanocages with solvent effects.

Using density functional theory, the adsorption of valproic acid onto the surface of fullerene-like nanocages was investigated. Valproic acid interacts with the nanocages through the carboxylic group with energies of - 144.14, - 109.71, - 105.22, and - 84.96kcal/mol. The frontier molecular orbital (FMO) energy levels were considerably altered upon adsorption, resulting in a reduction in energy gap and increase in electrical conductivity. This suggests that nanocages could be used as sensors as well as options for drug administration in biological systems. Solvation effects in water are also reported.

Two novel pyrazine Zn(II)-porphyrins complexes: Synthesis, photophysical properties, structure study, DFT-Calculation and assessment of an azo dye removal from aqueous solution

In the current work, two new zinc-porphyrinic complexes bearing pyrazine as axial ligand, i.e. (pyrazine)(meso-tetrakis-(4-phenoxyphenyl)porphyrinato)zinc(II) [Zn(TBOPP)(pyz)] (1) and (aqua)(pyrazine)(meso-tetrakis(3,4,5-trimethoxyphenyl)porphyrinato)zinc(II) monohydrate [Zn(TTMP)(pyz)(H2O)].H2O (2) were successfully synthesized. New complexes were extensively characterized using elemental analysis, 1H NMR, UV–visible, single-crystal X-ray, and mass spectrometry (ESI) techniques. Single crystal X-ray studies revealed penta-coordinated environment around each Zn(II) metal in complexes with pyrazine as an axial ligand. The complexes were stabilized by weak C–H … Cg π intermolecular interactions involving pyridyl, phenyl and pyrrole centroid rings. Optical absorption studies confirmed the medium band gap and semiconducting nature of the compounds. Emission studies indicated that the axial ligand has no significant effect on the fluorescence quantum yields (ɸf) and the lifetime (τf) values. The ability of calmagite dye (an anionic dye) to remove the free bases and the Zn(II) complexes from aqueous solution has also been presented. Frontier molecular orbital (HOMO-LUMO) energies for H2TBOPP, H2TTMP, [Zn(TBOPP)] and [Zn(TTMP)] with calmagite were determined using density functional theory (DFT) calculation showing the charge transfer within the molecule.

Synthesis, crystal structure, spectroscopic characterization, Hirshfeld surface analysis, DFT calculation and molecular modeling studies of 1-(4-Nitro-phenyl)-3,5-di-thiophen-2-yl-1H-pyrazole

Based on single crystal X-ray diffraction studies for 1-(4-nitrophenyl)-3,5-di-thiophen-2-yl-1H-pyrazole (2a), monoclinic crystal system with a space group of C2/c was determined, where a final residual value of R equals to 0.058. The synthesized compounds were characterized through 1H and 13C NMR spectroscopy, and its intermolecular interactions were considered utilizing 2D and 3D Hirshfeld surface studies. The optimized molecular geometry, vibrational frequencies, and frontier molecular orbital energies of the title molecule were explored using density functional theory. Molecular modeling study revealed feasible binding modes of the title compound to protein targets, which showed small binding free energies.

Bis(2-pyridyl)diimine as a naked eye colorimetric fluorescence turn off probe selectively for Fe(II) ions as a consequence of energy changes in the electronic states upon complexation

Bis(pyridyl)diimine, (1E,1′E)-N,N'-(ethane-1,2-diyl)bis(1-(pyridin-2-yl)methanimine) (L) has coordinating nitrogen atoms in effective positions to form stable chelates with metal ions and is capable of capturing a range of transition metal ions. However, the selective colorimetric response of Fe(II) by using L was observed. Colourless to purple coloured transition resulted on complexation of L with Fe(II) ions selectively and was not affected by the presence of other transition metal ions including Fe(III) ions. Photoluminescence studies have shown the quenching of emission maxima corresponding to L in the presence of Fe(II) ions along with appearance of new peaks at higher wavelength regions. Appearance of a specific color change, which can be visualized by naked eye and an added photophysical feature involving quenching of emission spectra, particularly for Fe(II) are associated with the changes in the electronic state energies of L upon complexation with Fe(II). Thermodynamic estimation of complex stability was done by determining the binding constant of the complex, which was found to be 7.2 × 1010 M−2 using Yoe Jones method. A binding ratio of 1:2 for L and Fe2+ was determined experimentally with help of mole ratio method, which hinted at the geometrical possibilities of the complex of L with Fe(II).). Limit of detection (LOD) for the identification of Fe(II) ions with L was determined using colorimetric naked eye method and was found to be 25 μM. Further L was also used to detect Fe(II) in real sample i.e. river water. NMR analysis supported the low spin state of Fe(II) in the Fe(II)-L complex. Anticipated geometry of the Fe(II)-L complex was optimized using Gaussian09 software through the B3LYP method, which upon investigation of the energies of frontier molecular orbitals, provided the details related to the electronic properties associated with the complexation of Fe(II) and L.

