Computational prediction for designing novel ketonic derivatives as potential inhibitors for breast cancer: A trade-off between drug likeness and inhibition potency.

Unlike simple molecular screening, a combined hybrid computational methodology has been applied which includes quantum chemical methods, molecular docking, and molecular dynamics simulations to design some novel ketonic derivatives. The current study contains the derivatives of an experimental ligand which are designed as a trade-off between drug likeness and inhibition strength. We investigate the interaction of various newly designed ketonic compounds with the breast cancer receptor known as the Estrogen Receptor Alpha (ERα). The molecular structures of all newly designed ligands were studied quantum chemically in terms of their fully optimized structures, 3-D molecular orbital distributions, global chemical descriptors, molecular electrostatic potentials and energies of frontier molecular orbitals (FMOs). All ligands under study show good binding affinities with the ERα protein. The ligands CMR2 and CMR4 exhibit improved molecular docking interactions. The intermolecular interactions indicate that CMR4 demonstrates better hydrophobic and hydrogen bonding interactions with protein (ERα). Furthermore, molecular dynamics simulations were conducted on ligands and reference drugs interacting with the ERα protein over a time span of 120 nanoseconds. The molecular dynamics results are interpreted in terms of ligand-protein stability and flexible behaviour based on their respective values of RMSD, RMSF, H-bonds, the radius of gyration, and SASA graphs. To analyse ligand-protein interactions throughout the entire 120 ns trajectory, a more advanced MM/PBSA method is utilized, where six selected ligands (CMR1, CMR2, CMR3, CMR4, CMR5 and CMR9) illustrate promising results for inhibition of the ERα receptor as assessed through MM/BBSA analysis. The CMR9 has the highest MM/BBSA binding free energy (-14.46 kcal/mol). The ADMET analysis reveals that CMR4 has maximum intestinal absorption (6.68) and clearance rate (0.1). All the compounds are non-toxic and safe to use. These findings indicate the potential of involving different computational techniques to design the ligand structures and to study the ligand-protein interactions for better understanding and achieving more potent synthetic inhibitors for breast cancer.

Theoretical, in Vitro Antiproliferative, and in Silico Molecular Docking and Pharmacokinetics Studies of Heteroleptic Nickel(II) and Copper(II) Complexes of Thiosemicarbazone-Based Ligands and Pefloxacin.

Twelve new heteroleptic nickel(II) and copper(II) complexes of the type [M(L1-6 )(Pfx)2 ] (1-12), where L1-6 =2-benzylidenehydrazinecarbothioamide (L1 ), 2-benzylidene-N-methylhydrazinecarbothioamide (L2 ), 2-benzylidene-N-phenylhydrazinecarbothioamide (L3 ), 2-(4-methylbenzylidene)hydrazinecarbothioamide (L4 ), 2-(4-methylbenzylidene)-N-methylhydrazinecarbothioamide (L5 ) and 2-(4-methylbenzylidene)-N-phenylhydrazinecarbothioamide (L6 ), Pfx=pefloxacin and M=Ni(II) or Cu(II) have been synthesised, and their structures were confirmed by different spectral techniques. The spectral data and density functional theory (DFT) calculations supported the bonding of pefloxacin drug molecule via one of the carboxylate oxygen atoms and the pyridone oxygen atom, and the thiosemicarbazone ligand via the imine nitrogen and the thione sulfur atoms with the metal(II) ion, forming distorted octahedral geometry. In vitro antiproliferative activity of the synthesized complexes was evaluated against three human breast cancer (T47D, estrogen negative (MDA-MB-231) and estrogen positive (MCF-7)) as well as non-tumorigenic human breast epithelial (MCF-10a) cell lines, which showed the higher activity for the copper(II) complexes. The interaction of the synthesized complexes with an oncogenic protein H-ras (121 p) was explored by in silico molecular docking studies. Further, in silico pharmacokinetics and ADMET parameters were also analysed to predict the drug-likeness as well as non-toxic and non-carcinogenic behavior, and safe oral administration of the complexes.

