Electron paramagnetic resonance excited states

The X-ray structure of zinc naphthalocyanate has been determined with Zn—N bond lengths of 1.983(4) A.829 Pentanuclear complexes with a zinc phthalocyanine core and four ruthenium subunits linked via a terpyridyl ligand demonstrate interaction between the photoactive and the redox active components of the molecule. The absorbance and fluorescence spectra showed considerable variation with the ruthenium subunits in place.830 Tetra-t-butylphthalocyaninato zinc coordinated by nitroxide radicals form excited-state phthalocyanine complexes and have been studied by time-resolved electron paramagnetic resonance.831... 

Excitation between electronic spin states Electron paramagnetic resonance, EPR... 

Time-resolved electron paramagnetic resonance served to detected the short-lived triplet state of the keto tautomer (238) of 2-(2-hydroxyphenyl)benzothiazole (239) generated by excited state intramolecular proton transfer (92CC641). 

Crystal reaction study mechanistic tools, 296 computer simulation, 297 electronic spectroscopy, 298 electron microscopy, 298 electron paramagnetic resonance (EPR), 299 nuclear magnetic resonance (NMR), 298 Raman spectroscopy, 299 Crystal reaction study techniques crystal mounting, 308 decomposition limiting, 309 polarized IR spectroscopy, 309 temperature control, 308 Cycloreversions, adiabatic photochemical involving anthracenes, 203 excited state properties of lepidopterenes, 206... 

Sporer (45) gives conclusive evidence for the presence of a radical intermediate [electron paramagnetic resonance (EPR), and radical polymerization] but fails to describe the path by which the intermediate radical is converted to the cation. As possibilities he cites the crossing of the excited molecule to another, undescribed state from which it reacts, and reaction during the internal conversion step in which a molecule in the excited state converts to a molecule in a high vibrational ground state. Kinetic studies by Brown et al. (46) support the formation of ion-pair intermediates in the dark reactions. 

The triplet state of the unpaired electrons of oxygen play a key role in both the photon excitation and the potential relaxation mode of the excited chromophores of vision. The paramagnetic properties of oxygen provide a definitive method of determining whether oxygen is present in the chromophores of vision, a condition that would eliminate the Shiff-base theory of retinol reaction with opsin to form rhodopsin. The evaluation of the electron paramagnetic resonance of the chromophores of vision is discussed in Chapter 7. 

Electron paramagnetic resonance (EPR) has been used in kinetics to detect various states of atoms and radicals, which may be reactants, products or transient intermediates [17]. EPR has been used to detect vibrationally excited OH radicals from reactions such as... 

---