• Volume 125, Issue 4

July 2013,   pages  705-958

• Team Change at the Journal of Chemical Sciences

• NO2-induced synthesis of nitrato-iron(III) porphyrin with diverse coordination mode and the formation of isoporphyrin

Two nitrato-iron(III) porphyrinates [Fe(4-Me-TPP)(NO3)] 1 and [Fe(4-OMe-TPP)(NO3)] 2 are reported. Interestingly, [Fe(4-Me-TPP)(NO3)] 1 has nitrate ion coordinated as monodentate (by single oxygen atom), while [Fe(4-OMe-TPP)(NO3)] 2 has nitrate coordination through bidentate mode. Compound 1 was found serendipitously in the reaction of [Fe(4-Me-TPP)Cl] with nitrous acid, which was performed for the synthesis of nitro-iron(III) porphyrin, [Fe(4-Me-TPP)NO2]. The compound 2 was synthesized by passing NO2 gas through a solution of [Fe(4-OMe-TPP)]2O. Upon passing NO2 gas through a solution of a 𝜇-oxo-dimer, [Fe(4-Me-TPP)]2O also produces 1. It is interesting that in more electron-rich porphyrin 2, binding of the nitrate in a symmetrical bidentate way while in less electron-rich porphyrin 1, binding of the anion is unidentate by a terminal oxygen atom. However, it is expected that the energy difference between the monodentate and bidentate coordination mode is very small and the interchange between these coordination is possible. Upon passing NO2 gas through a solution of 𝜇-oxo-dimeric iron(III) porphyrin, the nitrato-iron(III) porphyrin forms first, that later gets oxidized to 𝜋-cation radical to yield hydroxy-isoporphyrin in the presence of trace amount of water. These nitrato-iron(III) porphyrinates in moist air slowly converted back to their respective 𝜇-oxo-dimeric iron(III) porphyrins.

• Syntheses, molecular and crystalline architectures, and luminescence behaviour of terephthalate bridged heptacoordinated dinuclear lead(II) complexes containing a pentadentate N-donor Schiff base

One-pot synthesis using a 2:2:1:2 molar ratio of Pb(OAc)2·3H2O, L, piperidinum terephthalate (ptp) and NaClO4/NH4PF6 at room temperature affords two dinuclear compounds of the type [Pb2(L)2(𝜇- tp)](ClO4/PF6)2 (1/2) [L=N,N'-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine and tp = terephthalate dianion]. The compounds are characterized by microanalytical, spectroscopic, thermal and other physicochemical results. X-ray structural analyses of 1 and 2 reveal that each heptacoordinated lead(II) centre with a PbN5O2 chromophore are bound by five N atoms of L and connected through O atoms of a bis(bidentate) tp bridge. The arrangements of L and tp suggest a gap around the metal centre due to occupation of a stereo-active lone pair of electrons reflecting a hemidirected coordination around the metal centre. The complexes exhibit reasonable thermal stabilities with the tolerate temperatures ca. 255°C for 1 and 263°C for 2. The complexes display intraligand ($\pi-\pi^\ast$) fluorescence in the solid state and in DMF solutions at room temperature.

• Synthesis, molecular and crystalline architectures, and properties of a mononuclear complex [CoII (benzidine)2(NCS)2(OH2)2]

One mononuclear cobalt(II) compound of the type [Co(bnzd)2(NCS)2(OH2)2] (1) (bnzd = benzidine) has been isolated through a single-pot reaction of the molecular building components in MeOH-H2O solvent mixture at room temperature and characterized by physico-chemical and spectroscopic methods. The crystal structure of complex 1 has an octahedral geometry with trans, trans, trans orientations in the order (N$^a$,N$^a$), (N$^t$,N$^t$), (O$^w$,O$^w$) [N$^a$ = N(amine), N$^t$ = N(thiocyanate) and O$^w$ = O(water)]. In crystalline state, individual units of 1 are associated by weak cooperative O-H…N, O-H…S and N-H…S hydrogen bonds resulting in a 3D network structure. The compound is redox active and shows luminescence in MeOH solution. Thermal decomposition pattern of 1 reveals the presence of two coordinated water molecules. Variabletemperature magnetic susceptibility measurement shows significant orbital contribution and numerical matrix diagonalization method gives the best fit parameters: 𝛼 = Ak = 1.43; 𝜆 = −130 cm-1; 𝛥 = −864 cm-1; TIP = 0.000975; R = $1.19 \times 10^{−4}$.