Molecular design of D-π-A-π-D small molecule donor materials with narrow energy gap for organic solar cells applications.

CONTEXT: Developing novel materials present a great challenge to improve the photovoltaic performance of organic solar cells (OSCs). In this paper, we designed a series of the donor-π bridge-acceptor-π bridge-donor (D-π-A-π-D) structure molecules. These molecules consist of diketopyrrolopyrrole (DPP) moiety as core, 9-hexyl-carbazole moiety as terminal groups, and different planar electron-rich aromatic groups as π-bridges. The density functional theory (DFT) and time-dependent DFT (TD-DFT) computations showed that the frontier molecular orbital (FMO) energy levels, energy gaps, electron-driving forces (ΔEL-L), open-circuit voltage (Voc), fill factor (FF), reorganization energy (λ), exciton binding energy (Eb), and absorption spectra of the designed molecules can be effectively adjusted by the introduction of different π-bridges. The designed molecules have narrow energy gap and strong absorption spectra, which are beneficial for improving the photoelectric conversion efficiency of organic solar cells. In addition, the designed molecules possess large ΔEL-L, large Voc, and FF values and low Eb when the typical fullerene derivatives are used as acceptors. The FMO energy levels of the designed molecules can provide match well with the typical fullerene acceptors PC61BM, bisPC61BM, and PC71BM. Our results suggest that the designed molecules are expected to be promising donor materials for OSCs. METHODS: All DFT and TD-DFT calculations were carried out using the Gaussian 09 code. The computational technique chosen was the hybrid functional B3LYP and the 6-31G(d,p) basis set. The benzene and chloroform solvent effects have been considered using the polarized continuum model (PCM) at the TD-DFT level. The simulated absorption spectra of designed molecules were plotted by using the GaussSum 1.0 program.

1,3-Butadiynamides the Ethynylogous Ynamides: Synthesis, Properties and Applications in Heterocyclic Chemistry.

1,3-butadiynamides-the ethynylogous variants of ynamides-receive considerable attention as precursors of complex molecular scaffolds for organic and heterocyclic chemistry. The synthetic potential of these C4-building blocks reveals itself in sophisticated transition-metal catalyzed annulation reactions and in metal-free or silver-mediated HDDA (Hexa-dehydro-Diels-Alder) cycloadditions. 1,3-Butadiynamides also gain significance as optoelectronic materials and in less explored views on their unique helical twisted frontier molecular orbitals (Hel-FMOs). The present account summarizes different methodologies for the synthesis of 1,3-butadiynamides followed by the description of their molecular structure and electronic properties. Finally, the surprisingly rich chemistry of 1,3-butadiynamides as versatile C4-building blocks in heterocyclic chemistry is reviewed by compiling their exciting reactivity, specificity and opportunities for organic synthesis. Besides chemical transformations and use in synthesis, a focus is set on the mechanistic understanding of the chemistry of 1,3-butadiynamides-suggesting that 1,3-butadiynamides are not just simple alkynes. These ethynylogous variants of ynamides have their own molecular character and chemical reactivity and reflect a new class of remarkably useful compounds.

DFT analysis and in silico exploration of drug-likeness, toxicity prediction, bioactivity score, and chemical reactivity properties of the urolithins.

