Cubic Octasilsesquioxanes, Cyclotetrasiloxanes, and Disiloxanes Maximally Functionalized with Silicon-Bridged Interacting Triferrocenyl Units

Abstract

Redox-active, highly symmetrical cubic octasilsesquioxanes (OS) peripherally decorated with 24 ferrocenyl units, linked in threes around the periphery of a cubic cage, namely, [Fc 3 Si(CH 2 ) 2 Me 2 SiO] 8 Si 8 O 12 (6) and [Fc 3 Si-(CH 2 ) 2 ] 8 Si 8 O 12 (7) (Fc = (η 5 -C 5 H 4 )Fe(η 5 -C 5 H 5 )), have been synthesized. Such integrally ferrocenyl-functionalized cubic macromolecules 6 and 7, as well as the related smallmolecule models hexaferrocenyldisiloxane [Fc 3 Si-(CH 2 ) 2 Me 2 Si] 2 O (4) and dodecaferrocenyl cyclotetrasiloxane [Fc 3 Si(CH 2 ) 2 MeSiO] 4 (5), have been prepared by covalently linking, via Karstedt's-catalyzed hydrosilylation, triferrocenylvinylsilane (CH 2 CH)Si(Fc) 3 (3) around the surface of octasilsesquioxane cages T 8 (OSiMe 2 H) 8 and T 8 H 8 and linear [Me 2 SiH] 2 O and cyclic [MeSiHO] 4 siloxane scaffolds, respectively. All new polyferrocenyl oligosiloxanes have been thoroughly characterized using a combination of elemental analysis, multinuclear ( 1 H, 13 C, 29 Si) NMR spectroscopy, FT-IR, and MALDI-TOF mass spectrometry. The molecular structure of disiloxane 4, in the solid state, has been determined by single-crystal X-ray analysis. Hexametallic 4 shows a bent arrangement of the ferrocenyl-substituted disiloxane linkage (Si−O−Si angle of 147.6(5)°). Polyferrocenyl-OS 6 and 7 show good thermal stability and form iron-containing ceramics when pyrolyzed under nitrogen. The electrochemical behavior of polyferrocenyl OS and model linear and cyclic siloxanes 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 novel maximally ferrocenylfunctionalized oligosiloxanes exhibit a three-wave redox pattern, suggesting appreciable electronic interactions between the silicon-bridged triferrocenyl moieties as they are successively oxidized. OS 6 and 7 undergo remarkable oxidative precipitation in CH 2 Cl 2 /n-NBu 4 PF 6 and are able to form stable electroactive films on platinum electrode surfaces. They are the first redox-active OS showing significant electronic interactions between metal sites on the cage surface.

Noncovalent linkage of telechelic oligo(dimethylsiloxanes) via end group attachment of host‐cyclodextrins and guest‐adamantanes or guest‐ferrocenes

“…They show typical reversible redox reactions measured by cyclic voltammetry . The electrochemical properties of those compounds were also investigated in many other publications with regard to the chemical modification of electrodes and the usage as a neutral carrier for an anion sensor . A self‐assembly of ferrocene‐poly(dimethylsiloxanes) block copolymers has been reported by Manners and coworkers …”

“…[4][5][6][7][8][9][10] The electrochemical properties of those compounds were also investigated in many other publications with regard to the chemical modification of electrodes and the usage as a neutral carrier for an anion sensor. [11][12][13][14][15][16][17][18] A self-assembly of ferrocene-poly(dimethylsiloxanes) block copolymers has been reported by Manners and coworkers. [19][20][21] Furthermore, adamantane-modified poly(dimethylsiloxanes) have been described in the literature rarely.…”

Use of Polyhedral Oligomeric Silsesquioxane (POSS) in Drug Delivery, Photodynamic Therapy and Bioimaging

“…Carbon nanotubes/paclitaxel/anitbody Propyl ammonium chloride Amidation [41] Carbon dots Aminopropyl Amidation [42] BODIPY Propyl ammonium chloride Amidation [43] Fluorescein Azidopropyl Amidation/CuAAC [33] Gluconolactone/dansyl chloride Aminopropyl Sulfonamide bond [44] Tetraphenyl porphyrin Aminoproppyl Amidation, urea bond [27] Ce6/PEG Aminopropyl Amidation [45] Fluorescein labeled dipeptide Propyl ammonium chloride Amidation [46] DOX Succinic anhydride Amidation [47] DOX/PEG Succinic anhydride Amidation [48] Porphyrin Vinyl and hydroxyl Amidation and CuAAC [49] Porphyrin/OPVEs Vinyl and hydroxyl Amidation and CuAAC followed by Heck coupling [50] FITC/carboxylic acid Aminopropyl and isobutyl Amidation [31] Perfluorinated alkyl/silica nanoparticles or fluorophore Propyl ammonium chloride Amidation 2008, 2009, 2012, 2011 [51][52][53][54] Peptide/Ce6 Malemic acid Amidation [55] Protoporphyrin IX/linolenic acid Propyl ammonium chloride Amidation [56] Quantum dots Propyl ammonium chloride Amidation [57] Quantum dots Mercaptoropyl Capping agent [58] Ferrocene Hydrido or hydridodimethylsiloxy Karstedt's catalyzed reaction [59] Quaternized PDMA-poly (sulfobetaíne) Propyl ammonium chloride ARTP [60] Poly (fluorinated acrylate -PEG) Vinyl RAFT polymerization [61] Galactose or maltose Aminopropyl Amidation [66] Glycosides Vinyl Thiol-ene click reaction [67] Various carbohydrates Azidopropyl CuAAC [68] Sugar alkynes Azidopropyl CuAAc 2010, 2012 [18,69] Glycosides/Cysteine derivatives Vinyl Thiol-ene click reaction [70] Poly (lactic acid) Hydroxypropyl Microwave assisted ROMP [71] BODIPY Azidopropyl CuAAC [18] PVF Vinyl Heck couple reaction [72] Dipeptides or tripept...…”

Intervalence charge transfer across noncovalent interactions on vinyl silyl bridged biferrocenyl compounds

“…Among all metallocenes, ferrocene (Fc) is one of the most commonly used as building block, as its redox behavior is very well described in literature. It is because of this well-behaved redox chemistry of ferrocene that it constitutes an ideal test molecule to study the possibilities of new molecular bridges that link several metallocene units [4][5][6][7][8][9][10].…”