Search results for "Electronegativity"

Semiempirical correlation between the optical band gap of oxides and hydroxides and the electronegativity of their constituents

2000

AbstractOn the basis of new experimental results a previous proposed correlation between the optical band gap of oxides and the difference of electronegativity of their constituents is extended to mixed crystalline and amorphous TiO2-Fe2O3 (d,d-metal oxides) as well as to amorphous passive films grown on Al-Ta, Al-Ti, Al-Nb and Al-W alloys (sp,d-metal oxides). Moreover in analogy with previous results on anhydrous oxides, a correlation is proposed between the optical band gap of hydroxides and the electronegativities of their constituents after substituting the electronegativity of hydroxilic group to that of the oxygen. Like in the case of anhydrous oxides, two different interpolation line…

ChemInform Abstract: Mixed Group 14-Group 14 Bonds. Part 5. Six Perphenylated Propane Analogues Ph3M-M′Ph2-M′′Ph3 (M, M′, M′′: Si/Ge): Electronegativ…

2010

An Improved Force Field for O2, CO and CN Binding to Metalloporphyrins

2004

Parametrization of a molecular-mechanics program to include terms specific for five- and six-coordinate transition metal complexes is applied to heme complexes. The principal new feature peculiar to five and six coordination is a term that represents the effect of electron-pair repulsion modified by the ligand electronegativity and takes into account the different possible structures of complexes. The model system takes into account the structural differences of the fixing centre in the haemoglobin subunits. The customary proximal histidine is added. The macrocycle heme IX is wholly considered in our model. The calculations show clearly that certain conformations of heme IX–histidine models…

Nature of O2, CO, and CN binding to hemoprotein models

2004

Parametrization of a molecular-mechanics program to include terms specific for five- and six-coordinate transition metal complexes results in computer-simulated structures of hemo complexes. The principal new feature peculiar to five- and six-coordination is a term that measures the effect of electron-pair repulsion modified by the ligand electronegativity and takes into account the different structural possibilities. The work consists in the modification of program molecular mechanics for penta and hexacoordination. The model system takes into account the structural differences of the fixing center in the hemoglobin subunits. The customary proximal histidine is added. The macrocycle hemo I…

Nature of FeIII–O2, FeII–CO and FeIII–CN complexes of hemoprotein models

2003

Abstract Parametrization of a molecular-mechanics program to include terms specific for 5- and 6-coordinate transition metal complexes results in computer-simulated structures of hemo complexes. The principal new feature peculiar to 5- and 6-coordination is a term that measures the effect of electron-pair repulsion modified by the ligand electronegativity and takes into account the different structural possibilities. The work consists in the modification of program molecular mechanics for 5- and 6-coordination. The model system takes into account the structural differences of the fixing centre in the haemoglobin (Hb) subunits. The customary proximal histidine is added. The macrocycle hemo I…

Complexes of organometallic compounds. LI. The correlation between 119Sn Mössbauer isomer shifts and partial atomic charges on tin in R3SnL compounds

1985

Abstract The 119Sn Mossbauer isomer shift parameters, δ, of compounds R3SnL (R = AlK, Ph; L = F, Cl, OH, OR′, CN, NCS, NCO, N3) have been correlated to partial atomic charges on tin QSn, calculated according to a valence state electronegativity equalization procedure carried out by the CHELEQ program. A unique δ/QSn correlation has been obtained for all the five-coordinated R3SnL species by using average δ parameters for the AlK3IV derivatives.

Mössbauer spectroscopy of mono-organotin(IV) derivatives

1974

Abstract The Mossbauer parameters isomer shift, δ, and quadrupole splitting, ΔE, of mono-organotin compounds insofar investigated have been collected and tabulated. It is demonstrated that isomer shifts consistently depend on ligand electronegativities and coordination numbers, from which it is deduced that RSn IV behave much more as Sn IV rather than R 2 Sn IV and R 3 Sn IV derivatives. The changes of δ for RSn IV are then interpreted by hypotheses analogous to those advanced for Sn IV and its adducts and complexes. It is also inferred that in RSn IV compounds there is a consistent s-character in all tin-ligand atom bonds.

Ziegler–Natta catalysts based on vanadium halides: a DFT study

2003

Abstract Ziegler–Natta ethylene insertion into the carbon–metal bond for a number of fragments containing vanadium on different oxidation states as well as the halogen ligands has been studied by means of DFT. It is shown that the complexation and insertion energies are strongly influenced by the charge on the transition metal atom and, to some extent, by the electronegativity of the halogen atom. Complexation energy varies in the range −129 to −159 kJ/mol for charged species and −64 to −77 kJ/mol for neutral ones. Insertion energy follows a similar pattern and ranges from −28 to −62 and −82 to −100 kJ/mol, respectively. The calculated values are compared with the experimental results and d…

Modeling the magnetic properties of lanthanide complexes: relationship of the REC parameters with Pauling electronegativity and coordination number

2015

In a previous study, we introduced the Radial Effective Charge (REC) model to study the magnetic properties of lanthanide single ion magnets. Now, we perform an empirical determination of the effective charges (Zi) and radial displacements (Dr) of this model using spectroscopic data. This systematic study allows us to relate Dr and Zi with chemical factors such as the coordination number and the electronegativities of the metal and the donor atoms. This strategy is being used to drastically reduce the number of free parameters in the modeling of the magnetic and spectroscopic properties of f-element complexes. SPINMOL FP7-ERC-247384 ERC-CoG-647301 DECRESIM MAT2011-22785 MAT2014-56143-R CTQ2…

1H and13C n.m.r. spectra of dichloro(trans-2-chlorovinyl)arsine

1977

Proton and carbon magnetic resonance spectra of Lewisite or dichloro(trans-2-chlorovinyl)arsine have been measured and the results are compared with the n.m.r. spectral parameters of other trans-1,2-substituted ethylenes. The coupling constants can be rationalized by substituent electronegativity. The chemical shifts show an unusually large paramagnetic effect from the AsCl2 group.