Molecular Electrostatic Potential Values Research Articles

Supramolecular assemblies involving unusual N(nitrile)∙∙∙π(fum) and nitrile-nitrile non-covalent contacts in fumarato and succinato bridged polymers of Co(II) and Ni(II): Experimental and theoretical studies

Two new Co(II) and Ni(II) coordination polymers viz. [Co(H2O)2(μ-fum)(3-CNpy)2]n (1) and {[Ni(H2O)2(μ-succ)(4-CNpy)2]·2H2O}n (2) (where, fum= fumarate, CNpy = cyanopyridine, succ = succinate) have been synthesized and characterized using single crystal XRD, elemental analysis, spectroscopic (IR and electronic) techniques and TGA. Compound 1 crystallizes as a fumarato bridged Co(II) polymer; whereas, compound 2 is a succinato bridged Ni(II) polymer. The presence of various non-covalent interactions in the compounds stabilizes the layered assemblies of the compounds. Antiparallel nitrile∙∙∙nitrile interactions are observed in both the crystal structures involving the nitrile moieties of coordinated CNpy which provide rigidity to the compounds. Further analysis reveals that the N-atom of –CN group of 3-CNpy in 1 is involved in unusual N(nitrile)∙∙∙π(fum) interactions with the π-electrons of the C=C bond of fum. Enclathrated (H2O)2 cores within the supramolecular host cavity of compound 2 provides additional reinforcement to the crystal structure. We have also carried out theoretical studies to analyze the π-stacking and H-bonding interactions present in the crystal structure of compound 1 using quantum theory of atoms-in-molecules (QTAIM), non-covalent interaction plot (NCI plot) and molecular electrostatic potential (MEP) surface analysis. The MEP value at the N-atom of the cyano group of 1 is negative and the value is neutral over the double bond of the fum; indicating the possibilities of formation of N(nitrile)∙∙∙π(fum) interactions. Energetic analysis suggests that antiparallel π-stacking observed between the 3-CNpy moieties in 1 is the most dominating force followed by N(nitrile)∙∙∙π(fum) interaction and finally the H-bonds.

Exploring the Co-Crystallization Landscape of One-Dimensional Coordination Polymers Using a Molecular Electrostatic Potential-Driven Approach.

The ability of coordination polymers (CPs) to form multicomponent heteromeric materials, where the key structural features of the parent CP are retained, has been explored via molecular electrostatic potential-driven co-crystallization technologies. Thirteen co-formers presenting hydrogen-bond donors activated through a variety of electron-withdrawing functionalities were employed, and the extent of activation was evaluated using molecular electrostatic potential values. Attempted co-crystallizations of the seven most promising co-formers with a family of nine CPs ([CdX'2(X-pz)2]n; X' = I, Br, and Cl; X = I, Br, and Cl) resulted in six successful outcomes; all four of the structurally characterized compounds displayed the intended hydrogen bond. The rationalization of the main structural features revealed that strict structural and electrostatic requirements were imposed on effective co-formers; only co-formers with highly activated hydrogen-bond donors, and with a 1,4-orientation of electron-withdrawing moieties bearing effective acceptor sites, were successfully implemented into the three-dimensional architectures composed of one-dimensional building units of CPs.

Unconventional Dual Donor-Acceptor Topologies of Aromatic Rings in Amine-Based Polymeric Tetrahedral Zn(II) Compounds Involving Unusual Non-Covalent Contacts: Antiproliferative Evaluation and Theoretical Studies