Urolithins (Uro) are human microflora-derived metabolites of ellagic acid and ellagitannins. It has been shown to be a powerful modulator of oxidative stress, agents with potential anti-inflammatory, antiproliferative, and antiaging properties. The present study aimed to explore the drug-likeness, toxicity, and bioactivity score of urolithins that were required to be considered oral drug-active using the web-based softwares, Molinspiration, and protox_II. In addition, the chemical reactivity descriptors of the urolithins (Uro A, Uro B, Uro, C, Uro D) were also determined through density functional (DFT) calculations. Furthermore, electrostatic potential (MEP), natural bonds orbitals (NBO), HOMO-LUMO energies, chemical reactivity descriptors, dipole moment, and Fukui functions of all the urolithins were investigated by resorting the conceptual of DFT at the M06-2X/6-311++G (d, p) basis set as a tool to analyse and comprehend the molecular interaction. The results showed that all the urolithins comply with the Lipinski's rule of five and have biological activity. According to the toxicity predictions, Uro A, Uro C, and Uro D belong to class 4 while Uro B belongs to class 6. The chemical reactivity and stability features of the investigated compounds were evaluated using global chemical reactivity descriptors calculated from the Frontier Molecular Orbitals (FMOs) energies gap, which revealed that the stability order of the molecules was Uro B > Uro C > Uro D > Uro A. The present findings indicate that the urolithins could be a promising candidate for development into a therapeutic medication.Communicated by Ramaswamy H. Sarma.

Unraveling photo-induced proton transfer mechanism and proposing solvent regulation manner for the two intramolecular proton-transfer-site BH-BA fluorophore.

To expound specific excited state processes of the novel excitation wavelength dependent emission BH-BA fluorophore for better subsequent applications, this wok mainly focus on exploring photo-induced hydrogen bonding geometrical changes, excited state intramolecular proton transfer (ESIPT) mechanism and related regulated behavior via solvent polarity. The differences of structural parameters, infrared (IR) vibrational spectra, core-valence bifurcation (CVB) index as well as electronic densities ρ(r) between S0 and S1 states related to dual hydrogen bonds (O1-H2···N3 and O4-H5···N6) reveal S1-state hydrogen bonding strength facilitate ESIPT behaviors for BH-BA system. Of particular note, O4-H5···N6 plays a more dominant role. Photo-induced intramolecular charge transfer (ICT) and variations of Hirshfled and NPA charges over atoms related to hydrogen bonding moieties promote the ESIPT tendency for BH-BA. Combined potential energy surfaces (PESs), transition state (TS) and intrinsic reaction coordinate (IRC) paths, we illustrate the excited state intramolecular single proton transfer (ESISPT) mechanism of BH-BA should occur along with O4-H5···N6 hydrogen bonding wire, which could be adjusted by surrounding solvent polarity.

Determination of phenolic compounds and antioxidant potential of aqueous extracts of Curcuma longa L., Piper nigrum L. and Cuminum cyminum: an experimental and a quantum-mechanical study / Determinação de compostos fenólicos e potencial antioxidante dos extratos aquosos de Curcuma longa L., Piper nigrum L. e Cuminum cyminum: um estudo experimental e quanto-mecânico

Objectives: Evaluation of phenolic compounds and antioxidant activities of aqueous extracts of C. longa, P. nigrum and C. cyminum. In addition to proposing a quantum-mechanical model to evaluate the antioxidant activity. Methods: The aqueous extracts were prepared using roots of the Curcuma longa L., seeds of the Piper nigrum L. and seeds of Cuminum cyminum. The extracts were subjected to tests to detect and quantify phenolic compounds and to assess their antioxidant capacity by different methods. Furthermore, to investigate the electronic nature of the antioxidant activity of the main compounds present in these extracts, frontier molecular orbitals (FMOs) were obtained by the DFT/B3LYP/6-31G(d,p) level of theory. Results: After statistical analysis of the results, a greater number of phenolic compounds and better antioxidant activity was identified in the aqueous extracts of cumin (C. cyminum) in all three assays performed, when compared to the other extracts tested. The theoretical model based on the Pietro method is in agreement with the experimental results. Conclusion: This study has an innovative proposal with the trivial antioxidant activity combined with theoretical quantum-mechanical calculations that can serve to reduce costs and time and to predict the antioxidant activity of subsequent studies.

