Ferrocene and Silicon-Containing Oxathiacrown Macrocycles and Linear Oligo-Oxathioethers Obtained via Thiol–Ene Chemistry of a Redox-Active Bifunctional Vinyldisiloxane

Abstract

The application of 1,3-divinyl-1,3-dimethyl-1,3-diferrocenyldisiloxane [(CH 2 CH)FcMeSi] 2 O (1) as an efficient electroactive vinylsilane precursor for thiol−ene radical reactions is described. In order to determine if steric or electronic limitations due to the redox-active metallocene moiety might affect the bis(hydrothiolation) of the bifunctional vinylsilane, a model reaction was initially performed between 1 and 2-mercaptoethanol, resulting in the formation of the newly sulfur-containing carbosiloxane 2 in excellent yield. The bis(thiol−ene) reaction of 1 was successfully extended to 2,2′-(ethylenedioxy)diethanethiol, affording a series of novel precisely defined, redox-active oxathiacrown macrocycles (3 and 4 n ) and sulfur-bearing linear oligo-carbosiloxanes (5 n and 6 n ) with a backbone in which the −S(CH 2 ) 2 −O(CH 2 ) 2 O−(CH 2 ) 2 S− chain and the −Si−O−Si− bond, bearing pendant ferrocenes, are alternately linked by ethylene bridges. These reactions have been initiated either thermally (in toluene solution with AIBN) or by UV light irradiation in THF in the presence of 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator, even though UV photoinitiated thiol−ene reactions were found to be the most efficient hydrothiolations. All newly silicon-containing oxathioether-based ferrocenyl compounds 2−6 n have been thoroughly characterized using a combination of elemental analysis, multinuclear NMR spectroscopy, FT-IR, and MALDI-TOF mass spectrometry to establish their chemical structures and chain-end functionalities. The electrochemical behavior of 2−6 n has been examined by cyclic and square wave voltammetries, in dichloromethane solution using [PF 6 ] − and [B(C 6 F 5 ) 4 ] − as supporting electrolyte anions of different coordinating ability. The sulfur-rich cyclic and linear oligomers 4 n −6 n exhibit excellent chemisorption properties and spontaneously form robustly adsorbed electroactive films onto Au or Pt electrode surfaces. The cation complexation ability of diferrocenyl silaoxathiacrown ether 3 has been studied using electrochemical and 1 H NMR spectroscopic techniques. The voltammetric behavior of receptor 3 has proved to be very sensitive to the presence of Hg 2+ cation. The ability of macrocycle 3 to bind Hg 2+ has also been investigated through electronic structure calculations, being the interaction between the cation and one of the cyclopentadienyl rings the responsible of the different behavior of both redox-active centers.

Alkali and Alkaline Earth Metal Derivatives of Disila-Bridged Podands: Coordination Chemistry and Structural Diversity

“…These ligands can basically be divided into cyclosiloxanes, hybrid (di)­sila-crown ethers, and cryptands. Some exotic ligands such as silicon-containing oxathio-crown ethers were also described in the literature . In comparison to the corresponding organic crown type ligands, a significantly lower coordination ability of ligands bearing SiMe 2 units was found .…”

Siloxane Coordination Revisited: Si−O Bond Character, Reactivity and Magnificent Molecular Shapes

“…Hence, an unsupported bite angle of the crown‐type macrocycle reduces the cation binding ability significantly. The experimental findings are supported by the fact that a series of ring contracted and sila‐crown ethers bearing several −CH 2 −CH 2 −O− as well as one‐ or two −SiR 2 −O− units have been described in literature, [146−154] but, no coordination compounds have been isolated and crystallographically characterized to date.…”

Preparation and characterization of click-driven N-vinylcarbazole-based anion exchange membranes with improved water uptake for fuel cells

“…The thiol-ene reaction is a well-known click reaction usually triggered via a free-radical supported mechanism, with the assistance of photoinitiation by a suitable photoinitiator (PI) to produce radicals from thiols. 43 As such, we chose DMPA as an active PI to initiate the click reaction between silica-based thiol MPTES and NVC. Silica functionalized carbazole-based monomer TESPTEC was synthesized using a facile method in high yield.…”

“…46 Additionally, typical sharp intensity bands at around 1244 cm À1 and 785 cm À1 provided evidence of a Si-C (d and n) bond in TESPTEC. 43 In general, for all NVC-X membranes, the classical Menshutkin reaction was performed in NMP with BPPO, and the amount of TESPTEC varied. Fig.…”