Two Zn(II) coordination polymers, viz., [Zn2Cl2(H2O)2(µ-4-AmBz)2]n (1) and [ZnCl2(µ-3-AmPy)2]n (2) (4-AmBz = 4-aminobenzoate, 3-AmPy = 3-aminopyridine) have been prepared at room temperature and characterized using elemental analysis, FT-IR, electronic spectroscopy, TGA (thermogravimetric analysis) and single crystal XRD. Crystal structure analyses of the polymers unfold the presence of non-covalent anion–π, π-stacking and unusual NH2(amino)⋯π interactions which provide rigidity to the crystal structures. Unconventional Type I Cl⋯Cl interactions also play a pivotal role in the stability of compound 1. Molecular electrostatic potential (MEP) surface analysis reveals that the MEP values over the center of the aromatic rings of coordinated 4-AmBz and 3-AmPy moieties are positive on one side and negative on the other side which confirms the dual non-covalent donor-acceptor topologies of the aromatic rings and explains the concurrent formation of unusual non-covalent NH2···π and anion–π interactions. DFT (density functional theory) calculations, QTAIM (quantum theory of atoms in molecules) and NCI plot (non-covalent index) index analyses reveal that among various non-covalent contacts involved in the crystal packing of the compounds, H-bonds in compound 1 and π-interactions (NH2···π, π-π, anion–π) in compound 2 are energetically significant. We have explored in vitro cytotoxic potential of the compounds in Dalton’s lymphoma (DL) cancer cells using trypan blue and apoptosis assays. The studies show that compounds 1 and 2 can significantly exhibit cytotoxicity in DL cells with minimum cytotoxicity in healthy PBMC cells. Molecular docking studies reveal that the compounds effectively bind with the antiapoptotic target proteins; thereby establishing a structure activity relationship of the compounds.

A DFT approach towards understanding the thermal stability of TKX-50 and their key precursors through band gaps and MESP.

TKX-50 (dihydroxylammonium 5,5'-bistetrazolate-1,1'-dioxide) is a recent time invention by Klapotke et. al. in the field of high energy materials, and it outperforms all the existing materials by means of performance parameters. It is rising as potential energetic material due to favorable thermal insensitivity, low toxicity and safe handling. The decomposition temperature (Tmax) values of precursors such as glyoxime (I), 1,2-dichloroglyoxime (II), 1,2-diazidoglyoxime (III), and bistetrazoledihydroxide (IV) and ending products TKX-50 (V) and ABTOX (VI) have been attempted to correlate with the results obtained from molecular electrostatic potentials and band gaps calculated from the difference of ionization potential and electron affinity. The molecular electrostatic potential values of azido attached -NO group of III are much less than that of hydro/chloro attached -NO group of I/II and that of tetrazole groups IV, V, and VI. The band gaps calculated from stability trend in the increasing order of III < II < I < IV < V < VI are well corroborated with stability trend drawn from experimentally determined decomposition temperatures. Further, employing conceptual density functional theory (DFT) molecular descriptors, band gap values were calculated via the difference of ionization potential and electron affinity to understand the thermal stability of TKX-50, ABTOX, and its precursors.

Halogen Bond Motifs in Cocrystals of N,N,O and N,O,O Acceptors Derived from Diketones and Containing a Morpholine or Piperazine Moiety.

In this study, we investigate the halogen bond acceptor potential of oxygen and nitrogen atoms of morpholine and piperazine fragments when they are peripherally located on N,O,O or N,N,O acceptor molecules. We synthesized four acceptor molecules derived from either acetylacetone or benzoylacetone and cocrystallized them with 1,4-diiodotetrafluorobenzene and 1,3,5-triiodotrifluorobenzene. This resulted in eight cocrystals featuring different topicities and geometric dispositions of donor atoms. In all cocrystals, halogen bonds are formed with either the morpholinyl oxygen atom or the terminal piperazine nitrogen atom. The I···Omorpholine halogen bonds feature lower relative shortening values than I···Nterminal, I···Ocarbonyl, and I···Nproximal halogen bonds. The N and O halogen bond acceptor sites were evaluated through calculations of molecular electrostatic potential values.

Acid-Base and Anion Binding Properties of Tetrafluorinated 1,3-Benzodiazole, 1,2,3-Benzotriazole and 2,1,3-Benzoselenadiazole.

