Intersystem crossing yield

D. Lynch, J. F. Endicott. A Pulsed Photoacoustic Microcalorimeter for the Detection of Upper Excited-State Processes and Intersystem Crossing Yields. Appl. Spectroscopy 1989, 43, 826-833. 

Tryptophan at 77 K in rigid solution has a phosphorescence quantum yield of 0.17(20) and a lifetime of 6 s. These values at 77 K are relatively invariant from protein to protein and do not vary significantly between buried and exposed tryptophans.(21,22) If one assumes that the intersystem crossing yield is a constant, a calculation of the quantum yield of indole phosphorescence can be roughly estimated from the lifetimes. The phosphorescence yield is related to lifetime by... 

In the triplet counting technique the substance whose intersystem crossing yield is to be determined is used as a sensitizer for the photoisomerization of piperylene (1,3-pentadiene). Under conditions where essentially all of the sensitizer triplets are intercepted by diene, the quantum yield of isomerization is directly proportional to the intersystem crossing yield of the sensitizer. If the diene interferes with sensitizer singlets however, the yield of triplets will fall, resulting in an anomalously low value for 0,. 

Explanation of Table ET = triplet energy in kcal/mole from O—O phosphorescence band. Je = intersystem crossing yield from sensitized olefin isomerization method. tp - phosphorescence lifetime in a rigid glass at —196° (sec). Repetition of the data compiled by Arnold63 has in general been avoided. 

If excited states underwent only reactions which produce readily measurable effects, determination of intersystem crossing yields would be straightforward. For example, the earliest attempts to estimate... 

At least four applications of this technique can be cited. Quantum yields for triplet formation in benzene108 and fluorobenzene109 have been estimated by comparing the phosphorescence yields of biacetyl produced by sensitization to that produced by direct irradiation. Intersystem crossing yields of a number of organic molecules in solution have been obtained by measuring the quantum yield with which they photosensitize the cis-trans isomerization of piperylene (1,3-pentadiene) and other olefins.110 As will be discussed later, the triplet states of... 

The first example of Ndm and Ybm luminescence sensitized by Ru11 and ferrocene appeared in 2000. The authors noticed that [Ru(bpy)3]2+ has an intersystem crossing yield near unity and that it enables excitation with visible light up to 500 run. On the other hand, ferrocene has weaker absorption bands in the visible spectrum, but its low-lying triplet state (wl3 300 cm-1) matches fairly well the Ndm (4F3/2, 11300 cm-1) and Ybm (2Fs/2,... 

Radiationless Processes. The primary processes of 2-pentanone are similar to those of the other ketones. The dominant pathway for the depopulation of the first excited singlet state at lower energies is the S —intersystem crossing. Both a-cleavage (type I) and Norrish type II processes can occur from the singlet state and from the triplet state. The intersystem crossing yield has only been measured in solution (see ref. 247) With 313-nm excitation, a value of isC = 0.81 was measured by... 

King SM, Rothe C, Dai D, Monkman AP (2006) Femtosecond ground state recovery Measuring the intersystem crossing yield of polyspirobifluorene. J Chem Phys 124(23) 234903... 

---