Spectroscopic Properties and Electronic Structures

The electronic structures of lantern-type Pt(III) dimers are discussed on the basis of a general scheme for dimers with a d -d electronic configuration, as depicted in Fig. 20. HOMO is considered either the diT or the c 8 orbital of the Pt—Pt single bond. The LUMO is usually do- orbital. In the case of the Pt(II) dimers, HOMO is now dcr orbital 

Core vibrational frequencies obtained by Raman or resonance Raman spectrophotometric technique are summarized in Table V (53, 113, 116-118). The p(Pt—Pt) bands for the pop complexes [Pt2(pop)4] (PtdDa), [Pt2(pop)4X] - (Ptdl,111)2), and [Pt2(pop)4X2] - (Pt(III)2) increase in the order expected from increasing Pt—Pt interaction (53). Resonance Raman spectra have been used frequently for the assignment of the electronic transitions of complexes as listed in the table. Also, observation of the vibrational structure in the low-temperature luminescence spectra coupled with the data in the table has been useful for considering the nature of the transition of these diplatinum complexes. The resonance Raman spectra at the intervalence band of the three mixed-valence complexes, which are stable only in the solid state, indicate that [Pt2(pop)4Cl] is a localized valence species and the bromo and iodo analogues are nearly delocalized valence species (53). 

The pyrophosphite bridged lantem-t3q)e platinum(II) complexes are known to give strong emissions. Analogous complexes with methylene-bis(phosphonite) as a bridging ligand are also emitters. Their electronic structures and associated reactivities have been extensively studied and are summarized in a review article (8). Some further information 

Raman and Resonance Raman Bands (cm ) for the Lantern-Type Diplatinum Complexes 

Photophysical properties are more thoroughly investigated with the phosphate-bridged complexes (112). Three phosphate-bridged com- 

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The best understood oxo-metallo-bis(dithiolenes) possess the general formula [MO(dithiolene)2]". Although dioxo [M02(dithiolene)2]2 (33, 34, 70, 314, 391-393) and desoxo [MX(dithiolene)2] (X = OR, SR, or SeR) (58, 327, 394) complexes have also been studied, considerably less is known of their spectroscopic properties and electronic structures. Therefore, they will not be... 

J. Structural Characteristics of the Quadruply Bridged Platinum Dimers Spectroscopic Properties and Electronic Structures... 

E.I. Solomon (2001). Spectroscopic properties and electronic structure of low-spin Fe(III)-alkylperoxo complexes Homolytic cleavage of the 0-0 bond. J.Am. Chem. Soc. 123, 8271-8290. 

Subjects of recent publications on the spectroscopic properties and electronic structure of porphyrins include the photochemically induced dichroism of [(aetio)Zn]-,380 the absorption spectra of metallo-TPP compounds in SF , Ar, and n-octane matrices,361 the Zeeman effect in the absorption spectra of Pd-porphin in n-octane single crystals,362 the electronic spectra of Cu11- and Niu-corrin derivatives,363 m.c.d. studies on porphyrins,864 866 photoelectron spectra of porphyrins and pyrroles,366 and quantum mechanical calculations on porphyrins.367 368... 

Glaser et al. (1992 a, 1993 b) investigated the three types of phosphorus analogs 5.49-5.51 (R = CH3) with ab initio techniques at the RHF/6-31G MP2(full)/ 6-31G(df,p), and MP3/6-31GVRHF/6-31G levels. Stabilities, spectroscopic properties, and electronic structures (1992 a) and the potential energy surfaces and elec-... 

Praneeth VKK, Nather C et al (2006) Spectroscopic properties and electronic structure of five- and six-coordinate iron (II) porphyrin NO complexes effect of the axial N-donor ligand. Inorg Chem 45 2795-2811... 

Spectroscopic Properties and Electronic Structure of Low-Spin Fe(lll)-Alkylperoxo Complexes Homolytic Cleavage of the 0—0 Bond. 