• A new one-pot synthesis of 1,2,4-oxadiazoles from aryl nitriles, hydroxylamine and crotonoyl chloride

The reaction of aryl nitriles with hydroxylamine using acetic acid as a catalyst followed by subsequent addition of crotonoyl chloride to the intermediate amidoxime represents a straightforward one-pot access to new 1,2,4-oxadiazole synthesis under mild conditions. The course of the reaction was found to be high yielding and all new compounds were well characterized by nuclear magnetic resonance (NMR), mass spectrometry (MS) and elemental analysis.

• A simple synthesis of 𝐸-9-aryl-5-arylidene-1-oxo-1,2,3,4,5,6,7, 8-octahydroxanthenes and their lower analogues from 𝐸, 𝐸-𝛼,𝛼'-diarylidenecycloalkanones

A simple and efficient synthesis of 𝐸-9-aryl-5-arylidene-1-oxo-1,2,3,4,5,6,7,8-octahydroxanthenes and their lower analogues has been developed by amberlyst-15 catalysed cyclocondensation of 𝐸,𝐸-𝛼,𝛼'-diarylidenecyclohexanones and 𝐸,𝐸-𝛼,𝛼'-diarylidenecyclopentanones, respectively, with cyclohexan-1,3-diones. The products were obtained in moderate to good yield and their structures were confirmed from analytical and spectral data.

• Phenylboronic acid catalysed synthesis of 1,5-benzodiazepines via cyclocondensation of 𝑜-phenylenediamine and ketones

Phenylboronic acid has been found to be an efficient catalyst for the synthesis of 1,5-benzodiazepine derivatives via cyclocondensation of 𝑜-phenylenediamine and various ketones in good to excellent yields (82-91%) using acetonitrile as solvent at reflux condition. The remarkable advantages offered by this method are easy mild reaction condition, experimental work up and good to excellent yields of products.

• Synthesis of amidoalkyl naphthol via Ritter-type reaction catalysed by heteropolyanion-based ionic liquid

A facile and efficient procedure for the preparation of amidoalkyl naphthols via a Ritter-type reaction of 2-naphthol, aromatic aldehydes and amide in the presence of heteropolyanion-based functionalized ionic liquid has been described. The one-pot solvent-free three-component reaction is accomplished at 110°C for 5-10 min in reasonable to good yield ranging from 73% to 94%. The catalyst could be recovered and reused at least six times without noticeably decreasing the catalytic activity.

• Synthesis of novel N-, S-substituted-polyhalo-1, 3-butadienes and crystal structure of dibutadienyl homopiperazine

Polyhalogenated-2-nitro-1, 3-butadienes are important synthetic precursors for a variety of polyfunctionalized bioactive heterocycles. Herein, we report the reactions of 1, 1, 3, 4, 4-pentachloro-2-nitro-1, 3-butadiene 1 and 4-bromo-1, 1, 3, 4-tetrachloro-2-nitro-1, 3-butadiene 2 with amino and thiol containing nucleophiles to obtain highly functionalized (E)-polyhalodiene-2-nitro-1, 3-butadiene derivatives. Most of these reactions were found to be highly selective resulting in good to high yields of the products. All new compounds have been characterized by nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and Fourier transform infrared spectroscopy (FT-IR) spectroscopic data. Single crystal X-ray structure analysis of compound 8c is reported.

