Quantum chemical studies on structure, conformation and isomerization of nitroso, nitro substituted benzene and 1,3-cyclopentadiene

The molecular structure, conformational stability and isomerization of nitroso, nitro substituted benzene and 1,3-cyclopentadiene in gas phase have been investigated using ab initio and density functional theory methods. The molecular geometries and energetics of possible conformers were obtained by employing MP2, B3LYP and B3PW91 levels of theory implementing 6-31G* basis set. The relative stabilities of the conformations were evaluated from the energy differences of the structure. Chemical hardness (η) and chemical potential (μ) were calculated at HF/6-31G* level of theory for all the positional and geometrical isomers to study the maximum hardness principle. Each optimized structure has been tested against the imaginary frequencies at MP2/6-31G* level of theory in order to be sure they are located at energy minimum.     

Aggregation and Polymerization of PEG-Based Macromonomers with Methacryloyl Group as the Only Hydrophobic Segment

Aggregation behavior in aqueous solution of a series of poly (ethylene glycol) (PEG)-based macromonomers with methacryloyl group as the only hydrophobic segment has been investigated using surface tension, steady-state and time-resolved fluorescence spectroscopy using pyrene as a probe, and small-angle neutron scattering techniques. The general formula of these macromonomers is CH₂=C(CH₃)–CO–O–E_m–CH₃, where E is the ethylene glycol unit and m=8 (ME₈), 18 (ME₁₈), 49 (ME₄₉), and 120 (ME₁₂₀). The results indicate that a macromonomer with 8 ethylene glycol units forms as an aggregate above a certain critical concentration, which can be defined as critical aggregation concentration. The observed high value of I₁/I₃ in pyrene emission spectra at the interface of these aggregates and the inability to scatter a neutron beam by these aggregates indicate that the hydrophobic cluster formed by this macromonomer is remarkably solvated. ME₁₈ has a tendency to aggregate but others do not form any hydrophobic cluster. The homopolymerization behaviors of these macromonomers in an aqueous medium at 70°C are consistent with these possibi- lities.     

An ab initio and DFT study on the hydrolysis of carbonyl dichloride

Hydrolysis of carbonyl dichloride or phosgene (Cl₂CO) in gas phase has been investigated at Hartree–Fock, density functional and ab initio levels of theory. The effects of basis sets on the energetics of the reaction have also been explored. Calculations reveal that initially carbonyl dichloride and water form a weak complex and this complex can react further in two ways. In Path 1, water adds on to carbonyl dichloride across carbonyl bond in a concerted fashion to give dichloromethane diol, and this diol decomposes to form chloro formic acid by syn-1,2-elimination of HCl and forms CO₂ and HCl as final products. Path 2 is the concerted addition of water across carbon chlorine bond and elimination of HCl in a single step leading to the formation of chloro formic acid directly. This second path that skips the formation of dichloromethane diol is observed to be very low lying and hence is kinetically favored. Addition of second water molecule to the reacting system is found to catalyze the reaction by stabilizing the complex, intermediate and transition states and reduces the activation energy to 24.6 kcal mol⁻¹ compared to 29.9 kcal mol⁻¹ for a single water molecule.     

Divalent nickel,cobalt and copper complexes of a tetradentate N6 macrocyclic ligand

Summary Divalent nickel, cobalt and copper salts react with 2,6-diaminopyridine and acetylacetone to form complexes containing a 16-membered N₆ tetradentate macrocyclic ligand. The complexes are characterised as distorted octahedra of the M(TML)X₂ type where M=nickel(II), cobalt(II) and copper(II); TML=tetradentate macrocyclic ligand and X=Cl, Br, NO₃ or NCS. The ligand coordinates through all the four azomethine nitrogen atoms which are bridged by acetylacetone moieties. Pyridine nitrogen does not participate in coordination, a fact supported by far i.r. studies. The magnetic, electronic and i.r. spectral studies indicate that the complexes have lower symmetries and the amounts of distortion calculated in terms of DT/DQ applying normalised spherical harmonic Hamiltonian theory indicate that these complexes are moderately distored.     

