One‐Pot Sequential Heck–Suzuki Synthesis of 5‐Styryl‐9‐Hydroxy‐1 <i>H</i> ‐phenalen‐1‐ones with Tunable Optoelectronic Properties

Abstract For the preparation of novel 5‐styryl‐substituted 9‐hydroxy‐1 H ‐phenalen‐1‐ones, a sequential Pd‐catalyzed Heck vinylenation–Suzuki arylation one‐pot strategy was established, providing efficient access to a library of donor–acceptor chromophores. These multifunctional conjugates are characterized by a planar, highly conjugated backbone extended through vinyl substitution at the 5‐position. The obtained compounds were comprehensively investigated with respect to their electrochemical and photophysical properties. Cyclic voltammetry demonstrates that the reduction potentials remain largely unaffected by substituents, whereas the oxidation potentials show a pronounced dependence on the electronic nature of the aryl groups. UV–vis and fluorescence spectroscopy revealed bathochromic shifts of absorption and emission maxima for electron‐donating substituents, while electron‐withdrawing groups induce hypsochromic responses. Complementary Hammett correlations confirm the dominance of resonance effects, with the strongest linear relationships observed for the extended σ p+ parameter, highlighting mesomeric stabilization as the decisive factor in modulating electronic transitions. Quantum‐chemical (TD)DFT calculations reproduce the spectroscopic trends and provide detailed insight into orbital contributions and charge‐transfer characteristics. Solvatochromic analyses further evidence the polar nature of the excited states, supporting a pronounced intramolecular charge‐transfer character.