The influence of fluorination on the acid-base properties and the capacity of structurally related 6-5 bicyclic compounds - 1,3-benzodiazole 1, 1,2,3-benzotriazole 2 and 2,1,3-benzoselenadiazole 3 to σ-hole interactions, i. e. hydrogen (1 and 2) and chalcogen (3) bondings, is studied experimentally and computationally. The tetrafluorination increases the Brønsted acidity of the diazole and triazole scaffolds and the Lewis acidity of selenadiazole scaffold decreases the basicity. Increased Brønsted acidity facilitates anion binding via the formation of hydrogen bonds; particularly, tetrafluorinated derivative of 1 (compound 4) binds Cl- . Increased Lewis acidity of tetrafluorinated derivative of 3 (compound 10), however, is not enough for binding with Cl- and F- via chalcogen bonds in contrast to previously studied Te analog of 10. It is suggested that the maximum positive values of molecular electrostatic potential at the σ-holes, VS,max , can be a reasonable metric for design and synthesis of new anion receptors with selenadiazole-diazole/triazole hybrids as a special target. Related chlorinated compounds are also discussed.

Реакционная способность арилсульфонилгалогенидов как функция молекулярного электростатического потенциала реакционного центра

To study the reactivity of arylsulfonyl halides, the molecular electrostatic potential (MEP) was considered for the first time as a descriptor. The reaction of hydrolysis of aromatic sulfonyl halides in the medium of mixed acetone-water solvents (according to the literature data of rate constants) was used as a model. The calculation of the structural parameters of the molecules of substituted arylsulfonyl halides was carried out using the ADF2014 software package at the level of the DFT/M06/6-311+G* (PCM) theory. It was found that the magnitude of the MEP on the sulfonyl sulfur atom is very sensitive to changes in the structure of substrates, which makes it possible to determine the change in the ratio between the rate of nucleophilic attack and anionoid abstraction of the leaving group. In particular, using the example of the hydrolysis reaction of substituted thiophenesulfonyl chlorides, it was shown that the acceleration of the reaction is observed with an increase in the donor properties of the substituents and the associated increase in the negative MEP value on the sulfonyl sulfur atom. The antibate character of the dependence of the hydrolysis constant values on the IEP value indicates that not the nucleophilic attack is the rate determining in the interaction of thiophene sulfonyl chlorides and the hydroxyl anion in this sample, but the abstraction of the chloride anion. This reaction has an unstable mechanism, when the ratio between the degree of S-nucleophile bond formation and S-halogen bond cleavage changes. This makes it possible to use MEP as a descriptor of reactivity in the hydrolysis of aryl sulfonyl halides and to elucidate the details of changes in the structure of transition states during the implementation of mechanisms other than pure SN2 mechanism.

The interplay between anion-π and H-bonding interactions in X−···s-Triazine···(HF)n(HCl)3-n (X = F−, Cl− and CN−) complexes: DFT and DFT-D study

ABSTRACT Anion-π interactions play an important role in supramolecular chemistry. The aim of this work is to explore the effect of H-bonding between s-Triazine and separated molecules (HF)n(HCl)3-n on the strength of anion-π interaction in X−–s-Triazine–(HF)n(HCl)3-n (X− = F–, Cl– and CN–) complexes. The M06-2X/6-311++G(d,p) binding energies (BEs) were corrected by using B2PLYP, mPW2PLYP, M06-2X-GD3 and B2PLYP-GD3 functionals. The molecular electrostatic potential (MESP) analysis revealed that involving multiple binding sites in s-Triazine (TA) through N···H H-bonding can enhance the MESP value over the ring centre of TA so that for H-bonding complexes containing HF is greater than those of HCl. The BE results revealed that the stability of X−–TA–(HF)n(HCl)3-n anion-π complexes in each series increases as the number of HF involved in H-bonding increases. The results showed that the complexes owning F– anion with higher interaction energies display the strong cooperativity effects in the ternary systems. B2PLYP functional showed stronger intramolecular dispersion effects than M06-2X one. Besides, a correlation was found between BE, MESP, bond distances, natural bond orbitals (NBO) and atoms in molecules (AIM) data.

