Structural and spectral properties of 4-bromo-1-naphthyl chalcones: a quantum chemical study

The structural and optical properties of 4-bromo-1-naphthyl chalcones (BNC) have been studied by using quantum chemical methods. The density functional theory (DFT) and the singly excited configuration interaction (CIS) methods were employed to optimize the ground and excited state geometries of unsubstituted and substituted BNC with different electron withdrawing and donating groups in both gas and solvent phases. Based on the ground and excited state geometries, the absorption and emission spectra of BNC molecules were calculated using the time-dependent density functional theory (TDDFT) method. The solvent phase calculations were performed using the polarizable continuum model (PCM). The geometrical parameters, vibrational frequencies, and relative stability of cis- and trans-isomers of unsubstituted and substituted BNC molecules have been studied. The results from the TDDFT calculations reveal that the substitution of electron withdrawing and electron donating groups affects the absorption and emission spectra of BNC.     

Modification of the magnetic properties of a heterometallic wheel by inclusion of a Jahn-Teller distorted Cu(II) ion

An investigation into the physical consequences of including a Jahn-Teller distorted Cu(II) ion within an antiferromagnetically coupled ring, [R(2)NH(2)][Cr(7)CuF(8)((O(2)C(t)Bu)(16))] is reported. Inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR) spectroscopic data are simulated using a microscopic spin Hamiltonian, and show that the two Cr-Cu exchange interactions must be inequivalent. One Cr-Cu exchange is found to be antiferromagnetic and the other ferromagnetic. The geometry of the Jahn-Teller elongation is deduced from these results, and shows that a Jahn-Teller elongation axis must lie in the plane of the Cr(7)Cu wheel; the elongation is not observed by X-ray crystallography, due to positional disorder of the Cu site within the wheel. An electronic structure calculation confirms the structural distortion of the Cu site.     

Structural properties and the effect of 2,6‐diaminoanthraquinone on G‐tetrad,non‐G‐tetrads,and mixed tetrads—A density functional theory study

Telomerase inhibitor causes the attrition of telomere length and consequently leading to senescence which require a lag period for cancer cells to stop proliferating. Telomeric sequences form quadruplex structures stabilized by tetrads. The structural and electronic properties related with interaction of 2,6‐diaminoanthraquinone and tetrads are the key step to elucidate the anticancer activity. The present study has been focused on the stability of the isolated tetrads and the effect of interaction of 2,6‐diaminoanthraquinone with G‐tetrad, non‐G‐tetrads, and mixed tetrads using density functional theory method in both gas and aqueous phases. The solvent interaction with the molecular systems has increased the stability of the isolated tetrads and complexes. The sharing of electron density between the interacting molecules is shown through electron density difference maps. The atoms in molecules theory and natural bond orbital analysis have been performed to study the nature of hydrogen bonds in the inhibitor interacting complexes. The linear correlation is shown between electron density [ρ(r)], and its Laplacian [(²ρ(r)] at the bond critical points. The strong binding nature of 2,6‐diaminoanthraquinone with studied tetrads reveals that this inhibitor is suitable to stabilize the above tetrads and inhibit the telomerase activity. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Polyurethane-polyacrylamide IPNs. I. Synthesis and characterization

Hydrophobic-hydrophilic interpenetrating polymer networks (IPNs) of polyurethane and polyacrylamide have been synthesized. The IPNs have been characterized by IR, thermal, and mechanical studies. SEM studies indicate phase mixing of some IPNs. Solvent resistance and surface hydrophilicity as evidenced by contact angle measurements suggest that these IPNs could be used for biomedical applications.     

Metal chelates in vinyl polymerization. II. Mechanism of initiation by Fe(DPM)3

The nature of the interaction between the unsaturated monomer and the chelate, Fe(DPM)₃, is studied in detail. The interaction is found to occur only in solution. The stoichiometry of interaction and the equilibrium constant are evaluated. With the help of spectral evidence, attempts are made to point out the specific sites of interaction.     

