An Azobenzene-Bipyridinium Derivative as a Component in the Construction of Photoresponsive Pseudorotaxanes

Abstract

We describe the synthesis and characterization of a bipyridinium derivative conjugated with two azobenzene groups (Azo₂Bpy²⁺). The design maintains the ability of the photoswitches to undergo E to Z isomerization upon irradiation to generate a mixture of EE, EZ and ZZ isomers. Moreover, Azo₂Bpy²⁺ is able to undergo self-assembly with dibenzo[24]crown-8 ether to generate [3]-pseudorotaxanes, driven by the strong cooperative effects, for all its geometric isomers.

Key words

molecular devices - crown ethers - photochemistry - supramolecular chemistry - photoisomerization

Publication History

Received: 08 March 2025

Accepted after revision: 03 April 2025

Article published online:
07 May 2025

• References and Notes

• 1 Molecular Switches . Feringa BL, Browne WR. Wiley-VCH; Weinheim: 2011
• 2a Baroncini M, Silvi S, Credi A. Chem. Rev. 2020; 120: 200
• 2b Kassem S, van Leeuven T, Lubbe AS, Wilson MR, Feringa BL, Leigh DA. Chem. Soc. Rev. 2017; 9: 2592
• 3 Bruns CJ, Stoddart JF. The Nature of the Mechanical Bond: From Molecules to Machines . John Wiley & Sons; Hoboken: 2017
• 4a Ding J, Zheng C, Wang L, Lu C, Zhang B, Chen Y, Li M, Zhai G, Zhuang X. J. Mat. Chem. A 2019; 7: 23337
• 4b Madasamy K, Velayutham D, Suryanaraynan V, Kathiresan M, Ho K.-C. J. Mater. Chem. C 2019; 7: 4622
• 5 Andreoni L, Groppi J, Seven Ö, Baroncini M, Credi A, Silvi S. Angew. Chem. Int. Ed. 2025; 64: e202414609
• 6 Braunschweig AB, Ronconi CM, Han J.-Y, Aricò F, Cantrill SJ, Stoddart JF, Khan SI, White AJ. P, Williams DJ. Eur. J. Org. Chem. 2006; 1857
• 7 Sakata Y, Ogura T, Akine S. Chem. Commun. 2020; 56: 8735
• 8 Baroncini M, Groppi J, Corra S, Silvi S, Credi A. Adv. Opt. Mater. 2019; 7: 1900392
• 9 Cisnetti F, Ballardini R, Credi A, Gandolfi MT, Masiero S, Negri F, Pieraccini S, Spada GP. Chem. Eur. J. 2004; 10: 2011
• 10 1,1′-Bis(3-((E)-p-tolyldiazenyl)phenyl)-[4,4′-bipyridine]-1,1'-diium Dihexafluorophosphate (EE-3) 1,1'-Bis(2,4-dinitrophenyl)-4,4′-bipyridinium dichloride (0.5 g, 0.8 mmol) and compound 2 (0.4 g, 1.8 mmol) were dissolved in EtOH (40 mL) and the solution was stirred at reflux temperature for 48 h. The solvent was removed, and the solid residue was dissolved in water (50 mL) and EtOAc (50 mL). The aqueous phase was extracted with EtOAc (3 × 50 mL). A saturated aqueous solution of ammonium hexafluorophosphate (NH₄PF₆) was added to the aqueous phase, which contained the chloride salt of the product, to precipitate the product as the hexafluorophosphate salt. The obtained solid was filtered and washed with water and EtOH, then dried under vacuum. The product was an orange solid obtained in 71% yield (0.5 g). ¹H NMR (500 MHz, CD₃CN, 298 K): δ = 9.30 (d, J = 6.5 Hz, 4 H, H5), 8.71 (d, J = 6.5 Hz, 4 H, H6), 8.31 (d, J = 8.0 Hz, 2 H, H7), 8.29 (s, 2 H, H4), 7.98 (t, J = 8.0 Hz, 2 H, H8), 7.93–7.90 (m, 6 H, H3, H9), 7.45 (d, J = 8.2 Hz, 4 H, H2), 2.47 (s, 6 H, H1). ¹³C NMR (125 MHz, CD₃CN, 298 K): δ = 154.6, 151.6, 151.3, 146.9, 144.7, 144.1, 132.8, 131.2, 128.5, 127.7, 127.3, 124.1, 118.8, 21.6.
• 11 Porter WW, Vaid TP. J. Org. Chem. 2005; 70: 5028
• 12 Baroncini M, Silvi S, Venturi M, Credi A. Chem. Eur. J. 2010; 16: 11580