Anne-Christine Chamayou

Bio: Anne-Christine Chamayou is an academic researcher from University of Freiburg. The author has contributed to research in topics: Schiff base & Hydrogen bond. The author has an hindex of 15, co-authored 18 publications receiving 997 citations.

Polymorphs, enantiomorphs, chirality and helicity in [Rh{N,O}(η4-cod)] complexes with {N,O} = salicylaldiminato Schiff base or aminocarboxylato ligands

Abstract: The dimeric complex acetato(η4-cycloocta-1,5-diene)rhodium(I), [Rh(O2CMe)(η4-cod)]2 (cod = cycloocta-1,5-diene) reacts with N,O-chelating Schiff-base ligands or with N-phenylglycine to afford the diminato- or aminocarboxylato(η4-cycloocta-1,5-diene)rhodium(I) complexes [{Rh(η4-cod)}2(salen)] (1), [{Rh(η4-cod)}2(salophen)] (2), [Rh((S)-N-phenylglycinato)(η4-cod)] (3S), [Rh(rac-N-phenylglycinato)(η4-cod)] (3rac), [Rh((R)-N-(4-methoxphenyl)ethyl-2-oxo-1-naphthaldiminato)(η4-cod)] (4) and [Rh(N-(o-tolyl)-2-oxo-1-naphthaldiminato)(η4-cod)] (5) [salen2− = N,N′-ethylene-bis(salicylaldiminato), salophen2− = N,N′-(1,2-phenylene)-bis(salicylaldiminato)]. The complexes are characterized by IR-, UV/Vis-, 1H/13C-NMR- and mass-spectroscopy. Complexes 1, 2, 4 and 5 contain six-membered metallaaromatic Rh–(N–CCC–O)-chelate rings which accept C–H⋯π contacts. The crystal structure of 2 presents a polymorph (dimorph) (2a) to a previously reported structure (2b, CSD refcode SCLIRB10). Polymorphic forms 2a and 2b are traced to a different interlocking of adjacent dinuclear molecules with their corrugated van der Waals surface. The achiral N-phenylglycine ligand gives a chiral N-phenylglycinato complex [Rh(O2C–CH2–NHPh)(η4-cod)] (3) with the nitrogen atom becoming the stereogenic center upon metal coordination. Complex 3 can crystallize as the enantiomorph 3S in the tetragonal, chiral space groupP41 in a spontaneous resolution of the racemic mixture into homo-chiral helix-enantiomers due to inter-molecular N–H⋯O hydrogen bonding which connects only molecules of the same (S-) configuration into (right-handed or P-) 41-helical chains. Variation of the crystallization conditions gives 3 as a racemic polymorphic 3rac. R- and S-complexes 3 assemble in the polymorph 3rac in parallel chains along the 21-axes through N–H⋯O hydrogen bonding. Again, only molecules of the same configuration are combined into a chain, albeit neighboring chains have complexes of opposite configuration. The chiral enantiomeric naphthaldiminato complex 4 displays a herring-bone arrangement. Achiral compound 5 crystallizes in the non-centrosymmetric polar space groupCc where all molecules show the same orientation.

Chirality and Diastereoselection of Δ/Λ-Configured Tetrahedral Zinc Complexes through Enantiopure Schiff Base Complexes: Combined Vibrational Circular Dichroism, Density Functional Theory, 1H NMR, and X-ray Structural Studies

Abstract: The metal-centered Δ/Λ-chirality of four-coordinated, nonplanar Zn(A∧B)2 complexes is correlated to the chirality of the bidentate enantiopure (R)-A∧B or (S)-A∧B Schiff base building blocks [A∧B = ...

