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  • Stabilizing Contorted Doubly‐Reduced Tetraphenylene with Heavy Alkali Metal Complexation: Crystallographic and Theoretical Evidence
Title: Stabilizing Contorted Doubly‐Reduced Tetraphenylene with Heavy Alkali Metal Complexation: Crystallographic and Theoretical Evidence
Abstract The two‐fold reduction of tetrabenzo[a,c,e,g]cyclooctatetraene (TBCOT, or tetraphenylene,1) with K, Rb, and Cs metals reveals a distinctive core transformation pathway: a newly formed C−C bond converts the central eight‐membered ring into a twisted core with two fused five‐membered rings. This C−C bond of 1.589(3)–1.606(6) Å falls into a single σ‐bond range and generates two perpendicular π‐surfaces with dihedral angles of 110.3(9)°–117.4(1)° in the1TR2−dianions. As a result, the highly contorted1TR2−ligand exhibits a “butterfly” shape and could provide different coordination sites for metal‐ion binding. The K‐induced reduction of1in THF affords a polymeric product with low solubility, namely [{K+(THF)}2(1TR2−)] (K2‐1TR2−). The use of a secondary ligand facilitates the isolation of discrete complexes with heavy alkali metals, [Rb+(18‐crown‐6)]2[1TR2−] (Rb2‐1TR2−) and [Cs+(18‐crown‐6)]2[1TR2−] (Cs2‐1TR2−). Both internal and external coordination are observed inK2‐1TR2−, while the bulky 18‐crown‐6 ligand only allows external metal binding inRb2‐1TR2−andCs2‐1TR2−. The reversibility of the two‐fold reduction and bond rearrangement is demonstrated by NMR spectroscopy. Computational analysis shows that the heavier alkali metals enable effective charge transfer from the1TR2−TBCOT dianion, however, the aromaticity of the polycyclic ligand remains largely unaffected.  more » « less
Award ID(s):
2404031
PAR ID:
10590520
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Wiley-VCH
Date Published:
Journal Name:
Chemistry – An Asian Journal
Volume:
20
Issue:
8
ISSN:
1861-4728
Page Range / eLocation ID:
e202401498
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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