Vernier-templated synthesis, crystal structure, and supramolecular chemistry of a 12-porphyrin nanoring.

Journal article

Vernier templating exploits a mismatch between the number of binding sites in a template and a reactant to direct the formation of a product that is large enough to bind several template units. Here, we present a detailed study of the Vernier-templated synthesis of a 12-porphyrin nanoring. NMR and small-angle X-ray scattering (SAXS) analyses show that Vernier complexes are formed as intermediates in the cyclo-oligomerization reaction. UV/Vis/NIR titrations show that the three-component assembly of the 12-porphyrin nanoring figure-of-eight template complex displays high allosteric cooperativity and chelate cooperativity. This nanoring-template 1:2 complex is among the largest synthetic molecules to have been characterized by single-crystal analysis. It crystallizes as a racemate, with an angle of 27° between the planes of the two template units. The crystal structure reveals many unexpected intramolecular C-H⋅⋅⋅N contacts involving the tert-butyl side chains. Scanning tunneling microscopy (STM) experiments show that molecules of the 12-porphyrin template complex can remain intact on the gold surface, although the majority of the material unfolds into the free nanoring during electrospray deposition.

Authors: Kondratuk, D; Sprafke, J; O'Sullivan, M; Perdigao, L; Saywell, A

• Publication status: Published
• Journal: Chemistry (Weinheim an der Bergstrasse, Germany)
• Volume: 20
• Issue: 40
• Pages: 12826-12834
• Publication date: 2014-09-01
• DOI: 10.1002/chem.201403714
• EISSN: 1521-3765
• ISSN: 0947-6539
• Language: English
• Keywords: supramolecular chemistry; conjugation; porphyrinoids; macrocycles; template synthesis