CNRS Chemistry of Complex Matter

Strasbourg, France

CNRS Chemistry of Complex Matter

Strasbourg, France
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El Khoury Y.,CNRS Chemistry of Complex Matter | Hellwig P.,CNRS Chemistry of Complex Matter
Chemical Communications | Year: 2017

Far infrared spectroscopy is a technique that allows the probing of the low frequency region of vibrational spectra and reveals, among others, vibrational modes of inter- and intramolecular hydrogen bonding. Due to their collective nature, these modes are highly sensitive to the conformational state of the molecules as well as to their interactions. Far infrared spectroscopy is thus an emerging technique for the characterization of the low frequency motions of complex molecules, including polymers, peptides, proteins or ionic liquids. This technique is not limited by the molecule's size and can be applied to solids and liquids. An overview of far infrared studies on complex structures and their interactions is given revealing the potential of the approach. © 2017 The Royal Society of Chemistry.

Baudron S.A.,CNRS Chemistry of Complex Matter | Ruffin H.,CNRS Chemistry of Complex Matter | Hosseini M.W.,CNRS Chemistry of Complex Matter
Chemical Communications | Year: 2015

Coordination of two 2,2′-bisdipyrrin ligands, bearing methyl ester or methylthioether peripheral groups, with Zn(ii) cations leads not only to the formation of the expected linear helicates but also concomitantly to novel tri- and tetra-nuclear circular species that have been isolated and fully characterized in solution and by X-ray diffraction. © The Royal Society of Chemistry 2015.

Hellwig P.,CNRS Chemistry of Complex Matter
Biochimica et Biophysica Acta - Bioenergetics | Year: 2015

In bioenergetic systems quinones play a central part in the coupling of electron and proton transfer. The specific function of each quinone binding site is based on the protein-quinone interaction that can be described by means of reaction induced FTIR difference spectroscopy, induced for example by light or electrochemically. The identification of sites in enzymes from the respiratory chain is presented together with the analysis of the accommodation of different types of quinones to the same enzyme and the possibility to monitor the interaction with inhibitors. Reaction induced FTIR difference spectroscopy is shown to give an essential information on the general geometry of quinone binding sites, the conformation of the ring and of the substituents as well as essential structural information on the identity of the amino-acid residues lining this site. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems. © 2014 Elsevier B.V. All rights reserved.

Melin F.,CNRS Chemistry of Complex Matter | Hellwig P.,CNRS Chemistry of Complex Matter
Biological Chemistry | Year: 2013

Integral membrane proteins are encountered in fundamental natural processes, such as photosynthesis and respiration. The relation between the structure of the proteins and their function and dynamics are still not clear in most cases. Once fully understood, these processes could ultimately help researchers to develop alternative methods for producing energy, either from light or biomass. They could also lead to more efficient antibiotics, which would selectively inhibit a specific membrane protein of pathogenic bacteria. Since the chemical reactions involved in both photosynthesis and respiration are redox reactions, electrochemical methods can play a considerable role in uncovering their mechanisms. The electrochemical characterization of membrane proteins is, however, quite challenging. An overview on the techniques used for the characterization of membrane proteins, including classical approaches such as voltammetry and spectroelectrochemistry, and recent developments, such as their combination with surface-enhanced techniques is given.

Marets N.,CNRS Chemistry of Complex Matter | Bulach V.,CNRS Chemistry of Complex Matter | Hosseini M.W.,CNRS Chemistry of Complex Matter
New Journal of Chemistry | Year: 2013

Two chiral porphyrin based ligands bearing, at their opposite meso positions, two appended pyridyl or ethynylpyridyl units and chiral groups have been designed. For each ligand, both enantiomers were synthesised. In the presence of the Zn(ii) cation, the chiral ligands become self-complementary chiral metallatectons upon binding of the metal centre by the tetraaza core of the porphyrin. Owing to the presence of both free coordinating pyridyl units and Zn atoms offering one or two coordination sites within the same entity, depending on the coordination number adopted by the metal centre, chiral 1D stair type networks and 2D grid type architectures are formed. Surprisingly, for the 2D network, although the removal of CHCl3 solvent molecules leads to the loss of structural integrity, the solvent-free crystals are nevertheless formed by changing the crystallisation conditions and the solvent mixture. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Zigon N.,CNRS Chemistry of Complex Matter | Guenet A.,CNRS Chemistry of Complex Matter | Graf E.,CNRS Chemistry of Complex Matter | Hosseini M.W.,CNRS Chemistry of Complex Matter
Chemical Communications | Year: 2013

The synthesis of an organometallic turnstile based on a Pt(ii) centre as a hinge was achieved. Its dynamic behaviour in solution was investigated using 1D and 2D NMR techniques. Using Ag(i) cation as an effector, the switching between its open and closed states in solution was demonstrated. This journal is © The Royal Society of Chemistry 2013.

