Mono and dimetallic pyrene-imidazolylidene complexes of iridium (III) for the deuteration of organic substrates and the C-C coupling of alcohols

Three different Ir(III) complexes with pyrene-containing N-heterocyclic carbenes have been prepared and characterized. Two complexes contain a monodentate pyrene-imidazolylidene ligand, and have the formulae [IrCp*Cl2(pyrene-NHC)] and [IrCp*(CO3)(pyrene-NHC)]. The third complex is a dimetallic complex with a pyrene-di-imidazolylidene bridging ligand, with the formula [{IrCp*(CO3)}2(μ-pyrene-di-NHC)]. The catalytic activity of the three complexes was tested in the H/D exchange of organic substrates, and in the β-alkylation of 1-phenylethanol with primary alcohols. In the deuteration of organic substrates, the carbonate complexes are active even in the absence of additives. The dimetallic complex is the most active one in the catalytic coupling of alcohols, a result that may be interpreted as a consequence of the cooperativity between the two metal centres.We gratefully acknowledge financial support from the MINECO of Spain (CTQ2014-51999-P) and the Universitat Jaume I (P11B2014-02, P11B2015-24

On the fly multi-modal observation of ligand synthesis and complexation of Cu complexes in flow with ‘benchtop’ NMR and mass spectrometry

Exploring complex chemical systems requires reproducible and controllable ways to access non-equilibrium conditions. Herein we present a programmable flow system that can do both ligand synthesis and complexation on the fly, and the conditions of the reaction can be monitored using two simultaneous techniques, namely NMR and mass spectrometry. By using this approach we monitored the formation of unknown complexes, followed by crystallization that resulted in the characterisation of their structures giving 5 new compounds (4 isolated and fully characterised) which can be formulated as: Cu2(L1)4(μ-CO3)](BF4)2 (2); [Cu3(L1)6(μ-CO3)](PF6)2(OH)2 (3) [Cu2(L2)2](BF4)2 (4) and [Cu(L2)2](BF4)2·CH3CN (5)

From ligand to complexes: inhibition of HIV-1 Integrase by beta-diketo acid metal complexes

Recently, a class of compounds bearing a β-diketo acid moiety have emerged as the most promising lead in anti-HIV-1 IN drug discovery. It is believed that the β-diketo acid pharmacophoric motif could be involved in a functional sequestration of one or both divalent metal ions, which are critical cofactors at the enzyme catalytic site. This would subsequently block the transition state of the IN-DNA complex. In this scenario, it is of paramount importance to acquire information about the mode of action of diketo acids, which could then be useful in the design of new compounds as IN inhibitors

Immobilization of pyrene - adorned N - heterocyclic carbene complexes of rhodium (I) on reduced graphene oxide and study of catalytic activity

Twopyrene-tagged N-heterocyclic carbene (NHC) complexes of rhodium(I) wereobtained and characterized. Thetwo complexes were supported onto reduced graphene oxide (rGO), generating two new materials in which the molecular complexes are immob ilized by p–p stacking interactions onto the surfaceofthe solid. The catalytic activity of both complexes and solid hybrid materials were studied in the 1,4-addition of phenylboronic acid to cyclohex-2-one, and in the hydrosilylation of terminal alkynes. The studies showed that for both reactions,the dimetallic complex displayed better catalytic performances than the monometallic one. This accounted for both the reactions performed in homogeneous conditions and for the reactions performed with the solid. In the case of the addition of phenylboronic acid to cyclohexanone,the solid containing the dimetallic catalystcould be effectively recycled up to five times, with negligible loss of activity,whereas the monometallic catalyst rapidlybecame inactive. In the hydrosilylation of terminal alkynes, the selectivity towards the b-(Z)-vinylsilane was improved if the immobilized dimetallic catalyst was used, although the catalyst startedtolose activity after the second run

Polyaromatic N-heterocyclic carbene ligands and π-stacking. Catalytic consequences

