Frontier Orbital Energy Gap Research Articles

The interaction between beta-ionone and 2-hydroxypropyl-beta-cyclodextrin during the formation of the inclusion complex

As an aroma material, beta-ionone also has a range of pharmacological activities. To solve its problems such as low bioavailability, water-immiscibility, thermo-instability, and volatility, beta-ionone was successfully encapsulated in 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) in our previous work. However, the structure of the product, the interaction between beta-ionone and HP-beta-CD, and the mechanism of action were not clear. In this paper, in order to gain a more profound understanding of the structure and chemical behavior of beta-ionone-HP-beta-CD inclusion complex, the interaction between beta-ionone and HP-beta-CD was investigated by molecular simulation. The optimized structures, binding energy, deformation energy, charge transfer, frontier orbital energy gap, chemical hardness, chemical potential, and electrophilicity index were obtained. In the complex, beta-ionone denotes electrons to HP-beta-CD and carries a positive charge. The negative chemical potential of inclusion complex indicates that complex process is spontaneous. The complex shows a relatively higher reactivity and electrophilicity than beta-ionone and HP-beta-CD.

Oxidation of Weakly Interacting Diradicals: An Approach for Strong and Tunable Near-Infrared-Absorbing Dyes Based on Small Chromophores.

Near-infrared (NIR)-absorbing dyes are valuable for various applications, such as bioimaging and electronic devices. This work introduces a novel approach for designing NIR dyes, oxidation of weakly coupled diradicals. Our approach features a weak exchange interaction in diradicals, which potentially leads to bonding/antibonding molecular orbitals with a small energy gap. We found that removing one of two singly occupied molecular orbital electrons of the diradicals results in an exceptionally narrow frontier orbital energy gap. We examined a series of Blatter radical dimers, and the most weakly coupled diradical prepared in this work (ΔEST ∼ 0.12 eV) with a molecular weight of 590 Da exhibited a strong NIR absorption band reaching 2200 nm upon one-electron oxidation. The optical band gaps of the radical cations strongly correlate to the exchange interaction in the precursor neutral species, offering prediction and fine-tuning of the optical band gap in the NIR region.

Regulating Charge Transfer in Cyanine Dyes: A Universal Methodology for Enhancing Cancer Phototherapeutic Efficacy.

ConspectusDue to the advantages of spatiotemporal selectivity and inherent noninvasiveness, cancer phototherapy, which includes both photodynamic therapy (PDT) and photothermal therapy (PTT), has garnered significant attention in recent years as a promising cancer treatment. Despite the commendable progress in this field, persistent challenges remain. In PDT, limitations in dyes manifest as low intersystem crossing (ISC) efficiency and oxygen-dependent photoactivity, resulting in unsatisfactory performance, particularly under hypoxic conditions. Similarly, PTT encounters consistent insufficiencies in the photothermal conversion efficiency (PCE) of dyes. Additionally, the suboptimal phototherapeutic efficacy often exhibits a limited immune response. These factors collectively impose significant constraints on phototherapy in oncological applications, leading to limited tumor inhibition, tumor recurrence, and even metastasis.Unlike strategies that rely on external assistance with complicated systems, manipulating excited-state deactivation pathways in biocompatible dyes offers a universal way to systematically address these challenges. Our group has devoted considerable effort to achieving this goal. In this Account, we present and discuss our journey in optimizing excited-state energy-release pathways through regulating molecular charge transfer based on cyanine dyes, which are renowned for their exceptional photophysical properties and harmonious biocompatibility. The investigation begins with the introduction of amino groups in the meso position of a heptamethine cyanine dye, where the intramolecular charge transfer (ICT) effect causes a significant enlargement of the Stokes shift. Subsequently, ICT induced by introducing functional electron-deficient groups in cyanines is found to decrease the overlap of electron distribution or narrow the energy gaps of molecular frontier orbitals. Such modifications result in a reduction of the energy gaps between singlet and triplet states or an improvement in internal conversion, ultimately promoting phototherapy efficacy in both primary and distant tumors. Furthermore, with the intensification of the charge transfer effect aided by light, photoinduced intramolecular electron transfer occurs in some cyanines, leading to complete charge separation in the excited state. This process enhances the transition to the ground or triplet states, improving tumor phototherapy and inhibiting metastasis by increasing the PCE or the yield of reactive oxygen species, respectively. Shifting focus from intramolecular to intermolecular interactions, we successfully constructed and explored cyanines based on intermolecular charge transfer. These dyes, with excited-state dynamics mimicking natural photosynthesis, generate radicals and facilitate oxygen-independent hypoxic tumor PDT. Finally, we outlined the existing challenges and future directions for optimizing phototherapeutic efficacy by regulating molecular charge transfer. This Account provides molecular-level insights into improving phototherapeutic performance, offering valuable perspectives, and inspiring the development of functional dyes in other application fields.

[Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl2(OEt)] half-sandwich complexes: Synthesis, solid-state structure, hirshfeld surface analysis and theoretical studies

Indenyl-titanium trichloride complexes of type [Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl3] (R = SiMe3 (3a); R = tBu (3b)) were obtained by treatment of Li[1-(SiMe3)-3-(R)-C9H5] (R = SiMe3 (1a); R = tBu (1b)) with titanium tetrachloride (2) in a 1:1 molar ratio in the presence of isopropanol and SOCl2. Compounds [Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl2(OEt)] (R = SiMe3 (4a); R = tBu (4b)) are accessible by reacting 1a,b (R = SiMe3 (1a); R = tBu (1b)) with TiCl4 (2) in the presence of ethanol and SOCl2, or when 3a,b were treated with equimolar amounts of EtOH in refluxing benzene. Spectroscopic methods and single crystal X-ray diffraction analysis confirmed the piano-stool geometry of 3a and 4b in the solid state. Hirshfeld surface analysis using 2D fingerprint plots of 3a and 4b were conducted to elaborate non-covalent, intermolecular interactions existing in the solid state, which accounted for the strengthening of the crystal lattice. The molecular structures of the 3 and 4 were further investigated by quantum-chemical calculations. The geometries of the compounds were optimized at the B3LYP/6-31G(d)+LANL2DZ level of theory, and their related molecular parameters including frontier orbital energy gap and molecular electrostatic surface potential have also been calculated to better understand their properties.

Pd8(PDip)6: Cubic, Unsaturated, Zerovalent.

Atomically precise nanoclusters hold promise for supramolecular assembly and (opto)electronic- as well as magnetic materials. Herein, this work reports that treating palladium(0) precursors with a triphosphirane affords strongly colored Pd8(PDip)6 that is fully characterized by mass spectrometry, heteronuclear and Cross-Polarization Magic-Angle Spinning (CP-MAS) NMR-, infrared (IR), UV-vis, and X-ray photoelectron (XP) spectroscopies, single-crystal X-Ray diffraction (sc-XRD), mass spectrometry, and cyclovoltammetry (CV). This coordinatively unsaturated 104-electron Pd(0) cluster features a cubic Pd8-core, µ4-capping phosphinidene ligands, and is air-stable. Quantum chemical calculations provide insight to the cluster's electronic structure and suggest 5s/4d orbital mixing as well as minor Pd─P covalency. Trapping experiments reveal that cluster growth proceeds via insertion of Pd(0) into the triphosphirane. The unsaturated cluster senses ethylene and binds isocyanides, which triggers the rearrangement to a tetrahedral structure with a reduced frontier orbital energy gap. These experiments demonstrate facile cluster manipulation and highlight non-destructive cluster rearrangement as is required for supramolecular assembly.

From Molecules to Devices: Insights into Electronic and Optical Properties of Pyridine-Derived Compounds Using Density Functional Theory Calculations.