• Antileishmanial polyphenols from Corymbia maculata

An activity-guided fractionation was used to identify the antileishmanial compounds of Corymbia maculata. The hexane, ethyl acetate and methanol extracts were active in in vitro antileishmanial assay. Twelve polyphenols including 8-demethyl eucalyptin (1), eucalyptin (2), myrciaphenone A (3), myrciaphenone B (4), quercetin-3-𝑂-𝛽-D-xylopyranoside (5), myricetin-3-𝑂-𝛼-L-rhamnopyranoside (6), quercetin-3-𝑂-𝛽-D-galactopyranoside (7), quercetin-3-𝑂-𝛽-D-glucopyranoside (8), quercetin-3-𝑂-𝛼-L-rhamnopyranoside (9), syringic acid (10), gallic acid-3-methyl ether (11), gallic acid-4-methyl ether (12) and gallic acid (13) were isolated from the active extracts. All the tested compounds except 8-demethyleucalyptin and myrciaphenone B showed strong to moderate (6.9-24.5 𝜇M) antileishmanial activity against Leishmania donovani promastigotes. An HPLC-PDA method has been developed to detect/quantify 29 compounds in the extracts of C. maculata leaves. This validated method allows simultaneous quantitation of seven flavonoids, fourteen phloroglucinols and eight other polyphenols and can be applied for qualitative as well as quantitative determination of phytoconstituents in Eucalyptus matrices.

• Synthesis and transformations of 4𝐻-chromene 4-hydroxy-2𝐻-pyran-2-one and 4𝐻-chromene 4-hydroxycoumarin conjugates

The reaction of 𝑁-methyl-4-(methylthio)-3-nitro-4𝐻-chromen-2-amine and its derivatives with 4-hydroxy-6-methyl-2𝐻-pyran-2-one in EtOH reflux for 5 min furnish 4-hydroxy-6-methyl-3-(2-(methylamino)-3-nitro-4𝐻-chromen-4-yl)-2𝐻-pyran-2-ones in quantitative yield. By extending EtOH reflux for 2 h, the 4𝐻-chromene 4-hydroxy-2-pyranone conjugates get converted into acetoacetyl coumarins. Similar reaction of 𝑁-methyl-4-(methylthio)-3-nitro-4𝐻-chromen-2-amine and its derivatives with 4-hydroxycoumarin in EtOH reflux furnish 4-hydroxy-2'-(methylamino)-3'-nitro-2𝐻,4'𝐻-3,4'-bichromen-2-ones. In contrast to earlier system, prolonging reflux in EtOH or in 𝑛-PrOH reflux the product gets transformed into trans-ethyl 3-(2-hydroxyaryl)-4-oxo-3,4-dihydro-2𝐻-furo[3,2-c]chromene-2-carboxylates. Thus, facile synthesis and characterization of 4𝐻-chromene 4-hydroxy-2-pyrone, 4𝐻-chromene 4-hydroxycoumarin conjugates, acetoacetyl coumarins and trans2,3-disubstituted dihydrofuro[3,2-c]coumarins is described.

• Synthesis and characterization of poly(2-ethylhexyl acrylate) prepared via atom transfer radical polymerization, reverse atom transfer radical polymerization and radical polymerization

This investigation reports a comparative study of poly(2-ethylhexyl acrylate) (PEHA) prepared via atom transfer radical polymerization (ATRP), reverse atom transfer radical polymerization (RATRP) and conventional free radical polymerization (FRP). The molecular weights and the molecular weight distributions of the polymers were measured by gel permeation chromatography (GPC) analysis. Structural characterization of the polymers was carried out by 1H NMR and MALDI-TOF-MS analyses. Thermal properties of the polymers were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The polymerization results and the thermal properties of PEHAs prepared via ATRP, RATRP and FRP were compared.

• One-pot synthesis of new series 3,4,5-trisubstituted-dihydroisoxazoline derivatives via 1,3-dipolar cycloaddition of nitrile oxides with chalcones

We have synthesized a series of novel isoxazolines via 1,3-dipolar cycloaddition reaction. Aromatic aldoximes undergo oxidative-dehydrogenation with chloramine-T to give nitrile oxides, which were reacted with chalcones to afford of 3,4,5-trisubstituted 4,5-dihydroisoxazolines in a good yield.

• Microwave-assisted silica-promoted solvent-free synthesis of triazoloquinazolinone and benzimidazoquinazolinones

The derivative of triazolo/benzimidazoquinazolinones is prepared via silica-promoted solvent-free method using microwave irradiation with an excellent yield. The newly synthesized compounds were characterized by various techniques like IR, NMR and Mass spectroscopy. The compound with 1a was crystallized and analysed by single crystal X-ray diffraction studies.

