Lanthanides, coordination compounds

Absorption spectra and structure of lanthanide coordination compounds in solution. K. B. Yatsi-mirskii and N. K. Davidenko, Coord. Chem. Rev., 1979, 27, 223-273 (255). 

Misra, S.N., Gagnani, M.A., Devi, I, and Shukla, R.S. (2004) Biological and clinical aspects of lanthanide coordination compounds. Bioinorganic Chemistry and Applications, 2, 155-192. 

Lanthanide /3-diketonates are complexes of /3-diketone ligands (1,3-diketones) with lanthanide ions. These complexes are the most popular and the most intensively investigated luminescent lanthanide coordination compounds (see P-Diketonate). Three main types of lanthanide(III) /3-diketonate complexes have to be considered fra complexes, Lewis base adducts of the tris complexes (ternary lanthanide /3-diketonates), and tetrakis complexes. Most Eu +/3-diketonate complexes show an intense visible luminescence, but many /3-diketonates are not good ligands to sensitize the luminescence of Tb + ions. NIR luminescence can be... 

Yatsimirskii, K. B. Davidenko, N. K. Absoiption Spectra and Structure of Lanthanide Coordination Compounds in Solution, Coord. Chem Revs. 1979,27, 223. 

UV-visible absorption spectroscopy is most frequently used as a method for characterizing chemical equilibria. There are, however, some difBculties associated with its use for investigating the successive formation of lanthanide coordination compounds. The molar absorption coefficients of f-f transitions are very low (typically 0.1-10 mol cm" ) and the shifts upon stepwise complexation are very small, typically a few cm" only, so that absorption spectra of complexed species generally overlap. 

S. F. Mason, Localized systems mechanisms for f-f transition probabilities in lanthanide coordination compounds, Journal of the Less Common Metals, 93, 45-58 (1983). 

Carbon monoxide [630-08-0] (qv), CO, the most important 7T-acceptor ligand, forms a host of neutral, anionic, and cationic transition-metal complexes. There is at least one known type of carbonyl derivative for every transition metal, as well as evidence supporting the existence of the carbonyls of some lanthanides (qv) and actinides (1) (see AcTINIDES AND THANSACTINIDES COORDINATION COMPOUNDS). 

A closely related method does not require conversion of enantiomers to diastereomers but relies on the fact that (in principle, at least) enantiomers have different NMR spectra in a chiral solvent, or when mixed with a chiral molecule (in which case transient diastereomeric species may form). In such cases, the peaks may be separated enough to permit the proportions of enantiomers to be determined from their intensities. Another variation, which gives better results in many cases, is to use an achiral solvent but with the addition of a chiral lanthanide shift reagent such as tris[3-trifiuoroacetyl-Lanthanide shift reagents have the property of spreading NMR peaks of compounds with which they can form coordination compounds, for examples, alcohols, carbonyl compounds, amines, and so on. Chiral lanthanide shift reagents shift the peaks of the two enantiomers of many such compounds to different extents. 

Luminescence of Lanthanide Ions in Coordination Compounds and Nanomaterials... 

Coordination compounds composed of tetrapyrrole macrocyclic ligands encompassing a large metal ion in a sandwich-like fashion have been known since 1936 when Linstead and co-workers (67) reported the first synthesis of Sn(IV) bis(phthalocyanine). Numerous homoleptic and heteroleptic sandwich-type or double-decker metal complexes with phthalocyanines (68-70) and porphyrins (71-75) have been studied and structurally characterized. The electrochromic properties of the lanthanide pc sandwich complexes (76) have been investigated and the stable radical bis(phthalocyaninato)lutetium has been found to be the first example of an intrinsic molecular semiconductor (77). In contrast to the wealth of literature describing porphyrin and pc sandwich complexes, re-... 

Gillard, R. C., The Cotton Effect in Coordination Compounds Gillespie, Ronald J., see Sawyer, Jeffery F. Glasel, Jay A., Lanthanide Ions as Nuclear Magnetic Resonance Chemical Shift 7 215... 

Leonard JP, Nolan CB, Stomeo F, Gunnlaugsson T (2007) Photochemistry and photophysics of coordination compounds. In Balzani V, Campagna S (eds) Topics in Current Chemistry Photochemistry and Photophysics of Coordination Compounds. Vol II, Lanthanides, 281 1 13... 

The Lu—C cr-bonding distances range from 2.425(15) to 2.501(17) A. These distances are approximately 0.2 A shorter than the corresponding distance for a pentahapto cyclopentadienide lutetium bond as predicted from ionic radii. Coordination about the lutetium atom is a slightly distorted tetrahedron. The formal coordination number of four is extremely low for the lanthanides. The only other lanthanide complex with such a low coordination number is the 3-coordinate compound [Lu N(SiMes)2 3] 131). In both cases, the low coordination number is stabilized by the use of bulky hgands. 

Tris(i/5-cyclopentadienyl)lanthanides were the first authentic organolanth-anides to be prepared1 and bis(t/5-cyclopentadienyl)lanthanide(II) compounds have played a germinal part in the development of lower oxidation state organolanthanide chemistry.2 These cyclopentadienyls are sources of coordination compounds of structural interest and are reagents for the synthesis of other organolanthanides, for example, bis- and mono(t)5-cyclopentadienyl)lanthanide(III) derivatives.2... 

The study of coordination compounds of the lanthanides dates in any practical sense from around 1950, the period when ion-exchange methods were successfully applied to the problem of the separation of the individual lanthanides,131-133 a problem which had existed since 1794 when J. Gadolin prepared mixed rare earths from gadolinite, a lanthanide iron beryllium silicate. Until 1950, separation of the pure lanthanides had depended on tedious and inefficient multiple crystallizations or precipitations, which effectively prevented research on the chemical properties of the individual elements through lack of availability. However, well before 1950, many principal features of lanthanide chemistry were clearly recognized, such as the predominant trivalent state with some examples of divalency and tetravalency, ready formation of hydrated ions and their oxy salts, formation of complex halides,134 and the line-like nature of lanthanide spectra.135... 

The preceding discussion of the relationships between excited state electronic structure and photochemical reactivity focused primarily upon coordination compounds containing cP or low-spin cP transition metals. These relationships are generally applicable, however, to complexes of other d transition elements, the lanthanides and the actinides. A brief survey of the photochemical reactions of these latter systems is presented below. 

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