The electronic spectra of

The electronic spectra of benzenoid systems differ in a characteristic manner from their acyclic analogues. Thus benzene, unhke hexatriene. 

Use Configuration Interaction to predict the electronic spectra of molecules. The Configuration Interaction wave function computes a ground state plus low lying excited states. You can obtain electronic absorption frequencies from the differences between the energies of the ground state and the excited states. 

The acidity of a lydrocarbon can be determined in an analogous way. If the electronic spectra of the neutral and anionic forms are sufficiently different, the concentrations of each can be determined directly, and the equilibrium constant for... 

Apart from TiO and the lower halides already mentioned, the chemistry of these metals in oxidation states lower than 3 is not well established. Addition compounds of the type [TiCl2L2] can be formed with difficulty with ligands such as dimethylformamide and acetonitrile, but their magnetic properties suggest that they also are polymeric with appreciable metal-metal bonding. However, the electronic spectra of Ti in TiCl2/AlCl3 melts and also of Ti incorporated in NaCl crystals (prepared by... 

Dilute solid solutions of Ln ions in Cap2 may be reduced by Ca vapour to produce Ln ions trapped in the crystal lattice. By their use it has been possible to obtain the electronic spectra of Ln ions. 

The electronic spectra of actinide compounds arise from three types of electronic transition ... 

Theoretical studies of the relative stabilities of tautomers 14a and 14b were carried out mostly at the semiempirical level. AMI and PM3 calculations [98JST(T)249] of the relative stabilities carried out for a series of 4(5)-substituted imidazoles 14 (R = H, R = H, CH3, OH, F, NO2, Ph) are mostly in accord with the conclusion based on the Charton s equation. From the comparison of the electronic spectra of 4(5)-phenylimidazole 14 (R2 = Ph, R = R3 = H) and 2,4(5)-diphenylimidazole 14 (R = R = Ph, R = H) in ethanol with those calculated by using ir-electron PPP method for each of the tautomeric forms, it follows that calculations for type 14a tautomers match the experimentally observed spectra better (86ZC378). The AMI calculations [92JCS(P1)2779] of enthalpies of formation of 4(5)-aminoimidazole 14 (R = NH2, R = R = H) and 4(5)-nitroimidazole 14 (R = NO2, R = R = H) point to tautomers 14a and 14b respectively as being energetically preferred in the gas phase. Both predictions are in disagreement with expectations based on Charton s equation and the data related to basicity measurements (Table III). These inconsistencies may be... 

The electronic spectra of radicals 101 and 102 have two sets of absorption bands in the visible andnear-UV regions (Fig. 1, Table XXXII). 

Moffitt, W., Proc. Roy. Soc. [London) A218, 486, The electronic spectra of conjugated hydrocarbons." Allyl radical treated as an example. 

Very large hypsochromic shifts of — 20 to — 87 nm in the electronic spectra of the diazonium salt 4.19 in the presence of 15-crown-5, and even 12-crown-4, were found by Walkow (1988). Obviously they cannot be due to insertion complexes. 

The electronic spectra of tetragonal metal complexes — analysis and significance. A. B. P. Lever, Coord. Chem. Rev., 1968, 3,119-140 (31). 

The electronic spectra of the hexafluoro-complexes of the first row transition series. G. C. Allen and K. D. Warren, Struct. Bonding (Berlin), 1971, 9, 50-138 (137). 

Vibrational fine structure in the electronic spectra of transition metal compounds an experimental survey. M. Cicslak-Golonka, A. Bartecki and S. P. Sinha, Coord. Chem. Rev., 1980, 31, 251-288... 

Cooperative effects in the electronic spectra of inorganic solids. P. Day, Inorg. Chim. Acta, Rev., 1969, 3, 81-97 (84). 

