Premium
Dithienyl Acenedithiophenediones as New π‐Extended Quinoidal Cores: Synthesis and Properties
Author(s) -
Kawabata Kohsuke,
Osaka Itaru,
Sawamoto Masanori,
Zafra José L.,
Mayorga Burrezo Paula,
Casado Juan,
Takimiya Kazuo
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201605104
Subject(s) - homo/lumo , chemistry , thiophene , cyclic voltammetry , absorption spectroscopy , crystallography , open shell , spectroscopy , absorption (acoustics) , acceptor , electronic structure , photochemistry , materials science , molecule , computational chemistry , electrochemistry , physics , organic chemistry , electrode , quantum mechanics , composite material , condensed matter physics
We have synthesized two isomeric pairs of benzo‐ and naphthodithiophenediones with two flanking thiophenes and characterized them by single‐crystal X‐ray analysis, cyclic voltammetry, steady‐state optical electronic absorption and emission spectroscopies, transient absorption spectroscopy, and vibrational spectroscopies with in situ spectroelectrochemistry techniques, and then compared them with the thieno[3,2‐ b ]thiophene‐2,5‐dione counterpart that we previously reported. The results show that the central acenedithiophenedione cores have quinoidal conjugation with closed‐shell character. The π‐extension of the quinoidal core raises (lowers) the HOMO (LUMO) energy levels of the triads, resulting in the drastic reduction of their energy gaps from approximately 2.0 eV to 1.1 eV. Owing to the electron‐withdrawing nature of the carbonyl terminal group at the quinoidal core, the triads have low‐lying LUMO energy levels ranging from −3.9 eV to −4.3 eV, and can be regarded as strong electron‐acceptor building units. Interestingly, the pairs of structural isomers have similar electronic structures in both the neutral and charged states despite the different shapes (linear and angular) and/or symmetry ( C 2 h and C 2 v ) of the acenedithiophenedione cores.