Syntheses, Spectroscopic Studies, and Crystal Structures of Chiral [Rh(aminocarboxylato)(η4-cod)] and Chiral [Rh(amino alcohol)(η4-cod)](acetate) Complexes with an Example of a Spontaneous Resolution of a Racemic Mixture into Homochiral Helix-Enantiomers

Abstract: The dimeric complex acetato(η4-cycloocta-1,5-diene)rhodium(I), [Rh(O2CMe)(η4-cod)]2 (cod = cycloocta-1,5-diene), reacts with amino acids [HAA = L-alanine, (S)-2-amino-2-phenylacetic acid (L-phenylglycine), N-methylglycine, and N-phenylglycine] and with the amino alcohol (S)-2-amino-2-phenylethanol to afford the aminocarboxylato(η4-cycloocta-1,5-diene)rhodium(I) complexes [Rh(AA)(η4-cod)] (AA = deprotonated amino acid = aminocarboxylato ligand) and [(S)-2-amino-2-phenylethanol](η4-cycloocta-1,5-diene)rhodium(I) acetate, [Rh{(S)-HOCH2–CH(Ph)-NH2}(η4-cod)](O2CMe) (V). The complexes are characterized by IR, UV/Vis, 1H/13C NMR and mass spectroscopy. The achiral N-phenylglycine ligand gives a chiral N-phenylglycinato complex [Rh(O2C–CH2–NHPh)(η4-cod)] (IV) with the amine nitrogen atom becoming the stereogenic center upon metal coordination. Complex IV crystallizes in the tetragonal, chiral space group P43 and the crystal structure reveals twofold spontaneous resolution of a racemic mixture into homochiral helix-enantiomers. The investigated crystal contained only one type of helix, namely (left-handed or M-) 43-helical chains. This is traced first to an intermolecular N–H···O hydrogen bonding from the stereogenic amino group to a neighboring unligated carboxyl oxygen atom that connects only molecules of the same (R)-configuration into (left-handed or M-) 43-helical chains. This intrachain homochirality is supplemented, secondly, by the interlocking of adjacent chains with their corrugated van der Waals surface to allow for an interchain transmission of the sense of helicity, building the single crystal from the same homochiral helix-enantiomer. The enantiomeric amino alcohol complex V crystallizes in the monoclinic, noncentrosymmetric (Sohncke) space group P21. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

N-o-Vanillylidene-L-histidine: Experimental Charge Density Analysis of a Double Zwitterionic Amino Acid Schiff-Base Compound

Abstract: A double zwitterionic Schiff base was synthesized using the amino acid l-histidine and o-vanillin (2-hydroxy-3-methoxy benzaldehyde). Both the phenol and carboxyl groups are deprotonated, and the imine nitrogen atom and histidine-imidazole ring are protonated to give the double zwitterion with an intramolecular (imine)N−H+···−O(phenol) hydrogen bond (ketoamine form). Such a ketoamine form in a double zwitterion is assumed in the catalytic cycle of enzymatic transformations of amino acids with the cofactor (vitamin B6) pyridoxal-5′-phosphate (PLP). A high-resolution, low-temperature, single-crystal X-ray diffraction data set on N-o-vanillylidene-l-histidine (also named 3-methoxysalicylidene-l-histidine or N-(2-oxy-3-methoxy-benzylidene)-l-histidine, OVHIS) is used in the analysis of molecular electrostatic properties and intermolecular interactions. All oxygen atoms in the molecule (four in total) are mutually almost coplanar and located (externally) on the same side of molecule. These four O atoms carry s...

Supramolecular coordination: self-assembly of finite two- and three-dimensional ensembles.

