4,4′-[8b,8c-Bis(ethoxycarbonyl)-4,8-dioxo-2,3,5,6-tetrahydro-1<i>H</i>,4<i>H</i>-2,3a,4a,6,7a,8a-hexaazacyclopenta[<i>def</i>]fluorene-2,6-diyl]dipyridinium bis(tetrafluoridoborate)
Acta crystallographica. Section E