Post‐Formation of Fused Pentagonal Structure on Fjord Region of Polyaromatic Hydrocarbons under Hydrothermal Conditions.

This study explores the synthesis of cyclopenta‐fused polyaromatic hydrocarbons (CP‐PAHs) via Pt‐catalyzed cyclization in water, focusing on the formation of fused pentagonal rings within heavily fused PAH frameworks. Utilizing platinum catalysts at lower temperatures (200‐260 °C) in water, led to the successful synthesis of singly cyclized CP‐PAHs. The reaction conditions facilitated the mono‐cyclization of substrates such as dibenzo[g,p]chrysene and its isomers, yielding the desired products while suppressing the formation of bis‐cyclized compounds. The use of Fe2O3 as an additive in conjunction with PtO2 was effective to suppress hydrogenation of the substrates and products. The products exhibited a redshift in UV‐visible absorption and photoluminescence bands due to a decrease in the HOMO−LUMO energy gap. These findings highlight the potential of Pt‐catalyzed cyclization for the controlled synthesis of CP‐PAHs, with implications for various applications in materials science. [ABSTRACT FROM AUTHOR]