Spectroscopic and topological analysis and in vitro antimicrobial activity of phenothiazine

The vibrational spectral analysis of phenothiazine is done by experimental results and theoretical investigation for identifying its pharmaceutical nature. The experimentally observed vibrational wavenumbers are compared with the calculated vibrational frequencies. Natural bond orbital analysis interprets the intramolecular contacts of phenothiazine molecules. Ultraviolet-visible spectra of the phenothiazine have also been recorded and the electronic properties. The 1H and 13C nuclear magnetic resonance chemical shifts of the molecule have been calculated by the Gauge Independent Atomic Orbital method and compared with the experimental outcome. The interpreted frontier molecular orbital energies indicated the chemical stability of the molecules. Fukui function and Mulliken analysis on atomic charges of the phenothiazine have been discussed. Docking studies were performed for phenothiazine using the molecular docking software with 3 fungicidal active proteins. The stability of the title compound has been investigated via molecular dynamics simulations. The in-vitro analysis had done with fungal and bacterial pathogens, Aspergillus niger and E.Coli.

Rapid Computational Approach Towards Designing Singlet-Fission Chromophores by Tuning the Diradical Character of Heteroatom-Doped Polycyclic Aromatic Hydrocarbons Using the Atom-Specific Fukui Function.

Singlet fission (SF) is proposed as a promising method to circumvent the Shockley-Queisser threshold of single junction photovoltaics. Progress towards realizing efficient SF-based devices has been impeded by the fact that only a handful of molecules and their derivatives practically exhibit efficient SF. In the present work, we demonstrate a TDDFT-based rapid and cost-effective computational approach for designing SF chromophores by doping various atomic sites (substituting carbon atoms) of polycyclic aromatic hydrocarbons with nitrogen, phosphorus, and silicon. We establish a hitherto unexplored, direct correlation between the atom-specific chemical reactivity parameter─Fukui function─of these molecules with their frontier molecular orbital energies, diradical characters, and vertical singlet and triplet excitation energies. These quantitative correlations show exactly opposite trends for nitrogen-doped molecules and phosphorus- or silicon-doped molecules. The doped derivatives that have the Fukui function falling in a range of 0.03-0.14 possess the required intermediate diradical character and suitable singlet-triplet energies to qualify for SF candidature. Our findings enable one, at reasonable computational times and cost, to easily assess the doping criteria and to develop design rules for SF molecules in particular and for diradicaloids in general.

Binding and Photocleavage Studies of Ru (II) Polypyridyl Complexes with DNA: An In Silico and Antibacterial activity

The global crisis of bacterial infections, search for an effective antibacterial is of utmost clinical significance. Experimental and computational approaches used to study the DNA binding of [Ru(A)2L] (ClO4)2.2H2O, where A=ancillary ligand; phen=1, 10 Phenanthroline (1), dmp=4,4’-dimethyl-1,10 -orthophenanthroline (2), bpy = bipyridyl (3) & dmb=4, 4’-dimethyl 2, 2’- bipyridine (4), Lis a novel intercalator ligand MPPIP=(2-(1-(2-methoxyphenyl)-1H-pyrazol-4-yl)-1H-imidazo [4,5-f][1,10]Phenanthroline) and their antibacterial activity. The synthesized complexes and their DNA affinity studies were executed by absorption, emission, and viscosity techniques to show binding via intercalation. The intrinsic binding constant, Kb indicates that the simple ancillary ligands (phen and bpy) are more robust binding. The 3D Conformational analysis shows slight distortion from octahedron geometry. The molecular descriptors calculated from the frontier molecular orbital energy gap, ΔE point that the complex of phen show higher binding with DNA. Further analysis of the molecular attributes show that the pyrazole ring of the intercalator Ligand is significant for DNA binding. Furthermore, the molecular docking studies of the Ru (II)-MPPIP complexes with DNA exhibit an inclination towards Guanine-rich sites by the Nitrogen of the pyrazole ring. Biological investigations establish that all the complexes were active against S. aureus and E. coli.