• The Pd(0) nanoparticles stabilized by collagen fibres as a recyclable heterogeneous catalyst for the Stille reaction under aerobic condition

The stabilized palladium(0) nanoparticles by collagen fibres was a highly active, air-stable and recyclable heterogeneous catalyst that could be used for the Stille coupling reactions between aryl iodides and organostannanes under aerobic conditions. This method offered the several advantages: high yield under facile reaction condition and easy work-up procedure. The catalyst was easily recovered from the reaction mixture by filtration and reused multiple times without significant reduction or decrease in the activity.

• Study of TiO2 nanoparticle phase alteration and its catalytic effect on the chemoselective 𝑁-sulphonylation of amines and urazoles

Anatase and rutile are the two major crystalline phases of TiO2. Heat treatment can change crystal structure and physical properties of TiO2 nanoparticles. The effect of particles size on anatase-rutile phase transformation has been studied for the 𝑁-sulphonylation of amines and urazoles both under the conventional and ultrasound irradiation conditions. The main advantages allocated to this method are chemoselectivity, reduced reaction times, high yield, non-solvent green conditions and easy procedure. The catalyst can be easily recovered simply by filtration and reused with no significant loss in its reactivity.

• Efficient, green and solvent-free synthesis of tetrasubstituted imidazoles using SbCl3/SiO2 as heterogeneous catalyst

Antimony trichloride absorbed on silica gel (SbCl3/SiO2) efficiently catalyses the four-component cyclocondensation of 1,2-diketone, aldehyde, ammonium acetate, and primary amine under solvent-free conditions to afford the corresponding tetrasubstituted imidazoles in high yields. The main merit of this study is introducing a novel catalyst to successful synthesis of a wide range of 1,2,4,5-tetrasubstituted imidazoles for the first time. The proposed method involves features such as simplicity, generality, fairly good efficiency, and reusability of the catalyst.

• Sulphamic acid-functionalized magnetic Fe3O4 nanoparticles as recyclable catalyst for synthesis of imidazoles under microwave irradiation

Trisubstituted imidazoles have been synthesized in high yield in the presence of sulphamic acidfunctionalized magnetic Fe3O4 nanoparticles (SA-MNPs) as a novel solid acid catalyst under solvent-free classical heating conditions or using microwave irradiation. The heterogeneous catalyst could be recovered easily and reused many times without significant loss of catalytic activity.

• Brønsted acidic ionic liquid catalysis: An efficient and eco-friendly synthesis of novel fused pyrano pyrimidinones and their antimicrobial activity

A series of novel fused pyrano pyrimidinones were synthesized by the condensation of 2-amino-4-aryl-4H-benzo[h]chromene-3-carbonitriles with 2-oxo-2H-chromene-3-carboxylic acid under neat conditions employing an efficient, eco-friendly and reusable Brønsted acidic ionic liquid, (4-sulfobutyl)tris(4-sulfophenyl)phosphonium hydrogen sulphate as catalyst. All the synthesized compounds were characterized by their analytical and spectroscopic data and they were screened for in vitro antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Staphylococcus epidermidis as Gram- positive, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia as Gram-negative bacterial strains and antifungal activity against Aspergillus flavus, Saccharomyces cerevisiae, Candida rugosa and Candida albicans. Compounds 2c and 2d have shown good antibacterial activity against Escherichia coli while 2g has shown marked antifungal activity against Candida rugosa.

• Calcined eggshell (CES): An efficient natural catalyst for Knoevenagel condensation under aqueous condition

A convenient, eco-friendly and economic method for Knoevenagel condensation of aromatic aldehydes with active methylene compounds using calcined eggshell (CES) as an efficient natural catalyst in aqueous medium has been reported. CES is a new, ecologically safe and inexpensive green catalyst obtained from renewable resources.

