Annulated Azuleno[2,1,8‐ija]azulenes: Synthesis and Properties.

Non‐alternant non‐benzenoid hydrocarbons exhibit very different optical and electronic properties than their well‐studied benzenoid analogues. However, preparing such structures with extended conjugation length, remains challenging. Herein, we report the synthesis and properties of azuleno[2,1,8‐ija]azulene derivatives using a two‐step sequence involving a four‐fold aldol condensation between aromatic dialdehydes and readily available tetrahydropentalene‐2,5‐(1H,3H)‐dione. Molecules with band gap values ranging from 1.69 to 2.14 eV and molar extinction coefficients (ϵ) of nearly 3×105 M−1 cm−1 have been prepared. These annulene‐like structures exhibit significant diatropic ring currents (aromatic), as supported by 1H NMR spectroscopy and DFT calculations. Field‐effect transistors (OFETs) using azuleno[2,1,8‐ija]azulene derivatives as semiconductors exhibit charge mobility values of up to 0.05 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]