• Volume 125, Issue 5

September 2013,   pages  967-1292

• Aza-Morita-Baylis-Hillman reaction of maleimides with azodicarboxylates under neat conditions

Green approach on reaction of diisopropylazodicarboxylate or diethyl azodicarboxylate with maleimides proceeded smoothly under neat condition at 70°C to give the corresponding hydrazine substituted pyrrolidinone as aza-Morita-Baylis-Hillman adducts in moderate to good yields in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as nitrogen Lewis base.

• Nano 𝑛-propylsulphonated 𝛾-Fe2O3: A novel magnetically recyclable heterogeneous catalyst for the efficient synthesis of bis(pyrazolyl)methanes in water

Nano 𝑛-propylsulphonated 𝛾-Fe2O3 (NPS-𝛾-Fe2O3) was applied as a new magnetically recyclable heterogeneous catalyst for the efficient one-pot synthesis of bis(pyrazolyl)methanes in water. The catalyst was easily isolated from the reaction mixture by a magnetic bar and reused at least five times without significant degradation in activity.

• Montmorillonite K-10 as a catalyst in the synthesis of 5, 5-disubstituted hydantoins under ultrasound irradiation

The rapid and highly efficient synthesis of 5,5-disubstituted hydantoins achieved by threecomponent condensation of corresponding ketones and aldehydes, potassium cyanide and ammonium carbonate in an additional reaction under ultrasound irradiation by using montmorillonite K-10 as a heterogenous catalyst. Utilizing ultrasound irradiation and montmorillonite in this method has several benefits, for example short reaction time, high yield and use of recyclable catalyst.

• Methyltrioctylammonium chloride catalysed sonochemical synthesis of acridine diones

The greener, clean and efficient protocol for the synthesis of acridine diones derivatives has been achieved by reacting aromatic aldehyde, dimedone and amines using methyltrioctylammonium chloride (Aliquate 336) as a catalyst under ultrasonic irradiations.

• An efficient synthesis of 3'-indolyl substituted pyrido[1,2-𝑎]benzimidazoles as potential antimicrobial and antioxidant agents

A new class of indole-based pyrido[1,2-𝑎]benzimidazole derivatives 4a-r have been synthesized by one-pot cyclocondensation reaction of 2-phenyl-1𝐻-indole-3-carboxaldehyde 1a-i, malononitrile 2 and 2-cyanomethylbenzimidazole 3a-b in the presence of catalytic amount of NaOH. In vitro antimicrobial activity of the synthesized compounds were investigated against a representative panel of pathogenic strains specifically three Gram-positive bacteria (Streptococcus pneumoniae, Clostridium tetani, Bacillus subtilis), three Gram-negative bacteria (Salmonella typhi, Vibrio cholerae, Escherichia coli) and two fungi (Aspergillus fumigatus, Candida albicans) using broth microdilution MIC (minimum inhibitory concentration) method. In vitro antioxidant activity was evaluated by ferric-reducing antioxidant power (FRAP) assay method. Compounds 4c, 4e, 4l and 4q have been found to be most efficient antimicrobial members while compounds 4h and 4p possess better ferric reducing antioxidant power.

• Silver iodide nanoparticle as an efficient and reusable catalyst for the one-pot synthesis of benzofurans under aqueous conditions

Recyclable heterogeneous AgI nanoparticles were efficiently catalysed one-pot three-component reaction of aldehydes, secondary amines and alkyne in aqueous media. This method provides a novel and improved approach for the synthesis of 2,3-disubstituted benzo[b]furan derivatives to obtain excellent yields, short reaction times and low catalyst loading.

• Lewis acidic (choline chloride.3ZnCl2) ionic liquid: A green and recyclable catalyst for the one-pot synthesis of 4-((3-indolyl)(aryl)methyl)-N,N-dimethylanilines under solvent-free conditions

A green and convenient procedure for the one-pot multicomponent synthesis of 4-((3-indolyl)(aryl)methyl)-N,N-dimethylanilines using (choline chloride.3ZnCl2) ionic liquid as catalyst, at 100°C and under solvent-free condition is described. Utilizing environmentally benign reagents, elimination of organic solvents, enhanced rates, reusability and moisture stability of the catalyst are the remarkable features observed in the reported reaction system. The catalyst was recycled up to four times with no noticeable drop in activity.