The development of molecular orbital theory (MO theory) in the late 1920s overcame these difficulties. It explains why the electron pair is so important for bond formation and predicts that oxygen is paramagnetic. It accommodates electron-deficient compounds such as the boranes just as naturally as it deals with methane and water. Furthermore, molecular orbital theory can be extended to account for the structures and properties of metals and semiconductors. It can also be used to account for the electronic spectra of molecules, which arise when an electron makes a transition from an occupied molecular orbital to a vacant molecular orbital. 

A number of investigations of the copper-group oxides and dioxygen complexes have been reported. The electronic spectra of CuO, AgO, and AuO were recorded in rare-gas matrices (9), and it was found that the three oxides could be formed effectively by cocondensation of the metal atoms with a dilute, oxygen matrix, followed by near-ultraviolet excitation. The effective wavelengths for CuO or AgO formation were X > 300 nm and for AuO was X > 200 nm. In addition, the laser fluorescence spectrum of CuO in solid Ar has been recorded (97). 

The electronic spectra of a range of dithio- and perthiocarboxylato-nickel(II) complexes and their pyridine adducts show the presence of a variety of structures in solution, but complete interpretation of the spectra was prevented by lack of a complete MO treatment of these complexes (378). 

Allen GC, Warren KD (1971) The Electronic Spectra of the Hexafluoro Complexes of the First Transition Series. 9 49-138... 

Allen GC, Warren KD (1974) The Electronic Spectra of the Hexafluoro Complexes of the Second and Third Transition Series. 19 105-165 Alonso JA, Baibas LC (1993) Hardness of Metallic Clusters. 80 229-258 Alonso JA, Baibas LC (1987) Simple Density Functional Theory of the Electronegativity and Other Related Properties of Atoms and Ions. 66 41-78 Andersson LA, Dawson JH (1991) EXAFS Spectroscopy of Heme-Containing Oxygenases and Peroxidases. 74 1-40 Antanaitis BC, see Doi K (1988) 70 1-26... 

The Tz orbitals of butadiene (Scheme 18) qualitatively obtained from the orbitals of ethylenes are also supported by the electronic spectra of polyenes. The HOMO of butadiene is higher that the HOMO of ethylene since the former is the out-of-phase combination of the latter. The LUMO of butadiene is the in-phase combination of the LUMOs of ethylene and lies lower than the LUMO of ethylene. The energy gap between the HOMO and the LUMO is smaller in butadiene. In fact, the wavelength ( m ) is longer for butadiene (217 nm) than for ethylene (165 nm). The wavelength increases with the chain length of the polyenes. 

It is added that for molecules I, III and VII the excitation energies, particularly the lowest ones, calculated assuming the full symmetries D21) (cf. Table 1), turn out to be considerably smaller than those calculated assuming the reduced symmetries (Cj ) and experimental values. Recent calculations on the electronic spectra of pentalene and heptalene by Fernandez-Alonso and Palou ° do not agree with this conclusion. 

Another type of dimer is that which consists of two radical molecules stacked on each other in a n-n interaction. Such dimers have been observed e.g., with 9-ethylphenazyl radical, tetramethyl-p-phenylenediamine cation radical (167), 7,7,8,8-tetracyanoquinodimethane radical anion (168), methylviologen cation radical (169), and l-alkyl-4-carbomethoxypyridinyl radicals (170). Attempts have been reported (170, 171) to interpret the electronic spectra of dimers of this kind by MO calculations. 

Copper(II) complexes of 2,6-lutidylphenylketone thiosemicarbazone, 38, have been prepared from copper(II) chloride and copper(II) bromide [186]. Similar to 2-pyridyl thiosemicarbazones, 38-H coordinates via the ring nitrogen, the azomethine nitrogen and the thiol sulfur based on infrared spectral assignments. Magnetic susceptibilities and electron spin resonance spectra indicate dimeric complexes and both are formulated as [Cu(38-H)A]2 with bridging sulfur atoms. The electronic spectra of both halide complexes show band maxima at 14500-14200 cm with shoulders at 12100 cm S which is consistent with a square pyramidal stereochemistry for a dimeric copper(II) center. 

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