Polysiloxanes Bearing Pendant Redox-Active Dendritic Wedges Containing Ferrocenyl and (畏6-Aryl)tricarbonylchromium Moieties

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• 作者：Magdalena Zamora ; Sonia Bru帽a ; Beatriz Alonso ; Isabel Cuadrado
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：October 25, 2011
• 年：2011
• 卷：44
• 期：20
• 页码：7994-8007
• 全文大小：1236K
• 年卷期：v.44,no.20(October 25, 2011)
• ISSN：1520-5835

文摘

Novel highly functionalized polysiloxanes have been synthesized, which bear small pendant dendritic wedges containing two different redox-active organometallic moieties, namely the electron-donating ferrocenyl group and the electron withdrawing (畏⁶-aryl)tricarbonylchromium entity. Hydrosilylations of vinylsilyl-functionalized (CH₂鈺怌H)MePhSiFc (1) and allylsilyl-terminated dendron (CH₂鈺怌HCH₂)PhSi[(CH₂)₂MePhSiFc]₂ (3), with the Si鈥揌-containing polysiloxane backbones (Me₃SiO)(MeSiHO)_n(Me₂SiO)_m(SiMe₃) (n = 30鈥?5%, m = 65鈥?0%), and (Me₃SiO)(MeSiHO)_n(SiMe₃) (n 35) successfully afforded the novel siloxane-based copolymers 8 and 9 and homopolysiloxanes 10 and 11 possessing appended organometallic dendritic side chains. Thermal treatment of 8 with Cr(CO)₆ and reaction of 10 with (CH₃CN)₃Cr(CO)₃ further increased metal density of the polymers affording polysiloxanes 12 and 13 carrying (畏⁵-C₅H₄)Fe(畏⁵-C₅H₅) and (畏⁶-C₆H₅)Cr(CO)₃ moieties hanging from their polysiloxane chain. Similar reactions, starting from 1,1,3,3-tetramethyldisiloxane and phenyltris(dimethylsiloxy)silane, were also a convenient way to prepare the corresponding homo and heterometallic model compounds [MePhFcSi(CH₂)₂Me₂Si]₂O (5), [{(畏⁶-C₆H₅)Cr(CO)₃}MeFcSi(CH₂)₂Me₂Si]₂O (6), and PhSi[OMe₂Si(CH₂)₂MePhSiFc]₃ (7). These model compounds and the metallopolysiloxanes were characterized by IR, multinuclear NMR spectroscopies and mass spectrometry. Thermogravimetric analysis (TGA) established that dendronized polysiloxanes 9 and 11, with ferrocenyl dendrons derived from 3, possess higher thermal stability than parent ferrocenyl polysiloxanes 8 and 10. Ferrocenyl dendronized polysiloxanes 9 and 11 yield ceramic products, which have been characterized by SEM and EDX microanalyses. Solution electrochemical studies showed that all the ferrocenyl units present in polysiloxanes 8鈥?b>13 are electrochemically independent. Ferrocenyl polysiloxanes 8鈥?b>11, deposited electroactive films onto electrode surfaces. Their well-defined and persistent redox waves are characteristic of electrochemically stable, surface-confined reversible redox couples.