Room temperature electronic absorption spectrum

Figure 10.8 Room temperature electronic absorption spectrum recorded on a THF solution of 6. Bands are marked by the nominal Russell-Saunders multiplet to which the excitation occurs. (Adapted from Ref. [34], Copyright (2011) Nature Publishing Group.)...

Figure 24 displays the high energy (E > 25,000 cm-1) region of the room temperature electronic absorption spectrum for Zn(bpy)(tdt), where bpy = 2,2 -bipyridine. The LLCT transition occurs at 22,470 cm-1 (445 nm) with very weak absorption intensity (e = 72 M 1cm 1). The origin of the weak LLCT is a function of the symmetry of this psuedo-tetrahedral complex. A MO diagram for Zn(bpy)(tdt), derived from extended Hiickel calculations, is presented in Fig. 25. Irrespective of whether the metallo(diimine)(dithiolene) complex is square-planar or psuedo-tetrahedral, the point symmetry is C2V, and all intermediate geometries possess C2 symmetry. When the dithiolene and diimine planes are orthogonal (psuedo-tetrahedral geometry) the HOMO — LUMO transition represents a b2 —> b one-electron promotion and is electric dipole forbidden. However, the HOMO —> LUMO transition in a square-planar...

Figure 1 Spectral characteristics of oxidized Cu, Zn SOD (a) X-band EPR spectrum, 77 K (Used with permission from Ref 1. 1985 Division of Chemical Education, Inc) (b) room-temperature electronic absorption spectrum [protein] = 35mgmL ...

TTF)5Pt(CN)4.2 CH3CN (1) In this compound (Fig. la), the unit cell contains two independent Pt(CN)4(TTF)2 5 blocks [6]. The TTF molecules of each independent unit form centrosymmetric isolated pentamers. The Pt(CN)4 " dianions are separated by the disordered acetonitrile molecules. The structural features of the TTF molecules show that the central molecule of the pentamer is neutral, while the other four are fully oxidized, indicating mixed valence in the isolated pentamers. This new pq>e of organization has particular optical properties. The room-temperature electronic absorption spectrum (Fig. 2) e ibits the two... 

Figure 5.7 Room-temperature electronic absorption, excitation and emission spectra for 2 in aqueous solution. The excitation spectrum of 2 was recorded by monitoring emission at 400 nm. Reproduced with permission from [31]. Copyright (2004) Royal Society of Chemistry.

Although UFg has a conveniently high vapor pressure at room temperature, its absorption spectrum is much more complex than that of the metal because of the large number of vibrational and rotational states superposed on each electronic state. Moreover, at room temperature these bands are broadened sufficiently to preclude selective absorption. 

Other transient radicals such as (SCN)2 [78], carbonate radical (COj ) [79], Ag and Ag " [80], and benzophenone ketyl and anion radicals [81] have been observed from room temperature to 400°C in supercritical water. The (SCN)2 radical formation in aqueous solution has been widely taken as a standard and useful dosimeter in pulse radiolysis study [82,83], The lifetime of the (SCN)2 radical is longer than 10 psec at room temperature and becomes shorter with increasing temperature. This dosimeter is not useful anymore at elevated temperatures. The absorption spectrum of the (SCN)2 radical again shows a red shift with increasing temperature, but the degree of the shift is not significant as compared with the case of the hydrated electron. It is known that the (SCN) radical is equilibrated with SCN , and precise dynamic equilibration as a function of temperature has been analyzed to reproduce the observation [78],... 

It is worth noticing that, in contrast to what have been reported for the electron solvation dynamics in water and in alcohols at room temperature, we do not observe a hypsochromic translation of the electron absorption spectrum. 

The room temperature solution electronic absorption spectrum of (L-N3) MoO(bdt) is presented in Fig. 6. This spectrum is representative of virtually all (L-A i)MoO(dithiolene) complexes (19, 23) with the possible exception of (L-/Vi)MoO(qdt) (20, 22), where qdt = quinoxaline-2,3-dithiolate, see below. However, the transitions observed for (L-A MoChtdt) (19), where tdt = toluene-1,2-dithiolate, are generally shifted to slightly lower energies relative... 

Figure 6. Room temperature solution electronic absorption spectrum of (L-AyMoCXbdt). [Adapted from (23).]...

Figure 2. The electronic absorption spectrum of poly(di n-hexylsilane). (a) solution in cyclohexane, (b) a solid film (1) recorded after baking to 100 C 1 minute (2) after standing for 10 minutes at room temperature.

At room temperature, flash absorption studies revealed that an electron acceptor designated Aj was functioning under conditions where F and Fg were presumably reduced [37]. The state (P-700, A2 ) is formed upon flash excitation and recombines with tiu — 250 jUS. The difference spectrum due to its formation was analysed into contributions of P-700 and A2. The latter includes mainly a small and broad bleaching around 430 nm, and perhaps some absorption shifts in the red. These absorption properties, together with the disappearance of the A2 absorption signal when iron-sulfur proteins are denatured [38,39], indicate that Aj may be an iron-sulfur centre. 

An intervalence electron-transfer band, not present in the Fe analogue, was observed in the room temperature electronic spectrum at 13 800cm . Mossbauer spectra indicated distinct Fe" and Fe " sites at 17K while at 300 K a single absorption was observed. The thermal barrier to electron transfer in the trimer was estimated as about 470 cm. Triiron clusters of this type, in the presence of zinc powder, acetic acid, aqueous pyridine and oxygen, are reported " to effect the oxidation of saturated hydrocarbons. The exchange interactions in the series of complexes [Fe2 M 0(02 CMe)spyj] py (M = Mg, Mn, Co, Ni or Zn) which, M = Ni excepted, are isomorphous with the mixed valence complex referred to above have been measured. 

Figure I Electronic absorption spectrum of 1.42 x 10 M CH3Re03 in n-hexane at room temperature (1-cm cell).

Figure 3.19. Infrared absorption spectra of k-(ET)2. Cu2(CN)3 recorded at room temperature (RT) and at 7= 12 K (note the scale change on the abscissa at 2000 cm ). Inset electronic absorption spectrum observed at RT with a the mean absorption coefficient.

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