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

Synthesis and Photophysical Properties of Aza[n]helicenes

“…Such a shape contributes to the non-coplanar geometry, resulting in the reduction of effective π conjugation causing a blue shift in the fluorescence spectra of aza [6]helicene. 2b Interestingly, the emission maximum for aza[9]helicene was almost similar to the corresponding aza [7]helicene 29 probably due to combination of contradictory effects of distorted geometry (leading to more blue shift) and extended conjugation (resulting in red shift). 2b The angular−linear compound 8 showed a blue shift compared to the more linear π molecular systems 9 and 10; phenomenon might be attributed to the high dihedral angle which limits the delocalization of electrons throughout the molecule to some extent.…”

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

“…The presence of heteroatoms (S, N, O, P) in the fused polycyclic π-systems additionally contributes to altering electronic structure and helps to fine tune optoelectronic properties [1][2][3][4][5][6][7][8][9][10][11]20,[35][36][37]. The last decades highlighted heterohelicenes, incorporating one or two carbazole fragments, as a very attractive class of molecules [38][39][40][41][42][43][44][45][46][47][48][49][50][51]. This is not surprising, taking into account the excellent thermal stability, the strong electron-donating nature, a good hole-transporting ability of the carbazole unit and, as a consequence, numerous applications of the carbazole-based electroactive materials [52][53][54].…”

“…The latter are generally available via the Wittig, Heck-type or McMurry couplings. It is also a useful way to synthesize heterohelicenes, in particular, carbazole-based helicenes [39][40][41][42]44,47,48,50,51] (Scheme 1A). However, photocyclization of the stilbene substrates, having two non-equivalent ortho positions, leads to the formation of isomeric polynuclear molecules, which are often difficult to separate.…”

Enantiomerically Pure 5,13‐Dicyano‐9‐oxa[7]helicene: Synthesis and Study

“…Due to some interesting properties we have been involved in the synthesis and study of different types of aza[ n ]helicenes. [11] The oxygen analogues, oxa[ n ]helicenes have also been subject of active research and several reports on their synthesis and study are available. [12] In continuation of our work in this area [13] we have undertaken the present work to synthesize optically pure dicyano oxa[7]helicenes 1 , its helicenes like analogue 2 and discuss the findings of their response to circularly polarized luminescence (CPL) and optical rotation.…”