In this study, we delve into the electronic structure, spectroscopic, and optical properties of five benzo derivatives of pyridine, namely, 5-(4-chlorophenyl)-2-fluoropyridine (1), 2-fluoro-5-(4-fluorophenyl)pyridine (2), 4-(2-fluoropyridin-5-yl)phenol (3), 5-(2,3-dichlorophenyl)-2-fluoropyridine (4), and 5-(5-bromo-2-methoxyphenyl)-2-fluoropyridine (5). Utilizing quantum chemical density functional theory calculations at the B3LYP and Perdew-Burke-Ernzerhof levels of theory combined with the 6-311G(d,p) and 6-311++G(d,p) basis sets, we investigated the electronic and optical characteristics of these compounds. Band structure calculations were conducted for their crystalline structures, revealing a direct band gap varying from 3.018 to 3.558 eV, with the valence band maximum and conduction band minimum located at the G point in the Brillouin zone. The optical properties were analyzed, including the dielectric functions, reflectivity, and refractive index. Notably, reflectivity was found to be minimal in the photon energy range of 0.0-3.0 eV, and the static refractive index, n(0), ranged from 1.55 to 1.70. The research also involved assessing the reactivity of the compounds through calculation of the frontier orbital energy gaps (ΔE), indicating a significant charge transfer and high reactivity. Additionally, we performed frequency analysis to unveil the Fourier-transform infrared spectra of compounds 1-5 at room temperature. Molecular electrostatic potential surfaces of the optimized structures were employed to map the electrophilic and nucleophilic regions of the compounds. This investigation provides a comprehensive understanding of the electronic and optical properties of these pyridine derivatives, shedding light on their potential applications in optoelectronics.

Exploring the Nature of Anion-π Interactions: Complexes of π-Acceptors with Fluoro- or Oxoanions Compared to the Associations with Halides.

The variations in the nature and properties of the anion-π complexes with different types of anions are identified via experimental (UV-vis and X-ray crystallographic) measurements and computational analysis of the associations of tetracyanopyrazine, tetrafluoro-, or dichlorodicyano-p-benzoquinone. Co-crystals of these π-acceptors with the salts of fluoro- and oxoanions (PF6-, BF4-, CF3SO3-, or ClO4-) comprised anion-π bonded alternating chains or 1:2 complexes showing interatomic contacts of up to 15% shorter than the van der Waals separations. DFT computations confirmed that binding energies between the neutral π-acceptors and polyatomic noncoordinating oxo- and fluoroanions are comparable to those in the previously reported anion-π complexes with more nucleophilic halides. Yet, while the latter show distinct charge-transfer bands in the UV-vis range, the absorption spectra of the solutions containing oxo- and fluoroanions and the π-acceptors were close to those of the individual reactants. The natural bond orbital (NBO) analysis revealed a very small charge transfer of Δq = 0.01-0.02 e in the complexes with oxo- or fluoroanions as compared to the Δq = 0.05-0.22 e found for analogous complexes with halides. These distinctions were related to the smaller frontier orbital energy gap and better overlap in the complexes with halides (since the highest occupied orbitals of these monoatomic anions are closer in energy to the lowest unoccupied orbitals of the π-acceptors) as compared to that in the multicenter-bonded associations with polyatomic oxo- and fluoroanions. In accordance with these data, the energy decomposition analysis showed that while the complexes of neutral π-acceptors with the fluoro- and oxoanions are formed predominantly via electrostatic interaction, the associations with halides comprised significant orbital (charge-transfer) interactions and they explain their spectral and structural features.

Enhanced adsorption effect of defect ordering Mg/Al on layered double hydroxides nanosheets with highly efficient removal of Congo red

The non-conventional structure layered double hydroxides (LDHs) as pollutant adsorbents with significant adsorption efficiency are promising valuable research topics. In this work, the defect ordering MgAl-LDHs nanosheets for the highly efficient removal of Congo red (CR) are designed and fabricated by a facile environmental-friendly hydrothermal method based on solid insoluble substances magnesium oxide (MgO) and aluminum hydroxide (Al(OH)3) as precursors. The decrease of Mg/Al ordering changes the interlayer spacing of LDHs and improves the defect sites with low oxygen coordination on the LDHs laminate, which enhances the removal efficiency of CR from 45.6 to 97.7%. This study reveals that a defect enhancing combined mechanism of surface adsorption and the anion-exchange in MgAl-LDHs can obtain an outstanding adsorption efficiency for removing CR. The reactivity of the Mg/Al disorder with O defect on the LDHs laminate increases with the reduction of frontier orbitals energy gap (ΔEgap), resulting in a high adsorption capacity for CR. The uncover of the defect enhancing adsorption mechanism provides a new strategy to fabricate MgAl-LDHs with high capability for wastewater remediation.

