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A broad series of quinoxalinone-based π-conjugated donor-acceptor fluoro- and NLO-phores is characterized by means of Raman spectroscopy and single-crystal X-ray analysis supported by quantum chemical computations. Intense Raman spectroscopic markers that allow the differentiation of even closely related structures are identified. The intensities of these bands are shown to be related to the conjugation of the different molecular moieties, and they can provide an estimation of its extent. The intensity redistribution between these markers serves as a source of auxiliary structural information capable of pointing to a distortion of the conjugation or to the influence of aggregation effects in the condensed state. A simple relation between the intensity of the marker and the position and oscillator strength of the lowest-energy electronic absorption band of quinoxalinones allows a linking of the Raman effect with the optical properties of these compounds, which can be used for the rational design of novel species with improved optical characteristics.

International audience; The neuromuscular junction (NMJ) is a tripartite synapse in which not only presynaptic and post-synaptic cells participate in synaptic transmission, but also terminal Schwann cells (TSC). Acetylcholine (ACh) is the neurotransmitter that mediates the signal between the motor neuron and the muscle but also between the motor neuron and TSC. ACh action is terminated by acetylcholinesterase (AChE), anchored by collagen Q (ColQ) in the basal lamina of NMJs. AChE is also anchored by a proline-rich membrane anchor (PRiMA) to the surface of the nerve terminal. Butyrylcholinesterase (BChE), a second cholinesterase, is abundant on TSC and anchored by PRiMA to its plasma membrane. Genetic studies in mice have revealed different regulations of synaptic transmission that depend on ACh spillover. One of the strongest is a depression of ACh release that depends on the activation of α7 nicotinic acetylcholine receptors (nAChR). Partial AChE deficiency has been described in many pathologies or during treatment with cholinesterase inhibitors. In addition to changing the activation of muscle nAChR, AChE deficiency results in an ACh spillover that changes TSC signaling. In this mini-review, we will first briefly outline the organization of the NMJ. This will be followed by a look at the role of TSC in synaptic transmission. Finally, we will review the pathological conditions where there is evidence of decreased AChE activity.

The present study aims to investigate thein vitroantibacterial activities of several isophosphinoline-2-oxides that can be perceived as combined bio isosteres of coumarins and flavonoids. More specifically, antibacterial activity was evaluated against four bacterial strains, including the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa and the Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis by using disk diffusion assay. Notably, isophosphinoline-2-oxide compounds showed promising and highly selective antimicrobial activity against S. aureus.

Solvothermal synthesis involving tetrasubstituted carboxylic derivatives of [1.1.1.1]metacyclophane ( 1 – 2 ) bearing rigid phenyl spacer, that inherently adopt the 1 , 3 -Alternate conformation, with Manganese salts (acetate and nitrate) led to new 1D and 3D coordination polymers: { 1 3 -Mn 9 O 3 (CH 3 COO) 6 (C 5 H 5 N) 12 } ( 1 3 -Mn 9 ) and { 2 -Mn 2 (C 3 H 7 NO) 2 } ( 2 -Mn 2 ), respectively. The X-ray diffraction analysis revealed that: (i) ligand 1 , containing meta -benzoate coordinating sites, forms a 1D chiral helicoidal Coordination Polymer ( 1 3 -Mn 9 ) with trinuclear metallic clusters (Mn II Mn III 2 (μ 3 -O)) acting as linear connection nodes; (ii) ligand 2 , bearing para -benzoate moieties forms, a 3D diamond-like Coordination Polymer ( 2 -Mn 2 ) presenting Mn(II) polymeric chains bridged by tetrahedral-shaped ligand. The obtained Mn-based compounds are the first examples of coordination polymers based on tetrasubstituted [1.1.1.1]metacyclophane ligands bearing carboxylate coordinating groups.

Gold(I)-catalyzed reactions of electron-poor alkynes are still a challenging process. A straightforward synthesis of phosphorus-based heterocycles, namely, 2-phenyl 1H-isophosphinoline 2-oxides 1, is reported. The reaction used PPh3AuCl precatalyst in combination with triflic acid under microwave activation and afforded isophosphinoline 2-oxides 1 in moderate to quantitative yields through a fully regioselective 6-endo-dig hydroarylation cyclization, paving the way toward an effective synthesis of phosphorus heterocycles.

A combination of tetrasulfonylcalix[4]arene (3-4H) together with a calix[4]arene dicarboxylate derivative 2-4H led, in the presence of MII(NO3)2 (M = Co, Ni, Zn), to the formation of three novel isostructural metallomacrocycles of formula [M3(DMF)2(&mu, 3-H2O)-(2-2H)-3]. The structure of the prepared coordination compounds was studied in the solid state using single crystal/powder X-ray diffraction studies. The X-ray diffraction on single crystal revealed that the structure of the obtained supramolecular complexes is composed of a trinuclear metallic cluster [M3]+6 held between one di-deprotonated molecule of (2-2H)2&minus, offering two carboxylate groups for binding metal cations and one tetra-deprotonated compound 34&minus, where four oxygen atoms, belonging to four deprotonated phenolic moieties and three oxygen atoms coming from three SO2 groups, are coordinated with the cluster core. Thus, an example of an easily reproducible molecular recognition pattern involving two different types of calix[4]arene based ligands, displaying different coordination moieties, and trinuclear metallic clusters, is reported here. In addition, it has been shown that the cone moieties of the calixarene also encapsulate solvent molecules.

