Stabilizers thiol ligands

Schiffrin approach [148-152], the method has certain limitations with regards to the compatibihty of the stabilizing thiol ligands with the other reagents. 

Liaw et al. reported that conversions between the neutral sparteine [Fe(NO)2] complex 133 and the anionic Fe(NO)2 [Fe(NO)2(S2C3Hg)] 137 proceed via the cationic sparteine Fe(NO)2 -complex 135 through oxidation by NO" " and transfer of the [Fe(NO)2] -unit to the chelating ligand S-(CH2)3-S 136 (Scheme 35). The resulting anionic complex 137 is stable in contrast to the cationic complex 135. The cationic complex 135 also acts as a [Fe(NO)2] donor in the presence of the DNIC [(PhS)2Fe(NO)2] 138 to yield Roussin s red ester 139. The bidentate thiol ligand S-(CH2)3-S 136 promotes the stability of the anionic DNIC Fe(NO)2 ... 

Scheme 3.9 Thiol ligands used in the ligand exchange reaction with 1.5 nm PPh3-stabilized Au NPs.

Although thiol ligands are the most widely used as stabilizers in the synthesis of Au NPs, other organic ligands bearing amine, phosphine, phosphine oxide, carboxylate or other functional groups have been employed alone or in mixtures. 

Near monodisperse Au NPs in the size range of 1—4nm can be obtained using dodecylthioether end-functionalized PMMA as stabilizer. Particle size is controlled by varying the concentration of the stabilizing polymer, which can be readily displaced by thiol ligands to yield MPCs of the usual type [97]. 

The basicity constants of a series of diaminoamides in aqueous solution were determined potentiometrically.48 Among the sulfur carboxamide ligands, a series of benzoyl-protected dimercaptodiamides like (38) should be mentioned.49 This amide thiol ligand in the tetra-anionic form (R = H) spans the basal position of an expected square-pyramidal structure, increasing the kinetic stability of the low-spin TcO core which can be used in diagnostic nuclear medicine procedures. 

Electrodes modified by ferrocenyl polymers have been known for a long time.54,61,62 More recently, the Madrid group has extensively studied the derivatization of silylferrocenyl dendrimers.63 Nishihara s group has reported the first example of modified electrodes with AuNPs containing ferrocenyl thiol ligands, in which the stabilization of the modified electrodes is... 

Seifert S, Drews A, Gupta A et al (2000) Stability studies on 99m-technetium(III) complexes with tridentate/monodentate thiol ligands and phosphine ( 3+1+1 complexes). Appl Radiat Isot 53 431-438... 

The syntheses described in the preceding section can be performed using as stabilizers the classical ligands of organometalhc chemistry (e.g., amines, thiols, or phosphines) instead of polymers. The amount of ligand added allows control of the particle growth and therefore the size. 

Finally, the term steric stabihzation coifid be used to describe protective transition-metal colloids with traditional ligands or solvents [38]. This stabilization occurs by (i) the strong coordination of various metal nanoparticles with ligands such as phosphines [48-51], thiols [52-55], amines [54,56-58], oxazolines [59] or carbon monoxide [51] (ii) weak interactions with solvents such as tetrahydrofuran or various alcohols. Several examples are known with Ru, Ft and Rh nanoparticles [51,60-63]. In a few cases, it has been estab-hshed that a coordinated solvent such as heptanol is present at the surface and acts as a weakly coordinating ligand [61]. 

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