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Titulaire de la chaire de professeur à l’Université de Picardie Jules Verne (UPJV), au sein du Laboratoire de Glycochimie et des Agroressources d'Amiens (LG2A) mes travaux de recherche ont pour objectifs de conceptualiser, synthétiser et caractériser des matériaux fonctionnels basés sur les bioressources, de déterminer et de comprendre la relation structure-propriétés. L’enjeu est de développer des matériaux avancés dans le respect de l'environnement et à faible empreinte écologique pour le domaine de l’énergie, de la santé et de l’environnement. Ces matériaux sont utilisés pour la production d’hydrogène, la capture et la conversion du dioxyde de carbone, le stockage l’énergie ou encore le développement de dispositifs biomédicaux.
Organique, inorganique, état solide, chimie supramoléculaire, chimie réticulaire, chimie des matériaux, matériaux poreux, relation structure-propriétés; synthèse des metal-organic frameworks et covalent organic frameworks; production d’hydrogène, capture et conversion du dioxyde de carbone, batteries; stockage d’énergie, énergie propre et renouvelable, séparation et adsorption de gaz, catalyse, design molécules et matériaux pour la santé et l’environnement.
Concevoir, synthétiser et caractériser des matériaux fonctionnels pour le développement de l’énergie, la santé et l’environnement.
Isostructural coordination polymers of the tethering naphthalene anchored bis(2-methylpyridinecarboxamide) ligand: single crystal, XPS, EDS and theoretical studies |
Synthesis and preparation of poly (AM-co-AMPS)/GO nanocomposites hydrogel as a rheology modifier and fluid loss controller for use in oil well cementing |
Synthesis, characterization, and rheological behavior of HPG graft poly (AM-co-AMPS)/GO nanocomposite hydrogel system for enhanced oil recovery |
Two different pore architectures of cyamelurate-based metal–organic frameworks for highly selective CO2 capture under ambient conditions |
Missing puzzle in crystal engineering: 2-pyridone and [1,3,5]-triazine-2,4-diamine, the two most common cyclic hydrogen bonding sticky sites, in a single core |
An insight into sensitive detection of metal ions using a novel cobalt MOF: single crystal, photoluminescence, and theoretical studies |
Recent progress on the design and development of diaminotriazine based molecular catalysts for light-driven hydrogen production |
Comparative studies of synthesis, structure, optical properties and conductivity of the monoclinic phases Na2Co6Mn2(PO4)6 and Na2Co6Ni2(PO4)6 |
Synthesis of Na3Co7(PO4)6 by sol-gel and solid-state methods |
SrFe12O19 Powder and Polyvinyl Alcohol-Coated SrFe12O19 Films Synthesized Using Tartaric Acid and Study of their Structural, Magnetic, Morphological and Electrical Properties |
cis-[6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine](dichloride) Palladium(II)-Based Electrolyte Membrane Reactors for Partial Oxidation Methane to Methanol |
Defective Metal-Organic Framework-808@Polyaniline Composite Materials for High Capacitance Retention Supercapacitor Electrodes |
S-Heptazine N-ligand based luminescent coordination materials: synthesis, structural and luminescent studies of lanthanide-cyamelurate networks |
Novel dielectric response in B-site zirconium-doped CaCu3Ti4O12 ceramics: A structural, optical and electrical study |
Design, structural characterization and Hirshfeld surface analysis of Ni(II) and Zn(II) coordination polymers using mixed linker synthetic strategy based on tetratopic and macrocyclic N-donor ligands |
Photocatalytic Carbon Dioxide Reduction and Density Functional Theory Investigation of 2,6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine and Its Cobalt and Nickel Complexes |
New approach by electrospray technique to prepare a gas diffusion layer for the proton exchange membrane fuel cell anode |
Rheological and thermal stability of interpenetrating polymer network hydrogel based on polyacrylamide/hydroxypropyl guar reinforced with graphene oxide for application in oil recovery |
Hydrogen Bond Patterns of Dipyridone and Bis(Hydroxypyridinium) Cations |
Synthesis, characterization and Hirshfeld surface analysis of a mixed-ligand copper (II) coordination polymer from 1,4,8,11-tetraazacyclotetradecane and pyromellitic dianhydride |
Study of early P91 dual corrosion in steam and simulated combustion gases from a gas-fired boiler |
Flexible and porous 2D layered structures based on mixed-linker metal-organic frameworks for gas sorption studies |
Synthesis, crystal structure, characterization of pyrazine diaminotriazine based complexes and their systematic comparative study with pyridyl diaminotriazine based complexes for light-driven hydrogen production |
Design of a [FeFe] macrocyclic metallotecton for light-driven hydrogen evolution reaction |
Amidine/Amidinate Cobalt Complexes: One-Pot Synthesis, Mechanism, and Photocatalytic Application for Hydrogen Production |
Graphene oxide-induced interfacial transcrystallization of single-fiber milkweed/polycaprolactone/polyvinylchloride composites |