Synthesis and computational studies on a coumarin derivative: 4-chloromethyl coumarin-7-yl-methacrylate

In this article, we report the synthesis, X-ray structure determination, geometric parameters, vibrational frequencies, NMR, and UV spectra of a coumarin derivative titled 4-chloromethyl coumarin-7-yl-methacrylate (CCMA). In the study, the theoretical vibrational frequencies, NMR and UV spectra, and optimized geometric parameters were computed by using density functional theory with the hybrid methods B3LYP/6-31+G(d,p) basis set. The optimized geometric parameters, vibrational frequencies, and 1H and 13C NMR chemical shifts values were contrasted with experimental values of the title molecule. The theoretical vibrational frequencies were found in concordance with the matching experimental data. The electronic properties of the molecule were studied using the molecular frontier orbital energies, ESP surfaces, the natural bond orbital (NBO), and nonlinear optical (NLO) properties. The study findings show that the molecule has nucleophilic regions around O atoms and the transition from the ground state to the first excited state with the electronic absorption peaks at 318.19 nm in gas. In this study, the remarkable electron delocalization occurred between the donor (C4-C5) anti bond and acceptor (C6-C9) anti bond with 249.60 kcal/mol stabilization energy in the title molecule. Calculated NLO parameters show that CCMA can be used as the NLO material.

A combined experimental and theoretical study of alkyl 2-(3-benzoyl-4‑hydroxy-1,1-dioxido-2H-benzo[e][1,2]thiazin-2-yl)acetates: Synthesis, X-ray crystallography and DFT

Benzothiazine derivatives belongs to an important class of organic compounds with a wide range of application in the field of biotechnology and medicinal chemistry, and many of its derivatives have been considered in drug discovery. A series of three alkyl 2-(3-benzoyl-4‑hydroxy-1,1-dioxido-2H-benzo[e][1,2]thiazin-2-yl)acetates (3a–c) were synthesized from the sulfonimidamides through multistep reactions. The molecular geometry of these compounds has been investigated with the help of X-ray crystallography and quantum mechanical calculations. The molecular structural optimization and structural properties were calculated using the Density Functional Theory method and B3LYP hybrid functional with 6–311+G* basis set. Non-covalent interactions studies, energetics and reactivity properties of 3a-c compounds have been explored through local and global reactivity descriptors, UV-Visible spectral analysis and molecular electrostatic potential illustrations. It is found that the compound 3b is more reactive than others because of its lowest frontier molecular orbital energy gap (ΔE=3.46 eV) and low chemical hardness (η=0.23eV) than others. Furthermore, the investigations of Non-linear optical properties and thermodynamic parameters have also been carried out which shows that these compounds can be used as a non-linear optical material in the field of telecommunication and information technologies.

Backbone Configuration and Electronic Property Tuning of Imide‐Functionalized Ladder‐Type Heteroarenes‐Based Polymer Acceptors for Efficient All‐Polymer Solar Cells

AbstractElectron‐deficient ladder‐type π‐conjugated systems are highly desired for constructing polymer acceptors due to their unique electronic properties. Herein, two series of polymer acceptors PBTIn‐(F)T (n = 1–4) based on imide‐functionalized ladder‐type heteroarenes (BTIn) with tunable conjugation length are synthesized. Effects of their backbone configuration and electronic properties on film morphology and performance of all‐polymer solar cells (all‐PSCs) are systematically investigated through theoretical computation, Raman spectroscopy, grazing incidence wide‐angle X‐ray scattering, etc. It is found that the ladder‐type heteroarene size extension and polymer backbone fluorination gradually lower the frontier molecular orbital energy levels, leading to progressive bandgap narrowing with more efficient exciton dissociation. Furthermore, the centrosymmetric and axisymmetric characteristics of BTIn result in distinct backbone configuration with varied self‐aggregation and crystalline phases, hence determining the blend film morphology. The highest efficiencies in these two series are attained from PBTI3‐T and PBTI3‐FT with a curved backbone configuration. PBTI4‐(F)T with further extended heteroarenes shows linear backbone, negatively affecting film morphology and efficiency. This study provides fundamental material structure‐device performance correlations for ladder‐type heteroarenes‐based polymer acceptors for the first time and demonstrates that more extended ladder‐type backbones do not necessarily improve the device performance, offering guidelines for designing polymer acceptors to maximize all‐PSC performance.

Updated Calibrated Model for the Prediction of Molecular Frontier Orbital Energies and Its Application to Boron Subphthalocyanines.

A diverse range of computational methods have been used to calibrate against available data and to compare against the correlation for the prediction of frontier orbital energies and optical gaps of novel boron subphthalocyanine (BsubPc) derivatives and related compounds. These properties are of fundamental importance to organic electronic material applications and development, making BsubPcs ideal candidates in pursuit of identifying promising materials for targeted applications. This work employs a database of highly accurate experimental data from materials produced and characterized in-house. The models presented herein calibrate these properties with R2 values > 0.95. We find that computationally inexpensive semiempirical methods such as PM6 and PM7 outperform most density functional theory methods for calibration. We are excited to share these results with the field as it empowers the community to determine key physical properties of BsubPcs with confidence using free software and a standard laptop prior to the arduous synthesis and purification thereof. This study is a follow up to our previous work calibrating PM3, RM1, and B3LYP-6-31G(d), which used a smaller set of BsubPc derivatives at a past point when less data were available.

