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The control of single molecular processes through electron transport is a scientific challenge to assemble molecular electronic devices. Especially, in nano-bioelectronics, development of DNA based devices such as memories, molecular switches and logical elements are the focused areas. In the present work we have studied control of proton transfer through electronic charge transport in DNA base pairs by using DFT calculation at B3LYP/6-31G(d,p) level of theory. A variety of functional donor (D) substituents (O- and NH2) and acceptor (A) substituent CN are chosen to build D-spacer-A moiety to analyze the proton transfer process. It is shown that with the help of the charge transfer through DNA base pair by the substituents one can alter the intra-molecular proton transfer process. The proton transfer process is further analyzed by molecular electrostatic potential (MESP) topography. We hope that this study will help for further development of DNA based nanoelectronics.

The cooperativity effect in cyclic molecular clusters of hydrogen cyanide (HCN) and its isomeric form hydrogen isocyanide (HNC) is studied in the present work. The cyclic ring stabilization and molecular cooperativity of the (HCN)n and (HNC)n clusters n = 3 to 11 are studied as example with DFT method at B3LYP/6-31G(d,p) level of theory. The observed cyclic cooperativity increases with clusters size. Remarkable correlation between cyclic cooperativity energy (CCE) and hydrogen bond density critical point value (ρBCP) of the clusters is observed with molecular electron density (MED) topography. Higher cooperativity is observed in (HCN)n clusters than the respective (HNC)n ones.

Due to their promising opto-electronic properties, donor-π-acceptor (D-π-A) organic molecules have emerged as novel class of semiconducting photovoltaic materials. In this paper, we present a systematic study of substituent effect on electronic and absorption properties of the trans-polyacetylene oligomers, H-(CH=CH)n-H (n = 1, 2,······,13), as a function of the π-conjugation length. The HOMO-LUMO gap energies and maximum absorption wavelength (λmax) values of the oligomers connected to the donor and acceptor types of the substituents with varied π-conjugation length are correlated on the basis of the DFT and TD-DFT methods respectively. A non-linear behaviour of change in λmax with and without substituent as a function of n is observed. It is believed that such study can help to design D-π-A compounds for optoelectronic applications.

A derivative of 4-Thiazolidinone derivative endowing cyclopropyl ring substituted at 3-nitrogen positioned was synthesized that was further evaluated against cancerous cell lines MCF-7. The structure of synthesized compound (6) was well characterized by different spectral techniques such as FT-IR, UV-Visible, 1H-NMR, 13C-NMR and mass spectrophotometer. X-ray single crystal structure and Computational study (DFT) study revealed that compound (6) adopted (2Z, 5Z)-configuration. Preliminary In vitro study suggested that compound (6) displayed moderate activity bearing IC50(161.0 μM). The DNA binding studies (Ct-DNA) with compound (6) was performed. The study suggested that bound with DNA exhibiting binding constant Kb = 3.3 x 104 LMol-1). Furthermore, the binding study was complemented by Molecular docking possessingDNA binding studies (Ct-DNA) were performed. Final compound (6) exhibited moderate cytotoxicity effect (IC50 = 161.0 μM) and DNA binding ability (Kb = 3.3 x 104 LMol-1). The experimental findings were completed by molecular docking study.

This work reports a combined theoretical and experimental study on large phenol-acetylene clusters, Ph(Ac)n, 8 ​≤ ​n ​≤ ​12, extending our earlier work on the smaller clusters [Singh, G.; Nandi, A.; Gadre, S. R.; Chiba, T.; Fujii, A. J. Chem. Phys. 2017, 146, 154303]. Several trial cluster geometries are generated using the molecular electrostatic potential (MESP) for placing additional acetylene moieties, followed by geometry optimization at B97D/aug-cc-pVDZ level theory. The infrared spectra of energetically low-lying (within 0.5 ​mH window) isomers of the clusters are calculated and averaged. The O–H stretching band shows two peaks due to the presence of energetically close isomers differing in the arrangement of acetylenes around the O–H group. The acetylenic C–H stretching band appears around 3260 ​cm−1. The C–H band shows a red shift of about 3 ​cm−1 on going from n ​= ​8 to 12. Moderately size-selected IR spectra of Ph(Ac)n (n ​= ​~10 and ~13) prepared by a supersonic jet expansion are measured for the acetylenic C–H region by infrared-ultraviolet double resonance spectroscopy combined with time-of-flight mass spectrometry. The observed spectral features are in agreement with the trends of the frequency shift and asymmetric line shape of the C–H stretch band predicted by the theoretical calculations.