In the course of our most recent research, we demonstrated how homogeneous catalysts with polyaromatic functionalities possess properties that clearly differ from those shown by analogues lacking these polyaromatic systems. The differences arise from the ability of the polyaromatic groups to afford non-covalent interactions with aromatic molecules, which can either be substrates in a homogeneous catalysed reaction, or the same catalysts to afford self-assembled systems. This article summarizes all our efforts toward understanding the fundamental effects of p-stacking interactions in homogenous catalysis, particularly in those cases where catalysts bearing polyaromatic functionalities are used. The study reveals several important implications regarding the influence of ligand–ligand interactions, ligand–additive interactions, and ligand–substrate interactions, in the performance of the catalysts used. In particular, the electronic properties of ligands with fused polyconjugated systems, are modified if molecules with p-stacking abilities are added, via a ligand–additive interaction. Also, the kinetics of the reactions in which aromatic substrates and catalysts with polyaromatic ligands are used, are strongly influenced by the self-association of the catalysts and by the non-covalent interaction between the catalyst and the aromatic substrates. The nature and the magnitude of these supramolecular interactions were unveiled by using host–guest chemistry methods applied to organometallic catalysis. Finally, noncovalent interactions afford a very convenient approach for the immobilization of catalysts decorated with polyaromatic systems onto the surfaces of graphene derivatives, hence affording an easy yet extremely effective way to support catalysts and facilitate recycling. The results given have fundamental implications in the design of future catalysts containing rigid polyaromatic systems, and may inspire future researchers in the design of improved homogeneous catalysts, by taking into account that the activities of the metal complexes are strongly modified by supramolecular interactions.Financial support from the ‘Ministerio de Economía y Competitividad’ MINECO of Spain (CTQ2014-51999-P) and the Universitat Jaume I (P11B2014-02

Unprecedented layered coordination polymers of dithiolene group 10 metals: Magnetic and electrical properties

One-pot reactions between Ni(ii), Pd(ii) or Pt(ii) salts and 3,6-dichloro-1,2-benzenedithiol (HSC6H2Cl2SH) in KOH medium under argon lead to a series of bis-dithiolene coordination polymers. X-ray analysis shows the presence of a common square planar complex [M(SC6H2Cl2S)2]2- linked to potassium cations forming either a two-dimensional coordination polymer network for {[K2(μ-H2O)2(μ-thf)(thf)2][M(SC6H2Cl2S)2]}n [M = Ni (1) and Pd (2)] or a one-dimensional coordination polymer for {[K2(μ-H2O)2(thf)6][Pt(SC6H2Cl2S)2]}n (3). In 3 the coordination environment of the potassium ions may slightly change leading to the two-dimensional coordination polymer {[K2(μ-H2O)(μ-thf)2][Pt(SC6H2Cl2S)2]}n (4) that crystallizes together with 3. The physical characterization of compounds 1-3 show similar trends, they are diamagnetic and behave as semiconductorsWe thank financial support from MICINN (MAT2013-46753-C2-1-P, CTQ2014-52758-P and MAT2014-56143-R) and Generalitat Valenciana (PrometeoII/2014/076

Crystal structure of poly[[[μ4-5-(9H-carbazol-9-yl)isophthalato][μ3-5-(9H-carbazol-9-yl)isophthalato]bis-(di-methyl-formamide)(methanol)dizinc] di-methyl-formamide monosolvate].

The structure of the polymeric title compound, {[Zn2(C20H11NO4)2(C3H7NO)2(CH3OH)]·C3H7NO} n , comprises carbazolylisophthalate moieties connecting dimetallic tetra-carboxyl-ate zinc secondary building units (SBUs) parallel to [100] and [010], leading to a layer-like arrangement parallel to (001). Each SBU consists of two Zn atoms in slightly distorted tetra-hedral and octa-hedral coordination environments [Zn⋯Zn = 3.5953 (6) Å]. Three carboxyl-ate groups bridge the two Zn atoms in a μ2-O:O' mode, whereas the fourth coordinates through a single carboxyl-ate O atom (μ1-O). The O atoms of two di-methyl-formamide (DMF) and one methanol mol-ecule complete the Zn coordination spheres. The methanol ligand inter-acts with the noncoordinating DMF mol-ecule via an O-H⋯O hydrogen bond of medium strength. Carbazoles between the layers inter-digitate through weak C-H⋯.π inter-actions to form a laminar solid stacked along [010]. Two kinds of C-H⋯π inter-actions are present, both with a distance of 2.64 Å, between the H atoms and the centroids, and a third C-H⋯π inter-action, where the aromatic H atom is located above the carbazole N-atom lone pair (H⋯N = 2.89 Å). Several C-H⋯O inter-actions occur between the coordinating DMF mol-ecule, the DMF solvent mol-ecule, and ligating carboxyl-ate O atoms

Multiple stable conformations account for reversible concentration-dependent oligomerization and autoinhibition of a metamorphic metallopeptidase