Quantum Mechanical Investigation into the Adsorption Pattern of Clomipramine and Methotrimeprazine HCl with Graphene and Fullerene

The importance of impurity-related detection and certification in drug manufacture is highlighted in this study, which presents theoretical structural and spectral properties of clomipramine (CPA) and methotrimeprazine HCl (MPH) as well as their adsorption on graphene and fullerene. Investigating adsorption may reveal details about their reactivity, electronic and structural properties. The molecule’s frontier molecular orbitals (FMOs) energies and energy gaps were calculated. Three-dimensional visualization of the electrostatic potential diagrams was mapped. Docking was used to find the binding with the receptors. Enhancement for different wave numbers is seen in the graphene/fullerene complex-molecules assembly. Non-covalent interactions (NCI) can be characterized using topological analysis and the respective isosurfaces. In the CPA-graphene cluster, the graphene system shows strong repulsive non-covalent interactions (red portions). Two small green portions of the isosurface between CPA and graphene frameworks indicate weak non-covalent interactions.

Copper hydrazone complexes with different nuclearties and geometries: Synthesis, characterization, single crystal structures, Hirshfeld analysis and superoxide dismutase mimetic activities

Three new copper(II) hydrazone complexes [Cu(L)(neocuproine)]NO31, [Cu(L)(6-benzylaminopurine)ClO4] 2 and [Cu(L)μ(1,1-N3)Na(H2O)2] 3 with different nuclearties and geometries using acetic acid(2‑hydroxy-3‑methoxy-benzylidene)-hydrazide (HL) as proligand and neucuproine, 6-benzylaminopurine and sodium azide as co-ligands have been synthesized and characterized using several physico-chemical and spectral methods. Molecular structures of complexes were obtained by single crystal diffraction technique. The coordination sphere in complexes 1 and 2 can be illustrated as distorted square pyramidal geometry whereas 3 has distorted square planar geometry. Supramolecular structures were formed via different intermolecular interactions like hydrogen bondings and CH⋯π in 1, hydrogen bondings, CH⋯π and lp⋯π in 2 and hydrogen bondings, CH⋯π, lp⋯π and π⋯π(chelate-chelate) interactions in 3. The Hirshfeld surface analysis exhibited O⋯H, N⋯H and C⋯H interactions in all complexes. The optimized geometry of newly synthesized complexes were obtained by B3LYP/LANL2DZ model. From the differences in energies of frontier molecular orbitals (ΔEg), reactivity parameters like, ionization potential (IP), electron affinity (EA), electronegativity (χ), softness (S), hardness (η) and electrophilicity index (ω) were determined. In these complexes the Epr parameters (g-) showed the trend g∥>g⊥>2.0023, which is consistent with a dx2−y2 ground state in a square based geometry. Electrochemical properties also determined using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Additionally, superoxide dismutase catalytic activity measurements were performed by nitro blue tetrazolium chloride (NBT) assay in phosphate buffer. All complexes catalyzed the dismutation of superoxide at biological pH. Enhancement in the SOD activity of 2 can be credited to the coordinated poorly bound ClO4− ion which is easily replaced by O2·− ion.

Novel zinc (II) and nickel (II) complexes of a quinazoline‐based ligand with an imidazole ring: Synthesis, spectroscopic property, antibacterial activities, time‐dependent density functional theory calculations and Hirshfeld surface analysis

AbstractTwo complexes [Zn(L)2(CH3OH)2](NO3)2 (1) and [Ni(L)3]·(NO3)2 (2) (L = 2‐[2‐imidazolyl]‐4‐methyl‐1,2‐dihydroquinazoline‐N3‐oxide) were obtained successfully by means of slow evaporation solution technique (SEST) and characterized using elemental analysis, FT‐IR, UV–vis, and fluorescence spectroscopic. X‐ray diffraction revealed that the metal in complex 1 is chelated by two L ligands and two lattice methanol molecules, whereas in 2 by three L ligands, counterbalanced by nitrate ions. The crystal structures of both showed infinite 1‐D, 2‐D, and 3‐D supramolecular architecture due to intermolecular interactions. Most strikingly, Zn (II) complex showed different fluorescence properties in diverse solvents. The antimicrobial activities of all compounds were compared and showed perceptible efficiency against Gram‐negative and Gram‐positive bacteria. Electrostatic potential (ESP) calculation was used to predict the nucleophilic and electrophilic attack sites. Density functional theory (DFT) calculation results showed good agreement with experimental data, as well as the frontier molecular orbital energy gaps were detected by time‐dependent (TD)‐DFT method with HOMO–LUMO calculations. Additionally, the non‐covalent interactions of both complexes were further quantified and explored with the help of Hirshfeld surface analysis.