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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

Cis-Dioxido-molybdenum(VI) complexes of tridentate ONO hydrazone Schiff base: Synthesis, characterization, X-ray crystal structure, DFT calculation and catalytic activity

Ebrahimipour, S. Yousef ; Khabazadeh, , , Hojatollah ; Castro, Jesús ; Sheikhshoaie, Iran ; Crochet, Aurelien ; Fromm, Katharina M.

In: Inorganica Chimica Acta, 2015, vol. 427, p. 52–61

Two new cis-MoO₂ [MoO₂(L)(EtOH)] (1), [MoO₂(L)(Py)] (2) [L: (3-methoxy-2oxidobenzylidene)benzohydrazidato], complexes have been synthesized and fully characterized on the basis of elemental analysis, FT-IR, molar conductivity, ¹H NMR, ¹³C NMR and electronic spectra. The structure of complexes has been accomplished by single crystal X-ray...

Université de Fribourg

A new mixed-ligand copper(II) complex of (E)-N′-(2-hydroxybenzylidene) acetohydrazide: Synthesis, characterization, NLO behavior, DFT calculation and biological activities

Ebrahimipour, S. Yousef ; Sheikhshoaie, Iran ; Crochet, Aurelien ; Khaleghi, Moj ; Fromm, Katharina M.

In: Journal of Molecular Structure, 2014, vol. 1072, p. 267–276

A tridentate hydrazone Schiff base ligand, (E)-N′-(2-hydroxybenzylidene)acetohydrazide [HL], and its mixed-ligand Cu(II) complex [CuL(phen)], have been synthesized and characterized by elemental analyses, FT-IR, molar conductivity, UV–Vis spectroscopy. The structure of the complex has been determined by X-ray diffraction. This complex has square pyramidal geometry and the positions around...

Université de Fribourg

Crystallography for university research: some basic case studies

Crochet, Aurelien

In: CHIMIA International Journal for Chemistry, 2014, vol. 68, no. 5, p. 325–328

An overview of commonly available, state-of-the-art diffraction techniques for university research is presented based on some chemical case studies. Examples from the Fribourg crystallography service are presented, aimed at scientists who would like to learn about the principal possibilities that X-ray powder and single-crystal diffraction can offer, how these methods can serve to determine the...

Université de Fribourg

Polymorphism, what it is and how to identify it: a systematic review

Brog, Jean-Pierre ; Chanez, Claire-Lise ; Crochet, Aurelien ; Fromm, Katharina M.

In: RSC Advances, 2013, vol. 3, no. 38, p. 16905–16931

This review on polymorphism is a personal, non-comprehensive view on the field of polymorphism – a term which is often misused. Indeed, the discussion about polymorphism and related terms is still ongoing in the area of crystal engineering. This is why we felt it timely to look into the historical development of its definition and to delimit it. A short introduction to thermodynamic aspects and...

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

Ring a bell: Disubstituted calix[4]arene as ligand for transition metal chlorides

Crochet, Aurelien ; Fromm, Katharina M.

In: Polyhedron, 2012, p. -

Lower rim 1,3-disubstituted p-tert-butylcalix[4]arene is studied here in its deprotonated form as complexing ligand for iron and chromium chloride. Crystallization of the two complexes from dry THF gives two different stoichiometries and structures, a trinuclear iron compound and a second, mononuclear structure with chromium. In both cases, the ligand adopts an elliptical shape and the metal ions...

Université de Fribourg

Efficient amine end-functionalization of living ring-Opening metathesis polymers

Nagarkar, Amit A. ; Crochet, Aurelien ; Fromm, Katharina M. ; Kilbinger, Andreas F. M.

In: Macromolecules, 2012, vol. 45, no. 11, p. 4447–4453

An efficient strategy for the synthesis of monoamine end-functionalized living polymers using ring-opening metathesis polymerization with ruthenium initiators is reported. A new end-capping agent for this purpose was synthesized, and its efficiency for end-functionalization was evaluated using two common ruthenium-based initiators. Finally, terminal cross-metathesis was also explored as another...

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

Tautocrowns: a concept for a sensing molecule with an active side-arm

Antonov, Liudmil M. ; Kurteva, Vanya B. ; Simeonov, Svilen P. ; Deneva, Vera V. ; Crochet, Aurelien ; Fromm, Katharina M.

In: Tetrahedron, 2010, vol. 66, no. 24, p. 4292-4297

A new sensing molecule containing aza-15-crown-5 as a receptor and 4-(phenyldiazenyl)naphthalen-1-ol as a signal converter has been synthesized. In the free ligand, the hydrogen bonding between the tautomeric OH group and the nitrogen atom from the macrocycle fully shifts the tautomeric equilibrium towards the enol form. The complexation reverses the equilibrium as a result of the strong...