Radical ions - charged species with unpaired electrons - are easily generated by a number of methods that are discussed in more detail below. Their properties have been characterized by several spectroscopic techniques, and their structures and spin density contributions have been the subject of molecular orbital calculations at different levels of sophistication. The behaviour of radical ions in rearrangement and isomerization reactions as well as in bond-cleavage reactions has been extensively studied [for recent reviews see Refs. 11-13 and references cited therein]. Useful synthetic applications, such as the radical-cation-catalyzed cycloaddition [14-20] or the anfi-Markovnikov addition of nucleophiles to alkenyl radical cations [21-25], have been well documented. In... 

Only one electron is transferred to the MoFe-protein in each catalytic cycle of the Fe-protein. Thus, the cycle must be repeated eight times to accomplish the reduction of N2 + 2 H+. Where in the MoFe-protein does a transferred electron go EPR spectroscopic and other experiments with incomplete and catalyti-cally inactive molybdenum coenzyme40 have provided a clear answer. The electron is transferred first to one of the two P-clusters, both of which are close to the Fe4S4 cluster of the Fe-protein. The transfer causes an observable change both in the spectroscopic properties and in the three-dimensional structure of the P-cluster.23/40a Since protons are needed at the active site for the reduction reactions (the FeMo-coenzyme), it is probable that hydrolysis of ATP in the Fe-protein is accompanied by transport of protons across the interface with the MoFe-protein. Tire electron transfer from the P-cluster on to the FeMo-co center would be assisted by a protic force resulting from ATP cleavage. 

This review, which covers the literature up to mid-1968, presents the knowledge, which is available to date, concerning the molecular and electronic structure of pyrrole. It also surveys the spectroscopic and nonspectroscopic physical properties of pyrrole and its simple derivatives. During the past 25 years, as a result of developments and improvements in instrument design, the literature on the physicochemical properties of organic compounds has expanded rapidly. Mainly as a result of the instability or nonavailability of many compounds, however, the study of pyrroles has lagged somewhat behind... 

Porphyrin (1), the quintessential pyrrolic macrocycle, is one of the favorite structural motifs of organic chemistry [1], Its biological relevance, combined with a range of useful properties such as the rich electronic absorption spectra and the ability to coordinate metal ions, makes 1 a versatile building block for the synthetic chemist, as well as an important subject for physical investigations. Among the most conspicuous features of the porphyrin macrocycle is its aromatic character, which has a strong influence on the spectroscopic properties and chemical reactivity of 1 and its derivatives. 

DiMagno, S.G., Williams, R.A. and Therien, M.J. (1994) Facile synthesis of meso-tetrakis(perfluoroalkyl) porphyrins spectroscopic properties and X-ray crystal structure of highly electron-deficient 5,10,15,20-tetrakis (heptafluoropropyl) porphyrin. J. Org. Chem., 59, 6943. 

An extension of this approach led to the study of some simple molecules in which trivalent phosphorus is bonded to carbon by a double or a triple bond. These spectroscopic experiments have not only yielded conclusive identification but a wealth of molecular information such as geometric and electronic structural data. More importantly, the >C=P- and -CSp moieties could be considered as viable functional groups with interesting and well defined chemical properties. 

Based on spectroscopic properties, mainly electron paramagnetic resonance (EPR), the active sites of copper proteins have been classified into three groups, types I, II, and III. This nomenclature was originally applied to blue oxidases to distinguish the four copper ions contained in these proteins. The original classification has been extended to the copper sites of other proteins. The recent increase in structural information on the copper sites in proteins has, however, revealed greater diversity in the type of copper site. For instance, the type III and type II sites in ascorbate oxidase are in close proximity, forming a trinuclear site, in which all three copper ions are essential for the reactivity. Some proteins, once believed to contain a copper site with normal spectroscopic properties, and thus referred as type II, have been shown to contain copper coordinated by an unusual side chain. Therefore, in this review, new nomenclature is used to classify the copper sites more precisely with respect to their structural features and spectroscopic properties. The definitions are as follows ... 

SPECTROSCOPIC PROPERTIES, MOLECULAR STRUCTURES, ELECTROCHEMISTRY, AND ELECTRONIC STRUCTURES OF MLx 2( -C ) COMPLEXES... 

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