International audience; The efficient approach to novel water-soluble 2-aryl-substituted N-(phosphorylmethyl)pyrrolidines via acid-catalyzed elimination/cyclization/Friedel–Crafts reaction sequence of {[(4,4-diethoxybutyl)amino]methyl}phosphonates is proposed. Zwitterionic structure of N-(phosphorylmethyl) pyrrolidines has been proved by X-ray crystallography.

The macrocyclic ligand calix[4]arene (L1) and its sulphur-containing analogue thia[4]calixarene (L2) are promising precursors for functional molecular materials as they offer rational functionalization with various organic groups. Here, we present the first example of lanthanide-based coordination polymers built from the macrocyclic thiacalix[4]arene backbone bearing four carboxylic moieties, namely, ligand H4L3. The combination of H4L3 with the Tb3+ and Dy3+ cations led to the formation of 1D ladder-type coordination polymers with the formula [LnIIIHL3DMF3]·(DMF) (where DMF = dimethylformamide and Ln = Tb or Dy, denoted as HL3–Tb and HL3–Dy), which resulted from the coordination of the lanthanide cations with the partially deprotonated ligand HL33− that behaved as a T-shape connector. The coordination sphere around the metal was completed by the coordinated DMF solvent molecules. By combining both Tb3+ and Dy3+ cations, isostructural heterobimetallic solid solutions HL3–Tb1−xDyx were also prepared. HL3–Tb and HL3–Dy showed visible light photoluminescence originating from the f–f electronic transitions of pale green emissive Tb3+ and pale yellow emissive Dy3+ with efficient sensitization by the functionalized thia[4]calixarene ligand HL3. In the HL3–Tb1−xDyx solid solutions, the Tb/Dy ratio governed both the emission colour as well as the emission quantum yield, which reached even 28% at room temperature for HL3–Tb. Moreover, HL3–Dy exhibited a slow magnetic relaxation effect related to the magnetic anisotropy of the dodecahedral Dy3+ complexes, which were well isolated in the crystal lattice by expanded organic spacers.

International audience; Three zinc based coordination complexes were selectively generated in the crystalline phase using new flexible molecular "tweezers" calix[4]arene derivative ligand decorated with two appended carboxylic moieties and benzyl spacers ((3-4H)). Through the control of the metal/ligand ratio and the sythetic conditions, the coordination sphere around the zinc cations was found to be different, which influenced the nuclearity of the obtained complexes. The mononuclear complex (3-3H)2-Zn(DMF)2 was obtained while two partially deprotonated ligands (3-3H)cap the metallic cation, leading to non tubular "8"shaped structure with metal/ligand ratio equal to 1/2. The dinuclear (3-2H)2-Zn2py4 complex displays a tubular structure with metal/ligand ratio equal to 1/1 where two zinc cations act as linear metal linker between two (3-2H) 2species which adopts a cone conformation. Finally, the third trinuclear coordination complex (3-2H)4-Zn3(OH2) was obtained using (3-4H) and the highly coordinating sulfonylcalix[4]arene (4-4H), exhibiting 3/1/1 metal/3/4 ratio. Thus, it has been demonstrated that under self-assembly conditions, the nuclearity of the new complexes based on zinc cations and calix[4]arene dicarboxylate (3-4H) can be tuned, using different synthetic conditions (nature of solvent, crystallization method, use of a highly coordinating ligand (4-4H).

International audience; Two generations of phosphoric dendrimers with piperidine functional groups were synthesized for use in biology and medicine. Neutral samples are soluble in organic solvents but after protonation these dendrimers become water soluble and can be used for biological experiments. The FTIR and FT Raman spectra of two generations of dendrimers Gi constructed from the cyclotriphosphazene core, repeating units OC6H4CHNN(CH3)P(S)< and aminoethylpiperidine end groups NH(CH2)2C5NH11 were recorded. The study of the IR spectra shows that the NH groups form hydrogen bonds. The calculation of the molecular structure and vibrational spectra of the first generation dendrimer was performed by the method of DFT. This molecule has flat, repeating units and a plane of symmetry passing through the core. The calculation of the distribution of potential energy made it possible to classify the bands in the experimental spectra of dendrimers. Amine groups are manifested in the form of a band of NH stretching vibrations at 3389 cm−1 in the IR spectrum of G1. NH+ stretching bands located at 2646 and 2540 cm−1 in the IR spectrum of G2. The stretching vibrations of NH+ groups are noticeably shifted to low frequencies due to the formation of a hydrogen bond with the chlorine atom. The line at 1575 cm−1 in the Raman spectrum of G1 is characteristic for repeating units.

International audience; The combination, under mild conditions, of the methylenecarboxylic appended tetramercaptotetrathiacalix[4]arene (TMTCA) derivative 4, blocked in 1,3-Alternate conformation, with acetate salts of octahedral Copper(II), Manganese(II), Nickel(II) and Zinc(II), leads to the formation, in the crystalline state, of high dimensional coordination networks. Depending on the nature of the used metal cations and bases (pyridine or non-coordinating Et3N), six new different high-dimensional coordination polymers have been evidenced, presenting 4 different coordination patterns. All the compounds present a metal/4 ratio equal to 2/1. The formation of a 2D grid-like compound (4-Zn2(Py)4) as well as three different pseudo-diamandoid-like 3D compounds (4-Co2(Py)6(H2O), 4-Ni2(Py)6(H2O), 4-Mn2(Py)4(MeOH)2, 4-Mn2(DMF)2(MeOH)4 and 4-Zn2(MeOH)4) is observed.

