Aromaticity Concerto in Polycyclic Conjugated Hydrocarbons: Fusion Pattern on Combined Aromaticity Strategy Leads to Distinctive Excited State Photophysics of Dinaphthopentalenes
Understanding the structure–property relationships in polycyclic conjugated hydrocarbons (PCHs) is crucial for controlling their electronic properties and developing new optical function materials. Aromaticity is a fundamentally important and intriguing property of numerous organic chemical structures and has stimulated a myriad of experimental and theoretical investigations. Exploiting aromaticity rules for the rational design of optoelectronic materials with the desired photophysical characteristics is a challenging yet fascinating task. Herein we present an in-depth computational and spectroscopic study on the structure–property relationships of dinaphthopentalenes (DNPs). Results highlight that the different fusion patterns between 4n π and 4n+2 π units endow these polycyclic conjugated hydrocarbons (PCHs) with the tunable aromaticity in the ground state/excited state, which leads to the diverse electronic structures and consequently the distinctive excited state photophysics. Accordingly, we propose a combined aromaticity design strategy for rationally modulating and tailoring electronic and optical properties of PCH skeletons. These outcomes not only present a full picture of the excited state dynamics of the DNP system and afford a new class of efficient singlet fission-active materials but also provide some basic guidelines for exploiting aromaticity rules to design and develop new optical function materials.