2-Etoksi-6-[(E)-[(2-Hidroksifenil)imino]metil]fenol Türevi Schiff Bazlarının Sentezi ve Teorik Çalışmalar

2-Etoksi-6-[(E)-[(2-hidroksifenil)imino]metil]fenol türevi Schiff bazları (4-kloro-2-((3-etoksi-2-hidroksibenziliden)amino)fenol; 5S1 ve 2-((3-etoksi-2-hidroksibenziliden)amino)-4-metilfenol); 5S2 bileşikleri sentezlenmiştir. Karekterizasyonu 1H ve 13C NMR, elemental analiz ve FT-IR Spektrometresi ile yapılmıştır. Bileşiklerin ve olası tautomer formlarının kararlı konformasyonları teorik hesaplamalarla belirlenmiştir. Tüm hesaplamalar; kararlı konformasyonlar kullanılarak ve vakumda B3LYP/6-311g(2d,p) yöntemiyle yapılmıştır. Hesaplamalarda bileşiklerin enerjileri, kararlı taotomer formları, H-bağları, Mulliken yükleri, dipol momentleri, Çözücüyle erişilebilen yüzey alanı (Solvent accessibility surface), Moleküler elektrostatik potansiyel değerleri (MEP) (Molecular electrostatic potentials values), HOMO, LUMO ve enerji bant aralığı enerjileri (HOMO, LUMO and band gap energies) hesaplamaları yapılmıştır. Deneysel ve teorik IR, 1H ve 13C NMR uyumu incelenmiştir.

Quantum chemical, experimental exploration of biological activity and inhibitory potential of new cytotoxic kochiosides fromKochia prostrata(L.) Schrad

New cytotoxic steroidal glycoside of methanol extract from Kochia prostrata ([Formula: see text]) Schrad was investigated in this study. Bio-guided isolation from ethylacetate fraction of whole plant afforded steroidal glycosides named as 5-ene-dimethylcholest3-O-[Formula: see text]-D-glucoside (Kochioside 1A1), 5-ene-methylcholest3-O-[Formula: see text]-D-glucoside (Kochioside 2A1) and 4-ene-dimethylcholest3-O-[Formula: see text]-D-glucoside (Kochioside 3A1). Their structures were assigned by physical and spectroscopic methods. Kochiosides 1A1–3A1showed inhibitory potential against brine shrimp lethality bioassay with etoposide standard drug. The new steroidal glycoside kochiosides 1A1–3A1showed inhibition values of 8.3201, 8.8205 and 8.2310[Formula: see text][Formula: see text]g/mL, respectively with [Formula: see text] compared to standard etoposide [Formula: see text] (7.4625[Formula: see text][Formula: see text]g/mL) drug. Moreover, six new derivatives were designed by substituting the –NH2and –OCH3at R1, R2 and R3 positions in the isolated compounds. Herein, various molecular descriptors, frontier molecular orbitals (FMO), electron affinity, ionization potential and molecular electrostatic potential (MEP) were carried out to understand the active sites and biological active nature of the new cytotoxic steroidal glycoside kochiosides. The effect of electron donating groups (–NH2and –OCH3) was also investigated on the structural parameters and electronic properties in gas and solvent (DMSO) phases. The energy gap, MEP and reactivity descriptors values demonstrate that the kochioside 3A1retains good reactivity, which is in good agreement with current experimental studies.

Quantum chemical and experimental exploration of biological activity and inhibitory potential of new acylated oligosaccharides from Pistacia integerrima J. L. Stewart ex Brandis