International audience; FT Raman and infrared spectra of phosphotrihydrazone (S)P[N(CH3)N=CH_C6H4_OH]3-(G0) were recorded. This compound is a zero generation phosphorus dendrimer with terminal phenolic groups. Optimal geometry and vibrational frequencies were calculated for G0 using the density functional theory (DFT). The molecule studied has C3 symmetry. In the molecule G0, each_C6H4_CH=N_N(CH3)_P arm is flat. Optimized geometric parameters correspond to experimental data. The core of the dendrimer manifests itself as a band at 647 cm−1 in the Raman spectrum of G0 related to P=S stretching. Phenolic end functions exhibit a well-defined band at 3374 cm−1 in the experimental IR spectrum of G0. The observed frequency of the OH stretching vibrations of the phenolic groups is lower than the theoretical value due to the intermolecular O_H⋯O hydrogen bond. This hydrogen bond is also responsible for the higher intensity of this band in the experimental IR spectrum compared with the theoretical value. DFT calculations suggest full assignment of normal modes. Global and local descriptors characterize the reactivity of the core and end groups.

We report on the electronic absorption spectra, conformational behavior, and intra- and intermolecular hydrogen bonds of 2,3-(dibenzimidazol-2-yl)-quinoxaline (DBIQ). The experimentally found strong solvent dependence of the absorption spectra of DBIQ solutions cannot be assigned to electronic excitations of the equilibrium ground-state DBIQ structure. Extended consideration including the nonequilibrium structures within the framework of ab initio molecular dynamics (MD) revealed the importance of torsion molecular motions not covered by the static case. The strong impact of solute-solvent hydrogen bonding on stabilization of these nonequilibrium structures and on conformational composition of DBIQ was demonstrated. A presence of twisted nonplanar geometries along the whole MD trajectory was shown to drastically influence not only energies but also characters of electronic excitations, resulting in a change of local π-π* character in a solution of 1,2-dichloroethane to charge-transfer character in polar dimethylsulfoxide.

TD-DFT calculations with the use of hybrid PBE0 functional and def-TZVP Alrich's basis set are shown to provide an excellent cost-effective computational approach for the treatment of the excited states of phospholes. The general geometrical changes taking place upon excitation and bearing a common character in the series of considered phospholes have been revealed. It is demonstrated that conjugation of P-heterole with exocyclic aryl fragments makes the main impact on the ground-state (electronic absorption) properties of phospholes. The main structural transformations of the excited states responsible for emission properties are shown to occur mostly inside the P-hetorole ring causing change in bonds ordering upon excitation. The general good agreement between the experiments and the calculations found for the considered systems suggests that the applied theoretical approach can be used as an effective predictive tool for the rational design of luminescent phospholes.

The imidazole-containing N-4-tetradentate ligand N-(2-(1H-imidazol-2-yl)-3-(pyridin-2-yl)propyl)-2,6-diisopropylaniline (L2(H)) and its N-benzyl-protected variant (L2(Bn)) at the imidazole fragment have been synthesized and fully characterized. Both molecules contain an unresolved C-sp3 stereogenic center. The coordination behavior of the newly prepared ligands towards group IV metal ions (M-IV = Zr, Hf) has been examined through multinuclear H-1 and C-13{H-1} NMR spectroscopy and selected single-crystal X-ray structural analyses. The ability of the imidazole fragment to enter the metal coordination sphere as a neutral or a monoanionic system has also been investigated, unveiling quite original coordination modes as well as unexpected molecular architectures. When one N imidazole atom is blocked by a benzyl protecting group (L2(Bn)), the ligand reaction with M-IV(NMe2)(4) (M-IV = Zr, Hf) as metal precursor gives rise to discrete monometallic tris(dimethylamido) 5-coordinated compounds of general formula L2(Bn)M(NMe2)(3). The ligand chelates the metal ion as a bidentate monoanionic kappa(2){N-,N} system through the imidazole moiety and the anilido N donor while an uncoordinated picolyl arm dangles away from the metal center. Upon coordination to the metal ion, the unprotected L2(H) undergoes a unique self-assembly of the chiral racemic ligand to generate an achiral tetrameric network featuring a regularly alternating (R*,S*,R*,S*) configuration around the 6-coordinated metal centers. The resulting bis(dimethylamido) tetrameric architectures of formula [L2(H)M(NMe2)(2)](4) named "poker complexes" contain the imidazole fragment of each ligand bridging two adjacent M-IV ions in a mu-kappa{N}:kappa{N-} coordination hapticity. At the same time, the picolyl fragments of each chelating L2(H) ligand "sting" a neighboring metal center as unconventional scorpion's tails that impose further rigidity to the tetrameric structure.

International audience; Depending on the nature of the anion (NO3-or BF4-) and stoichiometry, combinations, under self-assembly conditions, of the [1.1.1.1]metacyclophane 2 adopting a blocked 1,3-alternate conformation and bearing four cyanomethylene groups, with silver cations, lead either to the formation of a 1D coordination network or a discrete binuclear metallomacrocycle.

International audience; Reported herein is the first example of a gold-catalyzed cyclization of bis(arylmethyl)ethynylphosphine oxides. This represents an original approach to bridgehead methanophosphocines 1, eight-membered heterocycles. Gold catalyst in combination with triflic acid activates alkyne and induces a double hydroarylation. Mechanistic studies suggest that the reaction proceeds stepwise, forming first the 1H-isophosphinoline 2-oxide 5. Reduction and protection of the corresponding phosphine oxides 1 described herein also highlight the effectiveness of our approach to this new class of electron-rich ligands.