Objetivos: avaliar os compostos fenólicos e atividades antioxidantes dos extratos aquosos de C. longa, P. nigrum e C. cyminum bem como propor um modelo quanto-mecânico para avaliar a atividade antioxidante. Métodos: os extratos aquosos foram preparados por meio da utilização de raízes de Curcuma longa L., sementes de Piper nigrum L. e sementes de Cuminum cyminum. Os extratos foram submetidos a ensaios para detectar e quantificar compostos fenólicos e atividade antioxidante por diferentes métodos. Além disso, com objetivo de investigar a natureza eletrônica da atividade antioxidante dos principais compostos presentes nesses extratos, orbitais moleculares de fronteira (OMFs) foram obtidos pelo nível de teoria DFT/B3LYP/6-31G(d,p). Resultados: após as análises estatísticas dos resultados, a maior quantidade de compostos fenólicos com maior atividade antioxidante foi identificada no extrato aquoso do cominho (C. cyminum) em todos os ensaios realizados, quando comparados com os outros extratos testados. O modelo teórico baseado no método de Pietro está concordante com os resultados experimentais. Conclusão: este estudo possui uma proposta inovadora com a atividade antioxidante trivial combinada com cálculos quanto-mecânicos que podem servir para reduzir custos e tempo para predizer a atividade antioxidante de estudos futuros.

Antioxidant activity of erlotinib and gefitinib: theoretical and experimental insights.

Erlotinib and gefitinib are quinazoline derivatives with antineoplastic properties. Usually, intake of antineoplastic agents results in much a greater degree of oxidative stress, i.e. the production of free radicals, than induced by cancer itself. Hence, anticancerous drugs must also exhibit antioxidant activity but this has not been studied thus far. In this study, the antioxidant activity of erlotinib and gefitinib was examined by experimental and computational studies. It was found that erlotinib and gefitinib exhibit good 2,2-dipheny l-1-picrylhydrazyl (DPPH) radical and hydroxyl radical scavenging (HRS) activities. In DPPH assay, the IC50 for erlotinib and gefitinib were 0.584 and 0.696 mM, respectively, while IC50 for HRS assay were 0.843 and 1.03 mM for erlotinib and gefitinib, respectively. Structural characteristics such as frontier molecular orbitals (FMOs), molecular electrostatic potential maps (MESPs), and global descriptive parameters were calculated at DFT/B3LYP/6-311++G (d,p) on the optimized geometries of erlotinib and gefitinib. UV-visible spectroscopy revealed the possible electronic transitions between the FMOs and their associated excitation energies of both drugs and found that erlotinib has π to π* transitions while gefitinib has π to π* and σ to π* transitions. To elucidate the antioxidant activity of erlotinib and gefitinib, three mechanisms namely hydrogen atom transfer (HAT), single electron transfer proton transfer (SETPT), and sequential proton-loss electron-transfer (SPLET) were employed and articulated the results in arithmetic parameters like bond dissociation energy (BDE), proton affinity (PA), ionization potential (IP), electron transfer enthalpy (ETE), and proton dissociation enthalpy (PDE). Further, molecular docking studies have been carried out to have a better understanding of binding sites and modes of interaction with a well-known antioxidant target protein monoamine oxidase-B (MAO-B) employing docking scores and types of interactions. All the calculated parameters point out that though gefitinib and erlotinib were interchangeable, erlotinib requires a lesser amount of energy for proton transfer and electron transfer, moreover it scavenges radicals easily.

Theoretical insights into the radical scavenging activity of glipizide: DFT and molecular docking studies.

Glipizide is an N-sulfonylurea compound used in the treatment of hyperglycemia in patients with type 2 diabetes mellitus. In the present study, DFT-based computational methods and molecular docking studies have been performed to systematically evaluate the radical scavenger behavior of the title molecule. Structural characteristics such as molecular descriptors, frontier molecular orbitals, molecular potential mapping, and Mulliken charge population have been investigated. Thermodynamic parameters like proton affinity (PA), ionization potential (IP), bond dissociation energy (BDE), electron transfer enthalpy (ETE), and proton dissociation enthalpy (PDE) related to three antiradical mechanisms namely hydrogen atom transfer (HAT), sequential electron transfer proton transfer (SETPT) and sequential proton loss electron transfer (SPLET) have been studied. Also, molecular docking studies have been carried out to have a theoretical understanding of the molecular mechanism and for the elucidation of binding mode/modes of a compound targeted through non-covalent interactions. The obtained results are of great significance in better understanding the reaction mechanism of the title molecule and opens a new perspective for the design of potent antioxidant agents.