Intercalated 2d+2d hydrogen-bonded sheets in co-crystals of cobalt salt with 1H,1'H-[3,3']bipyridinyl-6,6'-dione |
A Rational Design of Microporous Nitrogen-Rich Lanthanide Metal–Organic Frameworks for CO2/CH4 Separation |
Water-dispersible polyaniline/graphene oxide counter electrodes for dye-sensitized solar cells: Influence of synthesis route on the device performance |
Conversion of Methane into Methanol Using the [6,6?-(2,2?-Bipyridine-6,6?-Diyl)bis(1,3,5-Triazine-2,4-Diamine)](Nitrato-O)Copper(II) Complex in a Solid Electrolyte Reactor Fuel Cell Type |
Building coordination polymers using dipyridone ligands |
Controlling Molecular Organization by Using Phenyl Embraces of Multiple Trityl Groups |
Mimicking 2,2′:6′,2′′:6′′,2′′′-quaterpyridine complexes for the light-driven hydrogen evolution reaction: Synthesis, structural, thermal and physicochemical characterizations |
Programmed Molecular Construction: Driving the Self-Assembly by Coordination and Hydrogen Bonds Using 6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine with M(NO3)2 Salts |
Syntheses of mono and bimetallic cyamelurate polymers with reversible chromic behaviour |
Effect of precursors on the structural, magnetic, dielectric, microwave and electromagnetic properties of Co–Zr doped nanocrystalline strontium hexaferrites synthesized via sol–gel method |
Molecular Organization in Crystals of Bis(diaminotriazinyl)-Substituted Derivatives of Benzene, Pyridine, and Pyrazine |
Comparing crystallizations in three dimensions and two dimensions: Behavior of isomers of [2,2?-bipyridine]dicarbonitrile and [1,10-phenanthroline]dicarbonitrile |
Long-lived, red-emitting excited state of a Ru(II) complex of a diaminotriazine ligand |
This research work reports the synthesis of three novel coordination compounds with the formula {[M(L1)(C3H7NO)4].(ClO4)2}n (M = Cu(ii) 1, Co(ii) 2, and Zn(ii) 3), using M(ClO4)2?6H2O metal salt with L1 (where L1 = (N,N-bis(pyridin-4-ylmethyl)naphthalene-2,6-dicarboxamide). Diffraction study shows that these compounds are isostructural 1D coordination polymers which is also confirmed using XPac 2.0 software. In addition, information on the chemical state of metal ions, and chemical environments around different elements viz. C, N, O and Cl was obtained by the XPS analysis of these compounds. EDS analysis was done on these compounds, which further supports the findings of XPS and single crystal diffraction studies by showing the presence of respective elements of the ligand, perchlorate ion, and metal ions in the bulk samples. DFT studies on L1 and compounds 1-3 were performed considering the effect of solvent molecules on the HOMO-LUMO energy gap, which shows the order of 4.609 eV (2) < 4.737 eV (3) < 4.742 eV (1) < 4.752 eV (L1). Furthermore, the total energy (ETotal) of the metal ligand coordination bond in the compounds 1-3 is calculated, which is further decomposed into various contributing energies. A more negative value of ETotal in 1 reflects the effect of Jahn-Teller distortions and is in good agreement with the crystallographic metal ligand bond distance. Besides, various analytical techniques viz. NMR, IR, etc. were used to characterize the ligand and compounds as well. The phase purity of these compounds was determined using PXRD.
The aim of the present work is to evaluate the influence of graphene oxide (GO) on copolymer nanocomposites hydrogel structure based on acrylamide (AM) and 2-acryloamido-2-methylpropane sulfonic acid (AMPS) in the presence of the N, N-methylene-bis-acryl-amide (NMBA) by the free radical copolymerization technique. The influence of poly (AM-co-AMPS)/GO as a rheology modifier along with fluid loss controller on the rheological and mechanical properties of brine cement slurry was also investigated. The characterization results confirmed the synthesis of AM monomer and AMPS and showed their grafting with GO surface. The poly (AM-co-AMPS)/GO hydrogel improved the rheological properties of the cement slurry as compared to conventional cement slurry. Furthermore, free water and fluid loss of cement slurry declined by adding the copolymer nanocomposites hydrogel at elevated temperatures. Moreover, not only the thickening time of cement slurry dropped but also, the compressive strength increased with a rise of nanocomposites hydrogel concentrations. However, the nanocomposite hydrogels showed a great effect on early compressive strength than the final compressive strength. The results of this investigation revealed the excellent performance of crosslinked structure of copolymer nanocomposites hydrogel due to the linking of sulfonated AMPS and AM on the surface of GO nanosheet in the attendance of NMBA. This renders greater stability to the cement slurry against salinity and temperature changing of well formations during cementing operation. Thus, poly (AM-co-AMPS)/GO as a suitable rheology modifier and property enhancer can be applied in oil well cementing.