• Synthesis, characterization and photo-epoxidation performance of Au-loaded photocatalysts

Titanium silicalite-1 (TS-1) was synthesized by hydrothermal crystallization. Au-loaded TS-1 (Au/TS-1) was prepared by the photo-deposition method. The prepared photocatalysts have been fully characterized by Raman, Brunauer-Emmett-Teller (BET), transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet visible light spectroscopy to reveal their structure, surface morphology and chemical composition. Photocatalytic activity of these photocatalysts was ascertained by gas phase photo-epoxidation of propylene-to-propylene oxide in the presence of molecular oxygen only under light irradiation. No sacrificial reductant such as hydrogen was used during the photoreaction. Au/TS-1 photocatalyst remained highly stable under reaction conditions. It is found that the increased Ti3+ sites due to the incorporation of Au will not only enhance the selectivity of the photocatalyst to form epoxide but also its stability during C3H6 conversion.

• Binding of reactive organophosphate by oximes via hydrogen bond

In this contribution, the ability of simple oximes to bind a well-known nerve agent simulant (dimethylmethylphosphonate, DMMP) via hydrogen bond is reported. UV/Vis measurements indicate the formation of 1:1 complexes. 1H-, 31P-NMR titrations and T-ROESY experiments confirm that oximes bind the organophosphate via hydrogen bond.

• Activity, stability and kinetic parameters for 𝛼-chymotrypsin catalysed reactions in AOT/isooctane reverse micelles with nonionic and zwitterionic mixed surfactants

Reverse micelles (RMs) of sodium 1,4-bis(2-ethylhexyl)sulphosuccinate (AOT) in nonpolar organic solvents are widely known to have very high solubilization power for water. The method is applied to the hydrolysis of 𝑝-nitrophenyl acetate (PNPA) catalysed by 𝛼-chymotrypsin (𝛼-CT) in AOT/isooctane/buffer RMs. The increase in 𝛼-CT activity and stability was an optimum at wo ([H2O]/[AOT]) = 10, z [Isooctane]/[AOT]) = 5. Three typical surfactants were selected based on their head group charges: a non-ionic surfactant Triton-X 100 and two zwitterionic sulphobetaine surfactants of the type C$_n$H$_{2n+1}$N+Me2 (CH2)3 SO$^−_3$ (n = 10; SB3-10, n = 16; SB3-16). The kinetic parameters (such as $k_{\text{cat}}$ and $K_M$) of the 𝛼-CT at 27°C were determined and compared in the absence and presence of three surfactants. The effect of chain length of zwitterionic surfactant (SB3-10 and SB3-16) on the enzymatic efficacy of 𝛼-CT as a function of mixed surfactant addition has been investigated in AOT/isooctane RMs at pH 7.75.

• Molecular aggregation, solvato- and acidochromic properties of symmetrical ketocyanines

The absorption and fluorescence spectral characteristics of some symmetrical ketocyanine dyes have been investigated in different solvents of various polarities using steady-state absorption and emission spectroscopic techniques. The absorption spectral features are less sensitive to the solvent characteristics than the corresponding fluorescence spectra. A large excited state dipole moment parallel to the smaller ground state dipole moment was calculated. The large dipole moment change with the strongly solvatofluorochromic behaviour, as the solvent polarity increases, demonstrates the formation of an intramolecular charge-transfer (ICT) excited state, which is confirmed by theoretical calculation using semiempirical PM3 method. Also, the effect of dye concentration on the electronic absorption spectra for the investigated dyes has been studied in ethanol. In addition, the acidochromic behaviour of these dyes has been studied using sulphuric acid at different $H_o$ values. A progressive red-shift in the absorption and emission spectra has been observed upon increasing the concentration of sulphuric acid with dramatic changes in colour. This suggests the design of potential optical sensors for probing acidity of the medium or water content in sulphuric acid. The calculated excited state protonation constants $p K^{\ast}_a$) are lower than $pK_a$ values calculated for the ground state, indicating that the investigated ketocyanines become more basic in the first excited singlet state.

