On the suppression mechanism of the Pseudo-Jahn-Teller effect in middle E 6 (E = P, As, Sb) rings of triple-decker sandwich complexes

Quantum chemical calculations of the CpMoE 6MoCp (E = P, As, Sb) triple-decker sandwich complexes showed that E 6 fragments in the central decks of the complexes are planar. Analysis of molecular orbitals involved in vibrational coupling demonstrated that filling the unoccupied molecular orbitals involved in vibronic coupling with electron pairs of Mo atoms suppresses the PJT effect in the CpMoE 6MoCp (E = P, As, Sb) sandwich, with the E 6 ring becoming planar (D 6h) upon complex formation. The AdNDP analysis revealed that bonding between C 5H 5 - units and Mo atoms has a significant ionic contribution, while bonding between Mo atoms and E 6 fragment becomes appreciably covalent through the δ-type M → L back-donation mechanism. © 2012 American Chemical Society

Is graphene aromatic?

We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg

Peculiar transformations in the C xH xP 4-x (x = 0-4) series

In the current work, we performed a systematic study of the C xH xP 4-x (x = 0-4) series using an unbiased CK global minimum and low-lying isomers search for the singlet and triplet P 4-C 4H 4 species at the B3LYP/6-31G** level of theory. The selected lowest isomers were recalculated at the CCSD(T)/CBS//B3LYP/6-311++G** level of theory. We found that the transition from a three-dimensional tetrahedron-like structure to a planar structure occurs at x = 3, where planar isomers become much more stable than the tetrahedral structures due to significantly stronger π bonds between carbon atoms in addition to increasing strain energy at the carbon atom in the tetrahedral environment. © 2011 American Chemical Society

Peculiar transformations in the C xH xP 4-x (x = 0-4) series

In the current work, we performed a systematic study of the C xH xP 4-x (x = 0-4) series using an unbiased CK global minimum and low-lying isomers search for the singlet and triplet P 4-C 4H 4 species at the B3LYP/6-31G** level of theory. The selected lowest isomers were recalculated at the CCSD(T)/CBS//B3LYP/6-311++G** level of theory. We found that the transition from a three-dimensional tetrahedron-like structure to a planar structure occurs at x = 3, where planar isomers become much more stable than the tetrahedral structures due to significantly stronger π bonds between carbon atoms in addition to increasing strain energy at the carbon atom in the tetrahedral environment. © 2011 American Chemical Society

Exchange interaction of Mo with 3d and 4d metals in complexes with dithiooxamide: a theoretical modeling

Quantum chemical calculations of the molecular and electronic structure of the complexes [(L)2M13+(L)M22+(L)2]5− (M13+ is the Mo ion in the oxidation state +3; M22+ is the 3d and 4d transition-metal (Fe, Ru, Rh, Pd) ion in the oxidation state +2; and L is the dithiooxamide ligand) were carried out to search for pairs of metals corresponding to the maximum value of the exchange coupling constant J. Molecular structure calculations of the complexes were performed in the B3LYP/LANL2DZ approximation while the J constants were obtained from B3LYP/TZV calculations. It was shown that replacement of 3d transition-metal ions in the oxidation state +2 by 4d transition-metal ions in the oxidation state +2 leads to higher J values. It was established that the J values change in parallel with the difference between the total spin density on the M13+ and M22+ metal ions in the complexes and in the isolated M13+ and M22+ ions. © 2022, Springer Science+Business Media LLC

On the suppression mechanism of the Pseudo-Jahn-Teller effect in middle E 6 (E = P, As, Sb) rings of triple-decker sandwich complexes

Quantum chemical calculations of the CpMoE 6MoCp (E = P, As, Sb) triple-decker sandwich complexes showed that E 6 fragments in the central decks of the complexes are planar. Analysis of molecular orbitals involved in vibrational coupling demonstrated that filling the unoccupied molecular orbitals involved in vibronic coupling with electron pairs of Mo atoms suppresses the PJT effect in the CpMoE 6MoCp (E = P, As, Sb) sandwich, with the E 6 ring becoming planar (D 6h) upon complex formation. The AdNDP analysis revealed that bonding between C 5H 5 - units and Mo atoms has a significant ionic contribution, while bonding between Mo atoms and E 6 fragment becomes appreciably covalent through the δ-type M → L back-donation mechanism. © 2012 American Chemical Society

Is graphene aromatic?

We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg

Slow hindered rotation of CF3 group in radical anion of ortho nitrobenzotrifluoride in N,N′-dimethylformamide and reconstruction of EPR spectrum

The temperature dependence of the EPR spectrum of the 2-CF3-C6H4-NO*2 radical anion in anhydrous N,N′-dimethylformamide, caused by hindered internal rotation of the CF3 group with an extreme activation energy of 34700 J·mol-1, was experimentally studied and reconstructed. © 2007 by Allerton Press, Inc