The purpose of this study is to investigate the synthesis of graft copolymer nanocomposite based on hydroxypropyl guar (HPG) graft acrylamide (AM) and 2-acryloamido-2-methyl propane sulfonic acid (AMPS), reinforced with graphene oxide (GO), and study its suitability for the development of the copolymer-based hydrogel systems by chromium triacetate crosslinker to use in oil recovery applications. The characterization outcomes acknowledged the grafting of AM and AMPS onto HPG in the attendance of the GO. The uniform dispersion of GO at 0.1 wt.% was observed in the morphology analysis. Moreover, not only the viscosity but also, the storage and loss modulus of graft copolymer nanocomposites hydrogel improved by adding GO. The effect of graft copolymer nanocomposite and crosslinker concentrations on the performance of hydrogel was also evaluated and optimized by a rheological test. These results showed the outstanding performance of crosslinked hydrogel structure of HPG-g-poly (AM-co-AMPS)/GO, owing to the linking of AM with AMPS and grafting on the HPG chains and the surface of GO in attendance of chromium triacetate. This makes the copolymer hydrogel system more stable against salinity, shearing, and high temperatures. Therefore, this nanocomposite hydrogel system is potentially useful for oil recovery applications.
In the context of porous coordination materials toward CO2 capture and separation, two new metal–organic frameworks termed IRH-6 and IRH-7 were synthesized with square and rhombic microchannel pores, respectively. These materials exhibit high CO2 uptakes of 2.67 mol kg−1 (IRH-6) and 2.78 mol kg−1 (IRH-7) at 100 kPa and 298 K. Grand canonical Monte Carlo simulation demonstrated strong non-covalent interactions between quadripolar CO2 molecules and these nitrogen-rich frameworks. CO2/CH4 (50 : 50), CO2/N2 (15 : 85), and CO2/H2 (15 : 85) gas mixtures were investigated by ideal adsorbed solution theory and showed excellent CO2 selectivity under ambient conditions for both porous materials. In particular, a remarkable increase in the CO2 selectivity to 102 for IRH-7 over 31 for IRH-6 was observed for the CO2/CH4 binary mixture, which highlights the effect of pore aperture modification on preferential CO2 uptake over other conventional gases.
Herein, we report a facile method for the synthesis of eight structurally diverse compounds 1-8 bearing hydrogen bonding functional group - diaminotriazine (DAT) along with pyridine and polyether groups for 1-4 and DAT linked via C-C bond to a 2-pyridone for 5-8. These compounds are positional isomers and vary from each other in the position of DAT group with respect to the pyridine-nitrogen atoms. The successful synthesis of 1-8 was confirmed by infrared, mass spectrometry, and 1H and 13C nuclear magnetic resonance. Molecular structures and aggregations in the solid state of 1-5, and 7 were elucidated by single crystal X-ray diffraction (SCXRD) and showed predictable hydrogen bonding motifs for the DAT group. Among the four compounds with polyether chains, only 4 show an interdigitated pattern. The 2-pyridone group (in 5 and 7) shows none of the expected typical hydrogen bonding patterns. Rather, a heteroleptic hydrogen bonding motif involving the free hydrogen atom of the DAT group and the oxygen atom from the pyridones is observed. Overall, these hydrogen-bonded networks are mainly composed of layers (1 & 5), tapes (2), ribbons (3 & 7), and chains (4).
In this work, sensitive detection of various metal ions and anions using cobalt metal-organic frameworks has been studied. Furthermore, various sensor-analyte interactions that prompt changes in the fluorescence emission have been investigated and discussed in the realm of ?crystal engineering?. In this pursuit, three novel mixed ligand coordination compounds with the molecular formula {[Co3(L1)(mu-BDC)(BDC)2(L1)?(DMF)2]?DMF}n (1), {[Zn8(mu2-BTB)3(BTB)(O)2(L1)(DMF)2]?4DMF}n (2) and {[Ni(L1)(BDC)(EtOH/DMF)2]?EtOH}n (3) have been synthesized using a new naphthalene dicarboxamide ligand L1 (N2,N6-bis(pyridin-3-ylmethyl)naphthalene-2,6-dicarboxamide) and two carboxylic acid-based ligands, viz.H2BDC (1,4-benzene dicarboxylic acid) and H3BTB (1,3,5-tris(4-carboxyphenyl) benzene). Among these, 1 and 2 have solvent-accessible voids in the crystal structure but a single and stable fluorescence signal is observed only in the case of 1 and therefore it has been utilized for sensing studies. Various metal cations have been used in fluorescence titrations to test the sensing ability of 1, which is also referred to as Co-MOF in the following discussion. It was found that 1 is highly responsive to Fe+3, Ru+3, Pd+2, and Hg+2 ions and moderately responsive to Pb+2, Cd+2, Ni+2, Co+2, and Fe+2 ions. Interestingly, 1 gave no response upon the addition of Zn+2, Mn+2, Be+2 and all alkaline earth metal ions. Fluorescence experiments were also performed using different salts of Fe(iii) and Cu(ii) ions with different counterions. Distinct trends in the decrease in fluorescence intensity of 1 on varying the counter anions prompted us to perform anion sensing experiments. Addition of BF4?, I?, NO3?, and (SO4)?2 ions have caused a slight decrease in the fluorescence intensity of 1, while no response was observed towards ClO4?, Br?, and SCN? ions. The potential mechanism of sensitive detection was proposed with the aid of DFT calculations performed on a model Co(ii) complex, which illustrates that the excited state has a dominant contribution from naphthalene and carbonyl moieties and that the electron transfer can occur only if the analyte ions interact with either of the moieties or both. SCXRD reveals that compound 3 is a 3D coordination polymer with no solvent-accessible voids. Various characterization techniques, viz. NMR, SCXRD, PXRD, IR, TGA, and photoluminescence, were used to determine the structure and properties of L1 and 1-3.