• Photo-induced antimicrobial and DNA cleavage studies of indoloquinolines and 1,8-naphtharidine

Angular and linear isomers of indoloquinoline are synthesized from 4-hydroxyquinolin-2(1H)-one. The use of Vilsmeier-Haack reagent on 𝑁-phenylpropionamide yielded a new versatile method for the synthesis of 2-chloro-3-methylquinoline which is utilized as precursor in the synthesis of basic camptothecin core and quinoline fused with 1,8-naphthridine. The in vivo photoinduced antibacterial activity of all the synthesized compounds has been studied. The unique photo-bioactivity of 5𝐻-indolo[3,2-𝑐]quinolin-6(11𝐻)-one is further studied under the photo-DNA cleavage analysis. Theoretical calculations for the synthesized compounds are performed to determine further credentials of the biological results.

• Design, synthesis and cytotoxic activity of some novel compounds containing pyrazolo[3,4-𝑑]pyrimidines nucleus

Novel pyrazolo[3,4-𝑑]pyrimidines were designed and synthesized as antitumour agents against human breast cancer adenoma (MCF-7). Molecular modelling and pharmacological screening were performed against breast cancer cell line and also certain synthetic pathways were developed in order to introduce functionality onto C6 and N5 positions of pyrimidine moiety. Surprisingly, all the test compounds showed IC50 lower than that of the standard olomoucine I, especially compounds 4b, 8a, 10b, 11a and b, which showed IC50 between 0.009 and 0.004 𝜇M.

• Ionic liquid-mediated three-component synthesis of fluorinated spiro-thiazine derivatives and their antimycobacterial and DNA cleavage activities

A simple, green and catalyst-free novel protocol is developed for the synthesis of medicinally important spiro[indole-3,2'[1,3]-thiazine]-2,4'-dione and spiro[acenaphthylene-1,2'-[1,3]thiazine]dione libraries by the tandem reaction of readily available reagents in 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6]. The ionic liquid has been used as a solvent as well as catalyst for this reaction. This reaction proceeded smoothly in good to excellent yields and offered several other advantages including short reaction time, simple experimental workup procedure and no by-products. The synthesized compounds were subjected to antimycobacterial efficacy against Mycobacterium tuberculosis H37Rv strain and DNA cleavage activity.

• TMSCl-catalysed condensation of 𝛼-diketone compounds with urea/thiourea derivatives under solvent-free conditions

An efficient, rapid and green synthesis of glycoluril, imidazolidine-2-one, imidazole-2-one and imidazole-2-thiol derivatives have been accomplished by the reaction of urea/thiourea derivatives and 𝛼-diketone at 100°C in the presence of trimethylsilyl chloride (TMSCl) as Lewis acid catalyst under solvent-free conditions. This approach offers many advantages such as good product yields, various products, short reaction time, easy isolation of products, facile purification and environmentally benign reaction conditions.

• Green and solvent-free procedure for microwave-assisted synthesis of 2,4,6-triarylpyridines catalysed using MgAl2O4 nanocrystals

Design and development of a heterogeneous nanocatalyst for condensation reaction of acetophenone derivatives, aromatic aldehydes, and ammonium acetate to yield 2,4,6-triarylpyridines followed by microwave irradiation is described. Nanocrystalline MgAl2O4 as a novel heterogeneous recyclable catalyst shows high activity for the above reaction. In addition, the easily recoverable nanosized catalysts showed good reusability.

• Synthesis of some novel fluoro isoxazolidine and isoxazoline derivatives using 𝑁-benzyl fluoro nitrone via cycloaddition reaction in ionic liquid

1-Butyl-3-methylimidazolium-based ionic liquids are found to accelerate significantly the intermolecular 1,3-dipolar cycloaddition of 𝑁-benzyl-fluoro nitrone derived in situ from 2,6-difluoro benzaldehyde and 𝑁-benzylhydroxylamine, with activated alkenes and electron deficient alkynes to afford enhanced rates and improved yields of novel isoxazolidines and isoxazolines.

