Chelating Silicone Dendrons: Trying to Impact Organisms by Disrupting Ions at Interfaces

Abstract

The viability of pathogens at interfaces can be disrupted by the presence of (cationic) charge and chelating groups. We report on the synthesis of silicone dendrimers and linear polymers based on a motif of hexadentate ligands with the ability to capture and deliver metal ions. Mono-, di- or trialkoxysilanes are converted in G1 to analogous vinylsilicones and then, iteratively using the Piers-Rubinsztajn reaction and hydrosilylation, each vinyl group is transformed into a trivinyl cluster at G2. The thiol-ene reaction with cysteamine or 3-mercaptopropionic acid and the trivinyl cluster leads to hexadentate ligands 3 × N–S or 3 × HOOC–S. The compounds were shown to effectively capture a variety of metals ions. Copper ion chelation was pursued in more detail, because of its toxicity. On average, metal ions form chelates with 2.4 of the three ligands in a cluster. Upon chelation, viscous oils are converted to (very) soft elastomers. Most of the ions could be stripped from the elastomers using aqueous EDTA solutions, demonstrating the ability of the silicones to both sequester and deliver ions. However, complete ion removal is not observed; at equilibrium, the silicones remain ionically crosslinked.

Synthesis and characterization of sulfide/sulfone-containing 18-8-18-membered-ring ladder-type siloxanes

“…2a). In comparison to the 29 Si NMR spectrum of the precursor 6 (Fig. 2b), the peak at −3.17 ppm corresponding to the M-unit silicon of -SiMe 2 H entirely disappeared, which thus confirms the formation of a completely condensed tricyclic ladder-type structure.…”

“…S3 †). Furthermore, the structure of 5 was confirmed through 13 C, 29 Si NMR analysis, as well as MALDI-TOF mass spectroscopy (ESI Fig. S4, S5 and S20 †).…”

“…This is due to the restriction of free rotation of O-Si-(CH 3 ) 2 bonds in the presence of phenyl units in the side rings. In addition, the 29 Si NMR spectrum of the compound 7 exhibits only two distinctive peaks at −79.08 ppm and −11.19 ppm, which were assigned to the T-unit and D-unit silicon atoms respectively (Fig. 2a).…”

“…18,[20][21][22] Moreover, the Si-H groups of these all-cis-T 4 can be easily modified by effective hydrosilylation and the resulting compounds have potential in the field of coating or photoactive materials. [23][24][25] Also, the B(C 6 F 5 ) 3 -catalyzed Piers-Rubinsztajn reaction, a transition metal-free approach to preparing wellcontrolled branched polysiloxanes, [26][27][28][29] has recently become a powerful tool for extending hydrosilyl-substituted all-cis-T 4 with methoxybenzene derivatives. [30][31][32] All-cis-T 4 with pyrene groups obtained recently by this method were found to be selective sensors for detection of gold ions and L-cysteine.…”

13-8-13-Membered Tricyclic Ladder-Type Siloxanes Hybridized with BINOLs: Synthesis, Characterization, and Fluorescence Sensing of Fluorides

“…in the presence of a catalytic amount of Lewis acid B­(C 6 F 5 ) 3 . It has proven to be a highly effective approach for producing precisely controlled siloxane structures . The other reaction partners are four different substituted 1,1′-bi-2-naphthols (BINOLs), which can be readily prepared according to conventional methods. , Encouragingly, the desired BINOL hybrid 13-8-13-membered tricyclic ladder-type siloxane (TLS-BINOL, L1 ) was obtained in good yields (60% yield) when the reaction between BINOL and T4-(OSiMe 2 H) 4 was performed under the reported Piers–Rubinsztajn reaction conditions in the presence of catalytic B­(C 6 F 5 ) 3 at room temperature (Scheme ).…”