Organic-lanthanide complexes

The use of lanthanides are common for optical purposes because of their narrow and sharp bands, and distinguishable long lifetimes, accomparied by low transition probabilities due to the forbidden nature of the transitions [10-13]. Thus chromophoric sensitization of ligand to metal has been subjected to numerous theoretical and experimental investigations [14—16]. However, only limited classes of organic-lanthanide complexes have been developed and shown to display nonlinear processes [17-19]. Common nonlinear processes from lanthanide complexes include harmonic generation, photon up-conversion and multiphoton absorption induced emission. 

LeBozec and co-workers have reported nonlinear behavior in a series ofterpyri-dyl and dipicolinic acid complexes, with further studies on these complexes by Maury and co-workers [83, 84]. Their research was on new molecular materials for optoelectronics, with studies based on octupolar nonlinear optical molecules showing that molecular quadratic hyperpolarizability values were strongly influenced by the symmetry of the complexes [85]. Other studies on organic-lanthanide complexes with nonlinear optics have also reported second- and third-harmonic generation behavior with simultaneous multiphoton absorption properties [50]. Such studies have shown the importance of coordination chemistry as a versatile tool in the design of nonlinear materials. 

Law GL, Wong KL, Lap ST, Lau KK, Tanner PA, Wong WT (2010) Nonlinear optical activity in dipolar organic-lanthanide complexes. J Mater Chem 20 4074—4079... 

ATdc values for the lanthanide acetylacetonates are the reverse from that expected for the size effect. The explanation is hkely that the neutral complex with the formula LnAs is coordinatively unsaturated, which means that a hydrated complex exists in the aqueous phase (possibly also in the organic phase). The more coordinatively unsaturated lanthanide complexes (of the larger ions) can accommodate more water and thus are more hydrophilic. The result is a A dc several orders of magnimde lower for the lightest. La, than for the heaviest, Lu. 

Simon, W., Morf, W. E., and Meier, P. Ch. Specificity for Alkali and Alkaline Earth Cations of Synthetic and Natural Organic Complexing Agents in Membranes. Vol. 16, pp. 113—160. Sinha, S. P. Structure and Bonding in Highly Coordinated Lanthanide Complexes. Vol. 25. pp. 67-147. 

ILs are becoming useful solvenfs to investigate fhe specfroscopic behavior of both organic and inorganic lanthanide complexes in solution, especially of complexes with weakly binding ligands, which otherwise would be unable to compete with the solvent molecules for a binding site on the lanthanide ion [9]. 

A further application of relaxation rate measurements is that similar 1/71 ratios in a series of lanthanide complexes may be taken to indicate an isostructural series. However, this approach has the limitation that if only part of the complex is studied, perhaps an organic ligand, its 71 ratios would be independent of changes, for example changes in the extent of hydration in the remainder of the complex, provided that the conformation of the ligand relative to the lanthanide ion were preserved. An excellent example of the use of 71 data in a quite different way is its use to determine hydration numbers of lanthanide dipicolinate complexes.562... 

The central point in this consideration is the Ln-OH moiety, the preferred formation of which is considered to be a dilemma in organolanthanide chemistry. Organolanthanide compounds containing Ln-X a-bonds such as alkyls, amides and alkoxides readily hydrolyze when exposed to moist air, with the formation of the hydroxides. Lanthanide complexes with Ln-C linkages are considered to be oversensitive compounds [89]. Even ligands with lower pKa values than water, as exemplified by substituted phenol ligands, tend to hydrolyze in organic solvents because the insoluble hydroxides formed act as... 

Figure 135 Molecular structures of lanthanide complexes of europium (Eu), tris (thenoyltrifluoroacetonato) Eu3+ (a), tris(thenoyltri-fluoroacetonatoXmonophenanthroline) Eu3+ (b), and terbium (Tb), tris(acetylacetonato) Tb3+ (c) employed as narrow-band emitters in organic EL devices (see Ref. 19, 425, 534-536 and 539).

Figure 136 EL spectra of various organic LEDs employing lanthanide complexes as emitters, (a) ITO/TAD (triphenyldiamine derivative)/Eu(TTA)3(phen)(phen l,10-phenanthroline + 4,7-diphenyl-l,10-phenanthroline)/Alq3/MgAg (according to Ref. 425) (b) ITO/Eu (TTA)3 PBD/PBD/LiF/Mg, at the different voltages (after Ref. 539) (c) ITO/TPD/Tb (acac)3/Al, transitions of 4f electrons of the terbium Tb3+ ion are indicated on the sharp peak positions of this spectrum (after Ref. 19).

Phthalocyanines are tetraaza tetrabenzo analogues of porphyrins. Lanthanide complexes with phthalocyanines are prepared by the condensation of phthalonitrile (4 moles) with a lanthanide salt. The monocomplexes were prepared by heating a 1 4 mixture of lanthanide saltiphthalonitrile at 275°C. The molten solution solidified after an hour and purification of the complex is done by removal of excess phthalonitrile and impurities with organic solvents. Final purification is done by chromatography [85]. The bis complexes are prepared in a similar fashion but with a large excess of phthalonitrile [86]. Mixed ligand... 

The ligand p-t-butylcalix[4]arene fitted with phosphinoyl arms is synthesized by refluxing the tetrasodium derivative of p-t-butylcalix[4]arene and chloro(dimethylphosphinoyl) methane in toluene or xylene [88]. The resulting ligand L is reacted with lanthanum perchlorate in acetonitrile to obtain 1 1 and 1 2 complexes, LaL and LaL2- The majority of the supramolecular complexes of rare earths involves the use of organic solvents like toluene, hexane or acetonitrile for the synthesis of both the ligands and lanthanide complexes. 

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