Abstract: Fascination with supramolecular chemistry over the last few decades has led to the synthesis of an ever-increasing number of elegant and intricate functional structures with sizes that approach nanoscopic dimensions Today, it has grown into a mature field of modern science whose interfaces with many disciplines have provided invaluable opportunities for crossing boundaries both inside and between the fields of chemistry, physics, and biology This chemistry is of continuing interest for synthetic chemists; partly because of the fascinating physical and chemical properties and the complex and varied aesthetically pleasing structures that supramolecules possess For scientists seeking to design novel molecular materials exhibiting unusual sensing, magnetic, optical, and catalytic properties, and for researchers investigating the structure and function of biomolecules, supramolecular chemistry provides limitless possibilities Thus, it transcends the traditional divisional boundaries of science and represents a highly interdisciplinary field In the early 1960s, the discovery of ‘crown ethers’, ‘cryptands’ and ‘spherands’ by Pedersen,1 Lehn,2 and Cram3 respectively, led to the realization that small, complementary molecules can be made to recognize each other through non-covalent interactions such as hydrogen-bonding, charge-charge, donor-acceptor, π-π, van der Waals, etc Such ‘programmed’ molecules can thus be self-assembled by utilizing these interactions in a definite algorithm to form large supramolecules that have different physicochemical properties than those of the precursor building blocks Typical systems are designed such that the self-assembly process is kinetically reversible; the individual building blocks gradually funnel towards an ensemble that represents the thermodynamic minimum of the system via numerous association and dissociation steps By tuning various reaction parameters, the reaction equilibrium can be shifted towards the desired product As such, self-assembly has a distinct advantage over traditional, stepwise synthetic approaches when accessing large molecules It is well known that nature has the ability to assemble relatively simple molecular precursors into extremely complex biomolecules, which are vital for life processes Nature’s building blocks possess specific functionalities in configurations that allow them to interact with one another in a deliberate manner Protein folding, nucleic acid assembly and tertiary structure, phospholipid membranes, ribosomes, microtubules, etc are but a selective, representative example of self-assembly in nature that is of critical importance for living organisms Nature makes use of a variety of weak, non-covalent interactions such as hydrogen–bonding, charge–charge, donor–acceptor, π-π, van der Waals, hydrophilic and hydrophobic, etc interactions to achieve these highly complex and often symmetrical architectures In fact, the existence of life is heavily dependent on these phenomena The aforementioned structures provide inspiration for chemists seeking to exploit the ‘weak interactions’ described above to make scaffolds rivaling the complexity of natural systems The breadth of supramolecular chemistry has progressively increased with the synthesis of numerous unique supramolecules each year Based on the interactions used in the assembly process, supramolecular chemistry can be broadly classified in to three main branches: i) those that utilize H-bonding motifs in the supramolecular architectures, ii) processes that primarily use other non-covalent interactions such as ion-ion, ion-dipole, π–π stacking, cation-π, van der Waals and hydrophobic interactions, and iii) those that employ strong and directional metal-ligand bonds for the assembly process However, as the scale and degree of complexity of desired molecules increases, the assembly of small molecular units into large, discrete supramolecules becomes an increasingly daunting task This has been due in large part to the inability to completely control the directionality of the weak forces employed in the first two classifications above Coordination-driven self-assembly, which defines the third approach, affords a greater control over the rational design of 2D and 3D architectures by capitalizing on the predictable nature of the metal-ligand coordination sphere and ligand lability to encode directionality Thus, this third strategy represents an alternative route to better execute the “bottom-up” synthetic strategy for designing molecules of desired dimensions, ranging from a few cubic angstroms to over a cubic nanometer For instance, a wide array of 2D systems: rhomboids, squares, rectangles, triangles, etc, and 3D systems: trigonal pyramids, trigonal prisms, cubes, cuboctahedra, double squares, adamantanoids, dodecahedra and a variety of other cages have been reported As in nature, inherent preferences for particular geometries and binding motifs are ‘encoded’ in certain molecules depending on the metals and functional groups present; these moieties help to control the way in which the building blocks assemble into well-defined, discrete supramolecules4 Since the early pioneering work by Lehn5 and Sauvage6 on the feasibility and usefulness of coordination-driven self-assembly in the formation of infinite helicates, grids, ladders, racks, knots, rings, catenanes, rotaxanes and related species,7 several groups - Stang,8 Raymond,9 Fujita,10 Mirkin,11 Cotton12 and others13,14 have independently developed and exploited novel coordination-based paradigms for the self-assembly of discrete metallacycles and metallacages with well-defined shapes and sizes In the last decade, the concepts and perspectives of coordination-driven self-assembly have been delineated and summarized in several insightful reviews covering various aspects of coordinationdriven self-assembly15 In the last decade, the use of this synthetic strategy has led to metallacages dubbed as “molecular flasks” by Fujita,16 and Raymond and Bergman,17 which due to their ability to encapsulate guest molecules, allowed for the observation of unique chemical phenomena and unusual reactions which cannot be achieved in the conventional gas, liquid or solid phases Furthermore, these assemblies found applications in supramolecular catalysis18,19 and as nanomaterials as developed by Hupp20 and others21,22 This review focuses on the journey of early coordination-driven self-assembly paradigms to more complex and discrete 2D and 3D supramolecular ensembles over the last decade We begin with a discussion of various approaches that have been developed by different groups to assemble finite supramolecular architectures The subsequent sections contain detailed discussions on the synthesis of discrete 2D and 3D systems, their functionalizations and applications

