Characterization of the triplet excited state of the phenylxanthenium carbocation

1992 ◽  
Vol 70 (1) ◽  
pp. 280-282 ◽  
Author(s):  
L. J. Johnston ◽  
D. F. Wong
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Radical Cation ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Triplet Excited State ◽  
Triplet Absorption

The triplet excited state of the 9-phenylxanthenium cation has been observed directly by both luminescence and transient absorption techniques. The triplet–triplet absorption shows λmax ≤ 300 nm and decays over a period of several microseconds in the absence of easily oxidized donors. The triplet cation reacts with 9-phenylxanthydrol and biphenyl via electron transfer to give the corresponding radical and radical cation and also reacts rapidly with both oxygen and 1,3-cyclohexadiene. Keywords: carbocations, triplets, electron transfer, laser flash photolysis.

Formation and Direct Detection of Non-Conjugated Triplet 1,2-Biradical from β,γ-Vinylarylketone

2015 ◽  
Vol 68 (11) ◽  
pp. 1707 ◽  
Author(s):  
H. Dushanee M. Sriyarathne ◽  
Kosala R. S. Thenna-Hewa ◽  
Tianeka Scott ◽  
Anna D. Gudmundsdottir
Keyword(s):  
Rate Constant ◽  
Density Functional ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Direct Detection ◽  
Density Functional Theory Calculations ◽  
Laser Flash ◽  
Triplet Excited State ◽  
Functional Theory

Laser flash photolysis of 2-methyl-1-phenylbut-3-en-1-one (1) conducted at irradiation wavelengths of 266 and 308 nm results in the formation of triplet 1,2-biradical 2 that has λmax at 370 and 480 nm. Biradical 2 is formed with a rate constant of 1.1 × 107 s–1 and decays with a rate constant of 2.3 × 105 s–1. Isoprene-quenching studies support the notion that biradical 2 is formed by energy transfer from the triplet-excited state of the ketone chromophore of 1. Density functional theory calculations were used to verify the characterization of triplet biradical 2 and validate the mechanism for its formation. Thus, it has been demonstrated that intramolecular sensitization of simple alkenes can be used to form triplet 1,2-biradicals with the two radical centres localized on the adjacent carbon atoms.

Intramolecular photoinduced electron-transfer processes in buta-1,3-diynyl-benzene-linked porphyrin-fullerene dyad

2007 ◽  
Vol 11 (06) ◽  
pp. 397-405 ◽  
Author(s):  
Ken-ichi Yamanaka ◽  
Mamoru Fujitsuka ◽  
Yasuyuki Araki ◽  
Kentaro Tashiro ◽  
Azumi Sato ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Phenyl Group ◽  
Laser Flash ◽  
Ion Pair ◽  
Intramolecular Electron Transfer ◽  
Electron Transfer Processes ◽  
Absorption Measurements

Intramolecular electron-transfer process of porphyrin-fullerene dyad linked by phenyl buta-1,3-diynyl-phenyl unit ( ZnP - sp - C 60) was studied by laser flash photolysis. Picosecond fluorescence lifetime and transient absorption measurements revealed that photoinduced charge-separation takes place via the excited singlet state (1 ZnP *) with the rate constant of (1-2) × 1010 s −1. For the charge recombination, about a half of the radical-ion pair decayed quickly with 2.9 × 109 s −1 as evaluated from picosecond transient absorption measurements, whereas the remaining half was long-lived with slow decay (1.6 × 106 s −1) as estimated from nanosecond transient absorption measurements. The lifetime of the radical-ion pair of ZnP - sp - C 60 was longer than those of directly connected dyads with a buta-1,3-diynyl bridge and buta-1,3-diynyl-phenyl bridge by the insertion of an extra phenyl group in addition to the pyrrodino ring.

An extremely long-lived charge-separated state of zinc tetraphenylporphyrin coordinated with pyridylnaphthalene-diimide

2006 ◽  
Vol 10 (12) ◽  
pp. 1371-1379 ◽  
Author(s):  
Kenji Saito ◽  
Yukiyasu Kashiwagi ◽  
Kei Ohkubo ◽  
Shunichi Fukuzumi
Keyword(s):  
Photoinduced Electron Transfer ◽  
Lower Energy ◽  
Transient Absorption ◽  
Laser Excitation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Transient Absorption Spectrum ◽  
Triplet Excited State ◽  
Donor Acceptor

The nitrogen of pyridylnaphthalenediimide ( PyNIm ) coordinates to the metal center of zinc tetraphenylporphyrin ( ZnTPP ) to form a donor-acceptor complex: ZnTPP-PyNIm . Formation of the ZnTPP-PyNIm complex was probed by UV-vis, fluorescence and NMR spectra. The fluorescence of ZnTPP is strongly quenched and the fluorescence lifetime is shortened significantly in the complex. The transient absorption spectrum of the charge-separated state ( ZnTPP •+- PyNIm •-) is successfully detected by laser flash photolysis measurements of the ZnTPP-PyNIm system in benzonitrile. The charge-separated state of the complex produced by the photoinduced electron transfer has the longest lifetime, (450 μs) at 288 K, ever reported for donor-acceptor systems linked covalently or non-covalently in solution. However, when benzonitrile is replaced by benzene, the triplet excited state (3 ZnTPP* ), rather than the charge-separated state, is formed upon laser excitation of the ZnTPP-PyNIm complex, due to the lower energy of (3 ZnTPP* ) compared to the charge-separated state in benzene.

CO-Bond Cleavage of Esters with a Naphthyl Group in the Higher Triplet Excited State during Two-Color Two-Laser Flash Photolysis

2007 ◽  
Vol 13 (11) ◽  
pp. 3143-3149 ◽  
Author(s):  
Xichen Cai ◽  
Masanori Sakamoto ◽  
Minoru Yamaji ◽  
Mamoru Fujitsuka ◽  
Tetsuro Majima
Keyword(s):  
Excited State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Bond Cleavage ◽  
Laser Flash ◽  
Triplet Excited State
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