• Quasi-classical trajectory study of the reaction N(4S) + H2 and its reverse reaction: Role of initial vibrational and rotational excitations in chemical stereodynamics

To investigate the effects of reagent vibrational and rotational states on the stereodynamical properties of the N(4S) + H2(𝑣, 𝑗)→NH + H reaction and its reverse reaction of H(2S) + NH(𝑣, 𝑗)→N(4S) + H2, we reported a detailed quasiclassical trajectory study using the 4A" double many-body expansion potential energy surface and at the collision energy of 35 kcal/mol. The density distribution of $P(\theta_r)$ as a function of the angle between 𝑘 and 𝑗', and that of $P(\phi_r)$ as a function of the dihedral angle between the plane containing 𝑘-𝑘' and the plane containing 𝑘'- 𝑗', the normal differential cross-sections as well as the averaged product rotational alignment parameter $\langle P_2(𝑗'.𝑘)\rangle$ are calculated and reported. Comparison between the two reactions has showed that the degrees of alignment and orientation of products related to reagent rovibrational state have marked differences for the two reactive systems.

• Inductive effect of methyl group in a series of methylated indoles: A graph theoretical analysis in the light of density functional theory and correlation with experimental charge transfer transition energies

The inductive effect of methyl group has been quantified by expressing highest occupied molecular orbital (HOMO) and HOMO-1 energies of indole and a series of methylated indoles using a combination of graph theory (GT) and the Coulson-Longuett-Higgins perturbation method. By correlating these expressions with the corresponding Kohn-Sham orbital energies of the indoles obtained by density functional theory (DFT) calculation at the B3LYP/6-31++G(d,p) and M06-2X/6-31++G(d,p) levels of theory, the inductive effect parameter $h_{Me}$ has been estimated; the Coulomb integral 𝛼 of 𝜋-conjugated carbon atom also comes out from the analysis. A correlation of the GT results with the HOMO and HOMO-1 energies obtained by the HF/STO-3G method yield almost the same values of $h_{Me}$ and 𝛼. Finally, when these estimated $h_{Me}$ and 𝛼 are used to calculate the vertical ionization potentials of the methylated indoles in the series, an excellent correlation with experimental charge transfer transition energies of their molecular complexes with tetracyanoethylene is obtained which complies with Mulliken’s theory of charge transfer.

• Analysis of torsional barrier height of HSNO as the simplest S-nitrosothiol

Torsional barrier height of thionitrous acid is analysed with Gaussian-2(G2), quadratic complete basis set (CBS-Q) and DFT-B3LYP/CBS-Q (CBS-QB3) methods. In agreement with purely intuitive arguments, it was determined that the cis to trans barrier height is nearly 5.7-6.3 kcal mol-1. In addition, the stability of rotation as function of competing dissociation pathways and also result of natural bond orbital analysis are discussed.

• Theoretical investigation on crystal structure, detonation performance and thermal stability of a high density cage hexanitrohexaazaisowurtzitane derivative

Density functional theory calculations were performed to study the new polynitro cage compound with the similar framework of HNIW. IR spectrum, heat of formation and thermodynamic properties were predicted. The bond dissociation energies and bond orders for the weakest bonds were analysed to investigate the thermal stability of the title compound. The detonation and pressure were evaluated by using the Kamlet-Jacobs equations based on the theoretical density and condensed HOFs. In addition, the results show that there exists an essentially linear relationship between the WBIs of N-NO2 bonds and the charges -QNO2 on the nitro groups. The crystal structure obtained by molecular mechanics belongs to P21/C space group, with lattice parameters Z = 4, a = 12.3421 Å, b = 24.6849 Å, c = 20.4912 Å, 𝜌 = 1.896 g cm-3. The designed compound has high thermal stability and good detonation properties and is a promising high energy density compound.

