title: 1-, 3-, 6-, and 8-Tetrasubstituted Asymmetric Pyrene Derivatives with Electron Donors and Acceptors: High Photostability and Regioisomer-Specific Photophysical Properties.
abstract: The systematic synthesis of five 1-, 3-, 6-, and 8-tetrasubstituted asymmetric pyrenes with electron donor and acceptor moieties is presented, together with an examination of their photophysical properties. Pyrene derivative PA1, containing one formyl and three piperidyl groups, showed bright solvatochromic fluorescence from green (λem = 557 nm, ΦFL = 0.94 in hexane) to red (λem = 648 nm, ΦFL = 0.50 in methanol), suggesting potential applications for PA1 as an environmentally responsive probe. Although the synthesis of simple 1- and 3-disubstituted pyrene derivatives is considered difficult, PA13, with two formyl groups at the 1- and 3-positions and two piperidyl groups at the 6- and 8-positions, could be synthesized successfully. PA13 exhibited less pronounced solvatochromism, but displayed a narrow fluorescent band with high ΦFL in all solvents (ΦFL > 0.75). Moreover, its absorption band displayed an exceptional bathochromic shift compared to the other derivatives (e.g., λabs = 480 and 522 nm in ethanol for PA1 and PA13, respectively), suggesting that such modifications of pyrene may be quite important for the modulation of its energy gap. Additionally, all compounds exhibited exceptionally high photostability, which highlights the advantage of these new dyes and provides new insights on the design of photostable fluorophores.
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1-H-134 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Niko
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1-H-134 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Sasaki
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1-H-134 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Kaishi
authors.initials: K
authors.lastname: Narushima
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1-H-134 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Dharmendar Kumar
authors.initials: DK
authors.lastname: Sharma
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1-H-134 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Martin
authors.initials: M
authors.lastname: Vacha
authors.affiliation: Department of Organic and Polymeric Materials, Tokyo Institute of Technology , 2-12-1-H-134 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.|PRESTO Japan Science and Technology Agency , Tokyo 102-0076, Japan.
authors.forename: Gen-ichi
authors.initials: G
authors.lastname: Konishi