The reaction of 4-chloro- and 4-bromoresorcinol with 2-ethoxyvinylphosphonic acid dichloroanhydride has been investigated for the first time. It has been determined that the product of the reaction is the mixture of structural isomers of bicyclic phosphonates at the ratio of 9:1. The structure and composition of the compounds have been elucidated from 1H, 31P, and 13C NMR spectroscopy, mass-spectrometry (MALDI-TOF), as well as elemental and X-ray analysis.

International audience; Four new tetrasubstituted [1.1.1.1]metacyclophanes (4-7), that are inherently adopting a 1,3-Alternate conformation, bearing four or eight peripheral carboxylic binding sites, and appended with spacers group (alkyl or phenyl) differing by the flexibility, have been synthesised in high yields. The structures of the obtained compounds have been investigated in solution as well as in the solid state, for three of them, by using single-crystal X-ray analysis.

Accurate characterization of the high-lying excited state manifolds of organic molecules is of fundamental importance for the interpretation of the rich response detected in time-resolved nonlinear electronic spectroscopies. Here, we have characterized the singlet excited state manifold of benzophenone (BP), a versatile organic photoinitiator and a well-known DNA photosensitizer. Benchmarks of various multiconfigurational/multireference (RASSCF/PT2) and time-dependent density functional theory (TD-DFT) approaches allowed assignments of experimental linear absorption signals of BP in the ultraviolet (UV) region, with unprecedented characterization of ground state absorptions in the far UV. Experimental transient absorption spectra obtained by UV-vis pump-probe spectroscopy at very short time delays are shown to be directly comparable to theoretical estimates of excited state absorptions (from the low-lying nOπ∗ and π π∗ singlet states) in the Franck-Condon region. Multireference computations provided reliable interpretation of the PP spectra, with TD-DFT results yielding a fair agreement as long as electronic transitions featuring double excitations contributions are not involved. These results lay the groundwork for further computational studies and interpretation of experimental nonlinear electronic spectra of benzophenone in more complex systems, such as BP/DNA adducts.

International audience; The interaction of the phosphoric dendrimer with gold was performed by means of vibrational spectroscopy and quantum chemistry. Stable complexes are formed with a PN−PS linkage, whereas with an isolated PS bond this does not occur. The change in geometric parameters and delocalization of electric charge under the influence of gold was discovered. The classification of bands in the experimental vibrational spectra of the dendrimer and its complex was carried out. HOMO of molecule of the dendrimer is localized on the SPNP linkage, whereas the LUMO is located on the terminal group. In the SPNP linkage there is a noticeable delocalization of the charge which leads to a change in the reactivity of this group. Interaction energy was estimated as the difference between the energies of the complex and the energies of the molecules of the dendrimer G′0 and two molecules AuCl and is equal to 25.2 eV. The ionization energy IE and electron affinity EA for AuCl are higher than for dendrimer, therefore, when the complex is formed, these quantities increases. Chemical potential and the electrophilicity index in the complex also increases.

A new phosphorus-containing dendrimer of the first-generation with potential pharmacological activity was synthesized and studied by spectral methods. The FTIR, FT Raman, 1 H and 31 P NMR spectra of the first generation dendrimer G 1 with a cyclotriphosphazene core, six branches O C 6 H 4 CH N N(CH 3 ) P(S) O C 6 H 4 (CH 2 ) 2 NH CO C 5 NH 4 were recorded. Amide groups of the dendrimer participate in the formation of an intermolecular hydrogen bond. Structure, geometric parameters, the frequency and intensity of the bands in the vibrational spectra were calculated using DFT with PBE functional and TZ2P basis set. Spectral characteristics, charge distribution and reactivity of the core, repeating units and terminal groups of the dendrimer were determined. The first-generation dendrimer molecule has the shape of a concave lens with a slightly non-planar cyclotriphosphazene core and flat repeating units. Repeating units are arranged symmetrically on three on each side of the core, there are no steric hindrances in it and the end groups are able to enter into subsequent reactions and dendrimer has a sufficiently large cavity for accommodating guest molecules. The HOMO covers the repeating units with a noticeable conjugation and the LUMO belongs to the terminal groups.

The photophysical properties of a series of novel push-pull quinoxalinone-based chromophores that strongly absorb and emit light in the broad visible spectrum were comprehensively studied both experimentally and through quantum chemical methods. The drastic influence of the position of the electron-donor dimethylaminostyryl (DMAS) in the quinoxalinone core on its absorption and emission intensities as well as on the solvatochromic behavior of the concerned isomers has been established. No dependence of the photophysical properties of the chromophores on the conformation of the DMAS group was found. Quantum chemical computations provided a reliable theoretical rationalization of the observed spectral features, in particular, the important one related to Stokes shift. The local or intramolecular charge-transfer (ICT) character of the key electronic transitions has been assessed using a quantitative natural transition orbitals analysis and based on the novel topological descriptors of the electronic density rearrangement. This study shows that the ICT effects are not the primary factors contributing to the drastic difference in the emission efficiency of push-pull chromophores that are structurally very similar.

International audience; The solid-state structures of 1D-3D Coordination Polymers based on the macrocyclic calixarene backbone has been reviewed, based on the chemical nature of appended substituents of macrocycle platform. The coordination propensity of this class of ligands is analysed, taking into account the different coordinating atoms/groups that can be located on the macrocyclic ligand: (1) the unmodified inherently coordinating thiacalix[4]arene with the S bridge a donor atoms; (2) different conformations of calix[n]arene units, with appended O donor atoms; (3) the chemical modification of the upper rim of calix[n]arenes and thiacalix[n]arenes, with coordinating groups, in particular the use of the sulfonate groups and (4) calix[4]arenes, thiacalix[4]arenes and tetramercaptothiacalix[4]rene that have been modified at their lower rim (mono, di and tetra substitution) using coordinating groups like cyano, carboxylate, pyridyl and pyrazolyl groups. All the formed coordination networks have been described. A special attention has been drawn to the structural and functional properties of these extended networks: magnetic, luminescence, adsorption and catalytic properties. Perspectives and future challenges in this emerging field are also discussed.

