Substituent effects in arosemibullvalene photochemistry: the methylcyclopropane rearrangement of 1,8-dimethylbenzosemibullvalene

1982 ◽  
Vol 60 (15) ◽  
pp. 1942-1952 ◽  
Author(s):  
Christopher Owen Bender ◽  
Donald Laverne Bengtson ◽  
Douglas Dolman ◽  
Carolyn Elaine L. Herle ◽  
Seamus Francis O'Shea
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Substituent Effects ◽  
Interaction Energies ◽  
Direct Irradiation ◽  
Atom Interaction ◽  
Ci Calculations

1,6- and 1,8-Dimethylbenzotricyclo[3.3.0.02,8]octa-3,6-diene (16 and 14) are the major semibullvalene products formed from acetophenone sensitized irradiations of the barrelenes 2,6- and 2,3-dimethyl-1,4-dihydro-1,4-ethenonaphthalene (37 and 22), respectively (Φ37→16 = 0.65; Φ22→14=0.57). The direct (Φ14 = 0.017) or chlorobenzene sensitized (Φ14 = 0.12) irradiation of 14 yields 2,3-benzo-5-methyl-6-methylenebicyclo[3.3.0]octa-2,7-diene (17), a transformation typical of methylcyclopropanes. Gas phase thermolysis (420 °C/6 Torr) of 14 gives 6,7-dimethylbenzocyclooctatetraene (15). The direct irradiation (Φ39 = 0.003) or the gas phase thermolysis (395 °C/6 Torr) of 16 gives 6,9-dimethylbenzocyclooctatetraene (39). The rearrangement 14 → 17 is in accord with predictions based upon CNDO-CI calculations of changes in atom–atom interaction energies on excitation to the S1 or T1 excited states of 14.

Polar substituents in barrelene photochemistry: mechanistic aspects of the photochemistry of 2-cyanobenzobarrelene

1978 ◽  
Vol 56 (23) ◽  
pp. 3027-3037 ◽  
Author(s):  
Christopher Owen Bender ◽  
Dee W. Brooks ◽  
William Cheng ◽  
Douglas Dolman ◽  
Seamus F. O'Shea ◽  
...  
Keyword(s):  
Excited States ◽  
Interaction Energies ◽  
Direct Photolysis ◽  
Deuterium Labelling ◽  
Atom Interaction ◽  
Polar Substituents ◽  
Triplet Excited States ◽  
Ci Calculations

The direct photolysis of 2-cyanobenzobarrelene (4) yields 5- and 7-cyanobenzocyclooctatetraene [Formula: see text] and 1-cyanobenzosemibullvalene [Formula: see text], whereas the acetophenone sensitized irradiation of 4 yields only 8 [Formula: see text]. Deuterium labelling studies suggest that 7 derives from an initial 2Π + 2Π cycloaddition between the vinyl and vinylcyano bridges of 4, whereas 8, resulting from direct or sensitized irradiations of 4, derives from di-Π-methane rearrangement involving initial vinyl–vinylcyano bridging. The observed initial bonding preferences of the 2Π + 2Π cycloadditions and di-Π-methane rearrangement of 4 are in accord with predictions based upon CNDO-CI calculations of changes in atom–atom interaction energies between possible bridging sites in singlet and triplet excited states of 4.

Mechanistic and theoretical studies of the photochemistry of 5,6-dihydro-2-cyanobenzobarrelene

1979 ◽  
Vol 57 (21) ◽  
pp. 2804-2811 ◽  
Author(s):  
Christopher Owen Bender ◽  
Seamus F. O'Shea
Keyword(s):  
Excited States ◽  
Theoretical Studies ◽  
Interaction Energies ◽  
Deuterium Labelling ◽  
Atom Interaction ◽  
Ci Calculations

The direct (Φ6 = 0.04) or acetone sensitized (Φ6 = 0.51) photolysis of 2-cyano-1,4-dihydro-1,4-ethanonaphthalene (5) yields 1-cyanobenzotricyclo[3.3.0.02,8]octa-3-ene (6). Deuterium labelling studies suggest that 6 derives from a Zimmerman di-π-methane rearrangement and not from the McCullough 1-cyanocyclohexene rearrangement. The observed rearrangement and regioselectivity are in accord with predictions based upon CNDO-CI calculations of changes in atom–atom interaction energies on excitation to the S1 and T1 excited states of 5.

Zur Elektronenstruktur der Thiokumulene / The Electronic Structure of Thiocumulenes

1973 ◽  
Vol 28 (3-4) ◽  
pp. 188-195 ◽  
Author(s):  
Jürgen Kroner ◽  
Walter Strack ◽  
Florian Holsboer ◽  
Wolfgang Kosbahn
Keyword(s):  
Carbon Dioxide ◽  
Electronic Structure ◽  
Sulfur Dioxide ◽  
Gas Phase ◽  
Substituent Effects ◽  
Uv Spectra ◽  
Binding Energies ◽  
X Ray ◽  
The Core ◽  
Ci Calculations

The He(I) photoelectron(PE) spectra, the core binding energies according to X-ray photoelectron(ESCA) spectra, and the gas phase far UV spectra of the bent cumulenes sulfur dioxide, N-tert-butylsulnnylamine, and di-tert-butylsulfurdiimide are presented. The PE spectra are discussed by comparing them to those of the linear carbon analogues as carbon dioxide, tert-butylisocyanate and di-tert-butylcarbodiimide. Modified CNDO-CI calculations give satisfying interpretations of the substituent effects.

Substituent effects in the so-called cation⋯π interaction of benzene and its boron–nitrogen doped analogues: overlooked role of σ-skeleton

2019 ◽  
Vol 21 (12) ◽  
pp. 6453-6466 ◽  
Author(s):  
Sirous Yourdkhani ◽  
Michał Chojecki ◽  
Tatiana Korona
Keyword(s):  
Substituent Effect ◽  
Substituent Effects ◽  
Interaction Energies ◽  
Nitrogen Doped ◽  
Π Interactions ◽  
Atom Interaction ◽  
Classical Effect ◽  
Boron Nitrogen

By decomposing IQA atom–atom interaction energies to σ and π contributions, we have shown that the substituent effect in cation⋯π interactions is a nonlocal classical effect in which σ-polarization plays an important role.

Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

2019 ◽  
Author(s):  
Drew P. Harding ◽  
Laura J. Kingsley ◽  
Glen Spraggon ◽  
Steven Wheeler
Keyword(s):  
Gas Phase ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Stacking Interactions ◽  
Interaction Energies ◽  
Functional Theory ◽  
Binding Partner ◽  
Heavy Atoms ◽  
Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

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