With the depletion of fossil fuels and an increase in global warming, developing clean and sustainable energy resources is imperative. Among the different possible eco-friendly energy resources, H2 has a bright perspective since it is a clean, environmentally benign, and sustainable energy carrier. Sunlight-triggered H2 evolution reaction (HER) is a compelling solution to harvest the abundant and inexhaustible power of solar energy in chemical bonds in H2 molecules. At present, the primary concern relies upon the design of novel and efficient photocatalysts for the profitable production of H2. The article briefly reviews the recent development of molecular complexes and organic frameworks (e.g., MOFs, COFs, HOFs) as prominent H2 production photocatalysts, including their essential characteristics, mechanism of photocatalytic HER over these materials, and photocatalytic systems recently developed. More importantly, studies on the design of diaminotriazine-based molecular complexes ? an advanced photocatalyst class for light-driven H2 production are reviewed and discussed in detail. This article encloses the following discussion about diaminotriazine-based ligands, and their complexes: (i) advances in structures and properties, (ii) preparation strategies, and (iii) diaminotriazine based molecular catalysts developed for HER. Our recent works on this photocatalyst class are also highlighted, in which diaminotriazine-based catalysts developed by our group are compared with previous molecular catalysts in terms of structure and catalytic activity. The review is expected to provide a crucial basis and significant ideas contributing to the development of efficient molecular catalysts for H2 production.
New compounds, Na2Co6Mn2(PO4)6 and Na2Co6Ni2(PO4)6 have been synthesized by solid-state method. Rietveld refinement analysis of the powder X-ray diffraction patterns confirmed that both are isostructural, crystallizing in a pure phase with monoclinic P21/n space group and showed no evidence of secondary phase peaks. Microstructural analysis revealed that the particles, which size range between 1 and 10 mum, have a homogeneous composition. The XPS results showed that all transition metals are in their +2-oxidation state and the oxidation states of Na, P and O are +1, +5 and ?2, respectively. The band gap energies (Eg) for Na2Co6Mn2(PO4)6 and Na2Co6Ni2(PO4)6 based on the UV?vis diffuse reflectance spectra were found to be 1.78 eV and 1.86 eV, respectively. The total ionic conductivity of the two compounds is in the range of 2.29 ? 10?5 ? 1.21 ? 10?3 S/cm and 2.29 ? 10?5 ? 6.58 ? 10?4 S/cm from 674 to 874 K, respectively.
A new polycrystalline material Na3Co7(PO4)6 has been synthesized by solid-state (ST) and sol-gel (SG) methods and characterized using powder X-ray diffraction (XRD) to solve the structure, which is found to crystallize in the monoclinic system with a P21/c space group. Scanning electron micrographs showed the particles as aggregates with grain sizes ranging from 8 to 35 ?mum and 1 to 20 ?mum, for Na3Co7(PO4)6-ST and Na3Co7(PO4)6-SG, respectively. Energy-dispersive X-ray Spectroscopy (EDS) confirms the presence of Na, Co, P, O elements and their homogenous distribution in the samples. The X-ray photoelectron spectroscopy (XPS) results indicate that the oxidation states for these elements are Na(I), Co(II/III), P(V) and O(-II). The optical bandgaps of Na3Co7(PO4)6-ST and Na3Co7(PO4)6-SG were estimated to be 1.79 ?eV and 1.78 ?eV, respectively, based on the UV?Vis diffuse reflectance spectra. The ionic conductivity for both samples is found to be 3.7 ?? ?10-4 ?S/cm at 300 oC and 6.53 ?? ?10-2 ?S/cm at 450 oC.