Exploring space-energy matching via quantum-molecular mechanics modeling and breakage dynamics-energy dissipation via microhydrodynamic modeling to improve the screening efficiency of nanosuspension prepared by wet media milling.

Introduction: The preparation of nanosuspensions by wet media milling is a promising technique that increases the bioavailability of insoluble drugs. The nanosuspension is thermodynamically unstable, where its stability might be influenced by the interaction energy between the stabilizers and the drugs after milling at a specific collision energy. However, it is difficult to screen the stabilizers and the parameters of milling accurately and quickly by using traditional analysis methods. Quantum-molecular mechanics and microhydrodynamic modeling can be applied to improve screening efficiency.Areas covered: Quantum-molecular mechanics model, which includes molecular docking, molecular dynamics simulations, and data on binding energy, provides insights into screening stabilizers based on their molecular behavior at the atomic level. The microhydrodynamic model explores the mechanical processes and energy dissipation in nanomilling, and even combines information on the mechanical modulus and an energy vector diagram for the milling parameters screening of drug crystals.Expert opinion: These modeling methods improve screening efficiency and support screening theories based on thermodynamics and physical dynamics. However, how to reasonably combine different modeling methods with their theoretical characteristics and further multidimensional and cross-scale simulations of nanosuspension formation remain challenges.

Revealing the role of fluorine pharmacophore in chalcone scaffold for shifting the MAO-B selectivity: investigation of a detailed molecular dynamics and quantum chemical study.

The development of highly selective monoamine oxidase-B (MAO-B) inhibitors has great therapeutic benefit in treatment of various neurodegenerative disorders. Recent study documented that shifting of fluorine atom from para to ortho position on the phenyl B ring of heteroaryl chalcones shown a remarkable shift in the selectivity and potency between MAO-A and MAO-B isoforms. Despite the large plethora of the design of new selective MAO-B inhibitors, the current paper illustrates the role and orientation of fluorine atom with remarkable MAO-B selectivity of three compounds (O23, O24 and O25), which differ from all other substituents encountered in the chalcone scaffolds is recently reported by our group. Conformational analyses of differential inhibitory effects of O23, O24 and O25 on MAO-A and MAO-B, differential analyses of complementary interactions at MAO-A/-B active sites and differential analysis of affinity binding and per-residue energy contributions are calculated by molecular dynamics study. Density functional theory based electronic structure calculations were employed with special emphasis to electrostatic potential and frontier molecular orbitals. Results of the current study can be used for lead modification and a new insight for the development of novel fluorinated chalcones for the treatment of various neurodegenerative disorders. Communicated by Ramaswamy H. Sarma.

The effects of electron-withdrawing and electron-donating groups on the photophysical properties and ESIPT of salicylideneaniline.

The photophysical properties and excited state intramolecular proton transfer (ESIPT) of salicylideneaniline (1a) and its derivatives (1b-1e) with different substituents have been investigated using the DFT and TD-DFT methods. The calculated results indicate that the introduction of electron-withdrawing group CN weakens the intramolecular hydrogen bond (H···N). However, the introduction of electron-donating group N(CH3)2 strengthens it. When the CN and N(CH3)2 groups are introduced simultaneously, the intramolecular hydrogen bond (H···N) is weakened. In addition, swapping the CN and N(CH3)2 group positions can enhance the intramolecular hydrogen bond (H···N). Compared to 1a, the absorption and emission spectra of compounds 1b-1e are red-shifted. Frontier molecular orbital analyses prove that the more intense intramolecular charge transfer characters caused by CN and N(CH3)2 substituents is responsible for the red shift of spectra. Potential energy curves indicate that ESIPT in salicylideneaniline (1a) and the CN substituted derivative (1b) is a non-barrier process, while in the N(CH3)2 substituted derivative (1c) and the CN and N(CH3)2 co-substituted derivative (1d), ESIPT needs to overcome the energy barriers of 2.32 kcal/mol and 3.38 kcal/mol, respectively. Exchanging the positions of CN and N(CH3)2 groups (1e) makes the ESIPT into a barrier-free process. Therefore, the substitution and position of CN and N(CH3)2 groups can affect the ESIPT process and induce different photophysical properties.