• Ultrasonic synthesis and crystal structure analysis of two trimethylsilyloxy-substituted bicyclo[2.2.2]octene derivatives

The compounds: 11-trimethylsilyloxy-1,2,3,4,4a,9a-hexahydro-1,4-etheno-anthraquinone and 4-benzyl-8-trimethylsilyloxy-4-aza-tricyclo[5.2.2.0]undec-8-ene-3,5-dione were synthesized by the Diels-Alder [${}_4\pi_s +_2 \pi_s$] cycloaddition reaction of 2-(trimethylsilyloxy)-1,3-cyclohexadiene with naphthaquinoneand 𝑁-benzylmaleimide under ultrasonic conditions. The crystal structure analysis was done using single crystal X-ray diffraction method. In both the compounds, the trimethylsilyloxy- and naphthaquinone/𝑁-benzylmaleimide moieties are endo- to the bicyclic ring.

• The reaction of carbon disulphide with 𝛼-haloketones and primary amines in the presence of potassium iodide as catalyst

A simple, mild and convenient method has been developed for the synthesis of 3,4,5-trialkyl-1,3-thiazole-2(3𝐻)-thione derivatives through one pot three-component reaction between a primary amine, carbon disulphide, and 𝛼-haloketone in the presence of potassium iodide at room temperature conditions. The products were obtained with excellent yield and appropriate reaction times. This reaction represents a rapid and unprecedented route to the described molecules that have biological specifications.

• Synthesis and evaluation of some novel precursors of oxazolidinone analogues of chloroquinoline for their antimicrobial and cytotoxic potential

Some 3-(3-(7-chloroquinolin-4-ylamino)propyl-2-imino-5-(4-chloro/nitro/methoxy benzylidene) oxazolidin-4-one 4(a-c) and 4-(3-(7-chloroquinolin-4-ylamino) propyl)-2(4-chloro/nitro/methoxy benzylidene)-1,6-diox-4,9 diazaspiro[4,4]nonane-3,8-dione 5(a-c) derivatives were synthesized using appropriate synthetic route. The newly prepared compounds 5a-c demonstrated inhibitory effects on the growth of a MCF7 (hormone-dependant breast carcinoma cell line), HT29 (colon carcinoma cell line on leukemia). The MCF7 cell line was found to be very susceptible towards compound 5a with IC50 values of 16 𝜇g/ml. Similarly, the HT29 cell line was found to be moderately susceptible towards compounds 5a and 5c with IC 50 values of 32 and 49 𝜇g/ml, respectively.

• Synthesis of 2,6-diaminopyridine substituted 𝛼-oxoketene 𝑆,𝑁-acetals: Crystal structure and hydrogen bonding interactions

Polyaza 𝛼-oxoketene 𝑆,𝑁-acetals can exist as either enamino or imino tautomeric forms. Based on the spectroscopic data and structural analysis of one of the 𝑆,𝑁-acetals, the stereochemistry was unambiguously assigned as an all-𝐸-configuration. The crystal structure confirms the enamino structure and shows extensive use of C-H…X (X = N, O, and S) weak hydrogen bonding interactions, thereby generating a 3-dimensional network in solid state.

• Organocatalysis for the synthesis of optically active 𝛽-malonophosphonates

Method describes asymmetric reaction of triethyl phosphites and 2-arylidenemalononitrile catalysed by the chiral organocatalyst in solvent ethanol. The organocatalyst effectively catalyse reaction to give 𝛽-malonophosphonates in high yields (85-64%) and good to moderate enantiomeric excess (78-53%).

• Antiplasmodial and larvicidal compounds of Toddalia asiatica root bark

From the 𝑛-hexane, ethyl acetate and methanol extracts of Toddalia asiatica root bark were isolated eight compounds (1-8) which were identified on the basis of both spectroscopic and physical data as well as comparison with already published results. The crude extracts and isolated compounds showed moderate in vitro antiplasmodial activity against D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) strains of Plasmodium falciparum. The extracts and isolates also exhibited larvicidal activities against Aedes aegypti and coumarins were identified as the active compounds.