International audience; Three generations of phosphorus dendrimers with pyrrolidine end groups were synthesized for use in biology and medicine. Neutral samples are soluble in organic solvents but after protonation these dendrimers become water-soluble and can be used for biological experiments. The FTIR and FT Raman spectra of three generations of dendrimers Gi constructed from the cyclotriphosphazene core, repeating units OC6H4CHNN(CH3)P(S)< and aminoethylpyrrolidine end groups NH(CH2)2C4NH9 were registered. Analysis of the IR spectra of Gi shows that the NH groups form a hydrogen bond with chlorine atoms. The calculation of the vibrational spectra was performed for the optimal structure of the first generation dendrimer in the framework of the DFT method. The first-generation dendrimer molecule has flat, repeating units and a plane of symmetry passing through the cyclotriphosphazene core. Calculation of the distribution of the potential energy made it possible to assign the bands in the experimental vibrational spectra. Amine groups show NH stretching bands at 3397 and 3200cm−1, NH+ stretching bands occur at 2645 and 2546cm−1 in the IR spectrum of G1. The stretching vibrations of the NH+ group are significantly shifted to low frequencies due to the formation of a hydrogen bond with the chlorine atom. The line at 1577cm−1 in the Raman spectrum is characteristic of repeating units.

The FTIR and FT Raman spectra of the 11 generations of poly(phosphorhydrazone) dendrimers built from thiophosphoryl core with P−Cl ( G i ) and oxybenzaldehyde ( G' i ) terminal groups have been studied. Spectral pattern of dendrimers depends on the ratio of the number of end groups and repeating units. This ratio tends to r– 1 (r– functionality of the repeating unit) and becomes constant when the generation number exceeds 3. The experimental IR and Raman spectra of the different generations of dendrimers are very similar to each other in the agreement with the theory. Optimization of the structure and the analysis of normal vibrations was made for G' 0 and G 1 using the density functional theory (DFT). Calculations showed that the molecules of the first generation dendrimer have the form of a propeller with three blades and flat repeating units. Bond lengths and angles in the optimized geometry obtained by DFT show good agreement with experiment. Consideration of the molecular orbitals shows that in the repeating units and oxybenzaldehyde end groups of poly(phosphorhydrazone) dendrimers conjugation is realized. The oxybenzaldehyde terminal groups are characterized by a band 1702 cm −1 in the experimental IR spectra of G ’ i . The line in the Raman spectra of G i and G ’ i at 1576 cm −1 refers to the vibrations of the repeating units.

A phosphorus-containing dendrimer with pyrazine end groups that can be used for biological purposes has been synthesized. The vibrational spectra of the first generation dendrimer G 1 constructed from the cyclotriphosphazene core, six repeating units O C 6 H 4 –CH N N(CH 3 )–P(S) and twelve 4-oxyphenethylamidopyrazine end groups O C 6 H 4 –(CH 2 ) 2 –NH CO C 4 N 2 H 3 were registered. Analysis of the IR spectra of G 1 shows that the amide groups form an intermolecular hydrogen bond. Optimization of the structure and analysis of normal vibrations were carried out for dendrimer G 1 using the density functional theory (DFT). The six repeating units are arranged in a symmetric manner about the cyclophosphazene ring; each side of the ring contains three repeating units. It turned out that dendrimer G 1 is a double bowl with almost flat repeating units which represent the concave surface and a core as a bottom of the bowl. The assignment of bands in the vibrational spectra was carried out by analyzing the distribution of the potential energy. Amide groups show bands at 3393, 1675 cm −1 in the IR spectrum of G 1 . The line at 1577 cm −1 in the Raman spectrum is characteristic of repeating units.

International audience

International audience; Combinations of neutral tetrakis meta-pyridyl appended calix[4]arene derivatives in 1,3-A conformation as tectons 3 (Tetrakis-metapyridyl-tetrathiacalix[4]arene) and 4 (Tetrakis-meta-pyridyltetrathiatetramercaptocalix[4]arene) with MX2, behaving as a neutral metallatecton, lead to the formation of 2-and 3-D neutral coordination networks. In all cases, the metal centre adopts a distorted octahedral geometry with the two anions occupying the two apical positions. For the compound 3-CdX2 (X = Cl or Br), 4-CdBr2 and 4-FeCl2 similar porous diamondoid 3D networks, resulting from tetrakis monodentate behaviour of the organic tectons, are formed. In marked contrast, for 4-CoX2 (X = Cl or Br), only two out of the four pyridyl units take part in the connectivity pattern leading thus to the formation of 2D grid type architectures.

