Transition metal complexes Mossbauer spectroscopy

Anionic Rearrangement of Organosilicon and Germanium Compounds, 16, 1 Application of 13C-NMR Spectroscopy to Organo-Transition Metal Complexes, 19, 257 Applications of " "Sn Mossbauer Spectroscopy to the Study of Organotin Compounds, 9, 21... 

The incorporation of anionic transition-metal complexes into PPy has enabled a range of spectroscopic techniques to be employed (UV-visible, EPR and Mossbauer spectroscopy) which have provided information about the counter-anion s structure and local environment. A relationship is apparent between the room-temperature conductivity and the position of the absorption maximum in the 300-500 nm region of the UV-visible spectrum. The conjugation length of the bipolarons seems to be an important factor that... 

The chemistry of transition metal complexes containing alkylidene, allenylidene, and cumulenylidene ligands, [L M]=C(=C) =CRR n > 2), has been reviewed.An extensive series of Cp (dppe)Fe compounds with an end-bound hydrocarbon ligand have been synthesized, and the iron-carbon bonding studied using Fe Mossbauer spectroscopy. 

Of special Interest as O2 reduction electrocatalysts are the transition metal macrocycles In the form of layers adsorptlvely attached, chemically bonded or simply physically deposited on an electrode substrate Some of these complexes catalyze the 4-electron reduction of O2 to H2O or 0H while others catalyze principally the 2-electron reduction to the peroxide and/or the peroxide elimination reactions. Various situ spectroscopic techniques have been used to examine the state of these transition metal macrocycle layers on carbon, graphite and metal substrates under various electrochemical conditions. These techniques have Included (a) visible reflectance spectroscopy (b) laser Raman spectroscopy, utilizing surface enhanced Raman scattering and resonant Raman and (c) Mossbauer spectroscopy. This paper will focus on principally the cobalt and Iron phthalocyanlnes and porphyrins. 

The results from Mossbauer spectroscopy in applied magnetic fields clearly prove that the spin transition in the dinuclear compounds under study proceeds via [HS-HS][HS-LS][LS-LS]. Simultaneous spin transition in both metal centres of the [HS-HS] pairs converting the dinuclear pairs directly to [LS-LS] pairs can apparently be excluded, at least in the present systems. This is quite surprising in view of the fact that the present dinuclear complexes are centrosymmetric (in other words the two metal centres have identical surroundings, and should therefore experience the same ligand field strength and, consequently, thermal spin transition should occur simultaneously in both centres). 

A number of transition metal nuclei can be studied by Mossbauer techniques (e.g., Fe, Ni, Ru, W, Os, Ir, and Pt). Of these, only Ir, Ru, and Fe have been used to study nitrosyl bonding. The most detailed studies have been on the well-known iron complexes [Fe(CN)5(NO)] - (87. 89) and [Fe(NO)(dtc)z] (88-90) (dtc is N,N-dialkyldithiocarbamato). In the latter, high-spin/low-spin equilibria can be followed by Fe Mossbauer spectroscopy, and the Mossbauer parameters agree well with data from electron spin resonance (ESR) spectroscopy in determining the ground states of these complexes. 

Application of Mossbauer Spectroscopy in the Investigations of Some Transition Metal Nitrosyl Complexes... 

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