Dendrimeric Catalysts for the Activation of Hydrogen Peroxide. Increasing Activity per Catalytic Phenylseleno Group in Successive Generations

Abstract

Dendrimeric polyphenylselenides are prepared in high yield using propyloxy spacers to connect the phenyseleno groups to the dendrimeric core. The selenides catalyze the oxidation of bromide with hydrogen peroxide to give positive bromine species that can be captured by cyclohexene in two-phase systems. The increase in the rate of catalysis exceeds statistical contributions for the first few generations with 3, 6, and 12 phenylseleno groups.

Dendritic effects in functional dendrimer molecules

“…This was attributed to a much higher local density of the quaternary ammonium ions in the G2 dendritic surface that created a much more hydrophilic microenvironment for the rapid decarboxylation. A similar positive catalytic dendritic effect was also observed by Detty in his study of dendritic polyphenylselenides [3]. Positive catalytic dendritic effects were also noted by Jacobsen [4], in which the higher generation Co(salen) catalysts (e.g., 2) were far more effective than the lower ones due to interchain cooperative interactions among the catalytic sites located on the dendrimer surface.…”

Antifouling character of ‘active’ hybrid xerogel coatings with sequestered catalysts for the activation of hydrogen peroxide

“…After 1 h, Te powder (0.772 g, 6.06 mmol) was added and the resulting mixture was stirred for 15 min at 7788C and was then stirred at room temperature until the Te was completely consumed. The reaction mixture was cooled to 7788C, 3-bromopropyloxy-tertbutyldimethylsilane (1.82 g, 6.06 mmol) (Francavilla et al 2000(Francavilla et al , 2001 was added, and stirring was continued for 1 h at 7788C and for 15 h at room temperature. The reaction mixture was poured into 150 ml of water.…”

“…Diorganoselenoxides and diorganotellurides are efficient catalysts for the oxidation of halide salts with H 2 O 2 to produce the corresponding hypohalous acid (Francavilla et al 2000(Francavilla et al , 2001Higgs et al 2001;Drake et al 2003;Goodman and Detty 2004;Bennett et al 2008). If these catalysts were covalently sequestered within a porous film coating, the catalysts should react with the peroxide found in seawater (Cooper and Zika 1983;Willey et al 1999;Schiller 2000, 2001;Clark et al 2008) or that is produced by the biofilm (Chandrasekaran and Dexter 1993;Le Bozec et al 2001;Dexter et al 2003) and with the halide salts found in seawater to create a surface that is chemically inhospitable to settlement and adhesion.…”

Development of efficient methods for the immobilisation of multicomponent asymmetric catalysts

“…The structure, size, shape and solubility of the dendrimers are readily tunable and hence have attracted considerable attention as a new class of well-defined nanometer-scale materials [31]. Positive effects of dendrimers have already been realized in some cases [32][33][34][35][36][37][38][39][40][41]. Jacobsen et al reported on an example in which two catalytic sites at the terminal positions of a dendrimer assisted the ring opening of epoxides [42].…”