Assignment and vibrational analysis of the 600 nm absorption band in the phenoxyl radical and some of its derivatives

1993 ◽  
Vol 71 (10) ◽  
pp. 1655-1662 ◽  
Author(s):  
Linda J. Johnston ◽  
N. Mathivanan ◽  
Fabrizia Negri ◽  
Willem Siebrand ◽  
Francesco Zerbetto
Keyword(s):  
Ab Initio ◽  
Vibrational Analysis ◽  
Deformation Mode ◽  
Phenoxyl Radical ◽  
Dominant Mode ◽  
Vibrational Structure ◽  
Large Intensity ◽  
Phenyl Rings ◽  
Semi Empirical ◽  
Rigid Matrix

An experimental and theoretical study is reported of the 600 nm band system of phenoxyl and several methoxy substituted phenoxyls. These radicals, generated in freon, show a diffuse band in this region with a vibrational structure that is incompletely resolved but consistent with the 500 cm−1 "progression" observed earlier for phenoxyl in the vapour and in a rigid matrix. The low intensity of this band is considerably enhanced by ortho-methoxy substitution. To establish its assignment and analyze its structure, semi-empirical and ab initio quantum chemical calculations have been performed. It is found that, on the basis of the ordering of the states and the magnitude of their transition moments, all calculations favour a ππ* (2B2 → 2A2) rather than the earlier proposed nπ* assignment for this band. Of the methods used, only the (ab initio) CASSCF method is found to be able to simulate the observed vibrational structure adequately. This simulation is based on optimized structures and vibrational force fields calculated for the 1B2 and 1A2 states of phenoxyl. It identifies the dominant mode of about 500 cm−1 as ν6a the characteristic deformation mode of phenyl rings, but shows that higher members of the "progression" receive large intensity contributions from higher frequency modes. The chosen assignment and the assignments of higher-energy transitions reported in the literature are compared with those for the better known benzyl radical. It is shown that some of the phenoxyl assignments reported in the literature contain errors.

scholarly journals Ab initio and infrared spectral study of 4′-substituted phenylthiolbenzoates

2003 ◽  
Vol 1 (2) ◽  
pp. 98-107 ◽  
Author(s):  
Bojidarka Ivanova ◽  
Michail Arnaudov
Keyword(s):  
Solid State ◽  
Ab Initio ◽  
Vibrational Analysis ◽  
Basis Set ◽  
Frequency Assignment ◽  
Torsional Angle ◽  
Extended Form ◽  
Experimental Ir ◽  
Phenyl Rings ◽  
Infrared Spectral

AbstractThe geometry of the 4′-cyano-(4′-CNPTB) and the 4′-methoxy-(4′-MePTB) phenylthiolbenzoates were obtained by ab initio calculations employing 6–31G basis set at Hartee-Fock level of theory. The results predict an extended form of the molecules and torsional angle between the phenyl rings at 90.85(6)0 and 90.87(3)0, respectively. On the basis of vibrational analysis the frequency assignment was carried out. The calculated frequencies were compared with the experimental IR spectral data in carbon tetrachloride, carbon disulfide solutions and in solid state.

The ultraviolet absorption spectrum of methyl diimide vapor

1977 ◽  
Vol 55 (8) ◽  
pp. 1396-1400 ◽  
Author(s):  
S.K. Vidyarthi ◽  
C. Willis ◽  
R.A. Back
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Vapor Phase ◽  
Vibrational Analysis ◽  
Deformation Mode ◽  
Vibrational Structure ◽  
Ultraviolet Absorption Spectrum ◽  
Valence Shell ◽  
Long Wavelength ◽  
Rydberg Transitions

The vapor phase absorption spectra of CH3N=NH and CH3N=ND have been measured from 160–450 nm. There are three prominent features centered at 360 nm (ε = 6 M−1 cm−1), 208 nm (ε = 710 M−1 cm−1), and 170 nm (s = 2080 M−1 cm−1). The weak near-uv band is assigned to the valence shell transition π* ← n+ while the two far-uv bands are attributed to the 3s ← n+ and 3p ← n+ Rydberg transitions. The band at 208 nm has resolved vibrational structure on the long wavelength tail and a vibrational analysis shows the main progression excited is the ν10′ CNN deformation mode.

Unveiling anharmonic coupling by means of excited state ab initio dynamics: application to diarylethene photoreactivity

2019 ◽  
Vol 21 (7) ◽  
pp. 3606-3614 ◽  
Author(s):  
Maria Gabriella Chiariello ◽  
Umberto Raucci ◽  
Federico Coppola ◽  
Nadia Rega
Keyword(s):  
Excited State ◽  
Ab Initio ◽  
Vibrational Analysis ◽  
Time Resolved ◽  
Anharmonic Coupling ◽  
New Time

We adopted excited state ab initio dynamics and a new time resolved vibrational analysis to unveil coupling between modes promoting photorelaxation.

