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Molecular Switching: A Fully Reversible, Optically Active Photochemical Switch Based on a Tetraethynylethene‐1,1′‐Binaphthalene Hybrid System
Author(s) -
Gobbi Luca,
Seiler Paul,
Diederich Franc˛ois,
Gramlich Volker
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20000809)83:8<1711::aid-hlca1711>3.0.co;2-#
Subject(s) - chemistry , molecular switch , optically active , photochemistry , optical switch , combinatorial chemistry , optoelectronics , organic chemistry , molecule , physics
The synthesis, characterization, and physical properties of a novel, fully reversible, light‐driven molecular switch, ( R , R )‐ 1 /( R , R )‐ 2 , based on a tetraethynylethene‐1,1′‐binaphthalene hybrid system are presented. trans ‐Configured ( R , R )‐ 1 was synthesized in 57% yield by Stille cross‐coupling between stannylated tetraethynylethene 3 and 3‐iodo‐1,1′‐binaphthalene derivative ( R )‐ 4 ( cf. Scheme 2 ). The cis ‐isomer ( R , R )‐ 2 was prepared from ( R , R )‐ 1 by photoisomerization. X‐Ray crystal‐structure analyses were obtained for both cis ‐ and trans ‐forms of the photoswitch ( Figs. 1 and 2 ). In the crystalline state, molecules of the cis ‐isomer ( R , R )‐ 2 exhibit intramolecular edge‐to‐face (C−H⋅⋅⋅ π ) interactions between naphthalene rings of the two 1,1‐binaphthalene moieties ( Fig. 3 ). The switching properties were investigated by electronic absorption spectroscopy ( Table and Fig. 4 ): irradiation at λ =398 nm converts trans ‐isomer ( R , R )‐ 1 into cis ‐isomer ( R , R )‐ 2 , whereas switching occurs in the opposite direction upon irradiation at λ =323 nm. No thermal interconversion between the two isomers was observed in CH 2 Cl 2 at room temperature over a period of 2 – 3 months, and the system possesses good resistance against photofatigue ( Fig. 5 ). Investigations of the circular dichroism of ( R , R )‐ 1 and ( R , R )‐ 2 in CH 2 Cl 2 solution showed that the chiral binaphthalene moieties induce a weak Cotton effect in the achiral tetraethynylethene core ( Fig. 6 ). System ( R , R )‐ 1 /( R , R )‐ 2 represents one of the rare switches allowing two‐way photochemical interconversions, not perturbed by thermal‐isomerization pathways.