Chemistry of Polyvalent Iodine

Abstract: Starting from the early 1990’s, the chemistry of polyvalent iodine organic compounds has experienced an explosive development. This surging interest in iodine compounds is mainly due to the very useful oxidizing properties of polyvalent organic iodine reagents, combined with their benign environmental character and commercial availability. Iodine(III) and iodine(V) derivatives are now routinely used in organic synthesis as reagents for various selective oxidative transformations of complex organic molecules. Several areas of hypervalent organoiodine chemistry have recently attracted especially active interest and research activity. These areas, in particular, include the synthetic applications of 2-iodoxybenzoic acid (IBX) and similar oxidizing reagents based on the iodine(V) derivatives, the development and synthetic use of polymer-supported and recyclable polyvalent iodine reagents, the catalytic applications of organoiodine compounds, and structural studies of complexes and supramolecular assemblies of polyvalent iodine compounds. The chemistry of polyvalent iodine has previously been covered in four books1–4 and several comprehensive review papers.5–17 Numerous reviews on specific classes of polyvalent iodine compounds and their synthetic applications have recently been published.18–61 Most notable are the specialized reviews on [hydroxy(tosyloxy)iodo]benzene,41 the chemistry and synthetic applications of iodonium salts,29,36,38,42,43,46,47,54,55 the chemistry of iodonium ylides,56–58 the chemistry of iminoiodanes,28 hypervalent iodine fluorides,27 electrophilic perfluoroalkylations,44 perfluoroorgano hypervalent iodine compounds,61 the chemistry of benziodoxoles,24,45 polymer-supported hypervalent iodine reagents,30 hypervalent iodine-mediated ring contraction reactions,21 application of hypervalent iodine in the synthesis of heterocycles,25,40 application of hypervalent iodine in the oxidation of phenolic compounds,32,34,50–53,60 oxidation of carbonyl compounds with organohypervalent iodine reagents,37 application of hypervalent iodine in (hetero)biaryl coupling reactions,31 phosphorolytic reactivity of o-iodosylcarboxylates,33 coordination of hypervalent iodine,19 transition metal catalyzed reactions of hypervalent iodine compounds,18 radical reactions of hypervalent iodine,35,39 stereoselective reactions of hypervalent iodine electrophiles,48 catalytic applications of organoiodine compounds,20,49 and synthetic applications of pentavalent iodine reagents.22,23,26,59 The main purpose of the present review is to summarize the data that appeared in the literature following publication of our previous reviews in 1996 and 2002. In addition, a brief introductory discussion of the most important earlier works is provided in each section. The review is organized according to the classes of organic polyvalent iodine compounds with emphasis on their synthetic application. Literature coverage is through July 2008.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

Abstract: The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C–C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of...

MOFs, MILs and more: concepts, properties and applications for porous coordination networks (PCNs)

Abstract: This review (over 380 references) summarizes metal–organic frameworks (MOFs), Materials Institute Lavoisier (MILs), iso-reticular metal–organic frameworks (IR-MOFs), porous coordination networks (PCNs), zeolitic metal–organic frameworks (ZMOFs) and porous coordination polymers (PCPs) with selected examples of their structures, concepts for linkers, syntheses, post-synthesis modifications, metal nanoparticle formations in MOFs, porosity and zeolitic behavior for applications in gas storage for hydrogen, carbon dioxide, methane and applications in conductivity, luminescence and catalysis.

Recent advances in crystal engineering

Abstract: The articles published in the tenth anniversary issue of CrystEngComm are reviewed. The issue highlighted the state-of-the-art of crystal engineering and new trends and developing areas in crystal engineering. In particular, the following article emphasises developments in the areas of intermolecular interactions, notably hydrogen and halogen bonds; metal–organic frameworks or coordination polymers; polymorphism and solvates.