Carbonotropy

Olekhnovich, L. P.; Zhdanov, Yu. A.

doi:10.1007/978-94-009-1429-2_2

Cited by 8 publications

(45 citation statements)

References 101 publications

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“…In Figure a, it can be observed that a hydrogen atom is attached to the nitrogen atom of the bottom molecule (see the small box around the hydrogen), while in the geometry-I excited state (Figure b), this hydrogen atom is transferred to the nearby oxygen atom of the second molecule, resulting in the formation of a C–O–H bond. This inter -proton transfer can also be interpreted as a transition of the dimer from the lactam form to the lactim form. − Geometry-II (Figure c) also shows a proton transfer, but now it is an intra -proton transfer. The change in the hydrogen atom location leads to a high reduction of the de-excitation energy, which results in a significant red-shift in the emitted wavelength.…”

Section: Resultsmentioning

confidence: 96%

Proton-Transfer-Induced Fluorescence in Self-Assembled Short Peptides

et al. 2019

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We employ Molecular Dynamics (MD) and Time-Dependent Density Functional Theory (TDDFT) to explore the fluorescence of Hydrogen-bonded dimer and trimer structures of Cyclic FF (Phe-Phe) molecules. We show that in some of these configurations a photon can induce either an intra-molecular proton transfer, or an intermolecular proton transfer that can occur in the excited S1 and S2 states. This proton transfer, taking place within the Hydrogen bond, leads to a significant red-shift that can explain the experimentally observed visible fluorescence in biological and bioinspired peptide nanostructures with a β-sheet biomolecular arrangement. Finally, we also show that such proton transfer is highly sensitive to the geometrical bonding of the dimers and trimers, and that it occurs only in specific configurations allowed by the formation of Hydrogen bonds.

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Section: Resultsmentioning

confidence: 96%

Proton-Transfer-Induced Fluorescence in Self-Assembled Short Peptides

et al. 2019

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“…Prototropic tautomerism [1,2,3,4,5,6,7,8,9,10,11,12] is one of the most important phenomena in organic chemistry despite the relatively small proportion of molecules in which it can occur. Tautomers are the chameleons of chemistry, capable of changing by a simple change of environment from an apparently established structure to another, then back again when the original conditions are restored.…”

Section: Introductionmentioning

confidence: 99%

Tautomerism in Azo and Azomethyne Dyes: When and If Theory Meets Experiment

Antonov

2019

Molecules

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The performance of 26 hybrid density functionals was tested against a tautomeric dataset (TautData), containing experimental information for the keto-enol tautomeric equilibrium in 16 tautomeric azodyes and Schiff bases in cyclohexane, carbon tetrachloride and acetonitrile. The results have shown that MN12-SX, BHandH and M06-2X can be used to describe the tautomeric state of the core structures in the frame of ~0.5 kcal/mol error and correctly predict the tautomeric state in respect of dominating tautomeric form. Among them MN12-SX is the best performer, although it fails to describe the nonplanarity of some of the enol tautomers. The same experimental dataset was used to develop and test a special DFT functional (TautLYP) aimed at describing the tautomeric state in azo- and azomethyne compounds in solution when nonspecific solvents are used.

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“…Several years ago we reported the equilibrium between Co(III) and Co(II) redox isomers of a complex containing semiquinonate (SQ) and catecholate (Cat) ligands derived from 3,5-di- tert -butyl-1,2-benzoquinone (3,5-DBBQ) (eq 1) We referred to this equilibrium as valence tautomerism (VT), following references to equilibria of main group compounds that involve similar shifts in formal oxidation state . While shifts in charge distribution between redox-active metal−ligand combinations may potentially lead to similar equilibria, the quinone complexes of Co and Mn have spectroscopic and structural features indicating charge-localized electronic structures. , Charge delocalization of the type associated with “noninnocent” ligands such as the 1,2-dithiolenes and diimines is a relatively minor effect for the quinone complexes of first-row transition metal ions …”

Section: Introductionmentioning

confidence: 99%

Chelate-Ring-Dependent Shifts in Redox Isomerism for the Co(Me₂N(CH₂)_nNMe₂)(3,6-DBQ)₂(n= 1−3) Series, Where 3,6-DBQ Is the Semiquinonate or Catecholate Ligand Derived from 3,6-Di-tert-butyl-1,2-benzoquinone

Jung

Lee

et al. 1998

Inorg. Chem.

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Intramolecular electron transfer between CoII(SQ) and CoIII(Cat) redox isomers has been investigated for the series of complexes Co(N-N)(3,6-DBQ)2, where 3,6-DBQ is the semiquinonate or catecholate form of 3,6-di-tert-butyl-1,2-benzoquinone and N-N is tetramethylmethylenediamine (tmmda), tetramethylethylenediamine (tmeda), or tetramethylpropylenediamine (tmpda). Measurements of magnetic properties and changes in electronic spectra indicate that the transition temperature (T 1/2) for Co(III)/Co(II) redox isomerism in the solid state and in toluene solution is the lowest for Co(tmpda)(3,6-DBQ)2. This is attributed to the flexibility of the six-membered chelate ring of Co(tmpda) and a positive contribution to ΔS for the equilibrium. Transition temperatures for the tmmda and tmeda analogues are more than 150 deg higher than that for the tmpda species. Structural characterization of CoIII(tmmda)(3,6-DBSQ)(3,6-DBCat), CoIII(tmeda)(3,6-DBSQ)(3,6-DBCat), and CoII(tmpda)(3,6-DBSQ)2 has shown that the Co(tmmda) and Co(tmeda) chelate rings are conformationally ordered, while there is considerable disorder in the Co(tmpda) chelate ring. In toluene solution, T 1/2 is approximately 15 deg higher for Co(tmeda)(3,6-DBSQ)2 than for the tmmda analogue due to the more contracted chelate ring of CoIII(tmmda)(3,6-DBSQ)(3,6-DBCat). For the Co(N-N)(3,6-DBQ)2 series, T 1/2 varies as tmpda ≪ tmmda < tmeda.

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Carbonotropy

Cited by 8 publications

References 101 publications

Proton-Transfer-Induced Fluorescence in Self-Assembled Short Peptides

Proton-Transfer-Induced Fluorescence in Self-Assembled Short Peptides

Tautomerism in Azo and Azomethyne Dyes: When and If Theory Meets Experiment

Chelate-Ring-Dependent Shifts in Redox Isomerism for the Co(Me₂N(CH₂)_nNMe₂)(3,6-DBQ)₂(n= 1−3) Series, Where 3,6-DBQ Is the Semiquinonate or Catecholate Ligand Derived from 3,6-Di-tert-butyl-1,2-benzoquinone

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Carbonotropy

Cited by 8 publications

References 101 publications

Proton-Transfer-Induced Fluorescence in Self-Assembled Short Peptides

Proton-Transfer-Induced Fluorescence in Self-Assembled Short Peptides

Tautomerism in Azo and Azomethyne Dyes: When and If Theory Meets Experiment

Chelate-Ring-Dependent Shifts in Redox Isomerism for the Co(Me2N(CH2)nNMe2)(3,6-DBQ)2(n= 1−3) Series, Where 3,6-DBQ Is the Semiquinonate or Catecholate Ligand Derived from 3,6-Di-tert-butyl-1,2-benzoquinone

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Chelate-Ring-Dependent Shifts in Redox Isomerism for the Co(Me₂N(CH₂)_nNMe₂)(3,6-DBQ)₂(n= 1−3) Series, Where 3,6-DBQ Is the Semiquinonate or Catecholate Ligand Derived from 3,6-Di-tert-butyl-1,2-benzoquinone