Thiazolidi-4-one is a significant pharmacophore and has been known to exhibit a diverse range of biological activities for a long time. A new compound (6), thiazolidi-4-one was synthesized and characterized by spectroscopic techniques and X-ray single crystal structure. The stereochemistry of compound (6) was determined theoretically (DFT level) and experimentally (single crsytal X-ray structure) both. The DNA binding ability of the compound 6 has been assessed as using UV–Visible absorption studies and docking studies, MTT-assay study on MCF-7 cell line revealed non-toxic nature of the compound (6) in the concentration range 10–320 μM.

The gem-disubstituent effect in intramolecular alkyne-azide 1,3 dipolar cycloaddition (AAC) reaction is demonstrated with O-propargylated azido compounds 2a−d. The experimental kinetic data and thermodynamic parameters obtained from computational studies, were correlated with the 'gem-disubstituent effect'. In disubstituted compounds 2b and 2c, the decrease in internal angle (θ) increases the rate of AAC by 9.0 and 8.0 fold, respectively, as compared to reaction of unsubstituted 2a. This increase in rate was attributed to the decrease in Gibbs free energy of activation (ΔG#) for AAC reactions of 2a−c. While remarkable rate acceleration in AAC reaction of sugar derivative 2d (18.0 times more than 2a) was due to the collective effect of decrease in internal angle θ and 'reactive rotamer effect'. The steric assistance exerted by two O-isopropylidene groups in 2d compresses azide and alkyne groups so as to attain stereopopulation controlled increase in stability of 'syn-rotamer' by 0.59 kcal/mol as compared to its 'anti-rotamer'. This resulted in lowering of ΔG# for reaction of 2d (18.09 kcal/mol) against AAC of 2a (20.42 kcal/mol) which is responsible for the unusual rate enhancement in 2d by 18.0 fold to the extent that the reaction occurs at ambient temperature within 18 h, in high yield.

In this work, three novel bipolar host materials TPA-SA, 3CBZ-SA and 4CBZ-SA have been designed and synthesized by incorporating triphenyl amine and carbazole as donor and benzothiadiazine 1,1-dioxide as an acceptor. These molecules exhibit moderately high triplet energies and bipolar carrier transport characteristics (ambipolarity) which is useful for the exothermic energy transfer to the dopants and also for the balanced carrier injection/transport in the emissive layers. These materials exhibited good performances in PhOLEDs and furnished external quantum efficiency in the range of 10.0–15.0%. Notably, a red phosphorescent device using TPA-SA as the host doped with Ir(pq)2(acac) exhibited a maximum EQE, power efficiency and current efficiency of 15.0%, 16.0 lm/W, and 25.3 cd A−1, respectively.

We herein report the design and synthesis of novel donor‒acceptor (D‒A) type 2,3-di(thiophene-2-yl)pyrido[2,3-b]pyrazine and 2,3-di(furan-2-yl)pyrido[2,3-b]pyrazine amine derivatives by employing palladium catalyzed Buchwald‒Hartwig coupling reaction. The synthesized compounds have been characterized by spectroscopic, electrochemical and thermal methods. Absorption spectra of all dyes showed an intramolecular charge transfer (ICT) transitions (λmax = 438–473 nm) in solution and positive solvatochromism with emission maxima in blue‒orange region (λemm = 489–617 nm). Further, solid state emission was studied for aggregation‒induced emission (AIE) effect in THF–water system due to the nanoparticles formation, as confirmed by FEG‒SEM technique. The HOMO (−5.22 to −5.75 eV) and LUMO (−3.35 to −3.45 eV) energy level of these molecules were measured by cyclic voltammetry and correlated by DFT calculations. On the basis of comparable HOMO and LUMO energy level with reported ambipolar materials and efficient solid state emission warrants the application of synthesized compounds as emitter and ambipolar charge transport materials in organic electronics.

