Chemical reduction of pentacene (C22H14,
- PAR ID:
- 10491569
- Publisher / Repository:
- RSC
- Date Published:
- Journal Name:
- Organic Chemistry Frontiers
- Volume:
- 10
- Issue:
- 23
- ISSN:
- 2052-4129
- Page Range / eLocation ID:
- 5823 to 5833
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 1 ) with Group 1 metals ranging from Li to Cs revealed that1 readily undergoes a two‐fold reduction to afford a doubly‐reduced1 2−anion in THF. With the help of 18‐crown‐6 ether used as a secondary coordinating agent, five π‐complexes of1 2−with different alkali metal counterions have been isolated and fully characterized. This series of complexes enables the first evaluation of alkali‐metal ion binding patterns and structural changes of the1 2−dianion based on the crystallographically confirmed examples. The difference in coordination of the smallest Li+ion vs. heavier Group 1 congeners has been demonstrated. In addition, the use of benzo‐15‐crown‐5 in the reaction of1 with Na metal allowed the isolation of the unique solvent‐separated ion product with a “naked” dianion,1 2−. The detailed structural analyses of the series revealed the C−C bond alteration and core deformation of pentacene upon two‐fold reduction and complexation. The negative charge localization at the central six‐membered ring of1 2−identified by theoretical calculations corroborates with the X‐ray crystallographic results. Subsequent in‐depth theoretical analysis provided a detailed description of changes in the electronic structure and aromaticity of pentacene upon reduction. -
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Abstract Chemical reduction of OBO‐fused double[5]helicene with Group 1 metals (Na and K) has been investigated for the first time. Two doubly‐reduced products have been isolated and structurally characterized by single‐crystal X‐ray diffraction, revealing a solvent‐separated ion triplet (SSIT) with Na+ions and a contact‐ion pair (CIP) with K+ion. As the key structural outcome, the X‐ray crystallographic analysis discloses the consequences of adding two electrons to the double helicene core in the SSIT without metal binding and reveals the preferential binding site in the CIP with K+counterions. In both products, an increase in the twisting of the double helicene core upon charging was observed. The negative charge localization at the central core has been identified by theoretical calculations, which are in full agreement with X‐ray crystallographic and NMR spectroscopic results. Notably, it was confirmed that the two‐electron reduction of OBO‐fused double[5]helicene is reversible.
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Abstract Chemical reduction of OBO‐fused double[5]helicene with Group 1 metals (Na and K) has been investigated for the first time. Two doubly‐reduced products have been isolated and structurally characterized by single‐crystal X‐ray diffraction, revealing a solvent‐separated ion triplet (SSIT) with Na+ions and a contact‐ion pair (CIP) with K+ion. As the key structural outcome, the X‐ray crystallographic analysis discloses the consequences of adding two electrons to the double helicene core in the SSIT without metal binding and reveals the preferential binding site in the CIP with K+counterions. In both products, an increase in the twisting of the double helicene core upon charging was observed. The negative charge localization at the central core has been identified by theoretical calculations, which are in full agreement with X‐ray crystallographic and NMR spectroscopic results. Notably, it was confirmed that the two‐electron reduction of OBO‐fused double[5]helicene is reversible.
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null (Ed.)The consequences of four-electron addition to [8]cycloparaphenylene ([8]CPP, 1 ) have been evaluated crystallographically, revealing a significant core deformation. The structural analysis exposes an elliptical distortion observed upon electron transfer, with the deformation parameter (D.P.) increased by 28% in comparison with neutral [8]CPP. The C–C bond length alteration pattern also indicates a quinoidal structural rearrangement upon four-fold reduction. The large internal cavity of [8]CPP 4− allows the encapsulation of two {K + (THF) 2 } cationic moieties with two additional cations bound externally in the solid-state structure of [{K + (THF) 2 } 4 ([8]CPP 4− )]. The experimental structural data have been used as a benchmark for the comprehensive theoretical description of the geometric changes and electronic properties of the highly-charged [8]CPP 4− nanohoop in comparison with its neutral parent. While neutral [8]CPP and the [8]CPP 2− anion clearly show aromatic behavior of all six-membered rings, subsequent addition of two more electrons completely reverses their aromatic character to afford the highly-antiaromatic [8]CPP 4− anion, as evidenced by structural, topological, and magnetic descriptors. The disentanglement of electron transfer from metal binding effects allowed their contributions to the overall core perturbation of the negatively-charged [8]CPP to be revealed. Consequently, the internal coordination of potassium cations is identified as the main driving force for drastic elliptic distortion of the macrocyclic framework upon reduction.more » « less
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1 ), as revealed by single crystal X‐ray diffraction study performed in a broad range of temperatures. The C−C bond length between two C28H14.−bowls (1.560(8) Å) measured at −143 °C does not significantly change upon heating of the crystal to +67 °C. The single σ‐bond character of the C−C linker is confirmed by calculations. The trans‐disposition of two bowls in1 is observed with the torsion angles around the central C−C bond of 172.3(5)° and 173.5(5)°. A systematic theoretical evaluation of dimerization pathways of C28H14.−radicals confirmed that the trans‐isomer found in1 is energetically favored.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d3qo01282d