• Ab initio study on the paths of oxygen abstraction of hydrogen trioxide (HO3) molecule in the HO3 + SO2 reaction

The reaction paths of hydrogen trioxide (HO3) with sulphur dioxide (SO2) have been investigated on the doublet potential energy surface, theoretically. All species of the title reaction have been optimized at the PMP2(FC)/cc-pVDZ computational level. Energetic data have been obtained at the CCSD(T)//PMP2 level employing the cc-pVDZ basis set. No stable collision complexes have been found between the SO2 and HO3 molecules. Therefore, the SO2 + HO3 reaction starts without initial associations. The four possible paths, P1 through P4, have been obtained for the formation of SO3 (D$_{3h}$) + HOO$^{\bullet}$ product. Our results show that these four paths include relatively high energy barriers to produce the final product of the SO3 (D$_{3h}$) + HOO$^{\bullet}$. Therefore, the SO2 + HO$_3\to$SO3(D$_{3h}$) + HOO$^{\bullet}$ reaction is difficult to perform under atmospheric conditions. This means that the importance of SO2 + HO$_3 \to$ SO3 (D$_{3h}$) + HOO$^{\bullet}$ reaction increases with increasing temperature and, this reaction plays an important role in the SO3(D$_{3h}$) production as the main molecule of the formation of acid rain at high temperatures.

• Evaluation of intramolecular charge transfer state of 4-𝑁, 𝑁-dimethylamino cinnamaldehyde using time-dependent density functional theory

Intramolecular charge transfer of 4-𝑁,𝑁-dimethylamino cinnamaldehyde (DMACA) in vacuum and in five different aprotic solvents has been studied by using time-dependent density functional theory (TDDFT). Polarizable continuum model (PCM) was employed to consider solvent-solute interactions. The potential energy curves were constructed at different torsional angle of 𝑁,𝑁-dimethylamino moiety with respect to the adjacent phenyl ring. A large bathochromic shift in our calculated emission and absorption energies for polar solvents is a clear reminiscent of charge transfer nature of the excited state. Finally, the reported results are in agreement with experimental findings.

• Theoretical study of intramolecular hydrogen bonding in the halo derivatives of 1-amino-3-imino-prop-1-ene

Intramolecular hydrogen bonding (IHB) of 1-amino-3-imino-prop-1-ene (AIP), as the simplest resonance-assisted hydrogen bond system in symmetric N-H…N class, and its halo derivatives (F, Cl, and Br) have been studied at the DFT-B3LYP/6-311++G$^{\ast\ast}$ level of theory. For better understanding of the nature of substituent effects, nitro and methoxy derivatives of AIP were also added to our consideration. Good linear correlations between IHB energies based on Espinosa’s equation and $-G(r)/V(r)$ values, total electronic density, Laplacian of total electronic density in critical points, 𝜋-electron delocalization parameter (𝑄), hyper conjugative interaction energy of lp(N) → $\sigma^\ast$(N-H), ($F_{i,j}/S_{i,j}$)2 parameter, natural charges of bridged hydrogen, frequency shift of the N-H stretching vibration, and chemical shift of bridged hydrogen were obtained.

• Density functional theory, natural bond orbital and quantum theory of atoms in molecule analyses on the hydrogen bonding interactions in tryptophan-water complexes

The tryptophan-water (Trp-H2O) complexes formed by hydrogen bonding interactions were investigated at the 𝜔B97XD/6-311++G(d,p) level. Five Trp-H2O complexes possessing various types of hydrogen bonds (H-bonds) were characterized by geometries, energies, vibrational frequencies. The nature of the H-bonds were characterized by the natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analyses as well. The intramolecular H-bond formed between the amino and carboxyl oxygen atom of tryptophan was retained in most of the complexes, and the cooperativity between the intra and intermolecular H-bonds exist in some complexes. The intramolecular H-bond and some intermolecular H-bonds are strong and have partial covalent character. The H-bonds formed between carboxyl and oxygen/nitrogen atoms are stronger than other H-bonds. The H-bonds involving methylene of tryptophan as H-donor are weak H-bonds. For all complexes, $\Delta E_{\text{ele}}$ and $\Delta E_{\text{ex}}$ makes major contributions to the total interaction energy ($\Delta E_{\text{MP2}}$), while $\Delta E_{\text{disp}}$ is the smallest component of the interaction energy. Both hydrogen bonding interaction and structural deformation play important roles in the relative stabilities of the complexes. Regardless of strong H-bonds, the stabilities of some complexes are weakened by the serious structural deformations.

• Journal of Chemical Sciences

Volume 132, 2019
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Continuous Article Publishing mode

• Editorial Note on Continuous Article Publication

Posted on July 25, 2019