Electronic absorption spectra features

The core of the iron storage protein ferritin consists of a hydrated ferric oxide-phosphate complex. Various models have been proposed which feature Fe111 06 oct., Fe111 O4 tet. or Fe111 O4 tet. Fe111 06 oct. complexing the first listed is preferred by Gray (99) on the basis of the electronic absorption spectrum. The protein very closely related to ferritin which occurs in the mold Phycomyces blakesleeanus contains... 

The 5 K mull MCD-absorption overlay of (L-/V )MoO(bdt) is shown in Fig. 7. The electronic absorption spectrum exhibits five distinct features in the... 

Figure 2. Excited-state spectral features ofD -CuCl/-. A Energy level diagram showing the ligand-field (d - d) and charge-transfer (CT) optical transitions. The intensity of the transitions is approximated by the thickness of the arrow with the very weak ligand-field transitions represented as a dotted arrow. B Electronic absorption spectrum for D4h-CuCl42 (12). C Schematic of the a and tt bonding modes between the Cu 3dx2 y2 and Cl 3p orbitals.

The major feature of a transition metal coordination complex is the presence of an incomplete d shell in which the energies of the d orbitals, which are no longer fivefold degenerate, are determined by the stereochemistry of the complex. The electronic absorption spectrum and, therefore, the color of the complex depends upon the arrangement and energies... 

The calculations predict that the ground state of phenylnitrene has triplet multiphcity ( A2) in accordance with the earlier EPR experiment of Smolinsky et al. Figure 5.13 represents the electronic absorption spectrum of M9 in an Ether-pentane-alcohol (EPA) matrix at 77 There is a strong sharp band at 308 run, a broad structured band at 370 run, and a broad unstructured feature, which tails out to 500... 

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... 

The cytochromes P-450 are also known, and in fact named, for their novel spectral properties relative to other heme systems. Specifically, this derives from the 450-nm Soret band in the electronic absorption spectrum of the ferrous-CO complex. The ferrous-CO derivatives of most heme enzymes display this feature at 420 run [20-29, 36]. 

Spectroscopic studies have demonstrated that the MMOHs have the stable diiron centers of diferric Fe(III)Fe(III), mixed-valent Fe(II)Fe(III), and diferrous Fe(II)Fe(II) redox states [33]. Although the electronic absorption spectrum of the MMOH from M. capsulatus (Bath) shows an absorption peak at 280 nm due to the protein, there is no significant optical features that can be attributed to the iron prosthetic group. The Mdssbauer Fe enriched spectrum of the isolated MMOH from M. trichosporium OB3b shows two quadrupole doublets of equal area. Their parameters at 4.2 K are AEq =1.16 mm/s and the isomer shift 5 = 0.51 mm/s for site 1 and AEq = 0.87 mm/s and the isomer shift 6 = 0.50 mm/s for site 2 [34]. The Mdssbauer spectrum of the isolated MMOH from Af. capsulatus (Bath) at 80 K shows a quadrupole doublet having AEq = 1.05 mm/s and the isomer shift 6 of 0.50 mm/s [35]. These spectra show that the isolated MMOH is diferric form. 

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