SrFe12O19 (SHF) has been synthesized by tartrate-precursor sol?gel method and then has been coated with polyvinyl alcohol (PVA). The structural, magnetic and electrical properties of the prepared PVA-coated SHF films have been compared with SHF powder using powder X-ray diffractometer (PXRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and impedance analyzer. A retainment of hexaferrite structure is observed after PVA coating as evident from PXRD. A decrease in particle size, lattice constants a and c and cell volume is observed upon PVA coating indicating a compression of the SHF crystal lattice. SEM images show hexagonal SHF particles embedded in PVA sheets. An enhancement of dielectric constant is observed in PVA-coated SHF films compared to SHF powder in 20 ?120?MHz frequency range. The saturation and remanent magnetisation (MS and Mr, respectively) decrease in PVA-coated SHF; however coercivity (HC) remains constant. In addition, SHF powder synthesized herein, by slightly modifying the previously used reaction conditions in tartrate-precursor sol?gel method, shows a quite high value of MS (93.16?emu/g) which is among the highest values reported so far for undoped SHF powder prepared by sol?gel method. Besides, the value of HC is also relatively high. This study also highlights the fact that a slightest change in the reaction conditions determines the final properties of SHF powder. Graphical abstract: [Figure not available: see fulltext.]
Methane is an abundant resource and the main constituent of natural gas. It can be converted into higher value-added products and as a subproduct of electricity co-generation. The application of polymer electrolyte reactors for the partial oxidation of methane to methanol to co-generate power and chemical products is a topic of great interest for gas and petroleum industries, especially with the use of materials with a lower amount of metals, such as palladium complex. In this study, we investigate the ideal relationship between cis-[6-(pyridin-2-yl)-1,3,5-triazine-2,4-diamine(dichloride)palladium(II)] (Pd-complex) nanostructure and carbon to obtain a stable, conductive, and functional reagent diffusion electrode. The physical and structural properties of the material were analyzed by Fourier transform infrared (FT-IR) and Raman spectroscopies, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) techniques. The electrocatalytic activity studies revealed that the most active proportion was 20% of Pd-complex supported on carbon (m/m), which was measured with lower values of open-circuit and power density but with higher efficiency in methanol production with reaction rates of r = 4.2 mol L-1?h-1at 0.05 V.
Among their potential applications, metal-organic frameworks (MOFs) emerge as promising alternative electrode materials to overcome the disadvantages of low energy density supercapacitors. Although the potential of MOFs lies in their adjustable pore structure and high surface areas, they possess poor conductivity. In this context, composites with conductive matrices, including organic conductive polymers, have proved to enhance the electrochemical properties of MOFs and their structural stability in the long-term cycling process compared to the pristine MOF. In this study, we have chosen defective zirconium MOF-808 (d-MOF-808) as a porous material because of its resistance to strong acidic media in a postsynthetic modification process. As a conductive agent, polyaniline (PANI) was selected due to its high stability and facile synthesis. The obtained composites of d-MOF-808@PANI at d-MOF/PANI ratios of 15:1, 30:1, and 60:1 increase the charge transport properties compared to the pristine d-MOF-808 and PANI. Electrochemical evaluation of the new hybrid electrode materials was made to demonstrate the capacitance retention. Among the series of materials prepared, the 60:1 composite shows the highest capacitance (188 F/g at 30 mV s-1) in 1 M KOH and a notable capacitance retention of 99.8% for up to 10,000 cycles with 99.7% coulombic efficiency.
Various series of lanthanide metal-organic networks denoted Ln-Cy (Ln = La, Ce, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), were synthesized under solvothermal conditions using potassium cyamelurate (K3Cy) and lanthanide nitrate salts. All obtained materials were fully characterized, and their crystal structures were solved by single-crystal X-ray diffraction. Four types of coordination modes were elucidated for the Ln-Cy series with different Ln3+ coordination geometries. Structural studies were performed to compare the various coordination compounds of the Ln-Cy series. Moreover, the cyamelurate linkers of rich pi-conjugated and uncoordinated Lewis basic sites were used as an absorbing chromophore to enhance the luminescence quantum efficiency, the band emission and the luminescence lifetime of the coordinated Ln metal centers. Solid-state UV-visible measurements combined with density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations were performed to further explore luminescent features of the Ln-Cy series and their origins.
In this study, the CaCu3Ti4-xZrxO12 (with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) compounds were effectively synthesized through SSR method, and their crystalline structures, microstructures, optical, dielectric and electrical properties were analyzed and discussed in detail. A significant reduction in grain size is observed by Zr4+ doping for CCTZO ceramics. All CCTZO samples have an energy gap of ?2.08 eV. A relatively high dielectric permittivity (epsilon'>103) is exhibited by all studied ceramics and impedance spectroscopy shows that they are heterogeneous electrically. The presence of Ti3+ and Cu+ ions as well as the oxygen vacancy in all samples was confirmed by XPS, resulting in structural changes that greatly affect the materials dielectric behaviour. Interestingly, CCTZO with x > 0.5 ceramics showed a dielectric resonance behaviour and were more frequency-stable than pure CCTO. More importantly, the sample x = 0.7 exhibited a higher epsilon? at high frequencies which may be due to the enhancement of grains conductivity. The lowest value of dielectric loss while maintaining a relatively high epsilon? was possible with the Zr doping content x = 0.1, the reason was discussed. Furthermore, the Zr doping not only enhanced the frequency-stability but also the temperature-stability of pure CCTO ceramic.
