Extreme conformational constraints in pi-extended tetrathiafulvalenes : Unusual topologies and redox behavior of doubly and triply bridged cyclophanes.

Christensen, C.A.; Batsanov, A.S.; Bryce, M.R.

Abstract

Doubly and triply bridged 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (ex-TTF) derivatives have been synthesized. Key steps are the generation and macrocyclization reactions of ex-TTF-dithiolate reagents. The X-ray crystal structures of the doubly bridged cyclophanes 15 and 16 and the triply bridged system 23 show that the saddle-like conformation of the ex-TTF framework is enhanced by the short bridges between the dithiole rings. Unlike all previous ex-TTF derivatives (which display a single quasi-reversible two-electron oxidation wave, D0 → D2+), cyclic voltammetry of the cyclophanes reveals two reversible, one-electron oxidation steps (D0 → D•+ → D2+), with differences between the half-wave potentials (E21/2 − E11/2) of 0.22−0.26 V. The conformational changes and gain in aromaticity which drive the second oxidation process in unrestricted ex-TTF systems (including singly bridged cyclophanes) have been prevented by multiple bridging. The radical cation species gives rise to a very broad, low-energy band (λmax = 2175 and 2040 nm for 15 and 21, respectively), assigned to an intramolecular interaction. The steric constraints imposed by multiple bridging have become so extreme that the π-framework of 15, 16, 21, and 23 exhibits remarkable optical and redox behavior which is not characteristic of ex-TTF systems.

Citation

Christensen, C., Batsanov, A., & Bryce, M. (2006). Extreme conformational constraints in pi-extended tetrathiafulvalenes : Unusual topologies and redox behavior of doubly and triply bridged cyclophanes. Journal of the American Chemical Society, 128(32), 10484-10490. https://doi.org/10.1021/ja062358m

• Journal Article Type: Article
• Publication Date: 2006-07
• Journal: Journal of the American Chemical Society
• Print ISSN: 0002-7863
• Electronic ISSN: 1520-5126
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 128
• Issue: 32
• Pages: 10484-10490
• DOI: https://doi.org/10.1021/ja062358m