Experimental and theoretical study of the fluorescence emission of ferulic acid: Possible insights into the fluorescence properties of humic substances.

Ferulic acid ((E)-3-(4-hydroxy-3-methoxy-phenyl)prop-2-enoic acid, hereinafter FA) is a building block of plant cell walls that is commonly found in lignocellulose. As such, it is a potential component of humic substances produced by microbial degradation of plant spoils. The fluorescence excitation-emission matrix spectra of FA have an interesting humic-like shape, with bands that can be assimilated to the A and C regions of humic substances. Therefore, the study of FA photoluminescence might provide interesting insight into the still unknown processes that lay behind the fluorescence properties of humic compounds. FA is a weak diprotic acid that occurs in three different forms in aqueous solution (neutral H2FA, singly deprotonated HFA- and doubly deprotonated FA2-), which have slightly different absorption and emission properties. The "A-like" fluorescence emission of the FA species is accounted for by excitation from the ground singlet state S0 to singlet excited states higher than the first (S4 for H2FA, S5 for HFA-, and a state higher than S2 for FA2-), followed by radiationless deactivation to the first excited singlet state (S1), and by fluorescence emission according to the S1 → S0 transition. In contrast, the "C-like" emission is mainly caused by S0 → S1 excitation combined with S1 → S0 emission, but there is also a minor contribution from the S0 → S2 excitation that becomes significant for HFA-. The uneven variations with pH of the wavelengths of the maximum FA radiation absorption and fluorescence emission can be rationalised in the framework of the energy levels of the frontier (HOMO and LUMO) molecular orbitals of the different FA species. These levels are affected by charge interaction between the relevant electrons and the neutral (protonated) or negative (deprotonated) groups of each species.

Benchmark study of benzamide derivatives and four novel theoretically designed (L1, L2, L3, and L4) ligands and evaluation of their biological properties by DFT approaches.

Four novel ligands, namely N-benzhydryl benzamide, N, N-diphenethyl benzamide, N, N-dihexyl benzamide, and N, N-dioctyl benzamide (L1, L2, L3, and L4, respectively), based on the benzamide unit were designed and computed for their different properties, such as absorption spectrum, dipole moment, theoretically expected biological properties, and frontier molecular orbitals, by evaluating the HOMO/LUMO energy orbitals strength with DFT approaches and comparing these properties with the R benzamide properties available in literature. All molecules have a suitable frontier molecular orbital diagram and L1 exhibits maximum absorption at 246.8 nm due to the strong electron donating effect of the diphenylmethane ligand group. Moreover, strongly extended conjugated groups caused a redshift in absorption spectra. Newly designed molecules may show strong biological activities against cancer, bacterial diseases, and harmful fungal disorders. Graphical abstract Orbital energy, electron density and frontier molecular orbitals view of four designed novel benzamide derivates.

A series of blue-green-yellow-red emitting Cu(I) complexes: Molecular structure and photophysical performance.