Four new coordination polymers of mixed ligands have been synthesized under solvothermal conditions and fully characterized viz. [(Zn(cyclam)(H2BPTC)]n 1, [Ni2(cyclam)2(BPTC)]n 2, [Ni(cyclam)(H2TPTC)]n 3 and [(Zn(cyclam))1.5(TPTC)0.5(H2TPTC)0.5]n?(H2O) 4 (biphenyl-3,3?,5,5?-tetracarboxylic acid (H4BPTC), [1,1?,4?,1?]terphenyl-3,3?,5,5?-tetracarboxylic acid (H4TPTC) and cyclam= 1,4,8,11-tetraazacyclotetradecane). The products were structurally characterized by FT-IR spectroscopy and single-crystal X-ray diffraction (SCXRD), and the homogeneity of the bulk samples was confirmed by powder XRD (PXRD). All samples showed high thermal stability reaching 400 ?C. SCXRD reveals that 1 and 3 are build from one-dimensional (1D) chains, where the metal ions are coordinated to symmetrical carboxylate groups of bidentate H2BPTC2- and H2TPTC2? anions respectively, and the remaining free -COOH groups link adjacent chains by hydrogen bonds to form layered structures. Whereas structures of 2 and 4 display a 2D grid entirely made by coordination of ligands with metal ions. In the structures, hydrogen bonds also greatly participate to consolidate the 2D frameworks. 3D Hirshfeld surface analysis associated with 2D fingerprint plots were used to examine the contributions of the different intermolecular contacts for all compounds.
Carbon dioxide (CO2) is an important trace gas in Earth's atmosphere. Its high concentration in the environment causes serious problems. Thus, it has become imperative to develop efficient ways to reduce CO2. One of the best strategies to transform this greenhouse gas is the use of solar energy for the photochemical reduction of CO2. However, this process is challenging due to a number of drawbacks that should be overcome for it to become a promising alternative for generation of sustainable fuels and chemicals. In this work, we have engineered molecular photocatalysts based on 2,6-(Pyridin-2-yl)-1,3,5-triazine-2,4-diamine 1 which mimic [2,2?6?,2??]terpyridine (tpy) and its related complexes by coordination with transition metal ions. Because of the functional groups (-NH2group) and the electronic structural modification of 1 as compared with tpy, remarkable photocatalytic properties over the CO2reduction to CO were found for the free and metal ligands with turnover numbers (TONs) between 80-102 with BIH and 480-1370 with BID. An integrated method using structural characterization by X-ray diffraction analysis, experimental and density functional theory calculations was used to track the mechanistic pathways of the photocatalytic CO2reduction reaction.
The performance of the electrospray technique was applied to obtain a gas diffusion layer (GDL) for a proton exchange membrane fuel cell. It was confirmed by confocal microscopy that polytetrafluorethylene (PTFE) was impregnated into the backbone, forming a dispersed layer of microscopic size homogeneously distributed over the substrate. The PTFE layer was characterized by infrared spectroscopy and thermogravimetric analysis. In this work, we demonstrated that the use of the GDL prepared by electrospray increases the maximum power of the H2/O2 fuel cell by about 10% and decreases the diffusion loss of the electrode owing to a better distribution characteristic hydrophobic coating with low impedance to gas diffusion. Thus, our method is promising for the development of fuel cells by the production of diffusion layers.
Dipyridonyl-substituted derivatives 2?4 of benzene, pyridine, and pyrazine, respectively, were synthesized to examine the ability of 2-pyridone and its protonated species to direct the self-assembly by hydrogen bonding. Structural analysis by single-crystal X-ray diffraction (SCXRD) of 2 and 4 in trifluoroacetic acid demonstrated that salts are formed as a result of the transfer of protons from the acid to the base (organic species) to generate a bis(hydroxypyridinium) dication. However, if no proton transfer takes place like in the case of crystals of 3 grown from DMSO/H2O, the self-assembly is mainly directed by the typical R22(8) hydrogen bond motif of 2-pyridone. These results indicate that the process of converting a neutral 2-pyridonyl group into a hydroxypyridinium cation makes structure prediction difficult. Consequently, examination of proton transfer and assembly of dipyridone and its protonated species are of interest. In combination with SCXRD, Hirshfeld surface analysis (HSA) was also used to have a better understanding on the nature of intermolecular interactions within crystal structures of 2?4. The large number of F???H/H???F, H???O/O???H, H???H, and H???C/C???H contacts revealed by HSA indicates that hydrogen bonding and van der Waals interactions mainly contribute to crystal packing.
