Indeno[1, 2‐b]fluorene‐Based [2, 2]Cyclophanes with 4n/4n and 4n/[4n+2] π Electrons: Syntheses, Structural Analyses, and Excitonic Coupling Properties. Issue 30 (13th June 2019)

• Record Type: Journal Article
• Authors: Wang, Chi‐Shin; Wei, Yu‐Chen; Chang, Kai‐Hsin; Chou, Pi‐Tai; Wu, Yao‐Ting
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 30(2019)
• Page Start: 10158
• Page End: 10162
• Publication Date: 2019-06-13
• Subjects: aromaticity -- cyclophanes -- electronic structure -- noncovalent interactions -- structure elucidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201903561
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Indeno[1, 2‐ b ]fluorene‐based [2, 2]cyclophanes with 4 n /4 n and 4 n /[4 n +2] π‐electron systems were prepared, and their structures were identified by X‐ray crystallography. With short π–π distances around 3.0 Å, [2.2](5, 11)indeno[1, 2‐ b ]fluorenophane and its precursor [2.2](5, 11)indeno[1, 2‐ b ]fluorene‐6, 12‐dionophane exhibit remarkable transannular interactions, leading to their unusual electrochemical and photophysical properties. With the aid of femtosecond transient absorption spectroscopy, the transition from the monomeric excited state to the redshifted H‐type dimeric state was first observed, correlating to the calculated excitonic energy splitting and the steady‐state absorption spectra induced by charge‐transfer‐mediated superexchange interaction. Abstract : Hindsight is 20/20 : anti ‐[2.2](5, 11)Indeno[1, 2‐ b ]fluorenophane, which contains a rare 20/20 π‐electron system with a large overlapping π orbital and a short π–π distance, has a unique structure. This compound exhibits remarkable transannular interactions, resulting in photophysical and electrochemical properties, as well as photodynamics. The transition from the monomeric excited state to the redshifted H‐type dimeric state was observed for the first time.