Analysis of infrared spectra of palladium nanoparticles (NPs) immersed in the tri-tert-butyl-R-phosphonium-based ionic liquids (ILs) demonstrates that both cations and anions of the ILs interact with the NPs. According to quantum-chemical simulations of these interactions, the binding energy of anions to the Pd-6 cluster, taken as a minimal-size model of the NPs, increases from similar to 6 to similar to 27 kcal mol(-1) in the order [PF6](-) approximate to [BF4](-) < [Tf2N](-) < [OTf](-) < [Br](-) << [TFA](-). In contrast, the binding energy for all types of the [(Bu3PR)-P-t](+) cations slightly varies at about similar to 22 kcal mol(-1) only moderately depending on the choice of the R moiety (n-pentyl, 2-hydroxyethyl, 2-methoxyethyl, 2-ethoxy-2-oxoethyl). As a result, the energies of interaction between a Pd-6 cluster and various ion pairs, formed by the abovementioned counter-ions, follow the order found for the anions and vary from similar to 24 to similar to 47 kcal mol(-1). These values are smaller than the energy of addition of a Pd atom to a Pd-n cluster (similar to 58 kcal mol(-1)), which suggests kinetic stabilization of the NPs in phosphonium-based ILs rather than thermodynamic stabilization. The results are qualitatively similar to the trends found earlier for interactions between palladium clusters and components of imidazolium-based ILs, in spite of much larger contributions of the London dispersion forces to the binding of the [(Bu3PR)-P-t](+) cations to the cluster (up to 80%) relative to the case of 1-R-3-methylimidazolium cations (up to 40%).

A stereoselective synthesis of the cone stereoisomer of thiacalix[4]arene bearing four triazolyl coordinating sites at the lower rim, 2, has been achieved by the 1,3-dipolar cycloaddition of p-nitrophenylazide to tetrakis-(propargyloxy) thiacalix[4]arene, 1, in presence of copper(I) iodide. A combination of 2 with AgNO3 leads to the formation of hexanuclear silver(I) complex with M:L ratio of 6:2. The latter forms a 3D π-bonded molecular network in the crystalline phase.

A series of chromophores containing quinoxaline or quinoxalinone electron-acceptor (A) and dialkylaminostyryl electron-donor (D) units linked by π electronic bridge has been synthesized. Electronic emission and absorption spectra of the novel D-π-A, D-π-A-π-D or D-π-A-π-A-π-D systems cover a broad range from ultraviolet to near infrared. Positions and relative intensities of their absorption bands are shown to depend strongly on structural modifications of the molecules, while emission in solution strongly depends on both the structure of the solute and the solvent polarity. Quantum chemical modeling provided a reliable description of the observed absorption spectra and reproduced the positions of the emission bands. Quantum yields of emission are shown to be qualitatively predictable on the basis of empirical rules connecting the luminescence intensity with the chemical structures of both quinoxaline- and quinoxalinone-based luminopohores and the polarity of the solvents used. Theoretical assessment of the character of the main electronic transitions suggests that simultaneous presence of D and A units conjugated via π-bridges ensures the intramolecular charge-transfer effects probably underlying the observed similar solvatochromism for all the studied systems irrespective of their polarity.

0301-0104; Abstract The FTIR and FT Raman spectra of the first generation dendrimers, possessing carbamate (G1) or ammonium (G2) terminal groups were studied. The structural optimization and normal mode analysis were performed for dendrimers on the basis of the density functional theory (DFT). These calculations of G2 gave the frequencies of vibrations, infrared intensities and Raman scattering activities for the E- and Z-forms of azobenzene unit. The energy difference between the E- and Z-forms of G2 is 27.36 kcal/mol. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendrimers molecules have a concave lens structure with planar -O-C6H4-CHN-N(CH3)PS, and -O-C6H4-NN-C6H4-CHN-NH-CO-CH2-N fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendrimers G1 and G2 were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1605 cm−1 in the IR spectra show marked changes of the optical density in dependence of substituents in the aromatic ring. The differences in the IR and Raman spectra of G2 for the E- and Z-forms of azobenzene units were cleared up. During structural isomerization of azobenzene units, redistribution of band intensities appears to a much higher extent than frequency shifts.

Inhibition of human AChE (acetylcholinesterase) and BChE (butyrylcholinesterase) by an alkylammonium derivative of 6-methyluracil, C-547, a potential drug for the treatment of MG (myasthenia gravis) was studied. Kinetic analysis of AChE inhibition showed that C-547 is a slow-binding inhibitor of type B, i.e. after formation of the initial enzyme·inhibitor complex ( K i=140 pM), an induced-fit step allows establishment of the final complex ( K i*=22 pM). The estimated k off is low, 0.05 min−1. On the other hand, reversible inhibition of human BChE is a fast-binding process of mixed-type ( K i=1.77 μM; K i′=3.17 μM). The crystal structure of mouse AChE complexed with C-547 was solved at 3.13 A resolution. The complex is stabilized by cation–π, stacking and hydrogen-bonding interactions. Molecular dynamics simulations of the binding/dissociation processes of C-547 and C-35 (a non-charged analogue) to mouse and human AChEs were performed. Molecular modelling on mouse and human AChE showed that the slow step results from an enzyme conformational change that allows C-547 to cross the bottleneck in the active-site gorge, followed by formation of tight complex, as observed in the crystal structure. In contrast, the related non-charged compound C-35 is not a slow-binding inhibitor. It does not cross the bottleneck because it is not sensitive to the electrostatic driving force to reach the bottom of the gorge. Thus C-547 is one of the most potent and selective reversible inhibitors of AChE with a long residence time, τ=20 min, longer than for other reversible inhibitors used in the treatment of MG. This makes C-547 a promising drug for the treatment of this disease. * ACh, : acetylcholine; AChE, : acetylcholinesterase; BChE, : butyrylcholinesterase; ChE, : cholinesterase; h, : human; LGA, : Lamarckian Genetic Algorithm; LS, : local search; MG, : myasthenia gravis; m, : mouse; nAChR, : nicotinic acetylcholine receptor; PAS, : peripheral anionic site; SMD, : steered molecular dynamics; TAA, : tetra-alkylammonium

International audience; The FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2](3) have been performed. This compound is a zero generation dendrimer G(0) with terminal amine groups. Structural optimization and normal mode analysis were obtained for G(0) by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614 cm(-1) in the experimental IR spectrum and by bands at 3327, 3241 cm(-1) in the Raman spectrum of G(0). The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular N-H center dot center dot center dot S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on OFT calculations a complete vibrational assignment is proposed for the studied dendrimer.

