Conjugation Schiff-base ligands

Polynuclear Lanthanide Complexes with Conjugated Schiff-Base Ligands 282... 

POLYNUCLEAR LANTHANIDE COMPLEXES WITH CONJUGATED SCHIFF-BASE LIGANDS... 

Recently, the use of pthalocyanines and porphyrins by Ishikawa and coworkers enabled tiie synthesis of several so-called double-decker or triple-decker lanthanide complexes, described as stacked Ji-conjugate molecules. The photophysical properties of lantiianide ious depeud markedly on their coordination environments. Since a multidecker framework can effectively keep solvent molecules away from Ln centers, it is assumed that enhanced luminescent properties can be achieved witii these types of architectures. We discovered that the use of two conjugated Schiff-base ligands H2Lh can stabihze novel multidecker framewoiks (Scheme 1). 

Multidecker lanthanide complexes (1-5) have been synthesized from the reactions of lanthanide salts with conjugated Schiff-base ligands H2L . An interesting emerging feature exhibited by these complexes is the self-assembly of stacked multidecker stmctures in which Ln ions are sandwiched between alternating layers of the Schiff-base ligands. 

In 2000, Gennaii et al. discovered a new family of chiral Schiff-base ligands, with the general structure, Af-alkyl-p-(A -salicylideneamino)alkanesulfonamide, depicted in Scheme 2.28. These ligands were successfully implicated in the copper-catalysed conjugate addition of ZnEt2 to cyclic enones (Scheme 2.28) and, less efficiently, to acyclic enones such as benzalacetone (50% ee) or chalcone... 

Scheme 1 Conjugate (a) and flexible (b) Schiff-base ligands H2L ...

Two kinds of salen-type Schiff-base ligands, conjugated and flexible, have been used in the synthesis of polynuclear lanthanide complexes and lanthanide coordination polymers Lanthanides Coordination Chemistry, Rare Earth Metal Cluster Complexes. The stoichiometry and structures of these complexes are dependent on the Schiff-base... 

A phosphine-Schiff base ligand (17) has been used for copper-catalysed asymmetric conjugate addition of diethylzinc to various ( )-alkenyl aryl ketones where the aryl ring is either a phenyl group substituted by nitro, chloro, or methoxy groups or not substituted or a naphthyl group. When the conjugate addition has been performed in ethyl acetate... 

For the latter CNS receptor ligands, different types of chelators have been introduced to the basic receptor binding framework. Originally a bidentate Schiff base was introduced by the reaction of an aliphatic amine with pyridine-aldehyde. Labelling occurred at low concentration and the radio conjugate was physiologically stable. Although receptor affinity was fully retained, brain uptake was low [67]. ACp was introduced at the same position and, as described earlier, and receptor affinity was perfectly retained. No brain uptake data are... 

As with other polymers, the metal complex may be part of the polymer backbone, or attached to the backbone by a conjugated linker. Investigations into the conjugated polymers have been assisted by studies of model complexes.44 Polythiophenes incorporating organometallic complexes are discussed first, followed by those incorporating other coordination complexes with bipyridine, terpyridine, Schiff base, and other ligands. 

The nickel complex 11, with a fluorous Schiff base as ligand, was prepared from salicylaldehyde and 4-perfluorodecylaniline (Scheme 15). This fluorous Ni complex was used as a catalyst for the conjugate addition of -diketones to diethyl azodicarboxylate (DEAD). The mixture was stirred at 60 C in a mixture of... 

Scheme 2.27 Conjugate addition of diethyl malonate to a chiral Ni(ii) complex of a Schiff base of dehydroalanine in the presence of a TADDOL ligand.

Three new orthopalladated chromophores 87 (A,B = N02, NR2 A B) based on push-pull 7r-conjugated ligands have been prepared and characterized.Second-order molecular NLO activity has been determined by EFISH measurements. A related study with OH-functionalized orthopalladated Schiff bases was also published by the same group in 2004. ... 

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