The rare earth elements form a fascinating group, resembling each
other very closely in both physical and chemical properties. The
close similarity of the behaviour of the elements led to
difficulties in isolation of the elements in a state of high
purity. Now that the separation and purification of these elements
have been achieved, the chemistry and the industrial applications
of the rare earth elements are drawing the attention of many
scientists in the world, especially countries which possess vast
reserves of rare earth minerals. Some of the applications of mixed
rare earths are as metallurgical additives for ferrous and
non-ferrous metals, fluid cracking catalysts, lighter flints,
polishing compounds in glasses, carbon arc cores for lighting and
hydrogen absorbing alloys for rechargeable batteries. Some of the
salient applications of high-purity rare earth elements are cathode
ray tubes, automotive catalytic converters, permanent magnets in
computer technology and sound systems, lasers, phosphors, electric
motors, optical fibres, and possible future applications such as in
coloured pigments for plastics and paints, new catalysts,
refrigeration systems and solid oxide fuel cells.
In order to use rare earths successfully in various applications, a
good understanding of the chemistry of these elements is of
paramount importance. Nearly three to four decades have passed
since titles such as The Rare Earths edited by F.H. Spedding and
A.H. Daane, The chemistry of the Rare Earth Elements by N.E. Topp
and Complexes of the Rare Earths by S.P. Sinha were published.
There have been many international conferences and symposia on rare
earths, as well as the series of volumes entitledHandbook of
Physics and Chemistry of Rare Earths edited by K.A. Gschneidner and
L. Eyring. Thus, there is a need for a new title covering modern
aspects of rare earth complexes along with the applications.
The present title consists of twelve chapters. The first chapter is
an introduction covering definition, classification, properties,
world reserves, methods of processing from ores, methods of
separation both classical and modern, and analytical chemistry of
rare earths, including classical and modern methods.
The second chapter deals with quantum chemical considerations, s,
p, d and f orbitals, electronic configurations, Pauli's principle,
spin-orbit coupling and levels, energy level diagrams, Hund's
rules, Racah parameters, oxidation states, HSAB principle,
coordination number, lanthanide contraction, interconfiguration
fluctuations. This is followed by a chapter dealing with methods of
determination of stability constants, stability constants of
complexes, thermodynamic consideration, double-double effect,
inclined w plot, applications of stability constant data.
The fourth chapter deals with complexes of rare earth elements with
a variety of complexing agents, such as monocarboxylic acids,
dicarboxylic acids, polycarboxylic acids like citric,
nitrilotriacetic, ethylenediamine tetraacetic; beta diketones,
ligands with nitrogen donors, macrocyclic ligands, ligands with
sulphur donors, phosphines, cyanate, thiocyanate, selenocyanate,
perchlorate, decaborates, acyclic and macrocyclic Schiff's bases,
carboranes, selenides and tellurides.
Structural chemistry of lanthanide complexes dealing with low
coordination numbers, 6-, -7 and -8 coordination, dodecahedra,
square antiprisms, hexagonal bipyramids, cubes and other
structures, 9-coordination, high coordination numbers and
organometallic structures is discussed in the fifth chapter.
Organometallic complexes such as tris, bis and monocylopentadienyl
complexes, cyclooctatetraenyl complexes,
cyclopentadienyl-cyclooctatetraenyl complexes, indenyl complexes,
fluorenyl complexes, complexes with other aromatic _ ligands,
callixerene complexes, NMR spectroscopy of organometallic
complexes, vibrational spectra, and catalytic applications form the
theme of the sixth chapter.
Kinetics and mechanisms complex formation involving rate
expressions, rate laws, dissociative and associative pathways,
techniques used in probing reaction mechanisms, crystal field
effects are discussed in the following chapter.
Crystal field theory, intensities of 4f-4f transitions, Judd-Ofelt
theory of electric-dipole transitions, covalency model of
hypersensitivity, dynamic coupling mechanism, solution spectra,
spectral data for complexes, solvent effects, fluorescence and
photochemistry of lanthanide complexes are dealt with in
spectroscopy of lanthanide complexes.
Photoelectron spectroscopy of rare earths involving typical
spectra, core levels, splitting due to exchange, spin-orbit
coupling, binding energies, states arising due to ionization of fn
configuration, interconfiguration fluctuation and surface oxidation
phenomena are discussed in the next chapter. The following chapter
deals with the important topic of lanthanide NMR shift reagents and
their applications in elucidating structures. The penultimate topic
deals with ecological, physiological and environmental aspects
along withsome interesting biological applications.
In the final chapter, applications such as in metallurgy of steels,
corrosion inhibition, catalysis, paints, cinema arc carbon and
search light electrodes, polishing powders in optics, permanent
magnets, ceramic superconductors, lasers, garnet films for magnetic
bubble memory applications, nuclear applications, x-ray phosphors
for medical radiology, fiber optics, photonics, electronics,
magnetic resonance imaging (MRI) high-tech applications and fuel
cells are elucidated.
The authors studied in schools headed by pioneers in rare earth
chemistry, have a combined experience of one hundred and fifty
years in inorganic chemistry, rare earth complex chemistry, nuclear
and radiochemistry of rare earths and supramolecular chemistry. The
present monograph is a product of this rich experience.
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