Imidazole-Based Metal–Organic Framework for the “On1–Off–On2” Fluorescence-Based Detection of Picric Acid and the Adsorption of Congo Red

An imidazole-functionalized metal–organic framework (MOF), {[Ba2L (H3CCOO) (DMF)2] (DMF)}n, denoted as HBU-168, has been synthesized and characterized by single-crystal X-ray diffractometry. The synthesized MOF exhibits ligand-based luminescence, which can be attributed to coordination effects. Due to its excellent fluorescence performance, HBU-168 can be used to detect nitroaromatic compounds (NACs) and metal ions selectively and sensitively. The most striking properties of HBU-168 are the distinct red shift (∼34.8 nm) observed in the presence of picric acid (PA) with a Stern–Volmer constant (KSV) of 4.17 × 104. The mechanism of the change in luminescence in the presence of PA is determined by experiments and density functional theory calculations. The results indicate that the electron transfer between PA and the MOF has a reduction in the frontier orbital energy gap. Subsequently, HBU-168 is used to prepare a light-emitting-diode-based sensor (denoted HBU-168-LED), which can detect PA rapidly and visually. In addition, we find that HBU-168 can be used to detect metal ions, particularly magnesium ions. The metal detection mechanism is based on the turn-on fluorescence of HBU-168 caused by weak interactions between the MOF and metal ions. Finally, HBU-168 is found to be a good adsorbent for Congo red, achieving a removal efficiency of 98.89%. Therefore, the multifunctional HBU-168 MOF is a promising luminescent sensor and adsorbent.

Complexing agents for potassium oleate removal after cobalt chemical-mechanical polishing: Prediction, verification and mechanism

A systematic approach for predicting the capability of malic acid (MA), tartaric acid (TA), and citric acid (CA), as carboxylic complexing agents, to remove potassium oleate (PO) in the cleaning of cobalt (Co) film after chemical mechanical polishing was investigated. Several quantum-molecular descriptors (frontier orbital energies, energy gap, and dipole moment) were calculated to establish the relationship between descriptors and the effectiveness of complexing agents. Further, the diffusion simulation was carried out in the aqueous phase model, and the detailed adsorption analysis of the three carboxylic complexing agents on Co(111) surface was performed to reveal the behavior of complexing agents on the passive film and the variation of the adsorption state of PO. The prediction was verified by characterization techniques, including contact angle, potentiodynamic polarization and atomic force microscopy measurements. Results show that the calculated chemical descriptors and molecular dynamics simulations successfully predict the removal efficiency of the cleaning experiment, i.e., MA has the strongest removal ability of PO adsorbed on cobalt surface. As well, the appropriate concentrations of the three complexing agents were optimized: MA was 0.1 wt%, TA was 0.1 wt% and CA was 0.075 wt%. The cleaning mechanism of MA was elucidated by X-ray photo-electron spectroscopy, density functional theory, and charge density difference: MA could break bonds between PO and Co surface via the ligand-exchange mechanism or etch the cobalt surface to promote the desorption of PO. This work makes a major contribution to estimating the effectiveness of complexing agents and exploring the removal mechanism of organic residue.

Tuning of quadratic nonlinear optical activity of chromophores with indolizine donor moiety and polyene π-bridge on the basis of electrochemical data

