Electronic Structure Of Trans Research Articles

Novel p-tolylimido rhenium(V) complexes incorporating quinoline-2-carboxylate ion – Synthesis, X-ray studies, spectroscopic characterization and DFT calculations

Novel p-tolylimido rhenium(V) complexes trans-[Re(p-NC 6H 4CH 3)X 2(quin-2-COO)(PPh 3)] and cis-[Re(p-NC 6H 4CH 3)X 2(quin-2-COO)(PPh 3)]·MeCN have been obtained in the reactions of [Re(p-NC 6H 4CH 3)X 3(PPh 3) 2] (X = Cl, Br) with quinoline-2-carboxylic acid. The compounds were identified by elemental analysis IR, UV–Vis spectroscopy and X-ray crystallography. The electronic structures of trans- and cis-halide isomers of [Re(p-NC 6H 4CH 3)Cl 2(quin-2-COO)(PPh 3)] have been calculated with the density functional theory (DFT) method. Additional information about binding in the compounds [Re(p-NC 6H 4CH 3)Cl 2(quin-2-COO)(PPh 3)] with cis- and trans-halide arrangement has been obtained by NBO analysis. The electronic spectra of trans and cis isomers of [Re(p-NC 6H 4CH 3)Cl 2(quin-2-COO)(PPh 3)] were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ.

Solvatochromism, molecular and electronic structures of trans and cis isomers of a typical styryl pyridinium cyanine dye

This paper reports on solvatochromism and molecular and electronic structures of a typical styryl pyridinium cyanine dye, 1-methyl-4-( p- N, N-dimethyl-amino styryl) pyridinium iodide (Cy) in both ground and excited states. There is a hypsochromic shift of the longest absorption band, which is greater than that of the bathochromic shift of the fluorescence band, with a decrease of the Stokes shift as the solvent polarity decreases. The results confirm the importance of decreasing the dipole moment of Cy upon excitation and solvent polarity function F( D, n), which describes the orientation polarizability of the solvent, in the energetic stabilization of Cy dye in S o and S 1 states. Semiempirical molecular orbital calculations using the atom superposition and electron delocalization molecular orbital (ASED-MO) and PM3 methods were also performed. The change of the dipole moment upon excitation was explained on the basis of changes in the charge redistribution over the whole skeleton of the molecules, which agree well with the experimental results. Also, the nature and energy of the electronic transitions were elucidated and discussed in relation to the experimental data.

Electronic transitions in cis- and trans-dichloroethylenes and tetrachloroethylene

Electronic structures of trans- and cis-dichloroethylenes and tetrachloroethylene were studied using symmetry-adapted cluster configuration interaction theory. Basis sets up to the aug-cc-pVTZ of Dunning, Jr., augmented with appropriate Rydberg functions were used for the calculations. The results derived in the present study show good agreement with the available experimental values. In all cases, the main bright excitation was the pi-->pi( *) transition. The other vertical excitations, pi-->sigma( *), n-->sigma( *), and n-->pi( *), which have not been studied before, were also investigated. First Rydberg series involving transitions from the pi orbitals to one 3s, three 3p, and five 3d orbitals were identified clearly. Several new assignments and reassignments of features in the experimental spectra were suggested. Contrary to earlier prediction, two n-sigma( *) states, along with a pi-sigma( *) state in the dichloroethylenes, were calculated to be located above the main pi-pi( *) state. Accordingly, crossing between both the n-sigma( *) states with the bright pi-pi( *) state is highly likely, unlike conclusions made in the earlier studies. This indicates that the photodissociation mechanism proposed by the earlier calculations warrants revision. Several low-lying triplet excited states were also studied. Electronic spectra of trans-1-chloro-2-fluoroethylene and cis-1-chloro-2-fluoroethylene were also calculated. The pi-->pi( *) transitions of these haloethylenes are compared and interpreted in terms of the inductive and resonance effects.

Gapless Peierls transition.