Synthesis and characterization of chitosan–polyvinylpyrrolidone–bovine serum albumin-coated magnetic iron oxide nanoparticles as potential carrier for delivery of tamoxifen

The proposed study examined the preparation of chitosan (CS)–polyvinylpyrrolidone (PVP)–bovine serum albumin (BSA)-coated magnetic iron oxide (Fe₃O₄) nanoparticles (Fe₃O₄–CS–PVP–BSA) to use as potential drug delivery carriers for delivery of tamoxifen drug (TAM) . The anticancer drug selected in this study was tamoxifen which can be used for the human breast cancer treatment. These prepared nanoparticles were characterized by FTIR, XRD, SEM, AFM, TEM, CD and VSM techniques. The swelling studies have been measured at different (10, 20, 30, 40, 50%) drug loading. The mean particle size of the tamoxifen-loaded nanoparticles system (Fe₃O₄–CS–TAM, Fe₃O₄–CS–TAM–PVP and Fe₃O₄–CS–TAM–PVP–BSA) as measured by Malvern Zetasizer ranged between 350 ± 2.3 and 601 ± 1.7 nm. As well as these drug-loaded nanoparticles were positively charged. The zeta potential was in the range of 28.9 ± 3.5 and 50.8 ± 3.9 mV. The encapsulation efficiency was between 63.60 ± 2.11 and 96.45 ± 2.12%. Furthermore, in vitro release and drug loading efficiency from the nanoparticles were investigated. The cytotoxicity of prepared nanoparticles was verified by MTT assay. In vitro release studies were executed in 4.0 and 7.4 pH media to simulate the intestinal and gastric conditions and different temperature (37 and 42 °C). Hence, the prepared tamoxifen-loaded nanoparticles system (Fe₃O₄–CS–TAM, Fe₃O₄–CS–TAM–PVP and Fe₃O₄–CS–TAM–PVP–BSA) could be a promising candidate in cancer therapy.     

High level ab initio and DFT calculations of models of the catalytically active Ni-Fe hydrogenases

Multi-reference M?ller-Plesset calculations of a model of the Ni-SI state of nickel-iron hydrogenase predict a singlet rather than a triplet state for this species, and show that it is better described with a BP86 rather than a B3LYP functional.     

Oxidation of cyclohexane by a high-valent iron bispidine complex: a combined experimental and computational mechanistic study

Experimental data suggest that there are various competing pathways for the catalytic and stoichiometric oxygenation of cyclohexane, assisted by iron-bispidine complexes and using various oxidants (H(2)O(2), O(2), PhIO). Density functional theory calculations indicate that both Fe(IV)=O and Fe(V)=O species are accessible and efficiently transfer their oxygen atoms to cyclohexane. The reactivities of the two isomers each and the two possible spin states for the Fe(IV)=O and Fe(V)=O species are sufficiently different to allow an interpretation of the experimental data.     

Study of chemical bonding in H2 and HF molecules: Wave function and density functional theory (DFT) parameters approach

Balint Kurti's Fourier grid Hamiltonian method is employed to obtain the molecular wave function and equilibrium bond length for H₂ and HF molecules. The density functional theory parameter, namely, the chemical hardness (η) value, was determined for some diatomic hydride molecules using this wave function and the results are found to be in good agreement with the values obtained from the ab initio HF–SCF method. A new formula for chemical hardness (η=1/2Dr, where D is the proportionality constant and r is the internuclear distance) is introduced in binding energy and change of hardness equations to determine the chemical hardness and chemical potential values for different bond lengths. The binding energy and change of hardness values are calculated for H₂, H, H, HF, HF⁺, and HF⁻ molecules and the bond stability is discussed. Finally, the concept of an atom in a molecule is examined in the context of DFT parameters and comparison is made between an atom in a molecule and the isolated atom. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 76: 662–669, 2000