Synthesis and photophysical properties of bi-aza[5]helicene and bi-aza[6]helicene

Synthesis of two derivatives of bi-aza[n]helicenes is achieved by I-2-THF mediated photocyclization of corresponding bi-styryl derivatives. The cyclization furnished the desired angularly fused bi-aza[5] helicene and bi-aza[6]helicene in moderate yields. The structures are established by NMR spectroscopy and single crystal X-ray analysis. The crystal structure indicate an unusually planer central biphenyl unit in the bi-aza[6]helicene. It also indicates to the presence of 'P' and 'M' stereoisomer in the bi-aza[6] helicene making it a meso isomer. The series of synthesized bi-aza[n]helicenes were characterized by UV and fluorescence spectroscopy. (C) 2015 Elsevier Ltd. All rights reserved.