Excited-state properties

The uranyl ion luminesces in fluid solutions at room temperature2 201 202 thus providing a tool for the study of bimolecular excited state processes. In several cases, however, this study is complicated by the fact that the uranyl ion forms complexes with a variety of chemical species, so that it is often difficult to distinguish between intramolecular photochemical processes involving uranyl ion-ligand complexes and intermolecular photochemical processes involving reaction between an electronically excited UO + species and the substrate2,201,202  

The lifetime is affected by counter ions202,213 U02+ concentration212,214 and temperature212,214 Flash-photolysis experiments have shown that the lowest excited state possesses absorption in the visible and near IRregions212,2I5 218 which may be used to monitor excited state bimolecular processes. 

The standard reduction potential of the U02+/U02 couple is +0.06 V219 the oxidation potential of UO + is unknown but is expected to be extremely high. Thus, the lowest excited state of U02+, U02+, is expected to be a very good oxidant [Eq. (95)] and a very poor reductant (see Section 5). 

Photooxidation by UC 2+ has been demonstrated for a variety of organic and inorganic species. We will only review those systems in which an intermolecular 

If Q bears a hydrogen atom, then it may lose it in the form of a proton in a step concerted with (96) to give a neutral free radical (Eq. 97)  

Department of Chemistry G. Ciamician, University of Bologna, Via Selmi 2, 40126 Bologna, Italy e-mail paola.ceroni unibo.it 

Ceroni (ed.). The Exploration of Supramolecular Systems and Nanostructures by Photochemical Techniques, Lecture Notes in Chemistry 78, 

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Similar to the fullerene ground state the singlet and triplet excited state properties of the carbon network are best discussed with respect to the tliree-dimensional symmetry. SurjDrisingly, the singlet excited state gives rise to a low emission fluorescence quantum yield of 1.0 x 10 [143]. Despite the highly constrained carbon network,... 

Ebbesen T W, Tanigaki K and Kuroshima S 1991 Excited-state properties of Cgg Chem. Phys. Lett. 181 501-4... 

Tanigaki K, Ebbesen T W and Kuroshima S 1991 Picosecond and nanosecond studies of the excited state properties of C g Chem. Phys. Lett. 185 189-92... 

Excited-state properties of the cyanine and related dyes are complex. Most cyanine dyes exhibit small Stokes shifts for duorescence maxima. Typical carbocyanines (1) with n = 1 show 14- to 16-nm shifts in methanol solution with low quantum efficiencies for duorescence (Op ) of less than 0.05. The diearbocyanine analogues also show small Stokes shifts but higher quantum yields (Lpj = 0.3-0.5). 

A major discrepancy that remains unresolved in the excited-state properties of the [Fe384]° cluster in D. gigas Fdll concerns the existence of a low-lying, fully valence-delocalized state that becomes populated at temperatures above 25 K. 8uch a state is clearly apparent in the temperature-dependent Mossbauer studies of reduced D. gigas Fdll (29) and P. furiosus 3Fe Fd (198) and is represented by one quad-rupole doublet with AEq 0.9 mm/s and S = 0.45 mm/s. 8uch a... 

Another interesting example of aurophilic interactions influencing electronic excited state properties is the unusual photochemical cis to trans conversion observed in dinudear goldhalide bis(diphenylphosphino)ethylene complexes, Au2X2(dppee)... 

Pan, Q.-J. and Zhang, H.-X. (2003) Aurophilic attraction and excited-state properties of binuclear Au(I) complexes with bridging phosphine and/or thiolate ligands An ah initio study. Journal of Chemical Physics, 119, 4346-4352. 

As a consequence of the Hohenberg-Kohn theorem [14], a non-degenerate ground state electron density p(r) determines the Hamiltonian H of the system within an additive constant, implying that the electron density p(r) also determines all ground state and all excited state properties of the system. 

Stanton JF, Bartlett RJ (1993) The equation of motion coupled-cluster method - a systematic biorthogonal approach to molecular-excitation energies, transition-probabilities, and excited-state properties. J Chem Phys 98 7029... 

Shukla MK, Leszczynski J (2002) A theoretical investigation of excited-state properties of die adenine-uracil base pair. J Phys Chem A 106 1011—1018... 

A review16 with 89 references is given on the excited state properties of the low valent (0 and + 1) bi- and trinuclear complexes of Pd and Pt. Physical characterization of the nature of the lowest energy excited states along with their photoinduced chemical reactivities toward oxidative additions is discussed. 

While excited-state properties of monomeric carotenoids in organic solvents have been the subject of numerous experimental and theoretical studies (Polfvka and Sundstrom 2004), considerably less is known about excited states of carotenoid aggregates. Most of the knowledge gathered so far stems from studies of aggregation-induced spectral shifts of absorption bands of carotenoid aggregates that are explained in terms of excitonic interaction between the molecules in the aggregate. 

Parusel ABJ, Kohler G (2001) Influence of the alkyl chain length on the excited-state properties of 4-dialkyl-benzonitriles. A theoretical DFT/MRCI study. Int J Quantum Chem 84(2) 149-156... 

Shinohara Y, Arai T (2008) Effect of methoxy substituents on the excited state properties of stilbene. Bull Chem Soc Jpn 81(11) 1500—1504... 

Stiel, H., Teuchner, K., Paul, A., Leupold, D. and Kochevar, I. E. (1996). Quantitative comparison of excited state properties and intensity- dependent photosensitization by rose bengal. J. Photoch. Photobiol. B 33, 245-54. 

Ground and excited state properties and processes affecting FRET parameters... 

Due to the simplicity and the ability to explain the spectroscopic and excited state properties, the MO theory in addition to easy adaptability for modern computers has gained tremendous popularity among chemists. The concept of directed valence, based on the principle of maximum overlap and valence shell electron pair repulsion theory (VSEPR), has successfully explained the molecular geometries and bonding in polyatomic molecules. 

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