Synthesis and Characterization of Water-Soluble Cationic and Anionic Polyferrocenylsilane Polyelectrolytes

Abstract

Convenient routes to a range of water-soluble polyferrocenylsilane polyelectrolytes are reported. Direct reaction of the protected aminopropynyl reagent LiC⋮CCH2N(SiMe2CH2)2 (8) with the substitutionally labile ring-opened polymer [fcSiMeCl] n (3) (fc = Fe(η−C5H4)2), which is generated via Pt-catalyzed ring-opening polymerization of the silicon-bridged [1]ferrocenophane fcSiMeCl (6), afforded the polymer [fcSiMe{C⋮CCH2N(SiMe2CH2)2}] n (10). Polymer 10 was also obtained via ring-opening polymerization of the [1]ferrocenophane fcSiMe{C⋮CCH2N(SiMe2CH2)2} (9) prepared from the reaction of the lithium salt 8 and the substitutionally labile [1]ferrocenophane 6, which is readily accessible via the reaction of fcLi2·TMEDA with MeSiCl3. Deprotection of 10 was readily achieved using THF/MeOH to yield [fcSiMe(C⋮CCH2NH2)] n (11), which was conveniently reduced with hydrazine to the analogous aminopropyl polymer [fcSiMe(CH2CH2CH2NH2)] n (12). Treatment of polyferrocenylsilanes 11 and 12 with HCl generated the water-soluble cationic polyelectrolytes [fcSiMe(C⋮CCH2NH3Cl)] n (13) and [fcSiMe(CH2CH2CH2NH3Cl)] n (14), respectively. Cationic polyferrocenylsilanes 13 and 14 were obtained in three steps from polymer 3 with an overall yield of 40−50%. An unexpected rearrangement process took place during the lithiation of the protected aminopropyl bromide Br(CH2)3N(SiMe2CH2)2 (15) and a reaction of the resulting lithium salt with 6 yielded the novel [1]ferrocenophane fcSiMe{N(CH2)3SiMe2(CH2)2SiMe2} (17) with a rearranged, and ring-expanded, cyclic silylamino substituent. Species 17 underwent thermal ring-opening polymerization to afford [fcSiMe{N(CH2)3SiMe2(CH2)2SiMe2}] n (18). Treatment of polymer 10 with 1,3-propane sultone afforded the anionic polyelectrolyte [fcSiMe{C⋮CCH2N(CH2CH2CH2SO3Na)2}] n (19). Polymer 19 was readily reduced with hydrazine to give [fcSiMe{CH2CH2CH2NH(CH2CH2CH2SO3)(CH2CH2CH2SO3Na)}] n (20) bearing saturated side chains; subsequent deprotonation yielded the anionic polyelectrolyte [fcSiMe{CH2CH2CH2N(CH2CH2CH2SO3Na)2}] n (21). All three anionic polyelectrolytes 19−21 were obtained in 2−3 steps from 3 with 60−75% overall yields. The polyferrocenylsilane polyelectrolytes 13, 14, and 19−21 were readily soluble in water, making them potentially useful materials for a range of applications.

Electrostatic Assembly with Poly(ferrocenylsilanes)

“…The synthesis of water soluble poly(ferrocenylsilane) polyelectrolytes involves the ring-opening polymerization (ROP) of a silicon-bridged ferrocenophane followed by side-group modifications [18][19][20][21][22]. The starting silaferrocenophane monomers (Scheme 1) [18] are obtained from the reaction of 1,1¢-dilithioferrocene with a dichloroorganosilane (RR¢SiCl 2 ), in the presence of a complexing agent (tetramethylethylenediamine, TMEDA) [2].…”

“…Thus, the synthetic route leading to poly(ferrocenylsilane) polyelectrolytes often necessitates a side-group modification step after polymerization [21]. Figure 1 displays the water soluble poly(ferrocenylsilane) polyelectrolytes that have been studied in the electrostatic LBL selfassembly.…”

“…Along with other characteristics, such as the crystallinity [13a, 16] and glass transition temperature [6], the solubility of PFS [17][18][19][20][21][22] can be tuned by varying the size and type of the substituents. Modification of the polymer side groups has been shown to give access to watersoluble PFS [18][19][20][21][22]. Homopolymers of water-soluble PFS have potential uses as electrode modifiers and redox-active polymeric electrolytes for which the ionic conductivity might be tuned by oxidation of the iron centres.…”

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

“…Further water soluble polyelectrolytes were synthesised from PFS (R = Me, R' = C≡CCN(Me2SiCH2)2), which itself was readily obtained via a substitution reaction from poly(ferrocenylchloromethylsilane). 68 These polyelectrolytes remained stable in water even after a period of several months. The PFS, [Fe(η 5 -C5H4)2SiMe(N(CH2)3SiMe2(CH2)2SiMe2)]n was prepared by the ROP of a ferrocenophane precursor with a cyclic silylamino substituent via an unexpected rearrangement/ring expansion process.…”

“…The PFS, [Fe(η 5 -C5H4)2SiMe(N(CH2)3SiMe2(CH2)2SiMe2)]n was prepared by the ROP of a ferrocenophane precursor with a cyclic silylamino substituent via an unexpected rearrangement/ring expansion process. 68 Alternatively, the water soluble cation, poly(ferrocenyl(3-ammoniumpropyl)methylsilane) was produced by the ROP of [Fe(η 5 -C5H4)2SiCH3(CH2)3Cl]…”