Electrochemical data (CV peak potentials, DPV potentials, frontier orbitals energy values and energy gap ∆Eel) were used to characterize chromophores with isomeric indolizine donor moieties, different acceptors and polyene π-bridges of various length. A good correlation was found between the electrochemical ΔEel, optical ΔEopt and calculated ΔEqch (DFT) characteristics. Electrochemical data make it possible to determine the energies of frontier molecular orbitals independently, in contrast to ∆Eopt one, calculated from λmax (UV-vis spectra). This advantage allows us to understand the origin of the chromophore energy gap changes when the nature of the donor, acceptor, or bridge varies. The polyene π-bridges are shown to provide better charge transfer ability compared to the hetarene-containing bridges; they are responsible for chromophore energy characteristics variation with changes in building blocks. The effect of the bridge length and the donor/acceptor end fragments is discussed. Indolizine donors produce NLO-chromophores with high first hyperpolarizability, β. The smallest ΔEel = 0.91 eV and the highest first hyperpolarizability - 1007⋅10−30 esu are achieved for a chromophore with 1-methyl-2-(4-methoxyphenyl)indolizin-3-yl donor, 3-cyano-2-dicyanomethylene-5,5-dimethyl-2,5-dihydrofuran-4-yl acceptor and octatetraene π-bridge. The correlation between β and 1/(ΔEel)2 is nearly linear. Polyene π-bridges provide high sensitivity of redox potentials to the nature of the donor and acceptor compared to chromophores with hetarene-containing bridges.

Usage of the Y-Rule and the Effect of the Occurrence of Heteroatoms (N, S) on the Frontier Molecular Orbitals Gap of Polycyclic Aromatic Hydrocarbons (PAHs), and Asphaltene-PAHs.

The understanding of the molecular- and colloidal-structure of asphaltenes has seen a major progress; however, there are still issues that require answer. One of them is the location of the heteroatoms in the polycyclic aromatic hydrocarbon (PAH) fused aromatic ring (FAR) region of asphaltenes. Therefore, the effect on the frontier molecular orbitals (HOMO-LUMO) energy-gap due to the addition of a heteroatom (N or S) to PAHs, which are candidates of the PAH region in asphaltenes, has been systematically analyzed by placing S or N in various sites of the PAH molecule. The S is introduced as a thiophenic ring in a bay region, while the N is introduced as a pyridinic-N, which are prevalent forms in the asphaltene-PAH. 174 PAHs are studied with five fused aromatic rings (5FAR) to 10FAR. The π-electron allocation in resonant π-sextets and isolated double bonds is obtained using the Y-rule. The frontier orbitals optical transition is calculated with the ZINDO/S method. Within a FAR family an increment of π-sextets produces and increase of the HOMO-LUMO energy-gap. There is a linear relationship between the Y-rule mapping (percentage of fraction of π-sextet bond divided by nFAR) and the HOMO-LUMO energy-gap. In addition, the effect on the frontier orbitals energy-gap and on the π-electronic allocation due to the presence of N and S is negligible; therefore, to reach conclusions related to the asphaltene-PAH based on conclusions reached for PAH systems, with no heteroatoms, is a reasonable approach.

Anti-hypertensive properties of 2-[N-(4-methylbenzenesulfonyl)-1-phenylformamido]-n-(4-nitrophenyl)-3-phenylpropenamide: Experimental and theoretical studies

Experimental and theoretical investigation of the anti-hypertensive activity of novel 2-[N-(4-methylbenzenesulfonyl)-1-phenylformamido]-N-(4-nitrophenyl)-3-phenylpropenamide (MBPNPP) was carried out. The experimental approach followed the dietary induction of spontaneously hypertensive adult male Wistar rats (SHRs) using 66% w/v d-fructose and the angiotensin I-converting enzyme (ACE) inhibitory activity assay while the theoretical study was achieved using DFT calculations and molecular docking against hypertension responsive proteins. The Becke-3-Paramater-Lee-Yang-Parr (B3LYP) functional/6–311G++(d,p) basis set was adopted. The molecular electronic properties such as the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and other chemical reactivity parameters were evaluated to bring to light, the reactivity and stabilization mechanisms of MBPNPP. The highest daily oral dose of MBPNPP (10 mg/kg) significantly prevented increase in systolic blood pressure (SBP) comparable to positive and normal control groups receiving captopril (10 mg/kg/day) and distilled water (5 ml/kg) ad libitum respectively from 167.23 (negative control) to 124.50 and 120.17 (positive control). Molecular simulation was also carried out with target proteins; 2ydm, 2 × 8Y, and 3ZQZ, and the theoretical data expresses a much plausible therapeutic significance towards the control of hypertension. The frontier orbital energy gap of 3.066 eV was an indicator that the charge transfer interaction occurred within the molecule and indicates high chemical reactivity. Relative to the reference drug, Spironolactone, the compound under study showed a significant binding affinity of -9.0 kcal/mol, -8.3 kcal/mol, and -7.9 kcal/mol with the target proteins and better protein-ligand hydrogen bond interactions. The data gathered from the experimental and theoretical analysis including the docking scores showed excellent anti-hypertensive activity by MBPNPP.