The new biologically active integrisides A (1) and B (2) have been isolated from the methanolic extract of Pistacia integerrima J. L. Stewart ex Brandis. The antibacterial activity of both the integrisides were tested against four pathogenic bacterial strains, two Gram-positive (Staphylococcus aureus, Streptococcus pyogenes) and two Gram-negative (Escherichia coli, Pseudomonas aeruginosa) as well as four fungal strains (Microsporum canis, Aspergillus clavatus, Candida albicans and Candida glabrata). Both the isolated compounds showed significant results analogous with Imipenam and Miconazole standard drugs. Carbonic anhydrase-II inhibition of integriside A (1) and B (2) with IC50 value 1.56 µM and 2.85 µM respectively, as compared to standard drug acetazolamide (1.57 µM). Cholinesterase activity was carried out with acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) IC50 values of integriside A (1) (8.6, 4.8) and B (2) (0.91, 2.5) were found as compared with standard galanthamine (0.05, 0.92) and Eserine (0.6, 8.7). Here, various molecular descriptors, frontier molecular orbitals (FMO), electron affinity (E.A), ionization potential (IP), molecular electrostatic potential (MEP), and Hirshfeld analysis were carried out to understand the active sites and biological active nature of the integrisides A (1) and B (2). The energy gap, MEP, Hirshfeld analysis, and reactivity descriptors values demonstrate that the integriside A (1) and B (2) retain decent reactivity, which is in good agreement with current experimental and quantum chemical studies.

A High-Power Aqueous Zinc-Organic Radical Battery with Tunable Operating Voltage Triggered by Selected Anions.

In contrast to traditional rechargeable rock-chair metal-ion batteries, dual-ion batteries (DIBs) involve redox reactions with anions rather than cations in p-type cathodes. In principle, regulating the electrochemical performance of the DIB by different anion species is highly feasible. Herein, the anion effect on the electrochemical performance of a DIB, the aqueous Zn- organic radical battery (Zn-ORB), consisting of a poly(2,2,6,6tetramethylpiperidinyloxy-4-yl vinyl ether) cathode and a Zn anode, was investigated by DFT calculations. SO4 2- , CF3 SO3 - , and ClO4 - with different molecular electrostatic potential values were selected as anion models. DFT calculations revealed that a stronger electrostatic interaction of the anion with the organic radical resulted in a higher operating voltage of the Zn-ORB, which was consistent with experimental results. These results bring new insight into the redox chemistry of p-type organic radicals with anions and will promote the development of high-power aqueous Zn-ORBs as well as inspire more investigations into the anion effect towards novel battery designs.

Electronic effect of β‐diketonato ligands on the redox potential of fac and mer tris(β‐diketonato) iron(III) complexes: A density functional theory study and molecular electrostatic potential analysis

AbstractExperimental redox potentials of 16 derivatives of tris(β‐diketonato)iron(III) complexes (where β‐diketonato(R1COCHCOR2)─, with substituents R1 and R2 in different combinations of H, C4H3S, C4H3O, CH3, Ph, CF3, or C (CH3)3), and 11 additional isomers, were studied theoretically in terms of the electronic properties, substituent effects, electron affinity, and molecular electrostatic potential (MESP) analysis, using density functional theory methods. The computational methods reproduced the experimental reduction potential to a very high level of accuracy, especially when the M062X functional was used (with mean absolute deviation [MAD] = 0.054 and 0.093 and correlation R2 = 0.978 and 0.981 obtained by application of two slightly different free energy cycles, respectively). The most negative computed reduction potential corresponds to the most negative reported experimental reductions, which is indicative of the least favorable reduction potential, also in most cases the most stable molecules energetically. The calculated reduction potentials of the fac isomers of the molecules were generally higher (less negative) than that of the mer isomers when one of the ligand substituents R1 or R2 was CF3 (M062X results), indicating better ease of reduction, although in many cases, the experimental reduction potential agreed better with the calculated reduction potential of the mer isomer instead. The calculated reduction potentials were also affected by the substituents in the order of CF3 &gt; H &gt; C4H3S &gt; C4H3O &gt; Ph &gt; CH3 &gt; C(CH3)3 (the most negative value). The stronger the electron withdrawing tendency of the substituent, the more favorable (less negative value) the reduction potential becomes. In relation to the CH3‐substituted molecule 1 as a reference, the molecules with electron withdrawing substituents resulted in an electron‐deficient MESP iso‐surface, in both the neutral state and reduced state. All the molecules in their reduced state were characterized with an electron‐deficient MESP iso‐surface compared with the reduced CH3‐substituted molecule 1, with the deficiency increasing in mer compared with fac, for both the neutral and reduced molecules. The relative MESP values of ΔVFe in the reduced state of the molecules were able to predict the corresponding experimental reduction potential to a significant level of accuracy (with MAD = 0.091).