In this work, we designed a series of [Cu(NN)(PPh3)2]BF4 complexes with different optical edge values and emission colors from blue to red, where NN and PPh3 denoted a diamine ligand and triphenylphosphine, respectively. Six NN ligands with various conjugation chains (short π chain, modest π chain and long π chain) were selected. A systematical comparison between these Cu(I) complexes was performed, so that the correlation between NN structure and [Cu(NN)(PPh3)2] photophysical performance was tentatively discussed. Their single crystal structure was found consistent with literature ones, forming a typical tetrahedral coordination geometry. Density functional theory calculation indicated that their onset electronic transition showed a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Detailed analysis on photophysical parameters suggested that the absorption edge of [Cu(NN)(PPh3)2]BF4 complex was controlled by conjugation length in diamine ligand. A wide absorption edge needed a short conjugation chain in diamine ligand. Similar tendency was found for their emission spectra. In addition, a long conjugation chain in diamine ligand widened emission spectra obviously. Emission dynamics showed slim correlation with diamine ligand conjugation length since the excited state was controlled mainly by dynamic procedure and steric factor of diamine ligands.

Rational Design of Low-Band Gap Star-Shaped Molecules With 2,4,6-Triphenyl-1,3,5-triazine as Core and Diketopyrrolopyrrole Derivatives as Arms for Organic Solar Cells Applications.

A series of D-A novel star-shaped molecules with 2,4,6-triphenyl-1,3,5-triazine (TPTA) as core, diketopyrrolo[3,4-c]pyrrole (DPP) derivatives as arms, and triphenylamine (TPA) derivatives as end groups have been systematically investigated for organic solar cells (OSCs) applications. The electronic, optical, and charge transport properties were studied using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches. The parameters such as energetic driving force ΔE L-L, adiabatic ionization potential AIP, and adiabatic electron affinity AEA were also calculated at the same level. The calculated results show that the introduction of different groups to the side of DPP backbones in the star-shaped molecules can tune the frontier molecular orbitals (FMOs) energy of the designed molecules. The designed molecules can provide match well with those of typical acceptors PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) and PC71BM ([6,6]-phenyl-C71-butyric acid methyl ester). Additionally, the absorption wavelengths of the designed molecules show bathochromic shifts compared with that of the original molecule, respectively. The introduction of different groups can extend the absorption spectrum toward longer wavelengths, which is beneficial to harvest more sunlight. The calculated reorganization energies suggest that the designed molecules are expected to be the promising candidates for ambipolar charge transport materials except molecule with benzo[c]isothiazole group can be used as hole and electron transport material. Moreover, the different substituent groups do not significantly affect the stability of the designed molecules.

Molecular designing of four high performance pyrazine-based non-fullerene acceptor materials with naphthalene diimide-based small organic solar cells.

We design four high performance non-fullerene acceptor materials by applying strong electron withdrawing groups at the end of A-D-A-D-A type organic solar cells molecules and compute their different opto-electronic and photovoltaic properties, including absorption spectrum, electron density, solubility strength, charge mobilities for electrons and holes, stability of HOMO/LUMO energy orbitals, excitation energies required for charge transfer mechanisms, and morphology of device with the help of DFT approaches using the principles of quantum mechanics. The newly designed molecules showed strong absorption bands between 420 to 650 nm, low HOMO energy values from -7.24 to -7.28 eV, large % ETC from 35 to 65%, and small excitation energies from 2.28 to 2.47 eV in the organic solvent chloroform; 410 to 620 nm, 31 to 64%, and 2.42 to 2.56 eV, respectively, in gas phase conditions. Solubility strengths of the newly designed molecules were also high, varying from 5.3039 to 18.4749 Debye in the ground and excited states. Power conversion efficiencies of the designed molecules are expected to be high because they show better results than the R molecule. Open circuit voltages of designed molecules range from 3.67 to 3.54 V with respect to the PCBM. Reorganization energies for electron transport vary from 0.0153 to 0.0175 eV and for hole transport from 0.0231 to 0.0254 eV. This computational study proves that the newly designed molecules with non-fullerene acceptors are superior and thus are recommended for the future construction of high performance organic solar cells devices. Graphical Abstract Orbital's energy comparisons of four newly designed non-fullerene acceptor materials with naphthalene diimide-based small organic solar cells.

Geometric and Electronic Structural Contributions to Fe/O2 Reactivity.