Layered structures of flexible mixed-linker metal-organic frameworks termed IRHs-(4and5) (IRH = Institut de Recherche sur l'Hydrog?ne) were synthesized by mixing cyclam, tetrakis(4-carboxyphenyl)benzene (TCPB), and copper and zinc metal salts respectively. The new materials characterized by single-crystal X-ray diffraction exhibited the features of HOFs and MOFs. Their structures are formed by coordination and hydrogen bonds that link metallocyclam (with Cu or Zn) and TCPB to a 2D sheet which is further packed to form a 3D structure with 1D microchannels. Remarkably, the as-synthesized IRHs-(4and5) contain DMF in the channels that can be exchanged with DCM and afterward removed from the framework by heating without losing their single-crystallinity. This enabled an easy elucidation of the structural transformations by single-crystal and powder X-ray diffraction analyses. Experimental studies of single-component adsorption isotherms of pure CO2, CH4, and N2gases have been carried out for all activated IRHs. Based on the obtained adsorption isotherms, theoretical calculations using Ideal Adsorbed Solution Theory (IAST) have been performed to predict the selectivity of equimolar CO2/CH4and CO2/N2(1?:?1) binary mixtures. The simulations predicted outstanding selectivity for CO2/N2than for CO2/CH4at low pressures, reaching 185 for IRH-4and 130 for IRH-5at 1 bar.
The present world has a dire need to increase its energy input in order to meet with the demands of growing population. Combining the most abundant renewable energy source such as sunlight with a clean fuel having the capacity to store and carry renewable energy viz. hydrogen is a promising alternative to control the detrimental effects of fossil fuels on our environment. A sunlight-triggered hydrogen evolution reaction (HER) would be an interesting approach for the production of pure hydrogen. Working towards this direction, we have synthesized complexes 8?10 by the reaction of 6-(pyrazin-2-yl)-1,3,5-triazine-2,4-diamine (PzDAT), with Co(II), Ni(II) and Cu(II) respectively. As indicated by single-crystal X-ray diffraction, the molecular organization of all the complexes is mainly dictated by the coordination modes of the ligands and the hydrogen bonds involving the DAT groups with reliable patterns. In conjunction with the synthesis and characterization, we investigated and compared the catalytic activities for HER of 8?10 with 5?7 (complexes of pyridine DAT (PyDAT) with Co(II), Ni(II) and Cu(II)) that we have reported previously. In the presence of triethanolamine (TEOA) as the sacrificial electron donor, Ru(bpy)3(PF6)2 as the photosensitizer (PS) and aqueous HBF4 as the proton source under blue light, the highest turnover number amongst 5?10 is observed for PyDAT copper complex 7 with TON of 72 mol of hydrogen per mole of PS. This value is higher compared to some Cu complexes reported in literature.
Combining the two most fascinating fields of chemistry in the development of novel metal-organic architectures viz. macrocyclic chemistry and metallotectons, herein, we report the one-pot synthesis of a binuclear Fe(II) macrocyclic metallotecton 2 via coordination-driven assembly in excellent yield and purity. The single crystal structure of 2 indicates two units of cationic iron complex with ligand 1 (6- pyridin-2-yl- [1,3,5]-triazine-2,4-diamine) acting as metallotectons connected to each other by two [mu-PHO3CH3]- bridges forming a [FeFe] macrocycle embedded in two metallotectons. The pyridine and DAT rings of both ligands 1 are nearly coplanar in 2 and each iron(II) has a distorted octahedral geometry. Diaminotriazine groups incorporated in 2 direct multiple hydrogen bonding according to predictable motifs II to produce a final three-dimensional structure. Thermal stability, electronic properties and redox properties of 2 have been studied by thermogravimetric analysis, UV?Vis and cyclic voltammetry respectively. The hydrogen evolution reaction (HER) study of 2 reveals it as an efficient photocatalyst displaying a high turnover number (TON) and turnover frequency (TOF), which is much higher than other Fe based molecular catalysts reported in literature. Also, its photocatalytic activity outperforms the most reported standard reference cobaloxime catalyst (CoIII(dmgH)2(py)Cl). This is by far, the only report showcasing a macrocyclic metallotecton for photocatalytic HER. In addition, complex 2 can be regarded as the next level in supramolecular chemistry as it bridges the gap between macrocycles and metallotectons as well as it can be a future option for our deteriorating environment.
