skip to main content


Title: Site‐Directed Dimerization of Bowl‐Shaped Radical Anions to Form a σ‐Bonded Dibenzocorannulene Dimer
Abstract

Designed site‐directed dimerization of the monoanion radicals of a π‐bowl in the solid state is reported. Dibenzo[a,g]corannulene (C28H14) was selected based on the asymmetry of the charge/spin localization in the C28H14.−anion. Controlled one‐electron reduction of C28H14with Cs metal in diglyme resulted in crystallization of a new dimer, [{Cs+(diglyme)}2(C28H14−C28H14)2−] (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 in1is 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 in1is energetically favored.

 
more » « less
PAR ID:
10081706
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie
Volume:
130
Issue:
21
ISSN:
0044-8249
Page Range / eLocation ID:
p. 6279-6283
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Designed site‐directed dimerization of the monoanion radicals of a π‐bowl in the solid state is reported. Dibenzo[a,g]corannulene (C28H14) was selected based on the asymmetry of the charge/spin localization in the C28H14.−anion. Controlled one‐electron reduction of C28H14with Cs metal in diglyme resulted in crystallization of a new dimer, [{Cs+(diglyme)}2(C28H14−C28H14)2−] (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 in1is 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 in1is energetically favored.

     
    more » « less
  2. Abstract

    Whereas low‐temperature (−78 °C) reaction of the lithium dithiolene radical1.with boron bromide gives the dibromoboron dithiolene radical2., the parallel reaction of1.with (C6H11)2BCl (0 °C) affords the dicyclohexylboron dithiolene radical3.. Radicals2.and3.were characterized by single‐crystal X‐ray diffraction, UV/Vis, and EPR spectroscopy. The nature of these radicals was also probed computationally. Under mild conditions,3.undergoes unexpected thiourea‐mediated B−C bond activation to give zwitterion4, which may be regarded as an anionic dithiolene‐modified carbene complex of the sulfenyl cation RS+(R=cyclohexyl).

     
    more » « less
  3. Abstract

    Whereas low‐temperature (−78 °C) reaction of the lithium dithiolene radical1.with boron bromide gives the dibromoboron dithiolene radical2., the parallel reaction of1.with (C6H11)2BCl (0 °C) affords the dicyclohexylboron dithiolene radical3.. Radicals2.and3.were characterized by single‐crystal X‐ray diffraction, UV/Vis, and EPR spectroscopy. The nature of these radicals was also probed computationally. Under mild conditions,3.undergoes unexpected thiourea‐mediated B−C bond activation to give zwitterion4, which may be regarded as an anionic dithiolene‐modified carbene complex of the sulfenyl cation RS+(R=cyclohexyl).

     
    more » « less
  4. Abstract

    Chemical reduction of pentacene (C22H14,1) with Group 1 metals ranging from Li to Cs revealed that1readily undergoes a two‐fold reduction to afford a doubly‐reduced12−anion in THF. With the help of 18‐crown‐6 ether used as a secondary coordinating agent, five π‐complexes of12−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 the12−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 of1with Na metal allowed the isolation of the unique solvent‐separated ion product with a “naked” dianion,12−. 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 of12−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.

     
    more » « less
  5. null (Ed.)
    One-electron reduction of bowl-shaped indenocorannulene, C 26 H 12 , with Rb metal in THF affords [{Rb + (18-crown-6)} 2 (C 26 H 12 –C 26 H 12 ) 2− ]·4THF, as confirmed by single-crystal X-ray diffraction. The product consists of a dimeric σ-bonded dianion (C–C, 1.568(7) Å) having two endo -η 6 coordinated {Rb + (18-crown-6)} moieties (Rb–C, 3.272(4)–3.561(4) Å). The (C 26 H 12 –C 26 H 12 ) 2− dimer represents the first crystallographically confirmed example of spontaneous coupling for indenocorannulene monoanion radicals, C 26 H 12 ˙ − . Comprehensive theoretical investigation of the new dimer confirms the single σ-bond character of the linker and reveals a significant increase of both thermodynamic and kinetic stability of [σ-(C 26 H 12 ) 2 ] 2− in comparison with analogues formed by such π-bowls as corannulene and its dibenzo-derivative. The in-depth computational analysis and direct comparison of the series demonstrates the effect of curvature on radical coupling processes, allowing control over stability and reactivity of bowl-shaped π-radicals. 
    more » « less