While two classes of non-heme iron enzymes use ferric centers to activate singlet organic substrates for the spin forbidden reaction with 3O2, most classes use high spin ferrous sites to activate dioxygen. These FeII active sites do not exhibit intense absorption bands and have an integer spin ground state thus are mostly EPR inactive. We have developed new spectroscopic methodologies that provide geometric and electronic structural insight into the ferrous centers and their interactions with cosubstrates for dioxygen activation and into the nature of the intermediates generated in these reactions. First, we present our variable-temperature variable-field magnetic circular dichroism (VTVH MCD) methodology to experimentally define the geometric and electronic structure of the high spin ferrous active site. Then, we focus on using Nuclear Resonance Vibrational Spectroscopy (NRVS, performed at SPring-8) to define geometric structure and VTVH MCD to define the electronic structure of the FeIII-OOH and FeIV=O intermediates generated in O2 activation and the spin state dependence of their frontier molecular orbitals (FMOs) in controlling reactivity. Experimentally validated reaction coordinates are derived for the anticancer drug bleomycin in its cleavage of DNA and for an alpha- ketoglutarate dependent dioxygenase in its selective halogenation over the thermodynamically favored hydroxylation of substrate.

A systematic study of the effects of thionation in naphthalene dimide derivatives to tune their nonlinear optical properties.

In the present study, the number and position of sulfur atoms on naphthalene diimide (NDI) is systematically investigated to tune its nonlinear optical (NLO) response properties. Our DFT calculations for third-order polarizability (γ) show that the thionation significantly influences the nonlinear optical property of NDI as it is seen among its several designed derivatives (NDI-1 to NDI-10). The smallest and the largest γzzzz amplitudes are 503.49 × 10-36 and 1299.5 × 10-36 esu for NDI-1 (having tetraone group) and NDI-10 (having tetrathione group), respectively. The increase in γzzzz amplitude for NDI-10 is 796 × 10-36 esu, which is ∼150% from the γzzzz amplitude of NDI-1. A comparison of the γzzzz amplitudes of our designed derivatives are made with para-nitroaniline i.e. a prototype NLO molecule. The γzzzz amplitude of pNA is found to be 42.64 × 10-36 esu at the same B3LYP/DZVP2 level of theory. Using two-level model, the origin of larger γzzzz amplitudes is traced in lower transition energy of NDI-10. Furthermore, the calculation of vertical ionization potentials (VIPs) shows that the thionation does not affect the stability of designed derivatives, where a slight difference of 0.06 eV is seen between the VIPs of NDI-1 (6.63 eV) and NDI-10 (6.57 eV). Thus, a systematic comparison of the third-order polarizability and other electro-optical properties of our designed derivatives shows that our derivative systems possess good potential for their practical realization in the field of optical and NLO materials.

Experimental and theoretical investigations on debromination pathways of polybrominated biphenyls (PBBs) under ultraviolet light.

Polybrominated biphenyls (PBBs) are brominated flame retardants that are widely used in textiles and electronic products. Recently, many researches have been devoted to determining their concentrations in food and in the environment. Yet, their degradation behavior has been less investigated and is not well understood. Here, we have investigated the debromination pathways of PBBs by (UV) light in the case of 2,4,5-tribrominated biphenyl (PBB-29). Our investigation indicates that para-bromine substituent on PBB-29 was preferentially removed. By means of density functional theory (DFT), we found that the energies of the debromination products, the CBr bond length in the excited state (S1), the Mulliken charge of bromine in S1, and the lowest unoccupied molecular orbital (LUMO) in S1 correlated well with the debromination pathways of PBBs. Further, LUMO-based prediction of PBB debromination pathways in S1 suggests that the bromine substituent on all brominated positions (i.e. ortho-, meta- and para-) can be preferentially removed, as the debromination sequence is not based on the brominated position but on the specific brominated arrangement pattern. In addition, reductive debromination preferentially occurs on the benzene ring that has the highest number of bromine substituents. This study provided useful descriptors to predict the debromination pathways of PBBs, and the theoretical result greatly improve our understanding of photolytic debromination of PBBs.