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Issue 35, 2017
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Alkyl-substituted spiropyrans: electronic effects, model compounds and synthesis of aliphatic main-chain copolymers

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Abstract

The isomerisation behaviour of spiropyrans (SP) depends considerably on their substituents. This work investigates the synthesis, isomerisation behaviour and polymer chemistry of alkylated spiropyrans. While several Kumada- and Suzuki-based protocols failed to alkylate dibromo-spiropyran, classical 9-BBN chemistry is shown to proceed with high yield suitable also for polycondensation. Alkyl substituents strongly influence the acid-induced SP-merocyanine (MC)-protonated MC (MCH+) equilibrium and render the MCH+ form most stable. In agreement with measured isomerisation rates, density functional theory calculations corroborate the enhanced stabilisation of ethyl-substituted MCH+ as compared to phenyl-substituted MCH+. Aliphatic main chain spiropyran copolymers are synthesised from in situ generated bis-9-BBN monomers and dibromo-spiropyrans. The empirical optimisation of stoichiometry yields a molecular weight Mw of ∼15 kg mol−1 after purification. This approach to alkylated spiropyrans opens new opportunities to fine-tune the isomerisation behaviour of small molecules and polymeric SP derivatives for potential use as sensors and smart materials.

Graphical abstract: Alkyl-substituted spiropyrans: electronic effects, model compounds and synthesis of aliphatic main-chain copolymers

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Publication details

The article was received on 14 Jun 2017, accepted on 28 Jul 2017 and first published on 31 Jul 2017


Article type: Paper
DOI: 10.1039/C7PY00987A
Citation: Polym. Chem., 2017,8, 5407-5414
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    Alkyl-substituted spiropyrans: electronic effects, model compounds and synthesis of aliphatic main-chain copolymers

    S. B. Schmidt, F. Kempe, O. Brügner, M. Walter and M. Sommer, Polym. Chem., 2017, 8, 5407
    DOI: 10.1039/C7PY00987A

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