Excited-State Assignments

To determine the nature of the photoactive excited state in these hydride complexes, we examined the electronic absorption spectra of a series of iridium hydride complexes. The spectra showed only a few shoulders on a rising absorption into the uv, and no definitive excited state assignments could be made. 

TRRR measurements for [Re(dppz-X)(C0)3Cl], where dppz is dipyrido[3, 2-a 2/,3/-c]phenazine and X = Br and COOC2H5 were examined for dppz-X vibrations. The results were in agreement with a 3MLCT excited state assignment [71]. 

These include atomic spectral patterns, vibrational modes, bond covalency, and ground- and excited-state assignments consistent with the spin state and bonding structure. 

Photoinduced Electron-Transfer Reactions 13.4.1. Excited-State Assignments... 

Buckminsterfullerene (C q) has not escaped the attention of photochemists. Determination of luminescence and absorption spectra of 60 films has made some excited state assignments possible for this molecule. Some work has also been reported on the triplet state properties. 

A somewhat different situation is presented by the pressure effects seen in the emission spectra of the rhenium(I) complex ReBr(CO)3(phen) and the copper(I) cluster Cu4I4py4 (where py = pyridine) and related species. The former displays strong MLCT emission in ambient temperature fluid benzene [35] solutions while the latter displays a strong emission from an cluster centered (CC) excited state assigned as having mixed d-to-s metal-centered and iodide-to-copper charge-transfer character [36]. In each case, the emission is markedly dependent on the rigidity of the medium, and... 

The eight-coordinate (fi complexes [Mo(CN)g]" and [W(CN)g] undergo two wavelength-dependent photoreactions. Photolysis in the short-wavelength (254 nm) region leads to efficient photoelectron production from an excited state assigned as CTTS in character. Irradiation... 

Found in Tables 1 a-d is a list of known emissive metallo-1,2-enedithiolate complexes. The tables are arranged by ligand type and include excitation and emission maxima, excited state assignment, and lifetimes. 

There are emissive homoleptic bis(l-2-enedithiolate) Pt, Zn, Cd, and Hg dianions. Even though these complexes are isostructural, their excited state assignments differ. The homoleptic platinum complexes, [Pt(mnt)2] " and [Pt(qdt)2] ", have a lowest lying MLCT transition whereas the corresponding group UB complexes, [M(mnt)2] " (M = Zn, Cd, and Hg), [Zn(qdt)2] ", and [Zn(tdt)2] ", have what is best described as a lowest lying ILCT transition [16,29,36]. 

Complex Absorbance Km (nm) Emission Km (nm) glass solution Lifetime (ns) 298 K solution Excited state assignment Ref. 

Formally, a mechanism may be suggested which retains the "common excited state" assignment for J625 is assumed that BR q is... 

Any discussion of the feasibility of an excited-state assignment for either J525 should also consider fluorescence emission... 

Itagaki et al [76] have proposed that the decay kinetics observed for fluid solutions of poly(l-methoxy-4-vinylnaphthalene) (PMVN) may be explained in terms of two excimer species in addition to excited monomer. The proposal is based on variations in steady-state l,3-di(4-methoxy-1-naphthyl)propane (BMP) [77,78], presumes that the lower energy excimer comprises the normal structure with fully overlapped aromatic rings, whereas the second excimer is thought to comprise a partially overlapped structure. Steady state spectroscopy indicated a reasonable degree of evidence that three excited state species do indeed exist in the sterically hindered naphthalene systems. However the spectral and numerical deconvolution procedures adopted make the separation of intensity components used in the kinetic analysis, necessary for excited state assignment, rather optimistic. 

Since the 1200 nm band exhibits dipole-aUowed z-polarization, the excited state must be of Big or B2g symmetry. There is then only one possible excited-state assignment among the n - S and d n excitations, namely, d n ... 

Dalton, J.C., Shen, M., and Snyder, J.J., Mechanistic photochemistry of P,y-unsaturated ketones. An alternative excited state assignment for the 1,3-acyl shift reaction of alkyl P,y-enones, /. Am. Chem. Soc., 98, 5023,1976. 

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