Synthesis and Study of Photophysical Properties of 6,12‐Dicyano‐9‐oxa[7]helicene

Synthesis of 6,12‐dicyano‐9‐oxa[7]helicene is achieved from 4‐methoxybenzyl cyanide by several steps, including homocoupling of hydroxyl phenanthrene and cyclization of the diol. The oxa[7]helicene was characterized by single crystal X‐ray diffraction analysis and its photophysical properties were evaluated. Geometry optimization of this helicene was carried out using B3LYP/6‐31G level of theory and its HOMO‐LUMO energy gap was calculated. This paper reports synthesis of 6,12‐dicyano‐9‐oxa[7]helicene 4, along with the comparison of its photophysical properties with its isomer 5,13‐dicyano‐9‐oxa[7]helicene 3. The photophysical properties of helicene 4 were studied in solvents of different polarity. Theoretical calculations were performed for helicene 4 and 3 to calculate HOMO‐LUMO band gap, which was compared with the energy calculated from their absorption edge with the help of Tauc plot method. Thermal behaviour of helicene 4 was investigated.