Beziau A.,CNRS Chemistry of Complex Matter | Baudron S.A.,CNRS Chemistry of Complex Matter | Rogez G.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Hosseini M.W.,CNRS Chemistry of Complex Matter
Inorganic Chemistry | Year: 2015

A strategy for the conversion of homometallic coordination networks into mixed metal-organic frameworks (MM′MOFs) is proposed. Ni(II) complexes of dipyrrin (dpm) ligands bearing peripheral pyridyl or imidazolyl units have been shown to self-assemble into coordination polymers with the metal cation in an octahedral environment coordinated to two bis-pyrrolic chelates and two neutral monodentate coordinating units such as pyridyl or imidazolyl moieties. Taking advantage of the chelate effect, the two monodentate units may be replaced by a diimine ligand leading to the disassembly of the networks by the formation of discrete soluble complexes. The latter can be employed as metallatectons for the construction of heterometallic architectures upon reaction with a secondary metal salt. This approach was applied using either 1,10-phenanthroline (phen) or 2,2′-bipyrimidine (bpm) as chelates leading to a series of mono- and binuclear metallatectons of the (phen)Ni(dpm)2 and (bpm)[Ni(dpm)2]2 type. Subsequent assembly with CdCl2 afforded either interpenetrated 2D grid-type architectures or 3D MM′MOFs. © 2015 American Chemical Society.

Beziau A.,CNRS Chemistry of Complex Matter | Baudron S.A.,CNRS Chemistry of Complex Matter | Fluck A.,CNRS Chemistry of Complex Matter | Hosseini M.W.,CNRS Chemistry of Complex Matter
Inorganic Chemistry | Year: 2013

Both sequential and one-pot strategies for the preparation of a series of grid-type mixed metal-organic frameworks (MM′MOFs) based on dipyrrin ligands appended with either a pyridyl or a phenyl-imidazolyl moiety have been investigated. For the stepwise approach, the differentiation between the two coordination sites (nature, charge, and denticity) was exploited for the synthesis of a family of five discrete Zn(II), Cu(II), and Pd(II) complexes. Acting as metallatectons, these construction building blocks lead to the formation of a series of MM′MOFs upon self-assembly with CdCl2. In these rhombic grid-type architectures, four consecutive metallatectons are bridged by Cd(II) cations adopting an octahedral coordination geometry with the chloride anions occupying apical positions, thus behaving as square nodes. The shape of the rhombus grids as well as the way they are packed (stacking or interpenetration) in the crystalline phase are controlled by the nature of metallatectons and the solvent molecules present in the crystals. Consequently, the heterometallic assemblies display different accessible voids, although they are built on layers with the same connectivity. More interestingly, as demonstrated by X-ray diffraction on both single crystals and microcrystalline powders, the same MM′MOFs were obtained by a one-pot strategy through direct combinations of dipyrrin derivatives with the corresponding metal salts. This one-pot approach is efficient and more convenient than the sequential alternative, since the isolation, purification, and characterization of the, sometimes insoluble, metallatectons are not required. © 2013 American Chemical Society.

Baudron S.A.,CNRS Chemistry of Complex Matter
Dalton Transactions | Year: 2013

While they may have been overshadowed by the brightness of their BODIPY analogues, dipyrrin based metal complexes have recently appeared as novel interesting luminescent species owing to the development of various synthetic strategies for the preparation of such coordination compounds with appreciable quantum yields and tuneable emission wavelength. Not only the rigidification brought by functionalization of the dipyrrin backbone either at position 5 or positions 1 and 9, but also a careful choice of the ligands present in the complex coordination sphere have been key in these developments leading to bright and stable emitters. At position 5, equivalent to the meso position of a porphyrin, introduction of peripheral groups, such as the mesityl moiety hindering the rotational freedom of this unit, has been particularly targeted, hence limiting a favourable non-radiative deactivation pathway. Regarding positions 1 and 9, their proximity to the metal center has prompted their use for the introduction of additional coordinating units, thus providing a pseudo-macrocyclic character to the ligands. In this perspective article, the different types of modification of dipyrrin as well as the resulting metal complexes incorporating these derivatives, their photophysical properties and their applications in sensing and materials science are reviewed. This journal is © The Royal Society of Chemistry 2013.

Neehaul Y.,CNRS Chemistry of Complex Matter | Juarez O.,Rensselaer Polytechnic Institute | Barquera B.,Rensselaer Polytechnic Institute | Hellwig P.,CNRS Chemistry of Complex Matter
Biochemistry | Year: 2013

The Na+-pumping NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme that conserves energy by translocating Na + through the plasma membrane. Found only in prokaryotes, the enzyme serves as the point of entry of electrons into the respiratory chain in many pathogens, including Vibrio cholerae and Yersinia pestis. In this study, a combined electrochemical and Fourier transform infrared (FTIR) spectroscopic approach revealed that Na+-NQR undergoes significant conformational changes upon oxidoreduction, depending on the monovalent cation present (Na +, Li+, K+, or Rb+). In the presence of the inhibitor Rb+, additional conformational changes are evident, indicating a changed accessibility of the sodium binding sites. In electrochemically induced FTIR difference spectra, the involvement of deprotonated acid residues in the binding of cations, together with the spectral features, that point toward a monodentate binding mode for these acid residues in the oxidized form of the enzyme and bidentate binding in the reduced form could be identified. The measurements confirmed that NqrB-D397 is one of the acid residues involved in Na+ and Li+ binding. In the NqrB-D397E mutant, the spectral features characteristic of COO- groups are shifted, and a weakening of the hydrogen binding of the ion binding cluster is revealed. Finally, H-D exchange kinetics of amide protons confirmed that Na+-NQR adopts different conformations, with different accessibilities to the aqueous environment, depending on the cation present, which contributes to the selectivity mechanism of ion translocation. © 2013 American Chemical Society.

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