DFT Study on the Mechanism of Iron-Catalyzed Diazocarbonylation

The mechanism of the carbonylation of diazomethane in the presence of iron–carbonyl–phosphine catalysts has been investigated by means of DFT calculations at the M06/def-TZVP//B97D3/def2-TZVP level of theory, in combination with the SMD solvation method. The reaction rate is determined by the formation of the coordinatively unsaturated doublet-state Fe(CO)3(P) precursor followed by the diazoalkane coordination and the N2 extrusion. The free energy of activation is predicted to be 18.5 and 28.2 kcal/mol for the PF3 and PPh3 containing systems, respectively. Thus, in the presence of less basic P-donor ligands with stronger π-acceptor properties, a significant increase in the reaction rate can be expected. According to energy decomposition analysis combined with natural orbitals of chemical valence (EDA–NOCV) calculations, diazomethane in the Fe(CO)3(phosphine)(η1-CH2N2) adduct reveals a π-donor–π-acceptor type of coordination.

Spectra of the Energy Operator of Three-Electron Systems in the Impurity Hubbard Model.Second Doublet State

We consider the three-electron systems in the impurity Hubbard model and investigated the spectra of the system in the second doublet state in the ν-dimensional lattice Zν .

Effects of Polarization Function on the Spin Contamination and Distribution in β'- Me4P[Pd(dmit)2]2

The effects of polarization function on the spin contamination and distribution in β'-Me4P[Pd(dmit)2]2 were studied using the DFT cluster method. Two basis sets, SV and SVP were considered in the calculations, where B3LYP functional was employed in the doublet state of the one-fragment and dimer clusters. The values of <S2> before annihilation for both SV and SVP basis sets are excellent and very close to the perfect theoretical eigenvalue of 0.75. The values of the spin densities at thiolate and thione calculated using SVP were found to be smaller than the ones using SV. The difference, however, is less than eight percent. In contrast, the difference in the spin density at Pd atoms in both monomers is significantly larger for the SVP, being about 21%. The inclusion of polarization function resulted in the shifting of electron density from the sulfur atoms to the central Pd atoms. The calculated spin densities revealed the inhomogeneous distribution of the electron spin in the dimer that leads to the existence of electron-rich and electron-poor regions.

Spin the light off: rapid internal conversion into a dark doublet state quenches the fluorescence of an RNA spin label

The fluorescence of the RNA spin label Çm is quenched via rapid internal conversion into a dark doublet state, which is localized on the nitroxide group of the FNRO˙ compound.