Naphthoquinone based Chemosensor 2; 2-(2′-aminoethylpyridine)-3-chloro-1,4-napthoquinone have been synthesized and characterized. Chemosensor 2 crystallizes in the orthorhombic space group Pbcn and shows extensive intramolecular as well as intermolecular hydrogen bonding interactions. Each molecule of Chemosensor 2 showed interaction with five neighboring molecules via C–H⋯N, N–H⋯N, C–H⋯Cl and C–H⋯O interactions. Slipped π–π stacking interaction was observed in adjacent quinonoid and benzenoid rings. Chemosensor abilities of Chemosensor 2 ligand have been evaluated with metal ions viz. Cu2+, Ni2+, Zn2+, Co2+, Fe3+, Mn2+, Cr3+, Hg2+, La3+ and Cd2+ in methanol, methanol-water mixture and in presence of mild base triethylamine. Stoichiometry of Chemosensor 2 with metal ions such as Cu2+, Ni2+, Zn2+and Co2+ ions was determined by Jobs method in methanol and were found as 1:1 for Cu2+and 2:1 for Ni2+, Zn2+ Co2+. The variation in the metal ligand ratio is observed in aqueous media for Cu2+. Chemosensor 2 can be used selectively for naked eye detection of Cu2+ ions. The association constant obtained in methanol shows the trend Cu2+>Ni2+>Co2+. Cu2+ and two (Ni-1 and Ni-2) Ni2+ complexes were synthesized. Ni-2 complex showed coordination of Chemosensor 2 ligands was through pyridine nitrogen's only. The Chemosensor 2 and its deprotonated forms in methanol, water and triethylamine were also studied by TD-DFT studies.

Quinones are known to perform diverse functions in a variety of biological and chemical processes as well as molecular electronics owing to their redox and protonation properties. Electrostatics chiefly governs intermolecular interaction behaviour of quinone states in such processes. The electronic distribution of a prototypical quinone, viz., p-benzoquinone, with its reduction and protonation states (BQS) is explored by molecular electrostatic potential (MESP) mapping using density functional theory. The reorganization of electronic distribution of BQS and their interaction with electrophiles are assessed for understanding the movement of ubiquinone in bacterial photosynthetic reaction centre, by calculating their binding energy with a model electrophile viz., lithium cation ( $$\hbox {Li}^{+}$$ ) at B3LYP/6-311+G(d,p) level of theory. The changes in the values of the MESP minima of BQS states alter their interacting behaviour towards $$\hbox {Li}^{+}$$ . A good correlation is found between the value of MESP minimum of BQS and the $$\hbox {Li}^{+}$$ binding strength at the respective site. To acquire more realistic picture of the proton transfer process to quinone with respect to its reduction state in the photosynthetic reaction center, interaction of BQS with model protonated motifs of serine, histidine as well as $$\hbox {NH}_{4}^{+}$$ is explored. Further, the electronic conjugation of the reduced states of 9,10-anthraquinone is probed through MESP for understanding the switching nature of their electronic conductivity. Quinones perform important function of proton transfer in photosynthesis and also act as a switch in molecular electronics. This work explores the electronic distribution of reduction and protonation states of p-benzoquinone using molecular electrostatic potential, for understanding the mechanisms of quinone activity in the photosynthesis and its switching nature in electronic conductivity.