International audience; Combinations of six new coordinating tectons (3-8) tetrakis-pyrazolyl appended calix[4]arenes, blocked in 1,3-A conformation, based on 1 (tetrathiacalix[4]arene) and 2 (tetrathiatetramercaptocalix[4]arene) derivatives, with AgX salts (X = NO3-, BF4-, XF6-(X = P, As and Sb)) lead to nine new silver coordination networks. The flexible nature of tectons 3-8 (length of the spacer between the macrocycle and the pyrazolyl coordinating unit), their high number of potential coordinating sites and the loose coordination demand of Ag + cation lead to the formation of a large variety of networks with different dimensionality: from 1D (5-AgSbF6, 5-AgBF4, 7-AgSbF6 and 8-AgNO3) to extended 2D (6-AgBF4 and 8-AgSbF6) and to a series of three isostructural porous diamond-like 3D architectures (6-AgXF6 (X = P, As and Sb)).

International audience

The FTIR and FT Raman measurements of zero G c 0 ′ -H and first G c 1 ′ -H generations of phosphorus dendrimer built from cyclotriphosphazene core with phenoxy and deuterophenoxy terminal groups have been performed. In order to evaluate how much the frequencies, shift when changing the electronics of the system the FTIR and FT Raman spectra of phosphorus‒containing dendron with five terminal oxybenzaldehyde and one ester function G c i ′ have been also studied. Structural optimization and normal mode analysis were obtained for G c 0 ′ -H and G c 0 ′ -D by the density functional theory (DFT). It is discovered that dendrimer molecule exists in a stable conformation with six phenoxy terminal groups spaced above and below the flat cyclotriphosphazene core. Optimized geometric bond length and angles obtained by DFT show good agreement with a previously-published X-ray study. The phenoxy terminal groups are characterized by the well-defined line at 993 cm−1 in the experimental Raman spectrum of G c 0 ′ -H and by line at 960 cm−1 in the Raman spectrum of G c 0 ′ -D. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimers. The frequencies and relative intensity of the bands at 1589, 1487 cm−1 in the IR spectra show marked difference in dependence of the substituents on the aromatic ring.

International audience; Two tetrasubsituted derivatives of tetramercaptothiacalix[4]arene in 1,3-alternate conformation bearing either four (3-cyano)propyl (2) or (4-cyano)benzyl (3) moieties have been synthesized and characterized in solution as well as in the solid state by X-ray diffraction on single crystals. Their propensity to form coordination networks was investigated in the presence of silver cation as connecting metal and hexafluorophosphate as counter ion. Whereas the combination of AgPF6 and 2 bearing four (3-cyano)propyl groups leads to a 1D silver coordination network, for 3, containing four (4-cyano)benzyl units, a 3D diamond-like architecture is obtained.

Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl core with terminal P Cl groups, vinyl ( G 1 ) and azide ( G 2 ) functional group at the level of the core have been recorded. The optimized geometries of low energy isomers of G 1 and G 2 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of each structural part (core, branches, surface). It was found that the repeated branching units of G 1 and G 2 contain planar O C 6 H 4 CH N N(CH 3 ) P fragments. DFT results for the structure of G 1 and G 2 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G 1 and G 2 . The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core functional and terminal groups. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals why azide group linked to phosphorus has a different reactivity when compared to organic azides.

The FT-IR and FT–Raman measurements of 6 generations of phosphorus dendrimers G ′ ci built from cyclotriphosphazene core with phenoxy and deuterophenoxy terminal groups have been performed. Spectra of dendrimers depends on the ratio of end groups and repeated units. This ratio tends to be r – 1 ( r – functionality of repeated unit), and becomes constant, when the generation number is above 3. Experimental Raman spectra of generations of dendrimers are very closely similar in accordance with the theory. Structural optimization and normal mode analysis were obtained for G ′ c1 by the density functional theory (DFT). Calculations have shown that each O C 6 H 4 CH N N(CH 3 ) moiety is flat and six repeating units are located above and below the nearly flat cyclotriphosphazene ring. Optimized geometric bond length and angles obtained by DFT show good agreement with the experiment. The phenoxy terminal groups are characterized by the well-defined line at 1008 cm −1 in the experimental Raman spectrum of G ′ c 1 - H and by line at 968 cm −1 in the Raman spectrum of G ′ c 1 -D . The medium-intensity line in the Raman spectra of G ′ c 1 -H and G ′ c 1 -D at 1576 cm −1 refer to the repeating units vibrations.

International audience

Dendrimers are well-defined macromolecules whose highly branched structure is reminiscent of many natural structures, such as trees, dendritic cells, neurons or the networks of kidneys and lungs. Nature has privileged such branched structures for increasing the efficiency of exchanges with the external medium; thus, the whole structure is of pivotal importance for these natural networks. On the contrary, it is generally believed that the properties of dendrimers are essentially related to their terminal groups, and that the internal structure plays the minor role of an ‘innocent' scaffold. Here we show that such an assertion is misleading, using convergent information from biological data (human monocytes activation) and all-atom molecular dynamics simulations on seven families of dendrimers (13 compounds) that we have synthesized, possessing identical terminal groups, but different internal structures. This work demonstrates that the scaffold of nanodrugs strongly influences their properties, somewhat reminiscent of the backbone of proteins., The biological properties of dendrimers are thought to be largely dependent on the chemical nature of their surface. Here, the authors show that the internal scaffold of dendritic nanodrugs strongly influences their bioactivity, based on convergent information from biology and computation results.