• Oxidation of hydrogen peroxide by [NiIII(cyclam)]3+ in aqueous acidic media

The kinetics of oxidation of H2O2 by [NiIII(cyclam)]3+, [NiIIIL1], was studied in aqueous acidic media at 25°C and I = 0.5M (NaClO4). The [NiIIIL1] to [NiIIL1] reduction was found to be fast in the presence of Cu(II) ion than the oxidation of the cyclam ligand by ·OH. The rate constant showed an inverse acid dependence on H+ ion at the pH range 1-1.5. The presence of sulphate retards the reaction. Macrocylic ligand oxidation was followed spectrophotometrically by examining the oxidation of nickel(II) complexes of macrocyclic ligands such as 1,8-bis(2-hydroxyethyl)-1,3,6,8,10,13-hexaazacyclotetradecane (L2), 𝑚𝑠-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L3), rac-Me6[14]-4,11-dieneN4 (L4) by reaction with hydrogen peroxide. The rate constant for the cross reaction is discussed in terms of Marcus relationship.

• Kinetics and mechanism of interaction of some bioactive ligands with cis-diaqua(cis-1,2-diaminocyclohexane)platinum(II) in aqueous medium

The substitution reaction of cis-[Pt(cis-dach)(H2O)2]2+ (where `dach’ is cis-1,2-diaminocyclohexane) with 2-thiouracil (S, N), 1,2-cyclohexanedionedioxime (N, N) and acetylacetone (O, O) were studied in aqueous solution in 0.10 M NaClO4 under pseudo-first order conditions as a functions of concentration, pH and temperature using UV-Vis spectrophotometry. The substitution reaction proceeds via rapid outer sphere association complex formation, followed by two slow consecutive steps. The first of these involves ligand-assisted deaquation, while second involves chelation as the second aqua ligand is displaced. The association equilibrium constant (KE) for the outer sphere complex formation has been evaluated together with rate constants for the two subsequent steps. The rate constants increase with increasing ligand concentration and the evaluated activation parameters for all reactions suggest an associative substitution mechanism for both the aqua ligand substitution processes. The product of the reaction has been characterized by IR, NMR and ESI-MS spectral analysis; which throws more light on the mechanistic behaviour of platinum(II) antitumour complexes.

• Hydrolytic activity of 𝜇-alkoxide/acetato-bridged binuclear Cu(II) complexes towards carboxylic acid ester

Two 𝜇-alkoxide/acetate-bridged small molecule binuclear copper(II) complexes were synthesized, and used to promote the hydrolysis of a classic carboxylic acid ester, 𝑝-nitrophenyl picolinate (PNPP). Both binuclear complexes exhibited good hydrolytic reactivity, giving rise to 𝑐𝑎. 15547- and 17462-fold acceleration over background value for PNPP hydrolysis at neutral conditions, respectively. For comparing, activities of the other two mononuclear analogues were evaluated, revealing that binuclear complexes show approximately 150- and 171-fold kinetic advantage over their mononuclear analogues.

• Mechanism of electron transfer reaction of ternary dipicolinatochromium(III) complex involving oxalate as secondary ligand

Mechanism of electron transfer reaction of ternary Mechanism of the oxidation of [CrIII(DPA)(OX)(H2O)] (DPA = dipicolinate and OX = oxalate) by periodate in aqueous acidic medium has been studied spectrophotometrically over the pH range of 4.45-5.57 at different temperatures. The reaction is first order with respect to both [IO$^−_4$] and the complex concentration, and it obeys the following rate law: $$d[{\text Cr}^{\text{VI}}]/dt = k_6K_4K_6[{\text IO}^−_4][{\text{Cr}}^{\text{III}}]_{\text{T}}/\{([H^+] + K_4) + (K_5[H+] + K_6K_4)[{\text{IO}}^−_4]\}.$$

The rate of the reaction increases with increasing pH due to the deprotonation equilibria of the complex. The experimental rate law is consistent with a mechanism in which the deprotonated form [CrIII(DPA)(OX)(OH)]2− is more reactive than the conjugated acid. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO$^−_4$ to chromium(III). Thermodynamic activation parameters were calculated using the transition state theory equation.dipicolinatochromium(III) complex involving oxalate as secondary ligand

• DNA binding and cleavage activity by a mononuclear iron(II)Schiff base complex: Synthesis and structural characterization

