On the Quantum Chemical Nature of Lead(II) “Lone Pair”

We study the quantum chemical nature of the Lead(II) valence basins, sometimes called the lead “lone pair”. Using various chemical interpretation tools, such as molecular orbital analysis, natural bond orbitals (NBO), natural population analysis (NPA) and electron localization function (ELF) topological analysis, we study a variety of Lead(II) complexes. A careful analysis of the results shows that the optimal structures of the lead complexes are only governed by the 6s and 6p subshells, whereas no involvement of the 5d orbitals is found. Similarly, we do not find any significant contribution of the 6d. Therefore, the Pb(II) complexation with its ligand can be explained through the interaction of the 6s2 electrons and the accepting 6p orbitals. We detail the potential structural and dynamical consequences of such electronic structure organization of the Pb (II) valence domain.

Density functional theory study of the geometrical and electronic structures of GenV(0,±1)(n=1–9) clusters

Geometrical and electronic properties of Ge[Formula: see text]V[Formula: see text] clusters containing 1–9 Ge atoms and one V atom are calculated by using density functional theory (DFT) at the B3LYP level and the LanL2DZ basis sets. The growth pattern behavior, natural population analysis, relative stability, electronic property and magnetism of these clusters are discussed in detail. The calculation results of the geometrical show that the relative stable structures of Ge[Formula: see text]V[Formula: see text] clusters adopt 3D structures from [Formula: see text] to [Formula: see text]. The results of natural population analysis show that electrons transfer from the Ge atoms to the V atoms when [Formula: see text] while the electrons transfer from the V atoms to the Ge atoms when [Formula: see text]. The Ge[Formula: see text]V[Formula: see text] clusters possess higher stability and the GeV[Formula: see text], Ge3V[Formula: see text], Ge5V[Formula: see text], Ge7V[Formula: see text], and Ge9V[Formula: see text] have larger HOMO–LUMO gaps. Furthermore, the VIPs of Ge[Formula: see text]V clusters show a reverse trend in contrast to the AIPs.

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

Rh(CO)2Cl(NHC) complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C–H coupling constant of the respective imidazolium salts and the N–C–N angle of the N-heterocyclic carbene (NHC), a weaker σ-donor character than that of typical unsaturated NHCs is expected. However, the IR stretching frequencies of their Rh(CO)2Cl complexes suggest an electron-donor character even stronger than that of saturated NHCs. We ascribe this to the extremely weak π-acceptor character of the dipyrido-annelated NHCs caused by the conjugated 14 πe− system that thus allows for an enhanced Rh–CO backbonding. This extremely low π-acceptor ability is also corroborated by the 77Se NMR chemical shift of −55.8 ppm for the respective selenourea, the lowest value ever measured for imidazole derived selenoureas. DFT-calculations of the free carbene confirm the low σ-donor character by the fact that the σ-orbital of the carbene is the HOMO−1 that lies 0.58 eV below the HOMO which is located at the π-system. Natural population analysis reveals the lowest occupation of the pπ-orbital for the saturated carbene carbon atom and the highest for the pyrido-annelated carbene. Going from the free carbene to the Rh(CO)2Cl(NHC) complexes, the increase in occupancy of the complete π-system of the carbene ligand upon coordination is lowest for the pyrido-annelated carbene and highest for the saturated carbene.

A computational NPA and NMR study of Li-capped armchair GaN nanotubes

The geometrical structure, the nuclear magnetic resonance (NMR) parameters and natural population analysis (NPA) of the H-capped (raw) and Li-capped armchair single-walled gallium nitride nanotubes (GaNNTs) are computed and reported for the first time. Our results show that the variation of isotropic chemical shielding (ICS) parameters at the sites of 15N and 71Ga along the length of both models-raw and Li-capped- are reversed. The calculations were carried out with B3LYP-DFT method and 6–31G (d) standard basis sets using the Gaussian 03 suite of programs.