Para-quinodimethane-bridged perylene dimers and pericondensed quaterrylenes: The effect of the fusion mode on the ground states and physical properties
KAUST DepartmentKAUST Catalysis Center (KCC)
Physical Sciences and Engineering (PSE) Division
Chemical Science Program
Permanent link to this recordhttp://hdl.handle.net/10754/563659
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AbstractPolycyclic hydrocarbon compounds with a singlet biradical ground state show unique physical properties and promising material applications; therefore, it is important to understand the fundamental structure/biradical character/physical properties relationships. In this study, para-quinodimethane (p-QDM)-bridged quinoidal perylene dimers 4 and 5 with different fusion modes and their corresponding aromatic counterparts, the pericondensed quaterrylenes 6 and 7, were synthesized. Their ground-state electronic structures and physical properties were studied by using various experiments assisted with DFT calculations. The proaromatic p-QDM-bridged perylene monoimide dimer 4 has a singlet biradical ground state with a small singlet/triplet energy gap (-2.97 kcalmol-1), whereas the antiaromatic s-indacene-bridged N-annulated perylene dimer 5 exists as a closed-shell quinoid with an obvious intramolecular charge-transfer character. Both of these dimers showed shorter singlet excited-state lifetimes, larger two-photon-absorption cross sections, and smaller energy gaps than the corresponding aromatic quaterrylene derivatives 6 and 7, respectively. Our studies revealed how the fusion mode and aromaticity affect the ground state and, consequently, the photophysical properties and electronic properties of a series of extended polycyclic hydrocarbon compounds. A matter of fusion mode! Fusion of a para-quinodimethane (p-QDM) subunit at the peri and β positions of perylene dimers leads to systems with different ground states, that is, open and closed shell (see picture). These systems showed large two-photon absorption cross sections and ultrafast excited-state dynamics relative to their corresponding pericondensed aromatic quaterrylene counterparts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
SponsorsJ.W. acknowledges the financial support from the BMRC grant (10/1/21/19/642), MOE Tier 2 grant (MOE2011-T2-2-130), MINDEF-NUS JPP Grant (12-02-05), and IMRE Core funding (IMRE/13-1C0205). The work at Yonsei University was supported by a Mid-career Researcher Program (2010-0029668) and Global Research Laboratory (2013K1A1A2A02050183) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT (Information and Communication Technologies), and Future Planning. K. H. acknowledges financial support from KAUST. We thank Koh Lip Lin, Tan Geok Kheng, and Hong Yimian for the crystallographic analysis of 4.
JournalChemistry - A European Journal