Synthesis and characterization of a mononuclear Fe(II) compound [Fe(L)](ClO4)2 (1) [L = N-(1-pyridin-2-yl-phenylidene)-N'-[2-({2-[(1-pyridin-2-ylphenylidene)amino]ethyl}amino)ethyl] ethane-1,2-diamine] (1) is reported. 1 crystallizes in P-1 space group with a = 11.9241(3) Å, b = 12.1994(3) Å and c = 13.0622(4) Å. The binding property of the complex with DNA has been investigated using absorption and emission studies, thermal melting, viscosity experiments and circular dichroism studies. The binding constant ($K_b$) and the linear Stern-Volmer quenching constant ($K_{\text{sv}}$) of the complex have been determined as $3.5 \times 10^3$M-1 and $2.73 \times 10^4$M-1, respectively. Spectroscopic and hydrodynamic investigations revealed intercalative mode of binding of 1 with DNA. 1 is also found to induce oxidative cleavage of the supercoiled pUC 18 DNA to its nicked circular form in a concentration dependent manner.

• Growth and characterization of BCN nanotubes with high boron and nitrogen content

Multiwalled carbon nanotubes doped with boron and nitrogen (BCNTs) have been synthesized by chemical vapour deposition at temperatures ranging from 800°C to 950°C. Their morphological and structural features have been studied by transmission electron microscope, which reveal that BCNTs have bamboo-like structure. The results of X-ray photoelectron spectroscopy demonstrated that the atomic ratio of B, C and N of BCNTs is about 1:4:1, when temperature is 850°C. Electrooxidation performance of the BCNTs for NO at the modified electrodes was investigated. The results of cyclic voltammograms and the electrochemical impedance spectroscopy of BCNT-modified electrodes indicated that the activity of NO electrooxidation on 850°C-modified electrodes is much stronger than others and the charge transfer resistance of NO electroxidation BCNT-modified electrode is the least. By this means, BCNT-modified electrodes showed excellent electrode materials for NO detection and other potential applications.

• Influence of binder solvent on carbon-layer structure in electrical-double-layer capacitors

Porous activated-carbons with a large surface-area have been the most common materials for electrical-double-layer capacitors (EDLCs). These carbons having a wide pore distribution ranges from micropores to macropores in conjunction with a random pore connection that facilitates the high specific-capacitance values. Pore distribution plays a central role in controlling the capacitance value of EDLCs, since electrolyte distribution inside the active material mainly depends on the pore distribution. This has a direct influence on the distribution of resistance and capacitance values within the electrode. As a result, preparation of electrodes remains a vital issue in realising high-performance EDLCs. Generally, carbon materials along with some binders are dispersed into a solvent and coated onto the current collectors. This study examines the role of binder solvents used for the carbon-ink preparation on the microstructure of the electrodes and the consequent performance of the EDLCs. It is observed that the physical properties of the binder solvent namely its dielectric constant, viscosity and boiling point have important role in determining the pore-size distribution as well as the microstructure of electrodes which influence their specific capacitance values.

• Synthesis, characterization and catalytic activity of sulphonated multi-walled carbon nanotubes as heterogeneous, robust and reusable catalysts for the synthesis of bisphenolic antioxidants under solvent-free conditions

In this study, a simple and green method has been developed for the synthesis of bisphenolic antioxidants by the reaction of 2-tert-butyl-4-methylphenol and aldehydes in the presence of sulphonated multiwalled carbon nanotubes (MWCNTs-SO3H) as heterogeneous, robust and reusable catalysts under solventfree conditions. MWCNTs-SO3H was prepared and characterized by some microscopic and spectroscopic techniques including scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and Raman spectroscopy. Acidity of the catalyst was measured by acid-base titration. The catalyst was reused several times without efficient loss of its activity for the preparation of bisphenolic antioxidants. In addition, high yields of the products, relatively short reaction times, being solvent-free and non-toxicity of the catalyst are other worthwhile advantages of the present method.

• Electrochemical studies of ropinirole, an anti-Parkinson’s disease drug

The oxidation behaviour of a potent anti-Parkinson’s disease drug ropinirole hydrochloride was investigated over a wide pH range in aqueous solution at glassy carbon electrode using cyclic and square-wave voltammetry. The oxidation of drug is a pH dependent irreversible process and occurs in two steps. The mechanism of the oxidation process has been discussed. Using the sharp oxidation response in 0.1Msulphuric acid at a potential of +1.27V attributed to the oxidation of indol-2-one ring in drug molecule, rapid electroanalytical methods for the determination of ropinirole by pulse voltammetric techniques were developed and validated. The proposed voltammetric methods were applied to direct quantification of ropinirole in film-coated tablets, with results in close agreement (at 95% confidence level) with those obtained using a comparative HPLC method.

