Stimuli-Responsive Cyclopenta[Ef]Heptalenes: Synthesis And Optical Properties

Keywords

Azulene; Cyclopenta[ef]heptalene; Dyes/pigments; Electron transfer; Natural products; Photoacid generator; Photochromism; Sensitizers; Stimuli response

Abstract

We report the one-pot synthesis, 1D and 2D NMR characterization, and UV/Vis study of a series of cyclopenta[ef]heptalenes 4a-c that exhibit strong stimuli-responsive behavior, with a tunable energy gap as a result of perturbation of HOMO, LUMO, and LUMO+1 energies upon doping/dedoping with TFA/Et3N. The approach employed allows for the extension of conjugation at C-4 of the cyclopenta[ef]heptalene skeleton from X = H (4a) to X = CN (4b) and X = 2-thiophenyl (4c), resulting in longer absorption maxima and smaller optical energy gaps of the cyclopenta[ef]heptalenium cations 4a-c+. Additionally, in the presence of a UV-activated (< 300 nm) photoacid generator (PAG), protonation of 4c can be indirectly achieved by intermolecular photoinduced electron transfer (PeT) from the excited state of 4c to the PAG, upon which the latter undergoes photodecomposition resulting in the generation of acid. This phenomenon facilitates the use of cyclopenta[ef]heptalenes 4a-c as visible sensitizers of commercial PAGs.

Publication Date

1-1-2015

Publication Title

European Journal of Organic Chemistry

Volume

2015

Issue

10

Number of Pages

2271-2276

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1002/ejoc.201500059

Socpus ID

85027921493 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85027921493

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