For one-dimensional chains, transverse displacements of atoms produce zigzag structures, which are encountered in such diverse areas as polymers and metallic overlayers on semiconductor surfaces. Such displacements lead to an apparent reduction of translational symmetry but do not open a gap at the zone edge [gapless Peierls transition (GPT)]. The total energy remains analytic and hence the formation of zigzag chains on semiconductors is governed by material-specific interactions. The applications of the GPT ideas are illustrated by examining the stability issues and electronic structure of trans-(CH${)}_{\mathit{x}}$, Al chains on Si(001), and consequences of the tetragonal-orthorhombic transition in ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$.

Electronic structure of trans-[Cr(ox)2(py)2]- by the X.alpha.-scattered wave method

Electronic structure of trans-[Cr(ox)2(py)2]- by the X.alpha.-scattered wave method

Electronic structure of trans-[(η 5-C 5H 5)Fe(CO) 2] 2 by He(I) and He(II) photoelectron spectroscopy and AB initio calculations

He(I) and He(II) excited photoelectron spectra of trans-[(η 5-C 5H 5)Fe(CO) 2] 2 are reported. The assignment of the bands to the ionization events is based on experimental criteria as well as on the results of “ab initio” calculations. The agreement between computed and measured ionization energies appears satisfactory when the effect of the relaxation terms, especially important for ionization processes originating from predominantly metal orbitals, is taken into account.

Electronic Structure and Isomerization of Stilbene

AbstractThe electronic structures of trans‐ and cis‐stilbene are calculated using Pariser and Parr's semiempirical method. The resonance integrals are adjusted so as to give the best agreement with the spectroscopic data. In addition, the potential surfaces of various excited states in stilbene during its isomerization process are calculated. Our results differ significently from those of Borrell and Greenwood2) who did not realized the importance of a doubly excited singlet state to the potential surface of the ground state of stilbene. Our improved potential surfaces suggests mechanism of various radiationless leading to photoisomerization and sensitized isomerization.

The Electronic Structures of trans and cis Isomers of Some Halogenoethylenes

Abstract By using the closed-shell SCF MO method with the zero-differential overlap approximation for all valence electron systems previously presented by us, the electronic structures of trans- and cis- substituted ethylenes (treated substituent=CH3, Cl, Br, and I) are studied. The calculated values of the π and valence electron charges, and the total energies of these isomers are presented. The natures of the higher occupied MO’s, especially the lonepair MO’s, of chlorinated ethylenes are discussed in connection with the photoelectron observation. The calculated lowest π–π* singlet transition energies accord well with the observed values. As to the rotational energy changes, the calculated results show that, at the perpendicular configurations, the triplet states for all the treated compounds are lowest, while the intermediate states for the cis-trans isomerizations of these compounds may be common to both the isomers.

A CNDO CI Study of the Electronic Structure of Trans- and Cis-Diimide

Abstract The electronic spectra of cis— and trans-HN=NH have been the subject of a number of studies. The most interesting work in this area is probably that of Robin, Hart and Kuebler. They studied the two isomers both experimentally and theoretically and attempted to correlate their electronic states with that of ethylene.

Semi-Empirical SCF MO Treatment for Valence Electron Systems. Electronic Structures of trans- and cis-Isomers of Butadiene, Acrolein, and Glyoxal

Abstract Using a semi-empirical ASMO SGF method for all valence electron systems, but a method modified to include one-center exchange integrals and an off-diagonal core integral as estimated by the approximation in our previous treatment, the electronic structures of trans- and cis-isomers of butadiene, acrolein, and glyoxal are calculated. The energy sequence of the molecular orbitals, the charge distributions in lone-pair orbitals and π MO’s, and the charge distribution in these compounds are investigated. The n–π* and π–π* transition energies are also presented; the agreement between the calculated and observed values is almost entirely satisfactory. Further, the singlet-triplet oscillator strength in the trans-glyoxal is estimated by means of the obtained results.