• Recyclable hydrotalcite clay catalysed Baylis-Hillman reaction

The Baylis-Hillman reaction using ionic liquid/hydrotalcite clay catalytic system has been observed to be more reactive in terms of yield and reaction rate than DABCO/acetonitrile system. During the process, the reactants enjoy ionic liquid/hydrotalcite clay catalytic system and gives corresponding Baylis-Hillman reaction products in good yield. The application of our catalytic system has been diversifying for the synthesis of lactone ceramide analogue from (S)-Garner aldehyde-methyl acrylate using Baylis-Hillman reaction. Recycling of ionic liquid/hydrotalcite clay catalytic system has also been demonstrated in this report.

• Non-adiabatic rotational excitation of dipolar molecule under the influence of delayed pulses

We suggest a control scheme for choosing populations of molecular rotational states by wave packet interference. The rotational wave packets of LiCl molecule excited non-adiabatically by half cycle pulse (HCP) is controlled using the second ultrashort HCP. By adjusting the time delay between the two laser pulses, constructive or destructive interference among these wave packets enables the population to be enhanced or repressed for the specific rotational state. The role played by the field strength and the pulse duration is also calculated numerically. We have used fourth order Runge-Kutta method to study non-adiabatic rotational excitation (NAREX) dynamics.

• Nucleotide insertion initiated by van derWaals interaction during polymerase beta DNA replication

We present here an unambiguous theoretical analyses and to show that the exclusive biochemical reaction involved in a single nucleotide insertion into the DNA primer can be efficiently tracked using the renormalized van derWaals (vdW) interaction of a stronger type, the Hermansson blue-shifting hydrogen bond effect, and the Arunan composite hydrogen-vdW bond. We find that there are two biochemical steps involved to complete the insertion of a single base (cytosine) into the 3' end of a DNA primer. First, the O3' (from a DNA primer) initiates the nucleophilic attack on P$_{\alpha}$ (from an incoming dCTP), in response, O3$_{\alpha}$ (bonded to P$_{\alpha}$) interacts with H' (bonded to O3'). These interactions are shown to be strongly interdependent and require the forming and breaking of P—O and H—O covalent bonds, which in turn imply that we do not need any external energy supply.

• Quasi-classical trajectory study of the reaction H' + HS on a new ab initio potential energy surface H2S (3A")

Theoretical study on the dynamics of reactions H' + HS(𝑣 = 0, 𝑗 = 0\$)→H2 + S and H' + HS(𝑣 =0, 𝑗 = 0)→ H + H'S is performed with quasi-classical trajectory (QCT) method on a new ab initio potential energy surface for the lowest triplet state of H2S (3A") constructed in 2012 by Lv et al. The QCT-calculated reaction integral cross-sections are in good agreement with previous quantum wave packet results over the collision energy range of 0-50 kcal/mol. Both the abstraction and exchange reactions are governed by direct reaction dynamics and the trajectories follow the minimum energy path. The rotational angular momentum vector 𝑗' of products in the two reaction channels are not only aligned perpendicular to scattering plane but also oriented along the negative direction of the axis perpendicular to the scattering plane. With the increase in collision energy, the variation trends of product polarization in the two reaction channels are different and that may be attributed to the obviously different characteristic of the two channels on the potential energy surface.

• Role of substituents on the reactivity and electron density profile of diimine ligands: A density functional theory based study

In this paper, we study the reactivity of diimines like 2, 2'-bipyridine, 1, l0-phenanthroline and 1, 2, 4-triazines using density-based reactivity descriptors. We discuss the enhancement or diminution in the reactivity of these ligands as a function of two substituent groups, namely methyl (-CH3) group and phenyl (-C6H5) group. The global reactivity descriptors explain the global affinity and philicity of these ligands, whereas the local softness depicts the particular site selectivity. The inter-molecular reactivity trends for the same systems are analysed through the philicity and group philicity indices. The 𝜎-donor character of these ligands is quantified with the help of electron density profile. In addition, the possible strength of interaction of these ligands with metal ions is supported with actual reaction energies of Ru-L complexes.

