The photochemistry of 5-cyano-2,3-benzobicyclo[4.2.0]octa-2,4,7-triene

1989 ◽  
Vol 67 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Christopher Owen Bender ◽  
Douglas Dolman
Keyword(s):  
Excited State ◽  
Triplet Excited State ◽  
Deuterium Labelling ◽  
Direct Irradiation ◽  
Rearrangement Mechanism

The direct irradiation of 5-cyano-2,3-benzobicyclo[4.2.0]octa-2,4,7-triene (18) led to 6-cyanobenzocyclooctatetraene (17; Φ = 0.00075), 6-cyanobenzosemibullvalene (14; Φ = 0.0003), and 2-cyanonaphthalene (Φ = 0.00015). The triplet excited state of 18, generated by sensitization with a variety of ketone sensitizers (e.g., Michler's ketone and acetophenone), showed no unimolecular reactivity. Compound 18 does not participate in Zimmerman di-π-methane rearrangement; the potential product from such a transformation, 8-cyanobenzosemibullvalene (19), was, however, isolated from direct (Corex filter; Φ = 0,0010) irradiation of the semibullvalene 14. Deuterium labelling experiments suggest that 14 derives from a mechanism involving initial C4—C8 bonding of 18, and that cyclooctatetraene 17 is probably formed by simple electrocyclic opening of the cyclobutene ring of 18. Keywords: photochemistry, rearrangement mechanism, di-π-methane, semibullvalenes.

Photochemical behavior of some α, β-unsaturated lactams. Dependence of reaction path on multiplicity

1969 ◽  
Vol 47 (15) ◽  
pp. 2781-2786 ◽  
Author(s):  
E. Cavalieri ◽  
S. Horoupian
Keyword(s):  
Excited State ◽  
Spectral Properties ◽  
Reaction Path ◽  
Triplet Excited State ◽  
Excited Singlet ◽  
Cleavage Reaction ◽  
Dimer Formation ◽  
Cyclobutane Dimer ◽  
Direct Irradiation ◽  
Cyclobutane Dimers

Whereas direct irradiation (2537 Å) of 5,6-dihydro-4,6,6-trimethyl-2(1H)-pyridone 1 (1a) produced almost exclusively the cleavage products 2 and 3, the acetophenone sensitized reaction (3500 Å) gave a single cyclobutane dimer. In contrast, direct (2537 Å) or sensitized (acetophenone, 3500 Å) irradiation of the homo derivative 7 of compound 1 gave approximately the same mixture of two cyclobutane dimers. It was thus demonstrated that dimer formation proceeded by way of a triplet excited state and that the cleavage reaction most probably occurred via an excited singlet state.A structure for each cyclobutane dimer in the seven-membered series was proposed on the basis of its spectral properties.

scholarly journals Ultra long‐lived triplet excited state in water at room temperature: Insights on the molecular design of tridecafullerenes

2021 ◽  
Author(s):  
Javier Ramos-Soriano ◽  
Alfonso Pérez-Sánchez ◽  
Sergio Ramírez-Barroso ◽  
Beatriz M. Illescas ◽  
Khalid Azmani ◽  
...  
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Molecular Design ◽  
Triplet Excited State

scholarly journals Triplet energies and excimer formation in meta - and para -linked carbazolebiphenyl matrix materials

2015 ◽  
Vol 373 (2044) ◽  
pp. 20140446 ◽  
Author(s):  
Sergey A. Bagnich ◽  
Alexander Rudnick ◽  
Pamela Schroegel ◽  
Peter Strohriegl ◽  
Anna Köhler
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Spectroscopic Investigation ◽  
Triplet Excited State ◽  
Conjugation Length ◽  
Triplet Energy ◽  
Excimer Formation

We present a spectroscopic investigation on the effect of changing the position where carbazole is attached to biphenyl in carbazolebiphenyl (CBP) on the triplet state energies and the propensity to excimer formation. For this, two CBP derivatives have been prepared with the carbazole moieties attached at the ( para ) 4- and 4 ′ -positions ( p CBP) and at the ( meta ) 3- and 3 ′ -positions ( m CBP) of the biphenyls. These compounds are compared to analogous m CDBP and p CDBP, i.e. two highly twisted carbazoledimethylbiphenyls, which have a high triplet energy at about 3.0 eV and tend to form triplet excimers in a neat film. This torsion in the structure is associated with localization of the excited state onto the carbazole moieties. We find that in m CBP and p CBP, excimer formation is prevented by localization of the triplet excited state onto the central moiety. As conjugation can continue from the central biphenyls into the nitrogen of the carbazole in the para -connected p CBP, emission involves mainly the benzidine. By contrast, the meta -linkage in m CBP limits conjugation to the central biphenyl. The associated shorter conjugation length is the reason for the higher triplet energy of 2.8 eV in m CBP compared with the 2.65 eV in p CBP.

Investigation of the triplet excited state and application of cationic meso-tetra(cisplatin)porphyrins in antimicrobial photodynamic therapy

2021 ◽  
pp. 102459
Author(s):  
Dariane Clerici Jornada ◽  
Rafael de Queiroz Garcia ◽  
Carolina Hahn da Silveira ◽  
Lino Misoguti ◽  
Cleber Renato Mendonça ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Excited State ◽  
Antimicrobial Photodynamic Therapy ◽  
Triplet Excited State

scholarly journals Electron Transfer Initiated Reactions Photoinduced by Pterins

Pteridines ◽  
2011 ◽  
Vol 22 (1) ◽  
pp. 111-119 ◽  
Author(s):  
Carolina Lorente ◽  
Gabriela Petroselli ◽  
M. Laura Dántola ◽  
Esther Oliveros ◽  
Andrés H. Thomas
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Redox Reactions ◽  
Type I ◽  
Biological Processes ◽  
Type Ii ◽  
Triplet Excited State ◽  
Oxygen Production ◽  
Production Type ◽  
Transfer Mechanisms

Abstract Interest in the photochemistry and photophysics of pterins has increased since the participation of this family of compounds in different photobiological processes has been suggested or demonstrated in recent decades. Pterins participate in relevant biological processes, such as metabolic redox reactions, and can photoinduce the oxidation of biomolecules through both electron transfer mechanisms (Type I) and singlet oxygen production (Type II). This article describes recent findings on electron transfer-initiated reactions photoinduced by the triplet excited state of pterins and connects them in the context of photosensitized processes of biological relevance.

scholarly journals Singlet and Triplet Excited-State Dynamics Study of the Keto and Enol Tautomers of Cytosine

ChemPhysChem ◽  
2013 ◽  
Vol 14 (13) ◽  
pp. 2920-2931 ◽  
Author(s):  
Sebastian Mai ◽  
Philipp Marquetand ◽  
Martin Richter ◽  
Jesús González-Vázquez ◽  
Leticia González
Keyword(s):  
Excited State ◽  
Triplet Excited State ◽  
Excited State Dynamics

Triplet Excited State Behavior of Naphthalene-Based Pseudopeptides in the Presence of Energy Donors

2012 ◽  
Vol 116 (33) ◽  
pp. 9957-9962 ◽  
Author(s):  
Paula Bonancía ◽  
Laura Vigara ◽  
Francisco Galindo ◽  
Santiago V. Luis ◽  
M. Consuelo Jiménez ◽  
...  
Keyword(s):  
Excited State ◽  
Triplet Excited State ◽  
State Behavior
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