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Volumn 11, Issue 2, 2009, Pages 324-332

Counter-ion modulation of long-distance π-bonding of the open-shell p-benzoquinone anions

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EID: 58149095533     PISSN: 14639076     EISSN: None     Source Type: Journal    
DOI: 10.1039/b811816g     Document Type: Article
Times cited : (24)

References (59)
  • 6
    • 0003540777 scopus 로고
    • J. S. Miller, Plenum Press, New York
    • Extended Linear Chain Compounds, ed. J. S. Miller, Plenum Press, New York, 1983, vol. 2 and 3
    • (1983) Extended Linear Chain Compounds , vol.2-3
  • 8
    • 85033416665 scopus 로고    scopus 로고
    • Note that the counter-ion interactions were minimized in the earlier studies via the use of bulky cations and/or polar solvents
    • Note that the counter-ion interactions were minimized in the earlier studies via the use of bulky cations and/or polar solvents
  • 9
    • 85033430801 scopus 로고    scopus 로고
    • −. anion-radicals 7aconfirm the diamagnetic nature of their dimeric complexes, but the energetics of singlet/triplet transitions in these species requires a separate study and it will be deferred herein
    • −. anion-radicals 7aconfirm the diamagnetic nature of their dimeric complexes, but the energetics of singlet/triplet transitions in these species requires a separate study and it will be deferred herein
  • 15
    • 85033414811 scopus 로고    scopus 로고
    • Note that the term “pimer” was first employed by Kosower 7bto designate complexes between two (ion-)radical species, which are now described herein as the “dimer”
    • Note that the term “pimer” was first employed by Kosower 7bto designate complexes between two (ion-)radical species, which are now described herein as the “dimer”
  • 23
    • 85033422764 scopus 로고    scopus 로고
    • 2− dimers 8or equatorially, 9to support the π-bonding of the anionic monomers
    • 2− dimers 8or equatorially, 9to support the π-bonding of the anionic monomers
  • 24
    • 85033418494 scopus 로고    scopus 로고
    • −. anion-radicals with bulky, non-coordinating cations 5,12
    • −. anion-radicals with bulky, non-coordinating cations 5,12
  • 30
    • 85033412520 scopus 로고    scopus 로고
    • The difficulties in isolation of alkyl-substituted p-benzoquinone π-associates precluded the experimental evaluation of the ion-pairing effects in their anion-radicals π-bonding
    • The difficulties in isolation of alkyl-substituted p-benzoquinone π-associates precluded the experimental evaluation of the ion-pairing effects in their anion-radicals π-bonding
  • 31
    • 85033419966 scopus 로고    scopus 로고
    • Note that the bond-length values within the monoanionic benzoquinone moieties reported earlier 5a,15aand herein (vide infra) are intermediate between the quinonoid structure of the quinone and benzenoid structure of the hydroquinone. As such, the drawings in Charts 1 and 3 are intended only for schematic representation of benzoquinone molecules, and do not reflect the actual nature of their bonds
    • Note that the bond-length values within the monoanionic benzoquinone moieties reported earlier 5a,15aand herein (vide infra) are intermediate between the quinonoid structure of the quinone and benzenoid structure of the hydroquinone. As such, the drawings in Charts 1 and 3 are intended only for schematic representation of benzoquinone molecules, and do not reflect the actual nature of their bonds
  • 36
    • 85033424579 scopus 로고    scopus 로고
    • Reported earlier structure of KCA salt 17bshows vertical stacks of the potassium-coordinated chloranil moieties. However, the interatomic separations between cofacial anions in this salt are larger than the sum of the van der Waals radii-in contrast to the π-bonded dyads discussed herein
    • Reported earlier structure of KCA salt 17bshows vertical stacks of the potassium-coordinated chloranil moieties. However, the interatomic separations between cofacial anions in this salt are larger than the sum of the van der Waals radii-in contrast to the π-bonded dyads discussed herein
  • 46
    • 85033430021 scopus 로고    scopus 로고
    • The structural features of benzoquinone cores in M(L)A salts (Table S1 in the ESI) are consistent with the single negative charge residing on the p-benzoquinone moieties
    • The structural features of benzoquinone cores in M(L)A salts (Table S1 in the ESI) are consistent with the single negative charge residing on the p-benzoquinone moieties
  • 47
    • 85033415840 scopus 로고    scopus 로고
    • + cation exceed 5.0 Å(i.e. more than the sum of the potassium and oxygen van der Waals radii of 4.3 Å)
    • + cation exceed 5.0 Å(i.e. more than the sum of the potassium and oxygen van der Waals radii of 4.3 Å)
  • 48
    • 85033421935 scopus 로고    scopus 로고
    • 2−(2.83-2.99 Å). Noticeably, these interatomic separations are much shorter than the sum of the van der Waals radii to indicate strong intermolecular bonding between the monomers in all these dimers
    • 2−(2.83-2.99 Å). Noticeably, these interatomic separations are much shorter than the sum of the van der Waals radii to indicate strong intermolecular bonding between the monomers in all these dimers
  • 49
    • 85033427042 scopus 로고    scopus 로고
    • 2]-820 nm. Thus, the maxima of ion-paired species are blue-shifted relatively to those of separated dimers (the largest blue shift is observed with the NTD dimer). In solutions, the tendency is the same, but the blue shift of the dimers formed from CIP is much less pronounced (Table 2). However, a significant red-shift of solid state spectra relatively to the solutions (as commonly observed for dimeric species of various ion-radicals),5aand relatively minor differences between the solution spectra of various species do not allow to distinguish between various types of cation-coordinated dimers in solutions. As such, the specific modes of anion/cation coordination in solution are uncertain and the data in Table 2 most likely represent the average values characteristic of various types of cation-coordinated (tethered and non-tethered) dimers
    • 2]-820 nm. Thus, the maxima of ion-paired species are blue-shifted relatively to those of separated dimers (the largest blue shift is observed with the NTD dimer). In solutions, the tendency is the same, but the blue shift of the dimers formed from CIP is much less pronounced (Table 2). However, a significant red-shift of solid state spectra relatively to the solutions (as commonly observed for dimeric species of various ion-radicals),5aand relatively minor differences between the solution spectra of various species do not allow to distinguish between various types of cation-coordinated dimers in solutions. As such, the specific modes of anion/cation coordination in solution are uncertain and the data in Table 2 most likely represent the average values characteristic of various types of cation-coordinated (tethered and non-tethered) dimers
  • 51
    • 85033413079 scopus 로고    scopus 로고
    • 2−π-dimers) reveal that in the absence of the counter-ions, the π-dimer with the longitudial offset is more stable than that with the transversal offset (Table S2 in the ESI). However, the energy of sodium-tethered dimer is lower than the energy of the separated dimer (calculated, for consistency, with the two distant sodium cations)
    • 2−π-dimers) reveal that in the absence of the counter-ions, the π-dimer with the longitudial offset is more stable than that with the transversal offset (Table S2 in the ESI). However, the energy of sodium-tethered dimer is lower than the energy of the separated dimer (calculated, for consistency, with the two distant sodium cations)


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