• DFT-based inhibitor and promoter selection criteria for pentagonal dodecahedron methane hydrate cage

Density functional theory (DFT)-based simulations have been performed to provide electronic structure property correlation based reasoning for conceptualizing the effect of encapsulated methane molecule on the formation of methane hydrate cages, the role of methanol and ethylene glycol as inhibitor and the role of tetra-hydro-furan (THF) and cyclopentane as promoter of methane hydrate. Geometry optimization of 512 cage, 51262 cage and 51264 cage with and without encapsulated methane and the cluster of 512 cage with ethylene glycol, methanol, cyclopentane have been performed by density functional theory using 𝜔B97X-D/6-31++G(d,p) method. Methane hydrate formation inhibition by methanol and ethylene glycol as well as methane hydrate stabilization by cyclopentane and tetrahydrofuran are critically analysed based on the interaction energy, free energy change, dipole moment and infrared frequency calculation. Calculation of free energy change for formation of methane hydrate with/without reagents at various temperature and pressure using optimized structure is reported here. It is observed that hydrogen bond between water molecules of clathrate 512 cages become stronger in the presence of cyclopentane and tetrahydrofuran but weaker/broken in the presence of ethylene glycol and methanol. Simulated results correspond well with experimental findings and can be useful for designing new inhibitor and promoter molecules for gas hydrate formation.

• A comparative study of independent particle model based approaches for thermal averages

A comparative study is done on thermal average calculation by using the state specific vibrational self-consistent field method (ss-VSCF), the virtual vibrational self-consistent field (v-VSCF) method and the thermal self-consistent field (t-SCF) method. The different thermodynamic properties and expectation values are calculated using these three methods and the results are compared with full configuration interaction method (FVCI). We find that among these three independent particle model based methods, the ss-VSCF method provides most accurate results in the thermal averages followed by t-SCF and the v-VSCF is the least accurate. However, the ss-VSCF is found to be computationally very expensive for the large molecules. The t-SCF gives better accuracy compared to the v-VSCF counterpart especially at higher temperatures.

• Ab initio study of 1:1 complexes of nitrogen trifluoride with nitrous oxide and carbon dioxide in vacuo

Quantum chemical calculations are carried out in order to investigate the heterodimers of NF3 with isoelectronic and isostructure species of N2O and CO2 in gas phase within the MP2 (Møller-Plesset perturbation) and CCSD(T) levels. Three and four minima are located on the potential energy surfaces of NF3-CO2 and NF3-N2O systems at the MP2/aug-cc-PVDZ level, respectively. Single-point energy calculations at the MP2/aug-cc-PVTZ and CCSD(T)/aug-cc-PVDZ levels confirm results obtained at the MP2/aug-cc-PVDZ level show that atmospheric roles of NF3-N2O and NF3-CO2 systems are similar. The atom in molecules theory was applied to analyse the nature of intermolecular interactions. Also, natural bond orbital (NBO) analysis has been used in order to obtain charge transfer quota among heterodimers.

• Simulating chemical systems: MPI and GPU parallelization of novel SD algorithms

Molecular dynamics is used for simulating chemical systems with the goal of studying a large range of phenomena starting from cell structures to the design of new materials, drugs, etc. A very important component of molecular dynamics is the use of well-suited atomistic and molecular modelling of the chemical systems. This article presents the MPI and GPU-CUDA parallelization of novel stochastic-Langevin dynamics algorithm that is used in molecular dynamics for controlling the temperature of simulated systems. The research has been performed in the Molecular Dynamics Group of the University of Groningen and it is going to be included in the next version of Gromacs tool of molecular dynamics (www.gromacs.org). The Langevin algorithm implemented is original and is based on impulse application of friction and noise. Theoretical background, implementation, an efficiency discussion and relevant simulation results are presented in the different sections of this article. The simulations used Martini water. The parallelization of the algorithms was done in two versions: one in MPI using domain decomposition and another version was done in CUDA.

• # Journal of Chemical Sciences

Volume 132, 2019
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019