Double protonation of 1,5-bis(triarylaminoethynyl)anthraquinone to form a paramagnetic pentacyclic dipyrylium salt

J Am Chem Soc. 2010 Sep 8;132(35):12472-9. doi: 10.1021/ja105250f.

Abstract

Protonation-induced intramolecular cyclization reactions of new donor (D)-acceptor (A) and D-A-D conjugated molecules 1-triarylaminoethynylanthraquinone (1-AmAq) and 1,5-bis(triarylaminoethynyl)anthraquinone (1,5-Am(2)Aq), respectively, were achieved. The former undergoes monoprotonation with bis(trifluoromethanesulfone)imide acid (TFSIH) to give pyrylium salt [1-AmPyl]TFSI, whereas the latter undergoes a novel double proton cyclization reaction to yield 1,5-bis(triarylamino)dipyrylium salt [1,5-Am(2)Pyl(2)](TFSI)(2) with a new pentacyclic backbone. This divalent cationic salt can be reduced to give the neutral species 2,8-bis(triarylamino)benzo[de]isochromeno[1,8-gh]chromene ([1,5-Am(2)Pyl(2)](0)), which maintains the planar pentacyclic backbone. The obtained condensed-ring compounds show unique optical, electrochemical, and magnetic properties due to the extremely narrow HOMO-LUMO gap. In particular, the dication [1,5-Am(2)Pyl(2)](2+) shows paramagnetic behavior with two spins centered on two triarylamine moieties through valence tautomerization with the pentacyclic backbone.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anthraquinones / chemistry*
  • Crystallography, X-Ray
  • Magnetics*
  • Models, Molecular
  • Protons*
  • Pyrans / chemistry*
  • Salts / chemistry

Substances

  • Anthraquinones
  • Protons
  • Pyrans
  • Salts