Stereospecific Formation of the rctt Isomer of Bis-crown-Containing Cyclobutane upon [2 + 2] Photocycloaddition of an (18-Crown-6)stilbene Induced by Self-Assembly via Hydrogen Bonding

Timofey P Martyanov; Artem P Vorozhtsov; Nadezhda A Aleksandrova; Ilia V Sulimenkov; Evgeny N Ushakov; Sergey P Gromov

doi:10.1021/acsomega.2c05295

Stereospecific Formation of the rctt Isomer of Bis-crown-Containing Cyclobutane upon [2 + 2] Photocycloaddition of an (18-Crown-6)stilbene Induced by Self-Assembly via Hydrogen Bonding

ACS Omega. 2022 Nov 8;7(46):42370-42376. doi: 10.1021/acsomega.2c05295. eCollection 2022 Nov 22.

Authors

Timofey P Martyanov^{1

2}, Artem P Vorozhtsov^{1

2}, Nadezhda A Aleksandrova², Ilia V Sulimenkov³, Evgeny N Ushakov^{1

2}, Sergey P Gromov^{2

4}

Affiliations

¹ Federal Research Center of Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences, Chernogolovka, Moscow Region142432, Russian Federation.
² Photochemistry Center of RAS, FSRC "Crystallography and Photonics", Russian Academy of Sciences, Novatorov Str. 7A-1, Moscow119421, Russian Federation.
³ Chernogolovka Branch of the N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region142432, Russian Federation.
⁴ Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1-3, Moscow119991, Russian Federation.

Abstract

The formation and the spectroscopic and structural properties of 1:1 and 2:1 (ligand-to-dication) complexes of an (18-crown-6)stilbene with ethane-1,2-diammonium diperchlorate in MeCN were studied by UV-vis and NMR spectroscopy and by density functional theory calculations. Prolonged UV irradiation of 2:1 mixtures of the crown stilbene and the diammonium salt led to the formation of two main photoproducts, namely, the single syn-"head-to-head" photodimer of the crown stilbene (rctt cyclobutane) due to supramolecular-assisted [2 + 2] photocycloaddition and a crown ether derivative of phenanthrene due to a photoinduced electrocyclization reaction. The rctt cyclobutane was isolated by preparative photolysis, followed by chromatography. The selectivity of the [2 + 2] photocycloaddition is explained by supramolecular pre-organization of crown stilbene molecules into the 2:1 complexes that have a pseudo-sandwich structure with stacking interactions between the stilbene moieties.