amide-iminol tautomerism was studied for ionized oxamic acid (oa+•) in the gas phase using thedft method with the ub3lyp functional and various basis sets {6-31++g(d,p), 6-311+g(d,p), and augcc-pvdz}. among twenty tautomers-rotamers possible for oa+•, eleven isomers were found to bethermodynamically stable. similarly as for the neutral molecule, ionization (oa → oa+• + e) favors theamidization ...

The HOMA (Harmonic Oscillator Model of Aromaticity) index, reformulated in 1993, has been very often applied to describe π-electron delocalization for monoand polycyclic π-electron systems. However, different measures of π-electron delocalization were employed for the CC, CX, and XY bonds, and this index seems to be inappropriate for compounds containing heteroatoms. In order to describe proper...

The HOMA (Harmonic Oscillator Model of Aromaticity) index, reformulated in 1993, has been very often applied to describe π-electron delocalization for monoand polycyclic π-electron systems. However, different measures of π-electron delocalization were employed for the CC, CX, and XY bonds, and this index seems to be inappropriate for compounds containing heteroatoms. In order to describe proper...

An n→π* interaction stems from the delocalization of the electron pair (n) of a donor group into the antibonding orbital (π*) of a carbonyl group. Crystallographic analyses of five pairs of diastereoisomers demonstrate that an n→π* interaction can induce chirality in an otherwise planar, prochiral carbonyl group. Thus, a subtle delocalization of electrons can have stereochemical consequences.

Novel DNA base pair derivatives (A2CunU, A2CunC, G3CunU, and G3CunC) are designed by aromatic expansion of pyrimidine bases with four kinds of hetero-rings (denoted by nC and nU, n = 1, 2, 3, and 4) and metal-decoration through Cu replacement of hydrogens in the Watson-Crick hydrogen bond region. Their structures and properties are calculated for examining the cooperative effects of the two mod...

Carbonyl-carbonyl (C=O···C'=O') interactions are ubiquitous in both small and large molecular systems. This interaction involves delocalization of a lone pair (n) of a donor oxygen into the antibonding orbital (π*) of an acceptor carbonyl group. Analyses of high-resolution protein structures suggest that these carbonyl-carbonyl interactions prefer to occur in pairs, that is, one donor per accep...

This review aims to give an overview of the current status of our research on the synthesis of π-electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, ET) analogues prepared from 1,8-diketones via a ring forming reaction. The new synthesized π-electron donors have vinyl moieties producing extended π-electron delocalization over the substituent phenyl rings at the peripheries.

Amide-iminol tautomerism was studied for ionized oxamic acid (OA+•) in the gas phase using theDFT method with the UB3LYP functional and various basis sets {6-31++G(d,p), 6-311+G(d,p), and augcc-pVDZ}. Among twenty tautomers-rotamers possible for OA+•, eleven isomers were found to bethermodynamically stable. Similarly as for the neutral molecule, ionization (OA → OA+• + e) favors theamidization ...

Scalar fields provide an intuitive picture of chemical bonding. In particular, the electron localization function (ELF) has proven to be highly valuable in interpreting a broad range of bonding patterns. The discrimination between enhanced or reduced electron (de)localization within cyclic π-conjugated systems remains, however, challenging for ELF. In order to clearly distinguish between the lo...