Vibrational Studies of Gel Grown Ferroelectric RbHC4H4O6 and SrC4H4O6 4H2O Crystals

Single crystals of Rubidium Hydrogen Tartrate (RbHT) and Strontium Tartrate Tetrahydrate (SrTT) have been grown by a gel technique using a chemical reaction method. A controlled reaction has been employed between tartaric acid and feed solution (RbCl for RbHT and Sr(NO₃)₂) at room temperature. The laser Raman and FT-IR spectra of these crystals are recorded in the frequency range 100 - 4000 cm^-1. The presence of tartrate ion, monohydrogen tartrate ion, water molecules and external mode vibrational frequencies are identified and discused. The doublet and broad nature of tartrate ion vibrational frequencies have also been observed and analysed.     

Structure and conformational stability of CH2CHCH2X (X=F, Cl and Br) molecules—post Hartree–Fock and density functional theory methods

The molecular structure and conformational stability of CH₂CHCH₂X (X=F, Cl and Br) molecules were studied using ab initio and density functional theory (DFT) methods. The molecular geometries of 3-fluoropropene were optimized employing BLYP and B3LYP levels of theory of DFT method implementing 6-311+G(d,p) basis set. The MP2/6-31G^*, BLYP and B3LYP levels of theory of ab initio and DFT methods were used to optimize the 3-chloropropene and 3-bromopropene molecules. The structural and physical parameters of the molecules are discussed with the available experimental values. The rotational potential energy surface of the above molecules were obtained at MP2/6-31G^* and B3LYP/6-311+G(d,p) levels of theory. The Fourier decomposition of the rotational potentials were analyzed. The HF/6-31G^* and MP2/6-31G^* levels of theory have predicted the cis conformer as the minimum energy structure for 3-fluoropropene, which is in agreement with the experimental values, whereas the BLYP/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory reverses the order of conformation. The ΔE values calculated for 3-chloropropene at MP2/6-31G^*, BLYP/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory show that the gauche form is more stable than the cis form, which is in agreement with the experimental value. The same levels of theory have also predicted that the gauche form is stable than cis for 3-bromopropene molecule. The maximum hardness principle has been able to predict the stable conformer of 3-fluoropropene at HF/6-31G^* level of theory, but the same level of theory reverses the conformational stability of 3-chloropropene and 3-bromopropene molecules and MP2/6-31G^* level of theory predicted the stable conformer correctly.     

Global stability and uniqueness of an initial boundary value problem of a dusty gas model

In the present investigation, we obtain a universal stability theorem for a dusty gas model with constant number density of dust particles and as a consequence, we establish a uniqueness criterion for an initial boundary value problem. For a variable number density of dust particles, only a uniqueness theorem is obtained.     

Two sum theorems for topological spaces

Two general criterias for the union of topological spaces of a given type to be also of the same type, are presented.     

Oxadiazole: Synthesis,characterization and biological activities

The synthesis of novel achiral and chiral amides incorporating 1,3,4-oxadiazole ring are reported. All the synthesized amides are characterized ¹H, ¹³C, FTIR and elemental analysis techniques. Synthesized compounds are screened for microbial and cytotoxic activities.     

A pseudo trinuclear nickel–sodium complex containing tris(8-methyl-2-oxo-quinolidineamino ethylamine): Synthesis,spectral characterization,X-ray crystallography and in vitro biological evaluations

A new mixed nickel–sodium complex has been synthesized from Ni(ClO₄)₂ and tris(8-methyl 2-oxo-quinolidine amino ethylamine) with a 1:1 molar ratio in methanol and has been characterized by various analytical, spectroscopy and X-ray diffraction studies which confirmed an octahedral geometry around the nickel ion. Further, structural optimization of the complex was performed using DFT calculations. The ligand and complex were evaluated for their binding affinity with CT-DNA and an intercalative type of binding interaction was proposed from the absorption and fluorescence titration experiments. Albumin binding interaction of the ligand and complex was determined by absorption, fluorescence and synchronous spectral techniques at room temperature, suggesting the static quenching mechanism of BSA with the compounds. Antioxidant studies revealed the radical scavenging potential of Ni(II) complex. The anticancer activity of the ligand and complex was probed via in vitro cytotoxicity against human breast (MCF7) and lung (A549) cancer cell lines by MTT assay. Further, cytological changes observed in acridine orange/ethidium bromide and DAPI staining methods validated the cytotoxic potential of the complex.