Excited Singlet State Reactions of Thiopyrylium with Electron Donors:  Electron Transfer, Induction of Triplet by Internal and External Heavy Atom Effect, and Comparison of Pyrylium and Thiopyrylium Reactions

1998 ◽  
Vol 102 (3) ◽  
pp. 511-518 ◽  
Author(s):  
S. S. Jayanthi ◽  
P. Ramamurthy
Keyword(s):  
Electron Transfer ◽  
Singlet State ◽  
Heavy Atom ◽  
Electron Donors ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Heavy Atom Effect ◽  
Atom Effect

Photochemistry of Nitracrine and its Analogues: Acridine Derivatives as Electron Donors

1984 ◽  
Vol 39 (2) ◽  
pp. 195-200 ◽  
Author(s):  
J. Biedrzycki ◽  
J. Błażejowski ◽  
J. Szychliński ◽  
A. Ledòchowski
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Fluorescence Quenching ◽  
Triplet State ◽  
Uv Radiation ◽  
Electron Acceptor ◽  
Singlet State ◽  
Electron Donors ◽  
Excited Singlet State ◽  
Excited Singlet

Studies on the electron transfer in the excited state from electron donors: acridine, 9- aminoacridine and its derivatives, including nitracrine and its isomers, to CCl4 as a suitable electron acceptor, were undertaken. UV radiation (λ= 366 nm), absorbed only by acridine bases, generates CI- ions. The fluorescence quenching measurements indicate that no interaction appears between molecules of acridine bases in the excited singlet state and CCl4 molecule. A scheme of photochemical processes is proposed which assumes that the triplet state of the base molecule is the reactive one.

Heavy-atom effects on the excited singlet-state electron-transfer reaction

1991 ◽  
Vol 95 (1) ◽  
pp. 38-42 ◽  
Author(s):  
Koichi Kikuchi ◽  
Masato Hoshi ◽  
Taeko Niwa ◽  
Yasutake Takahashi ◽  
Tsutomu Miyashi
Keyword(s):  
Electron Transfer ◽  
Transfer Reaction ◽  
Singlet State ◽  
Heavy Atom ◽  
Electron Transfer Reaction ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
State Electron

Fluorescence of chloropentafluoroacetone

1970 ◽  
Vol 48 (16) ◽  
pp. 2611-2616 ◽  
Author(s):  
H. S. Samant ◽  
A. J. Yarwood
Keyword(s):  
Rate Constant ◽  
High Pressures ◽  
Singlet State ◽  
Radiative Lifetime ◽  
Heavy Atom ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Gaseous State ◽  
Fluorescent State

The fluorescence of chloropentafluoroacetone in the gaseous state at room temperature is reported. The fluorescence extends from 337 nm to greater than 560 nm with a maximum intensity at 420 nm and is unaffected by low pressures of oxygen. The energy of the first excited singlet state is estimated as about 83 kcal and the fluorescence data for 313 and "290" nm excitation indicate that fluorescence enhancement occurs as the pressure increases. The fluorescent yield at high pressures [Formula: see text] is independent of the nature of the gas used to attain the high pressure. The lifetime of the fluorescent state is 35.1 ± 0.3 ns.A simple mechanism correlates the experimental observations and the values of the rate constants are considered. The reciprocal of the natural radiative lifetime is calculated to be 6.6 × 105 s−1 and the rate constant assigned to intersystem crossing to the triplet is 2.8 × 107 s−1. A comparison with the data in the literature for hexafluoroacetone shows the effect of substitution by a heavy atom in the fluorinated ketone. It about doubles the value of the rate constant associated with intersystem crossing from the first excited singlet state in the gas phase.

scholarly journals The photochemistry of 1-naphthylmethyl carbonates and carbamates

1994 ◽  
Vol 72 (5) ◽  
pp. 1254-1261 ◽  
Author(s):  
T. Parman ◽  
J.A. Pincock ◽  
P.J. Wedge
Keyword(s):  
Electron Transfer ◽  
Singlet State ◽  
Radical Pair ◽  
Ion Pair ◽  
Excited Singlet State ◽  
Excited Singlet ◽  
Homolytic Cleavage ◽  
Product Yields ◽  
Oxygen Bond

The photochemistry in methanol of 1-naphthylmethyl phenyl carbonate (3) and 1-naphthylmethyl benzyl carbonate (4) has been studied. Products resulting from both the 1-naphthylmethyl cation and the 1-naphthylmethyl radical are obtained for 3, but only from the cation for 4. Similar results were obtained for the corresponding 1-naphthylmethyl derivatives 5 and 6 of N-phenyl and N-benzyl carbamic acids. The product yields for all four compounds can be explained by a mechanism of initial homolytic cleavage of the 1-naphthylmethyl carbon–oxygen bond from the excited singlet state. The radical pair generated then partitions between the two pathways: electron transfer to form the ion pair or decarboxylation. For PhO-CO-O• and PhNH-CO-O•, decarboxylation is rapid and competitive with electron transfer. For PhCH2O-CO-O• and PhCH2NH-CO-O•, decarboxylation is slower, electron transfer dominates, and only products from the ion pair are obtained.

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