Quantum-Chemical Study of the Influence of Substitution on Anti-Virus Activity of Hydroxyl Substituted Benzaldehydes and Related Compounds

Using the wave functions of the quantum chemical INDO method, the molecular electrostatic potential (MESP) of hydroxyl substituted benzaldehydes and related compounds exhibiting the ability to inhibit the reproduction of the herpes simplex virus type I has been calculated. It has been established that the degree of biological activity correlates not only with the magnitude of the proton-acceptor capacity of the substituted, but also with the geometry of biologically active molecules. The correspondence between the MESP values of hydroxyl groups and the effectiveness of the inhibitory ability of the investigated substitutions has been established.

Theoretical ab Initio Study on Cooperativity Effects between Nitro π-hole and Halogen Bonding Interactions.

This article analyzes the interplay between nitro's π-hole and halogen-bonding (XB) interactions in nitroarenes. Remarkable cooperativity effects are observed when π-hole and XB interactions coexist in the same complex. The nitroarene presents two π-holes, one approximately over the N atom of the nitro group and the other over the aromatic ring, being the former more positive. The interplay between both interactions has been analyzed in terms of energetic and geometric features of the complexes, which are computed at the RI-MP2/def2-TZVPD level of theory. Molecular electrostatic potential (MEP) surface calculations have been used to explore the variation of the MEP values at the π-hole upon the formation of halogen bonding interactions between the nitroarene and CF3 X (X=Cl, Br and I) molecules. In addition, the Bader's theory of atoms in molecules" (AIM) is used to characterize the interactions by means of the distribution of bond critical points and bond paths and to analyze their strengthening or weakening depending upon the variation of charge density at critical points. The aforementioned computational methods are adequate to examine how these interactions mutually influence each other. Natural bond orbital (NBO) and noncovalent interaction plot (NCIPlot) computational tools have been also used in some representative complexes to further analyze cooperativity effects. Finally, the Cambridge Structural Database (CSD) is used to provide some experimental evidence.

Theoretical study of the thermodynamic parameters of (CaO)n nanoclusters with n = 2–16 in the gas and solution phases: proton affinity, molecular basicity, and pKb values

Thermodynamic quantities such as proton affinity (PA) and molecular basicity (GB) for (CaO)n nanoclusters with n = 2–16 have been calculated using three computational models of the density functional theory (DFT) (Becke, 3-parameter, Lee-Yang-Parr (B3LYP), Minnesota 2006, Perdew-Wang 1991 (PW91), Coulomb attenuated method-B3LYP, and ωB97XD functionals); Moller-Plesset perturbation theory; and Hartree-Fock with the cc-PVNZ (n = D and T) basis set in the gas phase. Absolute deviation error (AAD%) indicates that obtained PA and GB values using DFT model and the B3LYP method with mean percentage errors of 0.77 and 0.90%, respectively, have the higher accuracy than the other methods and models. The values obtained for the proton affinity and gas-phase basicity of the nanoclusters were compared to experimental data reported in the literature. In order to confirm basicity properties, quantum descriptors of the molecular electrostatic potential (MEP) and valence natural atomic orbital energies (NAO) have been computed. The MEP and NAO values for species under probe display excellent correlation coefficient. The polarizable continuum model for investigating the solvents effect of water, DMSO, and benzene on the basicity of the CaO nanoclusters has been applied.

Exploring and predicting intermolecular binding preferences in crystalline Cu(ii) coordination complexes.