Vibrational analysis of an electron donor-acceptor substituted adamantane based on ab initio calculations

1997 ◽  
Vol 53 (12) ◽  
pp. 2079-2093 ◽  
Author(s):  
Mark Lilichenko ◽  
Jan W. Verhoeven ◽  
Anne B. Myers
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Donor ◽  
Vibrational Analysis ◽  
Donor Acceptor

Ab initio HF and DFT simulations, FT-IR and FT-Raman vibrational analysis of α-chlorotoluene

2010 ◽  
Vol 77 (1) ◽  
pp. 150-159 ◽  
Author(s):  
P.B. Nagabalasubramanian ◽  
S. Periandy ◽  
S. Mohan
Keyword(s):  
Ab Initio ◽  
Vibrational Analysis ◽  
Ft Ir ◽  
Dft Simulations ◽  
Ab Initio Hf ◽  
Ft Raman

Relation between Magnetic, Spectroscopic and Structural Properties of Binuclear Copper(II) Complexes of Pentadentate Schiff-base Ligand, Semi-empirical and ab-initio Calculations

2003 ◽  
Vol 58 (5-6) ◽  
pp. 363-372 ◽  
Author(s):  
Y. Elerman ◽  
H. Kara ◽  
A. Elmali
Keyword(s):  
Ab Initio ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Hartree Fock ◽  
Ligand Orbital ◽  
Rhf Calculations ◽  
The Difference ◽  
Semi Empirical

The synthesis and characterization of [Cu2(L1)(3,5 prz)] (L1=1,3-Bis(2-hydroxy-3,5-chlorosalicylideneamino) propan-2-ol) 1 and of [Cu2(L2)(3,5 prz)] (L2=1,3-Bis(2-hydroxy-bromosalicylideneamino) propan-2-ol) 2 are reported. The compounds were studied by elemental analysis, infrared and electronic spectra. The structure of the Cu2(L1)(3,5 prz)] complex was determined by x-ray diffraction. The magnetochemical characteristics of these compounds were determined by temperaturedependent magnetic susceptibility measurements, revealing their antiferromagnetic coupling. The superexchange coupling constants are 210 cm−1 for 1 and 440 cm−1 for 2. The difference in the magnitude of the coupling constants was explained by the metal-ligand orbital overlaps and confirmed by ab-initio restricted Hartree-Fock (RHF) calculations. In order to determine the nature of the frontier orbitals, Extended Hückel Molecular Orbital (EHMO) calculations are also reported.

Relativistic AB Initio calculations of the properties of ionic solids

1986 ◽  
Vol 320 (1553) ◽  
pp. 107-158 ◽  
Keyword(s):  
Ab Initio ◽  
Short Range ◽  
Correlation Energy ◽  
Electron Gas ◽  
Empirical Method ◽  
Coulombic Interactions ◽  
Ionic Solids ◽  
Electron Correlation Energy ◽  
Crystal Properties ◽  
Semi Empirical

Relativistic ab initio calculations of inter-ionic potential energies are used to develop a reliable non-empirical method for predicting the properties of ionic solids containing the heaviest ions. A physically realistic method for describing the non-negligible differences between free and in-crystal ion wavefunctions is described. Functions are presented for describing the partial quenching, arising from ion wavefunction overlap, of the standard long-range form of the inter-ionic dispersive attractions. These attractions are shown to be distinct from the contributions to the inter-ionic potentials that arise from that portion of the electron correlation energy which is nonzero solely because of overlap of the ion wavefunctions. The results presented for NaCl, MgO and the fluorides of Li, Na, Ag and Pb show that these modifications overcome the deficiencies of previous calculations. Ab initio predictions of the closest cation-cation and anion-anion short-range interactions, which are not available from semi-empirical fits to experimental data, are presented. The non-point coulombic interactions between pairs of anions, derived by adding the dispersive attractions to the short-range interactions, are compared with previous semi-empirical and approximate ab initio results. The uncorrelated short-range inter-ionic potentials computed exactly are compared with those predicted from electron-gas theory. The use of the electron-gas approximation to describe any of these potentials degrades the quality of the predicted crystal properties.

The phonons of the Al surfaces: comparison between semi-empirical and ab initio calculations

1992 ◽  
Vol 269-270 ◽  
pp. 146-151 ◽  
Author(s):  
A. Franchini ◽  
V. Bortolani ◽  
G. Santoro ◽  
J.A. Gaspar ◽  
A.G. Eguiluz
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Semi Empirical
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