Structure lanthanide complexes

Furthermore, lanthanides form stable complexes with polydentate chelators like DTPA, which exhibit a noncyclic structure. Two structures are depicted in Scheme 2. The following examples are only representatives for the variety of analyte molecules that can be determined by these kind of lanthanide complexes. Structure 9 employs a quinolyl ligand both as chromophore and acceptor for Zn ". The emission of the europium ion is strongly enhanced upon binding of Zn " and showing distinct selectivity over other biologically relevant metal cations in aqueous solution at neutral pH [29]. The luminescence of the chelate 10 is efficiently quenched by Cu " ions in aqueous medium [30]. The presence of Fe ", Co ", Ni ", Cr ", and Mn " interferes with the determination of Cu, although to a relatively small extent, whereas the ions Zn ", Cd ", Hg, and Pb do not interact with probe 10. 

Lanthanide coordination chemistry is still not completely understood, and many attempts are usually required to design specific Inminescent lanthanide complexes. As an alternative to rational design, a combinatorial approach shows promise for the development of specific luminescent lanthanide materials. Shinoda et al. built a combinatorial library to optimize luminescent lanthanide complexes structurally for the selective detection of amino acids. The lanthanide complex library included 196 combinations of 4 lanthanide centers, 7 pyridine ligands, and 7 amino acid substrates (Figure 16.16). The luminescence responses for amino acids depended on the nature of the ligand used. A series of Tb + complexes typically exhibited interesting luminescence responses. The TV+-picolinic acid complex and Tb -pyrazinecar-boxylic acid complex preferred zwitterionic Ala, Val, Phe, and Gin, whereas the Tb complex with dipicolinic acid favored anionic Gin and Asp. 

NMR investigation of molecular structure of paramagnetic lanthanide complexes with crown ethers in solutions 98ZSK714. 

Sinha SP (1976) Structure and Bonding in Highly Coordinated Lanthanide Complexes. 25 67-147... 

There has also been some interest in NHC-lanthanide complexes as polymerisation catalysts. Indenyl and fluorenyl functionalised NHC complexes of structures 14 and 15 (Fig. 4.5) were evaluated for isoprene polymerisation following activation... 

As the atomic number increases, so does the positive charge of the nucleus, and the electrons are bound with a higher energy. However, this increase is not linear. For example, the electrons in the d orbital of the third shell have a higher energy than those in the s orbital of the fourth shell, and hence the latter are filled first. The consequence is the unexpected behavior of the first ten transition elements. In the case of the actinides and lanthanides, even more inner orbitals are occupied. Nature is not so simple, but the scheme should help to visualize this complex structure. And if one can assign the electrons of an element, one is a step closer to successfully unraveling the mysteries of the Periodic Table. 

Figure 2 Structures of some lanthanide complex phosphors (a) [Eu(TTFA)3(phen)], (b) [Tb(ACAC)3 (phen)], (c) [Dy(BTFA)3(phen)], (d) [Eu(DBM)3(phen)], (e) [Eu(DBM)3(bath)] and (f) [Eu(TTFA)3(TPPO)2]...

Determination of Ligand-field parameters and f-electronic structures of Double-Decker Bis(phthalocyaninato)lanthanide complexes. Inorg. Chem., 42, 2440 - 2446. 

As was mentioned in Section 6.2.3, phenomenological CF models have been extensively used in the past to rationalize the electronic structure of lanthanide complexes [4, 40-50], and they are still in use nowadays [38, 39, 78, 79]. The ab initio approach described above is, in principle, able to provide accurate energies and wave functions of multiplets in lanthanide complexes. Nevertheless, even if ab initio calculations appear to be successful, CF description is still of great... 

Two-Step Approach for the Calculation of Electronic Structure of Polynuclear Lanthanide Complexes... 

Probably, the first series of lanthanide complexes with neutral oxygen donor ligands is that of AP with the lanthanide nitrates. In 1913, Kolb (79) reported tris-AP complexes with lighter lanthanide nitrates and tetrakis-AP complexes with heavier lanthanide nitrates. Subsequently, complexes of lanthanide nitrates with AP which have a L M of 6 1 and 3 1 have also been prepared (80-82). Bhandary et al. (83) have recently shown through an X-ray crystal and molecular structure study of Nd(AP)3(N03)3 that all the nitrates are bidentate and hence the coordination number for Nd(III) is nine in this complex. Complexes of AP with lanthanide perchlorates (81, 84), iodides (81, 85), and isothiocyanates (66, 86, 87) are known. While the perchlorates and iodides in the respective complexes remain ionic, two of the isothiocyanates are coordinated in the corresponding complexes of AP with lanthanide isothiocyanates. 

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