Gallic acid-cholesterol conjugate: Synthesis spectroscopic characterization and quantum chemical calculations-an experimental and theoretical approach

Gallic acid is the major constituent in fruits Phyllanthusemblica (amla), of the family phyllanthaceae. Gallic acid was first methylated to 3,4,5 trimethoxygallic acid, which upon esterification using steglich method with cholesterol resulted in the product (3S,8S,10R,13R,17R) -10,13-dimethyl-17-((R)-6-methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro - 1H - cyclopenta[a]phenanthren-3-yl 3,4,5-trimethoxybenzoate. The synthesized compound has been characterized by 1H NMR, 13C NMR, UV, FT-IR and mass spectroscopy. Density functional theory (B3YLP) using a 6-31G (d,p) basis set has been used for quantum chemical calculations. The reactive site and reactivity within the molecule are rendered by global and local reactivity descriptors, whereas AIM (Atom in a molecule) approach illustrated weak molecular interactions within the molecule. The energies of HOMO and LUMO and frontier orbital energy gap are calculated by time dependent DFT approach using the IEFPCM model. A small value for the HOMO-LUMO energy gap indicates easier charge transfer within the synthesized compound. The nucleophilic and electrophilic reactivity is determined by MEP (molecular electrostatic potential) studies. The values calculated for polarizability, dipole moment, and first hyperpolarizability are used to depict the NLO (nonlinear optical) property of the synthesized compound.

Recent Advances in Organic Room-Temperature Phosphorescence of Heteroatom (B/S/P)-Containing Chromophores

Recent Advances in Organic Room-Temperature Phosphorescence of Heteroatom (B/S/P)-Containing Chromophores

Interaction of cisplatin anticancer drug with C20 bowl: DFT investigation

This study investigated the cisplatin (anticancer drug) interaction with C20 bowl and C20H10(Bowl) molecule including hydrogen-saturated with using mPW1PW91 functional. The stability of the various isomers of drug interaction with C20 bowl was investigated. The interaction energy values were estimated in these systems. Changes in the structural parameters and the frontier orbital energy and HOMO-LUMO gap values were evaluated. Charge transfer between fragments were shown with electrophilicity-based charge transfer (ECT). The Octanol–water partition coefficient (log P) and molecular volume (Vm) of these drug precursor molecules were studied. Also, Pt-C bond characterizations were illustrated using QTAIM analysis. The results showed that C20 bowl can be a promising nanocarrier for cisplatin anticancer drug.

Theoretical studies, Hirshfeld surface analysis, and crystal structure determination of a newly synthesized benzothiazole copper(II) complex

A mononuclear copper(II) complex [Cu(LBTZ)2] was synthesized from the Schiff base HLBTZ (2-(benzo[d]thiazol-2-yl)-6-ethoxyphenol). The structural validation of the compounds was carried out with the help of different studies viz., elemental (C, H, and N), FT-IR, NMR (1H and 13C), and for [Cu(LBTZ)2], by X-ray crystal diffraction method. The complex was crystallized out in the orthorhombic Pbcn space group and exhibits a highly distorted tetrahedral geometry. Hirshfeld surface (HS) analysis using 2D fingerprint plots of the [Cu(LBTZ)2] was conducted to elaborate on different kinds of non-covalent, inter, and intramolecular interactions that existed in the solid crystalline scaffolds, which accounted for the strengthening of the crystal lattice. The molecular structures of the HLBTZ and [Cu(LBTZ)2] were further investigated by optimizing them with the help of DFT using the B3LYP hybrid method, and the Def2-TZVP basis set. The optimized geometries of the compounds and their related molecular parameters like frontier orbital energy gap, dipole moment, molecular electrostatic potential map, and natural bond orbitals calculation have also been used to understand the properties.

