Synthesis and Properties of Annulated 2-(Azaar-2-yl)- and 2,2'-Di(azaar-2-yl)-9,9'-spirobifluorenes

A series of 9,9'-spirobifluorene-derived N-heterocycles were prepared by the reactions of 8,9-dihydrospiro(benzo[b]fluorene-11,9'-fluoren)-6(7H)-one and 8,8',9,9'-tetrahydro-11,11'-spirobi(benzo[b]fluorene)-6,6'(7H,7'H)-dione with a series of 2-amino-arenecarbaldehydes such as 2-aminobenzaldehyde, 2-aminonicotinealdehyde, 1-amino-2-naphthaldehyde, and 8-aminoquinoline-7-carbaldehyde. In addition to the absorption maxima based on the parent 9,9'-spirobifluorene skeleton in the 225–234, 239–280, 296–298, and 308–328 nm regions, the absorptions due to the π-π* transitions of the heterocycles were observed in the 351–375 nm region in the UV absorption spectra. All the compounds showed strong photoluminescences in the 390–430 nm region.