Crystal and molecular structure of 2,2'-bis(6-methyl-3-pyridinol)

Vogt, Lester H.; Wirth, J. G.

doi:10.1021/ja00750a015

Cited by 22 publications

(8 citation statements)

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“…[17] The two molecules in the unit cell present some bond-length variation. As previously observed in the structure of symmetrical 6,6'-dimethyl-3,3'-dihydroxy-2,2'-bipyridine, [17] the C À C and C À O bonds implied in the BP(OH) 2 tautomeric equilibrium are about halfway between the accepted values for single and double bond distances (Table 1) The crystal packing of compound 5 ( Figure 3) can be regarded as dimers made of headto-tail molecule stacks that form waving sheets parallel to (À2 0 2). The distances between the two molecules of the dimer is approximately 3.5-3.6 , the shorter distance between the two acetylenic bonds is 3.52 .…”

Section: Resultsmentioning

confidence: 99%

Luminescent Excited‐State Intramolecular Proton‐Transfer (ESIPT) Dyes Based on 4‐Alkyne‐Functionalized [2,2′‐Bipyridine]‐3,3′‐diol Dyes

Ulrich

Nastasi

Retailleau

et al. 2008

Chemistry A European J

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Functionalized 6,6'-dimethyl-3,3'-dihydroxy-2,2'-bipyridine dyes (BP(OH)(2)) exhibit relatively intense fluorescence from the relaxed excited state formed by excited-state intramolecular proton transfer (ESIPT). Bromo functionalization of (BP(OH)(2)) species followed by palladium(0)-catalyzed reactions allows the connection (via alkyne tethers) of functional groups, such as the singlet-emitter diazaboraindacene (bodipy) group or a chelating module (terpyridine; terpy). The X-ray structure of the terpy-based compound confirms the planarity of the 3,3'-dihydroxy-bipyridine unit. The new dyes exhibit relatively intense emission on the nanosecond timescale when in fluid solution, in the solid state at 298 K, and in rigid glasses at 77 K. In some cases, the excitation wavelength luminescence was observed and attributed to 1) inefficiency of the ESIPT process in particular compounds when not enough vibrational energy is introduced in the Franck-Condon state, which is populated by direct light excitation or 2) the presence of an additional excited state that deactivates to the ground state without undergoing the ESIPT process. For some selected species, the effect of the addition of zinc salts on the absorption and luminescence spectra was investigated. In particular, significant fluorescence changes were observed as a consequence of probable consecutive formation of a 1:1 and 1:2 molecular ratio of ligand/zinc adducts owing to coordination of Zn(II) ions by the bipyridyldiol moieties, except when an additional terpyridine subunit is present. In fact, this latter species preferentially coordinates to the Zn(II) ion in a 1:1 molecular ratio and further inhibits Zn(II) interaction. In the hybrid Bodipy/BP(OH)(2) species, complete energy transfer from the BP(OH)(2) to the bodipy fluorophore occurs, leading to exclusive emission from the lowest-lying bodipy subunit.

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Section: Resultsmentioning

confidence: 99%

Luminescent Excited‐State Intramolecular Proton‐Transfer (ESIPT) Dyes Based on 4‐Alkyne‐Functionalized [2,2′‐Bipyridine]‐3,3′‐diol Dyes

Ulrich

Nastasi

Retailleau

et al. 2008

Chemistry A European J

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“…While this result is consistent with a widely held view (Katritzky & Lagowski, 1963) that e-and y-hydroxypyridines exist predominantly as pyridones, we note that Boer & Turley (1972) have recently shown that tetrachloro-4hydroxypyridine (TCHP) exists as the hydroxy or pyridinol tautomer in the solid. (fl-Hydroxypyridines are of course expected to exist as pyridinols; a recent structure determination of the internally hydrogenbonded dimer 2,2'-bis-(6-methyl-3-pyridinol) by Vogt & Wirth (1971) exemplifies this type of structure). The structural arguments for the oxo form appear to be quite conclusive.…”

Section: Resultsmentioning

confidence: 99%

The crystal structure of clopidol (3,5-dichloro-2,6-dimethyl-4-pyridinol)

Boer¹

1972

Acta Crystallogr Sect B

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“…1). The proton transfer mechanism of BP(OH) 2 has attracted great interest in the last decade [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Based on the almost independence of the absorption and fluorescence band maxima of BP(OH) 2 to the polarity of the solvent and also on the basis of results from semi-empirical calculations, Bulska et al [5,6] concluded that photoexcitation of the molecule gives rise to a cooperative double proton transfer process.…”

Section: Introductionmentioning

confidence: 99%