Substituent Effects in Buta-1,3-diene Photochemistry: A CAS-SCF Study of 2,3-Dimethylbutadiene and 2-Cyanobutadiene Excited-State Reaction Paths

1994 ◽  
Vol 116 (5) ◽  
pp. 2034-2048 ◽  
Author(s):  
Massimo Olivucci ◽  
Fernando Bernardi ◽  
Stefano Ottani ◽  
Michael A. Robb
Keyword(s):  
Excited State ◽  
Substituent Effects ◽  
Reaction Paths

Asymmetric reaction paths for ground- and excited-state 1,3,5-hexatriene to 1,3-cyclohexadiene cyclizations

1989 ◽  
Vol 188 (1-2) ◽  
pp. 129-140 ◽  
Author(s):  
Vladimir A. Pichko ◽  
Boris Ya. Simkin ◽  
Vladimir I. Minkin
Keyword(s):  
Excited State ◽  
Reaction Paths ◽  
Asymmetric Reaction

Substituent effects on homolytic versus heterolytic photocleavage of (1-naphthylmethyl)trimethylammonium chlorides

1987 ◽  
Vol 65 (7) ◽  
pp. 1599-1607 ◽  
Author(s):  
B. Foster ◽  
B. Gaillard ◽  
N. Mathur ◽  
A. L. Pincock ◽  
J. A. Pincock ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Hydrogen Atom ◽  
Charge Distribution ◽  
Rate Constants ◽  
Bond Cleavage ◽  
Substituent Effects ◽  
Hydrogen Atom Transfer ◽  
Singlet Excited State ◽  
State Rate

Singlet excited state rate constants have been measured for both the heterolytic and homolytic photocleavage of 3- and 4-methoxy and 3- and 4-cyano (1-naphthylmethyl)trimethylammonium chlorides, 6–10. The results are interpreted in terms of the meta effect or changes in charge distribution upon excitation and the competition between bond cleavage, electron transfer, and hydrogen atom transfer in the contact pairs resulting from the two types of cleavage.

The photochemistry of indenyl alcohols and esters: Substituent effects on the competition between ion- and radical-derived products

2003 ◽  
Vol 81 (10) ◽  
pp. 1083-1095 ◽  
Author(s):  
J A Pincock ◽  
I S Young
Keyword(s):  
Excited State ◽  
Ground State ◽  
Fluorescence Emission ◽  
Substituent Effects ◽  
Sharp Contrast ◽  
Carboxylate Anion ◽  
Excited Singlet ◽  
Heterolytic Cleavage ◽  
Singlet States ◽  
Excited Singlet States

The photochemistry of the indenyl acetates 1 and pivalates 2, substituted with X = H, 5-CH3O, and 6-CH3O, have been examined in both methanol and cyclohexane. The precursor alcohols 3 were also found to be photoreactive. Although only radical-derived products were obtained in cyclohexane, both ion- and radical-derived products were formed in methanol. The absence of significant fluorescence emission from any of the substrates 1, 2, and 3 indicates that the excited singlet states are highly reactive. A mechanism is proposed for the ion-derived products that proceeds through direct heterolytic cleavage to give an indenyl cation – carboxylate anion pair. The indenyl cations generated are anti-aromatic in the ground state and their efficient generation by this photochemical solvolysis is in sharp contrast to the very low reactivity of related ground-state substrates. For the pivalate esters 2, an excited-state migratory decarboxylation is proposed for the formation of tert-butyl derived products.Key words: ester photochemistry, indenyl cations, indenyl radicals.

scholarly journals Structure-Photochemical Function Relationships in Nitrogen-Containing Heterocyclic Aromatic Photobases Derived from Quinoline

2019 ◽  
Author(s):  
Sophya Alamudun ◽  
Kyle Tanovitz ◽  
April Fajardo ◽  
Kaitlind Johnson ◽  
Andy Pham ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Systematic Study ◽  
Experimental Studies ◽  
Substituent Effects ◽  
Vertical Excitation ◽  
Vertical Excitation Energy ◽  
Heterocyclic Aromatics ◽  
A Charge

<p>Photobases are compounds which become strong bases after electronic excitaton into a charge-transfer excited state. Recent experimental studies have highlighted the photobasicity of the 5-R quinoline compounds, demonstrating a strong substituent dependence to the pK<sub>a</sub><sup>*</sup>. Here we describe our systematic study of how the photobasicity of four families of nitrogen-containing heterocyclic aromatics are tuned through substituents. We show that substituent position and identity both significantly impact the pK<sub>a</sub><sup>*</sup>. We demonstrate that the substituent effects are additive and identify many disubstituted compounds with substantially greater photobasicity than the most photobasic 5-R quinoline compound identified previously. We show that the addition of a second fused benzene ring to quinoline, along with two electron-donating substituents, lowers the vertical excitation energy into the visible while still maintaining a pK<sub>a</sub><sup>*</sup> > 14. Overall, the structure-function relationships developed in this study provide new insights to guide the development of new photocatalysts that employ photobasicity. </p>

Substituent effects upon efficiency of excited-state acetophenones produced on thermolysis of 3,4-diaryl-3,4-dimethyl-1,2-dioxetanes

1987 ◽  
Vol 52 (14) ◽  
pp. 3143-3150 ◽  
Author(s):  
William H. Richardson ◽  
Diana L. Stiggal-Estberg ◽  
Zhangping Chen ◽  
John C. Baker ◽  
David M. Burns ◽  
...  
Keyword(s):  
Excited State ◽  
Substituent Effects
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