Controlled Tautomerism: Is It Possible?

Antonová, Daniela; Antonov, Liudmil

doi:10.1002/9783527695713.ch12

Cited by 13 publications

(15 citation statements)

References 103 publications

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“…Due to dramatic structural change, the excited tautomer possesses photophysical properties, different from those of the ground state specie. The ESIPT exhibiting molecules have become a field of active research [ 6 ] in the last decades, due to their applications as light-emitting materials and laser dyes [ 7 , 8 , 9 ], photo stabilizers [ 10 ] and photo switches [ 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

“…Historically, the term “proton crane” was used for the first time by Varma et al [ 15 , 16 , 17 , 18 ], who designed a single bond axle system, 8-(morpholinomethyl)quinolin-7-ol ( 1 in Scheme 2 ), where the proton is exchanged between O and N in the 7-hydroxyquinoline upon irradiation [ 19 ]. Proton crane 1 and its mimics [ 12 , 20 , 21 ] are based on an excited state proton transfer pathway upon irradiation as the only possibility to reach the energetically unfavorable end state. Another intriguing concept is the design of systems, where a moderate energy gap between tautomers of the tautomeric sub-unit provides proton exchange in a ground state [ 12 , 22 , 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

“…Proton crane 1 and its mimics [ 12 , 20 , 21 ] are based on an excited state proton transfer pathway upon irradiation as the only possibility to reach the energetically unfavorable end state. Another intriguing concept is the design of systems, where a moderate energy gap between tautomers of the tautomeric sub-unit provides proton exchange in a ground state [ 12 , 22 , 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

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8-(Pyridin-2-yl)quinolin-7-ol as a Platform for Conjugated Proton Cranes: A DFT Structural Design

Georgiev

Antonov

2020

Micromachines

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Theoretical design of conjugated proton cranes, based on 7-hydroxyquinoline as a tautomeric sub-unit, has been attempted by using ground and excited state density functional theory (DFT) calculations in various environments. The proton crane action request existence of a single enol tautomer in ground state, which under excitation goes to the excited keto tautomer through a series of consecutive excited-state intramolecular proton transfer (ESIPT) steps with the participation of the crane sub-unit. A series of substituted pyridines was used as crane sub-units and the corresponding donor-acceptor interactions were evaluated. The results suggest that the introduction of strong electron donor substituents in the pyridine ring creates optimal conditions for 8-(pyridin-2-yl)quinolin-7-ols to act as proton cranes.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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8-(Pyridin-2-yl)quinolin-7-ol as a Platform for Conjugated Proton Cranes: A DFT Structural Design

Georgiev

Antonov

2020

Micromachines

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“…The ion recognition is based on the existence of two molecular states (ligand and complex) with different optical properties and a structure that allows fast transfer from the ligand to the complex upon addition of the desired metal ion [7]. The tautomeric proton exchange has the same properties when the equilibrium is switched from one to the other tautomer.…”

Section: Introductionmentioning

confidence: 99%

“…The tautomerism can be controlled by metal ion addition, when an ionophore unit is implemented in the tautomeric backbone. The conceptual idea to achieve the pure enol tautomer through intramolecular hydrogen bonding with the ionophore [7–8] is shown in Scheme 1. The complex formation ejects the tautomeric proton and stabilizes the keto tautomer.…”

Section: Introductionmentioning

confidence: 99%

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

Deneva

Dobrikov

Crochet

et al. 2019

Beilstein J. Org. Chem.

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The concept for sensing systems using the tautomerism as elementary signaling process has been further developed by synthesizing a ligand containing 4-(phenyldiazenyl)naphthalene-1-ol as a tautomeric block and an amide group as metal capturing antenna. Although it has been expected that the intramolecular hydrogen bonding (between the tautomeric hydroxy group and the nitrogen atom from the amide group) could stabilize the pure enol form in some solvents, the keto tautomer is also observed. This is a result from the formation of intramolecular associates in some solvents. Strong bathochromic and hyperchromic effects in the visible spectra accompany the 1:1 formation of complexes with some alkaline earth metal ions.

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Acylhydrazone Subunits as a Proton Cargo Delivery System in 7‐Hydroxyquinoline

Nakashima

Petek

Hori

et al. 2021

Chemistry A European J

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The reimagined concept of long‐range tautomeric proton transfer using crane subunits is shown by designing and synthesising two new acylhydrazones containing a 7‐hydroxyquinoline (7‐OHQ) platform. The acylhydrazone subunits attached to the 7‐OHQ at the 8th position act as crane arms for delivering proton cargo to the quinoline nitrogen. Light‐induced tautomerization to their keto forms leads to Z/E isomerization of the C=C axle bond, followed by proton delivery to the quinoline nitrogen by the formation of covalent or hydrogen bonds. The axle‘s being either an imine or ketimine bond is the structural difference between the studied compounds. The −CH3 group in the latter provides steric strain, resulting in different proton transport pathways. Both compounds show long thermal stability in the switched state, which creates a tuneable action of bidirectional proton cargo transport by using different wavelengths of irradiation. Upon the addition of acid, the quinoline nitrogen is protonated; this results in E/Z configuration switching of the acylhydrazone subunits. This was proven by single‐crystal X‐ray structure analysis and NMR spectroscopy.

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Controlled Tautomerism: Is It Possible?

Cited by 13 publications

References 103 publications

8-(Pyridin-2-yl)quinolin-7-ol as a Platform for Conjugated Proton Cranes: A DFT Structural Design

8-(Pyridin-2-yl)quinolin-7-ol as a Platform for Conjugated Proton Cranes: A DFT Structural Design

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

Acylhydrazone Subunits as a Proton Cargo Delivery System in 7‐Hydroxyquinoline

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