A simple model focusing on electrostatic contributions to interaction energies was found to be very effective for rationalizing the appearance of specific supramolecular interactions in a series of Cu(ii) coordination compounds. The experimental space was provided by a combination of Cu(ii) cations with acac-based anions (hexafluoracetylacetonato and trifluoracetylacetonato) and a series of pyridine-oxime ligands (3-pyridinealdoxime, methyl 3-pyridyl ketoxime, 4-pyridinealdoxime, methyl 4-pyridyl ketoxime, phenyl 4-pyridyl ketoxime). The calculated molecular electrostatic potential (MEP) values at competing hydrogen-bond acceptor sites, for ten structurally characterized complexes, provided guidelines for predicting supramolecular connectivity in cases when the MEP difference exceeded certain cut-off values, while two different and well-defined outcomes are possible within the so called 'grey zone', delineated by a range of MEP differences. It was also shown that the structural outcome within this region is determined by the influence of relatively weak, but distinct, auxillary interactions.

Exploring Effective Factors on Energy Data of Some Benzofuran Derivatives

Benzofuran derivatives have many useful applications. Computational quantum chemistry method was used to study the relationship between energy data and molecular properties of the 5,6-dihydroxy-2-methyl-1-benzofuran-3-carboxylate derivatives (molecules 3a–3f). Results indicate that there is a good relationship between intramolecular hydrogen bond lengths and energy data of these molecules. Also, X-ray of molecule 3e was used to compare experimental and computational geometrical parameters. Chemical hardness, chemical potential and electronegativity values were calculated to recognize relation between energy data and reactivity of these molecules. Atomic net charges and molecular electrostatic potential values were employed for better insight regarding energy data of the molecules. Electronic charge densities were calculated using atoms in molecules method. The correlation coefficients between experimental and computational 13 C NMR chemical shifts were examined. Total spin– spin coupling constant and its components were evaluated to understand the contribution of these properties in energy data of the molecules. The relation between energy data of the molecules and aromaticity of the rings was also determined.

Electronic Rearrangement in Molecular Plasmons: An Electron Density and Electrostatic Potential-Based Study.

Plasmonic modes in single-molecule systems have been previously identified by scaling two-electron interactions in calculating excitation energies. Analysis of transition dipole moments for states of polyacenes based on configuration interaction is another method for characterising molecular plasmons. The principal features in the electronic absorption spectra of polyacenes are a low-intensity, lower-in-energy peak and a high-intensity, higher-in-energy peak. From calculations using time-dependent density functional theory with the B3LYP/cc-pVTZ basis set, both these peaks are found to result from the same set of electronic transitions, that is, HOMO-n to LUMO and HOMO to LUMO+n, where n varies as the number of fused rings increases. In this work, the excited states of polyacenes, naphthalene through pentacene, are analysed using electron densities and molecular electrostatic potential (MESP) topography. Compared to other excited states the bright and dark plasmonic states involve the least electron rearrangement. Quantitatively, the MESP topography indicates that the variance in MESP values and the displacement in MESP minima positions, calculated with respect to the ground state, are lowest for plasmonic states. The excited-state electronic density profiles and electrostatic potential topographies suggest the least electron rearrangement for the plasmonic states. Conversely, high electron rearrangement characterises a single-particle excitation. The molecular plasmon can be called an excited state most similar to the ground state in terms of one-electron properties. This is found to be true for silver (Ag6 ) and sodium (Na8 ) linear chains as well.

Theoretical study: Electronic structure and receptor interaction of four type bis-1,4-dihydropyridine molecules

The structure of four type bis-1,4-dihydropyridine molecules was completely optimized employing semiempirical (PM3), ab initio (HF/3-21G(d), B3LYP/6-31G(d) and B3LYP/6-311++G(d,p) methods. The B3LYP/6-311++G(d,p) theory level provided a flat boat conformation. The observed ring distortions were not found to be influenced to a great extent by the position of the substituent present in the 4-phenyl ring, the second dihydropyridine ring. The HOMO, LUMO, chemical hardness, global softness, chemical electrophilicity and molecular electrostatic potential values were also appropriately calculated. The electronic parameters allowed to establish the reactivity of the four bis-1,4-dihydropyridine molecules. Moreover, the interactions between these compounds with two models of the voltage-gated calcium channel receptor were evaluated in connection to the reported vasodilator activity of these compounds.