M(BO)k+1- Anions: Novel Superhalogens Based on Boronyl Ligands.

Superhalogens have been a subject of continuous attraction in the last four decades due to their unusual structures and interesting applications. In the quest for new superhalogens based on boronyl (BO) ligands, we investigate M(BO)k+1- anions using a high-level ab initio CCSD(T) and B3LYP density functional method for M = Li, Na, K, Be, Mg, Ca, B, and Al. Their structures are linear for M = Li, Na, K; trigonal planar for M = Be, Mg, Ca; and tetrahedral for M = B, Al. These anions are energetically and thermodynamically stable against various fragmentations. Their superhalogen property has been established due to their higher vertical detachment energy (VDE) than halogen, being in the range 4.44-7.81 eV. For a given k, the stability and VDE of M(BO)k+1- anions decrease with an increase in the size of M, which is due to the decrease in charge delocalization on BO moieties. There exists a linear correlation between frontier orbitals energy gap and VDE with coefficient R2 = 0.93888. It was also noticed that the BO ligand, due to the lower dimerization energy, can be preferably used as an inorganic analogue of CN. However, the structural relaxation in BO-based neutral species significantly affect the VDE and, hence, their superhalogen nature. We believe that these findings should be interesting for researchers working in superatomic chemistry as well as in boron chemistry.

Synthesis, spectroscopic characterization, DFT calculations, and molecular docking studies of new unsymmetric bishydrazone derivatives

Three new unsymmetric isatin bishydrazone compounds; Comp. I, II, III, were synthesized by the condensation of 3,5-dichloro-salicylaldehyde, 3-bromo-5-chloro-salicylaldehyde, and 3,5-dibromo-salicylaldehyde with isatin monohydrazone, respectively. The synthesized compounds were characterized by elemental analysis, 1H-NMR, FT-IR, UV-Vis spectroscopy, and mass spectrometry technique. For studied molecules, chemical parameters like frontier orbital energies, energy gap, electronegativity, chemical potential, chemical hardness, softness, electrophilicity, nucleophilicity, electrodonating power, electroaccepting power, polarizability, and dipole moment were calculated and discussed. Investigating the validity of well-known electronic structure principles like Maximum Hardness, Minimum Polarizability, and Minimum Electrophilicity Principles in the study, it was determined which compound is more stable compared to others. In recent days, a new software having PRIMorDIA name was developed to explore reactivity and electronic structure in large biomolecules by some of the authors of this paper. Molecular docking studies for these newly synthesized molecules were performed using PRIMorDIA software. Considering the intramolecular interactions, NBO analyzes of three bishydrazone derivatives were conducted to evaluate the chemical behavior.

Theoretical Study of the Binding of the Thiol-Containing Cysteine Amino Acid to the Silver Surface Using a Cluster Model.

Computational approaches within the framework of density functional theory (DFT) were employed to elucidate the binding mechanism of the cysteine amino acid on silver nanoparticles using several small silver clusters Agn with n = 2-10 as surface models. The long-range corrected LC-BLYP functional and correlation consistent basis sets cc-pVTZ-PP and cc-pVTZ were used to determine the structural features, energetics, and spectroscopic and electronic properties of the resulting complexes. In vacuum and highly acidic conditions, cysteine molecules prefer to adsorb on silver clusters via their amine group. In aqueous solution, the thiolate head turns out to be the most energetically favorable binding site. The cysteine affinity of silver clusters is greatly altered in different conditions, i.e., acidic solution < vacuum < aqueous solution, and is strongly dependent on the cluster size. As compared to free clusters, the frontier orbital energy gap of the ones capped by cysteine is significantly improved, which corresponds to stronger stability, especially in aqueous solution. The analysis of frontier orbitals also reveals that both forward and backward electron donations exhibit comparable contributions to the enhancement of stabilizing interactions. As for an application, a chemical enhancement mechanism of the surface-enhanced Raman scattering (SERS) procedure of cysteine by silver clusters was also analyzed.