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Molecular plasticity controls enzymatic activity: the native fold of a protein in a given environment is normally unique and at a global free-energy minimum. Some proteins, however, spontaneously undergo substantial fold switching to reversibly transit between defined conformers, the >metamorphic> proteins. Here, we present a minimal metamorphic, selective, and specific caseinolytic metallopeptidase, selecase, which reversibly transits between several different states of defined three-dimensional structure, which are associated with loss of enzymatic activity due to autoinhibition. The latter is triggered by sequestering the competent conformation in incompetent but structured dimers, tetramers, and octamers. This system, which is compatible with a discrete multifunnel energy landscape, affords a switch that provides a reversible mechanism of control of catalytic activity unique in nature. Shape shifting: A minimal metamorphic, selective, and specific caseinolytic metallopeptidase, selecase, reversibly transits between several different states of defined three-dimensional structure (monomer and tetramer represented in picture). The competent conformation is sequestered in incompetent but structured dimers, tetramers, and octamers, which are associated with loss of enzymatic activity due to autoinhibition.This study was supported in part by grants from European, Spanish, and Catalan agencies (FP7-HEALTH-2010-261460 “Gums&Joints”; FP7-PEOPLE-2011-ITN-290246 “RAPID”; FP7-HEALTH-2012-306029-2 “TRIGGER”; BFU2012-32862; CSD2006-00015; Fundació “La Marató de TV3” grant 2009-100732; 2009SGR1036; and “Pot d’Idees” FGB301793) and FPI Ph.D. fellowships from the former Spanish Ministry for Science and Technology, currently of Economy and Competitiveness, to M.L.-P. and A.C.-P. P.B. acknowledges funds from ANR-CHEX (project SPIN-HD) and ATIP-AvenirPeer Reviewe

Pincer-CNC mononuclear, dinuclear and heterodinuclear Au(III) and Pt(II) complexes supported by mono- and poly-N-heterocyclic carbenes: synthesis and photophysical properties

A family of cyclometallated Au(III) and Pt(II) complexes containing a CNC-pincer ligand (CNC = 2,6-diphenylpyridine) supported by pyrene-based mono- or bis-NHC ligands have been synthesized and characterized, together with the preparation of a Pt–Au hetero-dimetallic complex based on a Y-shaped tris-NHC ligand. The photophysical properties of all the new species and of two related Ru(II)–arene complexes were studied and compared. Whereas the pyrene-based complexes only exhibit emission in solution, those containing the Y-shaped tris-NHC ligand are only luminescent when dispersed in poly(methyl methacrylate) (PMMA). In particular, the pyrene-based complexes were found to be emissive in the range of 373–440 nm, with quantum yields ranging from 3.1 to 6.3%, and their emission spectra were found to be almost superimposable, pointing to the fluorescent pyrene-centered nature of the emission. This observation suggests that the emission properties of the pyrene fragment may be combined with some of the numerous applications of NHCs as supporting ligands allowing, for instance, the design of biological luminescent agents.We gratefully acknowledge financial support from MINECO of Spain (CTQ2014-51999-P) and the Universitat Jaume I (P11B2014-02). The authors are grateful to the Serveis Centrals d’Instrumentació Científica (SCIC) of the Universitat Jaume I for providing spectroscopic and X-ray facilities. We are very grateful to Prof. M. Concepción Gimeno (CSIC-Universidad de Zaragoza) for the measurement of the photophysical properties of the samples in PMMA films. We are also grateful to Prof. Francisco Galindo (Universitat Jaume I) for his help in the emission lifetime measurements

Evidence for a Dinuclear Active Site in the Metallo-β-lactamase BcII with Substoichiometric Co(II): A New Model for Uptake

Metallo-β-lactamases are zinc-dependent enzymes that constitute one of the main resistance mechanisms to β-lactam antibiotics. Metallo-β-lactamases have been characterized both in mono- and dimetallic forms. Despite many studies, the role of each metal binding site in substrate binding and catalysis is still unclear. This is mostly due to the difficulties in assessing the metal content and site occupancy in solution. For this reason, Co(II) has been utilized as a useful probe of the active site structure. We have employed UV-visible, EPR, and NMR spectroscopy to study Co(II) binding to the metallo-β-lactamase BcII from Bacillus cereus. The spectroscopic features were attributed to the two canonical metal binding sites, the 3H (His116, His118, and His196) and DCH (Asp120, Cys221, and His263) sites. These data clearly reveal the coexistence of mononuclear and dinuclear Co(II)-loaded forms at Co(II)/enzyme ratios as low as 0.6. This picture is consistent with the macroscopic dissociation constants here determined from competition binding experiments. A spectral feature previously assigned to the DCH site in the dinuclear species corresponds to a third, weakly bound Co(II) site. The present work emphasizes the importance of using different spectroscopic techniques to follow the metal content and localization during metallo-β-lactamase turnover