Naphthoquinone based redox active chemosensor 1; 2-(2′-aminomethylpyridine)-3-chloro-1,4-naphthoquinone ligand has been synthesized and characterized. Chemosensor 1 crystallizes in monoclinic space group P21/n. Molecules showed intramolecular N–H⋯O and N–H⋯N, intermolecular N–H⋯O, C–H⋯O and slipped π–π stacking interactions. Chemosensor 1 showed orange colored solution in methanol and specifically detects Cu2+ ions by deprotonation of N–H. The deprotonation of amino N–H can also be achieved by mild base viz. triethylamine and chemosensor 1 can be used to detect several metal ions for example Ni2+, Mn2+ etc. that could observed by naked eye. Color changes observed were monitored by UV–visible and fluorescence spectra. Chemosensor 1 could provide either bidentate or tridentate coordination sites to metal ions. Redox nature of chemosensor 1 was evaluated by cyclic voltammetry studies. Electronic transition wavelengths of chemosensor 1 ligand have been evaluated in methanol, water and triethylamine by TD-DFT studies and comparative studies were performed with experimental results.

The spectral features of lawsone (2-hydroxy-1,4-naphthoquinone), an active component of the natural dye henna, are analyzed in ethanol using experimental and computational methods. The calculated UV-Vis absorption spectrum from the time-dependent density functional theory (TD-DFT) approach is compared with the experimental results, allowing a detailed assignment of the UV-Vis spectral features based on molecular orbitals. Further, we have analyzed the light intensity dependent J–V characteristics and electrochemical impedance spectrum of a dye sensitized solar cell fabricated with lawsone and a ZnO photoanode. The photovoltaic data of the sensitizer adsorbed on ZnO films exhibited a reasonable power conversion efficiency, i.e. 0.68% at 26 mW cm−2 light intensity.

The broad range of applications of $$\pi $$ -conjugated polymeric materials in industries such as automobiles, textiles, packaging, medical etc. have led to their extensive studies in both academic and industrial fields. Predicting the structure of these polymers is important for the study of their properties. The present work uses a ‘divide and conquer’-type approach for the ab-initio studies of these polymeric systems. The method employs a fragmentation technique with independent fragment optimization for obtaining optimized geometries of the oligomers of various polymeric materials such as polyfuran, polypyrrole, polythiophene and other such $$\pi $$ -conjugated polymers. A few test calculations performed in the study provide fair concurrence between the energies and the HOMO–LUMO energy gaps obtained using the fragmentation-based approach with those obtained using the full optimization of the whole oligomer. Also, a significant reduction in time complexity occurs for the present fragment-based approach compared to the parent system optimization. The results are encouraging and prompt for studies of large polymeric materials.

The structural evolution and variation of electronic properties of alkaline-earth metal fluoride clusters (MF2)n (M = Mg, Ca, Sr, Ba; n = 1–6) are investigated using density functional theory. All these clusters demonstrate ionic-bonding dominated through all sizes considered here, and generally show a preference of 3D structures when n ⩾ 4. It is found that the structural evolution of (MgF2)n clusters are distinct from the rest of the alkaline-earth clusters owing to the competitive interplay of much smaller ionic radius of Mg and the stronger Mg–F bond. In the ground state configurations, (MgF2)n clusters prefer the planar building units, whereas the rest of the (MF2)n clusters prefer the 3D building units of a M2F3 type maximizing the coordination number of the constituent metal atoms. The variations of the binding energy, the ionization potential, the electron affinity and the HOMO–LUMO gap with the cluster size are explained in terms of the change in the ionic radius and the basicity of the constituent metal ions in going from (MgF2)n to (CaF2)n, (SrF2)n, and (BaF2)n.

The molecular electrostatic potential (MESP) and polarization-corrected MESP (PMESP) minima for some small molecules are calculated on the surface generated by rolling cations (Li + and Na + ) on their van der Waals surfaces. The cation binding energies of these molecules are obtained with HF/6-31G ** level ab initio calculations. A noteworthy outcome of the present study is that the plot of these binding energies and the corresponding PMESP surface minimum values turns out to be remarkably linear with a slope close to unity. The PMESP is thus found to work as a powerful tool for unearthing the patterns of cation binding sites and energetics for molecular systems.

