Metal Ions Drive Thermodynamics and Photochemistry of the Bis(styryl) Macrocyclic Tweezer

✍ Scribed by Elena V. Tulyakova; Gaston Vermeersch; Elena N. Gulakova; Olga A. Fedorova; Yuri V. Fedorov; Jean Claude Micheau; Stéphanie Delbaere

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 531 KB
• Volume: 16
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200903226

✦ Synopsis

Abstract

UV/Vis and NMR spectroscopy were used for the structural elucidation and thermodynamic and photochemical studies of the metal‐coordinated crown‐containing macrocyclic tweezer (E,E)‐1. The bis(styryl) tweezer (E,E)‐1 formed two types of complexes with magnesium(II): a 1:1 intramolecular asymmetric sandwich complex [(E,E)‐1]⋅Mg^2+^ and a 1:2 complex [(E,E)‐1]⋅(Mg^2+^)~2~. In the former case, there is direct cation intramolecular exchange (0.299 s^−1^, Δ__G__^≠^=69.4 kJ mol^−1^) between two parts of the bis(styryl) tweezer (E,E)‐1. Addition of barium(II) to the bis(styryl) tweezer (E,E)‐1 led to an intramolecular centrosymmetric sandwich 1:1 complex [(E,E)‐1]⋅Ba^2+^. Irradiation of [(E,E)‐1]⋅Ba^2+^ afforded reversible intramolecular [2π+2π] photocyclization with excellent stereoselectivity and quantitative yield. In contrast, irradiation of [(E,E)‐1]⋅(Mg^2+^)~2~ resulted in reversible stepwise E,Z‐isomerization.