International audience

International audience; The Fourier transform IR and Raman spectra of the zero generation dendrimer G1 with two PNPS linkages and four terminal aldehyde groups have been recorded. The optimized geometry of low energy isomer of G1 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of PNPS linkages. DFT results for the structure of G1 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals that the softness and electrophilicity of sulfur atom in the core of the dendrimer G1 is higher than that of sulfur atoms and of the dendron G2. Thus PNPS linkage has a high electron density on sulfur which allows the regiospecific complexation of gold, whereas the other PS groups do not react this way. This explains why PN bond in PNPS linkage is much more stable than isolated PN bonds, which are easily hydrolyzed.

International audience; The FTIR and FT Raman spectra of the second generation dendrimer G′2 built from thiophosphoryl core with terminal aldehyde groups have been recorded. The structural optimization and normal mode analysis were performed for model compound C, consisting of thiophosphoryl core, one branch with three repeated units, and four 4-oxybenzaldehyde terminal groups on the basis of the density functional theory (DFT) at the PBE/TZ2P level. The vibrational frequencies, infrared and Raman intensities for the t,g,g- and t,-g,g-conformers of the terminal groups were calculated. The t,g,g-conformer is 2.0 kcal/mol less stable compared to t,-g,g-conformer. A reliable assignment of the fundamental bands observed in the experimental IR and Raman spectra of dendrimer was achieved. For the low generations (G′1 to G′3) the disk form of studied dendrimer molecules is the most probable. For higher generations, the shape of dendrimer molecules will be that of a cauliflower.

The FT Raman spectra of the zero (Gv0) and first generations (Gv1) of phosphorus-containing dendrons with terminal carbamate groups and one ester function and [2-(4-hydroxyphenyl)ethyl]-carbamic acid tert-butyl ester (C) have been recorded and analyzed. The lines of free ν(CO) bonds are not observed in the experimental Raman spectrum of C and thus association of carbamate groups by hydrogen bonds occur. The frequencies of ν(CO) lines in the experimental Raman spectrum reveal the presence of the different types of H-bonds in the amorphous state of Gv0. Density functional theory (DFT) calculations of C gave geometrical parameters for the t-g-, g-g-, tg-, gg-conformers. The most stable is the gg-conformer. The structural optimization and normal mode analysis were performed for dendrons on the basis of the DFT. The calculated geometrical parameters, harmonic vibrational frequencies and Raman intensities are predicted in a good agreement with the experimental data. The experimental Raman spectra of dendrons were interpreted by means of potential energy distribution. Relying on DFT calculations the lines of a core, repeating units and terminal groups of dendrons were assigned. The polarizabilities and lipophilicity of dendrons were estimated.

International audience; The Fourier transform IR and Raman spectra of the first generation dendron G1 built from thiophosphoryl core with terminal PCl groups and azide functional group have been recorded. The optimized geometries of low energy isomers of G1 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of each structural part (core, branches, surface). It was found that the repeated branching units of G1 contain planar OC6H4CHNN(CH3)P< fragments. DFT results for the structure of G1 are in good agreement with recent X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals why azide group linked to phosphorus has a different reactivity when compared to organic azides.

0924-2031; Abstract The FT Raman spectra of the zero and first generations of phosphorus-containing dendrimers built from thiophosphoryl, cyclotriphosphazene and phthalocyanine core with terminal oxybenzaldehyde groups have been recorded and analyzed. The structural optimization and normal mode analysis were performed for dendrimers on the basis of the density functional theory (DFT). The calculated geometrical parameters, harmonic vibrational frequencies and Raman scattering activities are predicted in a good agreement with the experimental data. The experimental Raman spectra of dendrimers were interpreted by means of potential energy distribution. Relying on DFT calculations the lines of the cores, repeating units and terminal groups of dendrimers were assigned. The influence of the encirclement on the line frequencies and intensities was studied and due to the predictable, controlled and reproducible structure of dendrimers the information, usually inaccessible is obtained. The strong line at 1600 cm−1 show marked changes of intensity in dependence of aldehyde (CHO) or azomethyne (CHN) substituents in the aromatic ring. The polarizabilities and lipophilicity of dendrimers were estimated.

International audience; The enzyme citrate synthase is used by all living cells to catalyze the first step of the citric acid cycle. In this work, we have investigated the enolization and condensation steps catalyzed by citrate synthase, using ab initio (B3LYP/def2-TZVP and MP2/aug-cc-pVDZ) quantum chemical/molecular mechanical hybrid potentials in conjunction with reaction-path-location algorithms and molecular dynamics free energy simulations. The results of the latter indicate that the catalytic His238 residue is in its neutral form, and also argue strongly for the presence of a water molecule in the enzyme's catalytic center. Such a water is observed in some, but not all, of the experimentally resolved structures of the protein. The mechanism itself starts with an enolization that proceeds via an enolate intermediate rather than the enol form, which is much more unstable. This is in agreement with the results of other workers. For the condensation step, we investigated two mechanisms in which there is a direct nucleophilic attack of the enolate intermediate on the oxaloacetate carbonyl carbon, and found the one in which there is no proton transfer from the neighboring arginine to be preferred. Although this residue, Arg329, is not implicated directly in the reaction, it helps to stabilize the negative citryl-CoA formed during the condensation step.