Ab initio quantum chemical methods as well as simulation/dynamics programs have been conventionally used for probing the hydration of molecules, an important problem in chemistry and biology. However, very few attempts have as yet been reported for understanding the stepwise patterns in hydration processes at the molecular level. The present work investigates the problem of hydration of the 18-crown-6 (18C6) molecule based on rigorous topography mapping of molecular electrostatic potential (MESP) followed by an application of a simple electrostatic model (electrostatic potential for intermolecular complexation) for obtaining trends in energetics. Structures and energies of the hydrated species, 18C6·nH2O (n = 1, 2, 3, 4, 6) have been studied by the EPIC model followed by ab initio HF/6-31G** investigations. The remarkable agreement between the model and ab initio results highlights the utility of MESP topography for exploring the lock-and-key features in a hydration process via cooperative electrostatic e...

The molecular electrostatic potential (MESP) and the corresponding polarization corrected one (PMESP) of some saturated hydrocarbons, viz., methane, ethane, cyclopropane, cyclobutane, n-butane, and cyclohexane, have been examined at the ab initio SCF level. The topography of PMESP has been employed for predicting coordination of Li+ with these hydrocarbons. Coordination site of Li+ usually turns out to be in the direction guided by the corresponding PMESP critical points (CPs) of these hydrocarbons. An ab initio level minimum energy search along this direction is used to generate possible starting configurations of hydrocarbon···Li+ complexes. Hartree−Fock and second-order Moller−Plesset (MP2) calculations with 6-31G** basis set are performed with these starting geometries for investigating the structures and energetics of the complexes. A remarkable correlation has been found between the PMESP values at CPs and the corresponding Li+ binding energies. General trends in geometries and interaction energies ...

Molecular electrostatic potentials (MESP) of the most common building blocks of organic π-conjugated systems, viz. ethylene, acetylene, benzene, furan, pyrrole, thiophene and phenylvinylene, are examined at the B3LYP/6-311++G(2d,2p) level. The topography of MESP is employed for mapping the strength of electronic conjugation between these building blocks. When electron-rich molecular regions are connected to each other, the MESP value of the corresponding conjugation critical point (CCP) is able to provide a quantitative measure of the strength of the conjugation. The systems with stronger conjugation are generally seen to possess a larger negative value of CCP and a smaller difference (ΔV(CM-CCP)) between the MESP values of respective conjugated minimum (CM) and the CCP, in agreement with the experimental as well as other theoretical results. The present MESP topography-based approach thus offers a measure of the quantitative strength of π-conjugation in molecules.

The chapter focuses on molecular recognition via electrostatic potential. A sound knowledge of structure-and energy-related information is available from the experimental and computational studies mentioned in the chapter. A variety of theoretical models have been developed forunderstanding the weak intermolecular interactions. The latter are predominantly electrostatic in character based on the properties of the interacting molecules and the long-range electrostatic forces operative between them. Four of such rules/models are discussed in this chapter: those because of Legon and Millen, Buckingham and Fowler, Dykstra and Alhambra, Luque and Orozco. The chapter discusses the topography of molecular scalar fields, molecular electron density, and electrostatic potential. In this chapter, molecular electrostatic potentials (MESP) topography is used as a predictive tool for obtaining the intermolecular interaction parameters. The graphics illustrations in the present work are generated employing a PC-based package UNIVIS. The MESP driven atomic charges are obtained using the GRID program. All the calculations are performed on an HP-9000/715 Apollo workstation and a PC-486. The MESP topographical features of the molecules discussed in this chapter are represented by the corresponding ball-and-stick model.

It is shown that a negative molecular electrostatic potential (MESP) surface completely surrounds all the atoms in any surfactant anion; further, negative MESP at the hydrocarbon ends of n-dodecanoate and n-decylsulfate is almost six times that for the n-dodecane and n-decane molecules respectively; this negative MESP build-up from the polar head group through the molecule up to the end of the hydrocarbon tail leads to finite, decreasing hydration probability along the chain.