Université de Fribourg

Tautomerism and self-association in the solution of new pinene-bipyridine and pinene-phenanthroline derivatives

Solea, Atena B. ; Cornu, Ivan ; Deneva, Vera ; Crochet, Aurelien ; Fromm, Katharina M. ; Antonov, Liudmil ; Allemann, Christophe ; Mamula, Olimpia

In: Molecules, 2020, vol. 25, no. 2, p. 298

Two novel pinene-type ligands have been synthesized and their tautomeric and self-associating behavior studied in solution and in the solid state. The first ligand, an acetylated derivative of 5,6-pinene-bipyridine, displays keto-enol tautomerism in solution. This tautomeric equilibrium was studied by NMR and UV-Vis spectroscopy in various solvents, and the results were compared with the...

Université de Fribourg

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

Deneva, Vera ; Dobrikov, Georgi ; Crochet, Aurelien ; Nedeltcheva, Daniela ; Fromm, Katharina M. ; Antonov, Liudmil

In: Beilstein Journal of Organic Chemistry, 2019, vol. 15, no. 1, p. 1898–1906

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...

Université de Fribourg

Isomerization and aggregation of 2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-dione: Recent evidences from theory and experiment

Hristova, Silvia ; Kamounah, Fadhil S. ; Crochet, Aurelien ; Hansen, Poul Erik ; Fromm, Katharina M. ; Nedeltcheva, Daniela ; Antonov, Liudmil

In: Journal of Molecular Liquids, 2019, vol. 283, p. 242–248

The title compound potentially can exist as four isomers in solution. Recently Lycka has proposed a protocol for distinguishing two of them based on 15N NMR. This approach has been confirmed theoretically, in the current study, and further developed into a logical scheme that allows the existence of each of the isomers to be proven in solution. The experimental data, obtained by NMR and...

Université de Fribourg

Controlled tautomeric switching in azonaphthols tuned by substituents on the phenyl ring

Antonov, Liudmil ; Deneva, Vera ; Simeonov, Svilen ; Kurteva, Vanya ; Crochet, Aurelien ; Fromm, Katharina M. ; Shivachev, Boris ; Nikolova, Rositsa ; Savarese, Marika ; Adamo, Carlo

In: ChemPhysChem, 2015, vol. 16, no. 3, p. 649–657

A series of new tautomeric azonaphthols are synthesized and the possibilities for molecular switching are investigated using molecular spectroscopy, X-ray analysis and density functional theory quantum chemical calculations. Two opposite effects that influence switching are studied: attaching a piperidine sidearm, and adding substituents to the phenyl ring. On the one hand, the attached...

Université de Fribourg

Controlled tautomerism – switching caused by an ‘underground’ anionic effect

Antonov, Liudmil ; Deneva, Vera ; Kurteva, Vanya ; Nedeltcheva, Daniela ; Crochet, Aurelien ; Fromm, Katharina M.

In: RSC Advances, 2013, vol. 3, no. 47, p. 25410–25416

In a previous communication, we demonstrated a conceptual idea for a tautomeric switching system based on implementation of a flexible piperidine unit in 4-(phenyldiazenyl)naphthalen-1-ol (1). The results showed that a directed shift in the position of the tautomeric equilibrium can be achieved through protonation/deprotonation in a number of solvents. However, the effect of the counter ion in...

Université de Fribourg

Tautomerism in 1-phenylazo-4-naphthols: experimental results vs quantum-chemical predictions

Antonov, Liudmil ; Kurteva, Vanya ; Crochet, Aurelien ; Mirolo, Laurent ; Fromm, Katharina M. ; Angelova, Silvia

In: Dyes and Pigments, 2012, vol. 92, no. 1, p. 714–723

The reliability in the description of the tautomerism of 1-phenylazo-4-naphthol by using of HF and MP2 ab initio levels of theory and DFT methods with variety of pure GGA (OLYP), hybrid (B3LYP and B3PW91), long range corrected (LC-BLYP) and double-hybrid (B2PLYP and mPW2PLYP) functionals with large number of basis sets was estimated. In this evaluation three criteria were used: reproduction of...

Université de Fribourg

Solid state tautomerism in 2-((phenylimino)methyl)naphthalene-1-ol

Nedeltcheva, Daniela ; Kamounah, Fadhil S. ; Mirolo, Laurent ; Fromm, Katharina M. ; Antonov, Liudmil

In: Dyes and Pigments, 2009, vol. 83, no. 1, p. 121-126

The solid state tautomerism of 2-((phenylimino)methyl)naphthalene-1-ol was studied using X-ray measurements and absorption spectroscopy. In the solid state, the keto tautomer predominates. The observed shift in the equilibrium from the enol (dilute solution) to the keto (solid state) forms is explained by the formation of dye aggregates using ab initio quantum chemical calculations.