Dendron thiol

Bioreactive surfaces on gold were prepared by self-assembly of hydroxyl-terminated dendron thiols self-assembled on gold and subsequent bridging reactions using generation-two amine-terminated dendrimers. The hydroxylated SAM was activated by the homobifunctional cross-linker yV,yV-disuccinimidyl carbonate (DSC), and linked to amine-terminated dendrimers via bridging reactions. 

PBE dendrons coordinate to the surface of II-VI semiconductor nanocrystals (e.g., CdSe [33] and CdSe/ZnS core/shell structure [34, 35]) to modulate the photoluminescence of the nanocrystals [32]. Trioctylphosphine oxide (TOPO)-capped II-VI semiconductor nanocrystals of several-nanometers diameter have been synthesized by a pyrolysis reaction of organometallics in TOPO [33-35]. The capping ligand (TOPO) can be replaced by stronger ligands such as thiol compounds [36], suggesting that dendrons bearing sulfur atom(s) at the focal point replace TOPO as well. 

Figure 7.26 Dendrimers made with a disulfide-containing core can be reduced to produce dendrons having free thiol groups for surface modification. Dative binding of these thiol-dendrons to gold or metallic surfaces can provide a high density of amine groups for coupling proteins or other molecules.

Huang, B., and Tomalia, D.A. (2005) Dendronization of gold and CdSe/cdS (core-shell) quantum dots with tomalia type, thiol core, functionalized poly(amidoamine) (PAMAM) dendrons. J. Lumin. Ill, 215-223. 

The third class of AuNPs-dendrimer nanomaterials is Nanoparticle Cored Dendrimers (NCDs). The first report on this topic describes a new strategy in which Frechet-type dendrons with a single thiol group at the focal point were used as a surface stabilizer of Au NPs. These dendronized Au NPs were synthesized using a modification of the two-phase Brust-Schiffrin method, giving rise to highly stable and very monodisperse Au NPs of small size (about 2.4—3.1 nm) [129] (Figure 3.13). 

Daniel et al. have also reported on the use of thiol-functionalized dendrons as stabilizers for the synthesis of NCDs of about 2.1 nm. The synthetic procedure... 

Chloroacetyl K2K and related dendrons are popular and convenient to prepare because of their reactivity with thiol moieties placed on peptide dendrimers for convergent syntheses.1P3 90 91 Furthermore, these dendrons are stable to acidic cleavage by either TFA or HF. The synthesis of a chloroacetyl K2K dendron 20c by Boc chemistry is illustrated in Scheme 8. 

The second type of weak bases for imine ligations are 1,2- or 1,3-heterosubstituted amines of amino thiols and amino alcohols. Of the two, the amino thiols appear to be the more suitable choice because they form stable thiazolidine derivatives under very mild reaction condi-tions 84"89,114 121 140 Furthermore, the 1,2-and 1,3-aminothiol moieties are found in cysteines and homocysteines that form a stable heterocyclic ring with an aldehyde within ten minutes at pH 4-5. Thiazolidine ring formation has been successfully used to ligate both linear and constrained peptides to K2K dendron types of cores and proteins containing a-oxoacyl groups. 

Finally, Donnio et al. showed that capping gold nanoparticles with an alkyl thiol (dodecanethiol) as well as a second generation dendron, providing mixed monolayer-capped gold nanoparticles (15 in Fig. 21), results in the formation of a... 

AB9 thiol gave good results (Scheme 5). Two closely related AB9 dendrons were used leading to an assembly of about 10% resp. 20% of AB9 thiolate dendrons around 2.9-nm AuNPs bearing around 200 thiolate hgands overall. This means that these AuNPs contain about 180 resp. 360 equivalent silylferrocenyl groups at the periphery [93,94]. 

Titration of ATP2 with AuNPs functionalized with the nonaferrocenyl thiol dendron of Scheme 7 (c = 3.8xl0"6 M)... 

Torigoe, Yonezawa, and co-workers prepared dendron type-thiol-stabilized gold nanoparticles by NaBH4-reduction process [72]. As dendron is bulky structures, it prevents hexagonal close packing of nanoparticles and show quasi ID structures by just casting on a carbon grid. 

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