Sharif Digital Repository

The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.0 2,7]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicar-bonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product  

This paper presents synthesis and photophysical investigation of a very rare type of the ReI diimine complexes, [Re(diimine)(CO)3(OPR3)]+, R = Ph, Cy; diimine – phenanthroline and neocuproine, containing monodentate (unsupported) phosphine oxide ligands. The obtained compounds have been structurally characterized in solid phase by using XRD crystallography, which revealed unusual distortions in the pseudo octahedral rhenium environment, which may be ascribed to intramolecular interligand (phosphine oxide – diimine) interaction rather than to crystal packing effect. Optimization of the ground state structure of these molecules with the DFT method also confirmed intramolecular origin of the... 

The energetics and kinetic energy barriers of vacancy/atom exchange in a 37-atom truncated octahedron Ag-Pt binary cluster in the Ag-rich range of compositions are investigated via a first-principles atomistic approach. The energy of the local minima obtained considering various distributions of a single vacancy and a few Pt atoms within the cluster and the energy barriers connecting them are evaluated using accurate density-functional calculations. The effects of the simultaneous presence of a vacancy and Pt atoms are found to be simply additive when their distances are larger than first-neighbors, whereas when they can be stabilizing at low Pt content due to the release of strain by the... 

The formation and diffusion of a vacancy in a silver nanocluster are studied via a combination of first-principles and statistical mechanics simulations. A 38-atom truncated-octahedral (TO) arrangement and its homologue with 37 Ag atoms and one vacancy are considered, and density-functional calculations are performed to derive the energies of the local minima and the energy barriers connecting them. These data are then used as an input for a study of the system dynamics via a kinetic Monte Carlo algorithm, evaluating site occupancies, diffusion coefficient and equilibration time. It is found that vacancy formation and diffusion represents a viable path for atom-atom exchange in these... 

In this study, adsorption of important pollutant cations on the surface of graphitic carbon nitride (g-C3N4) was investigated by density functional theory. The calculations indicated that N6 cavity surrounded by triazine units is the most probable adsorption site on this surface. The structural optimizations also predicted a planar surface for Cr3+, and Ni2+/g-C3N4 systems while the structure of the surface for other systems indicated a considerable distortion with strong dependency on the cation size. Also, g-C3N4 surface exhibited the high adsorption energies for Cr3+, As3+, and Sb3+ ions in the gas phase. However, formation energies of the metal-aquo complexes of these cations indicated... 

We have calculated the electronic structure of SrRu1-xMn xO3 using the full potential linearized augmented plane wave method by LSDA and LSDAU. The antiparallel alignment between the Mn and Ru ions are consistent with the competition between ferromagnetism and antiferromagnetism in the low Mn-doped polycrystalline samples. This is in contrast to the appearance of quantum critical point and FM and AFM transitions in the single crystal measurement. Our results show that the discrepancy between different experimental phase diagrams is related to the conditions of sample preparation and also the difference between the degree of magnetic interactions between the Mn and Ru moments. The DOS and the... 

We have investigated the electronic structure of Sr(Ca)Ru1-xCrxO3 using the full potential linearized augmented plane wave method by different approximation such as LSDA and LSDA+U. The LSDA calculation suggest that Cr4+-Ru4+ hybridization is responsible for the high Curie temperature TC in SrRu1-xCrxO3, but it cannot completely describe its physical behavior. Our LSDA+U DOS results for SrRu1-xCrxO3 clearly establishes renormalization of the intra-atomic exchange strength at the Ru sites, arising from the Cr-Ru hybridization. The antiferromagnetic coupling of Cr3+ with Ru4+,5+ lattice increases the screening, which is consistent with the low magnetic moment of the Ru ions. The more distorted...