A new synthetic route was carried out via a one-pot reaction to prepare a novel series of amidine/amidinate cobalt complexes 8-10 by mixing ligand 2 (6-pyridin-2-yl-[1,3,5]-triazine-2,4-diamine) with Co(II) in acetonitrile or benzonitrile. We observed that a change of solvent from methanol (used in complex 7, previously reported) to nitrile solvents (MeCN and PhCN) led to the in situ incorporation of the amidine group, ultimately forming 8-10. So far, this is a unique method reported to introduce amidine/amidinate groups into a pyridinyl-substituted diaminotriazine complex. Remarkably, the single crystal X-ray diffraction study (SCXRD) of these new compounds reveals associations involving Janus DATamidine and Janus DATamidinate. A mechanism is proposed to explain the formation of amidine/amidinate groups by investigating the single crystal structures of the possible intermediates 11 and 12 where the cobalt ion acts as a template. These amidine/amidinate cobalt complexes were used as a model to assess the photocatalytic activity for the hydrogen evolution reaction (HER). Complexes 9 and 10 show a 74% and 86% enhancement, respectively, of the catalytic activity towards the HER compared to complex 7. This highlights the structure-property relationship. By examining the novel cobalt complexes described here, we discovered the following: (i) a method to introduce an amidine group into a pyridine DAT-based complex, (ii) the efficiency of amidine complexes to form multiple hydrogen bonds to direct the molecular organization, (iii) the plausible mechanism of formation of amidines based on the SCXRD study, (iv) the modification of the final structure and hence the final properties by varying the reaction conditions, and (v) the utility of amidine complexes towards photocatalytic HER activity.
Understanding the interfacial crystallization is crucial for semi-crystalline polymer/natural fiber composites because it links to the final properties. This work reports, for the first time, the interfacial crystallization of a miscible blend between polycaprolactone (PCL) and polyvinylchloride (PVC) with milkweed fibers. We have first described the morphology of the fibers and the chemical composition of waxes covered on its surface. Our findings show that the transcrystallization (TC) layer of PCL/PVC could appear at the interface by simply coating with a layer of graphene oxide (GO) on the milkweed fiber. In our study, atomic force microscopy?infrared spectroscopy analysis shows that the crystallinity of the blends is higher at the vicinity of the interface compared to that in the bulk. The kinetic of the interfacial crystallization in terms of spherulite morphology and crystal growth rates at the nanoscale is examined. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy were used to analyze the prepared GO and evaluate its relationship with the interfacial crystallization behavior of the blends.
Co-crystals of Co(II) salt and 1H,1=H-[3,3=]bipyridinyl-6,6=-dione 1 with the composition 1?Co(CHOO)2(H2O)4 were obtained by mixing both reactants. The single-crystal structure reveals that the metal salt and organic ratio is 1:1. The supramolecular organization of the two components in the co-crystal was mainly dictated by hydrogen bonds between 1 and Co(II) complex. Infrared and powder X-ray diffraction were used to confirm the homogeneity and the phase purity of the bulk crystalline sample of 1?Co(CHOO)2(H2O)4. TGA/DTA was recorded to evaluate the thermal stability of the co-crystals.
Three new lanthanide metal–organic frameworks IRHs-(1–3) supported by cyamelurate linkers have been synthesized and structurally characterized. The incorporation of numerous heteroatoms (N and O) into the pore walls and the relatively small microchannels of these porous solids enhance bonding force of the host–guest interactions, thus promoting the adsorption of carbon dioxide (CO2) over methane (CH4). The nonpolar covalent bonds in methane also favor the less uptake due to the hydrophilic walls of these frameworks. Grand canonical Monte Carlo simulations were performed to determine the origin of the adsorption. The density isocontour surfaces show that CO2 is mainly adsorbed on the walls composed of organic linkers and around the metal sites, whereas no specific adsorption site is observed for CH4, which indicates weak interactions between the framework and the adsorbed gas. As expected, the simulations show that CH4 is not observed around the metal center due to the presence of H2O molecules. The excellent selectivity of CO2/CH4 binary mixture was predicted by the ideal adsorbed solution theory (IAST) via correlating pure component adsorption isotherms with the Toth model. At 25 °C and 1 bar, the CO2 and CH4 uptakes for IRH-3 were 2.7 and 0.07 mol/kg, respectively, and the IAST predicated selectivity for CO2/CH4 (1:1) reached 27, which is among the best value for MOF materials.
The fabrication of efficient and platinum-free counter electrodes (CE) is a highlighted topic for the development of advanced dye-sensitized solar cells (DSSCs). Here, we developed water-dispersible polyaniline/graphene oxide (PANI-GO)-based CEs, which can be straightforwardly prepared by deposition of the nanocomposite dispersion onto FTO substrate. The water-dispersibility properties of PANI-GO allow the formation of smooth films without organic solvents making it a promising material for high-scalable, reduced cost and ?greener? fabrication of energy conversion-storage devices. Aqueous dispersions of PANI-GO nanocomposites were prepared by two different routes: physical mixture of PANI and GO, and in situ polymerization of aniline in GO aqueous dispersion. DSSC assembled with emeraldine salt polyaniline (PANI-ES)-based CE generated current density (Jsc) of 12.37 mA/cm2 and power conversion efficiency (PCE) of 5.09percent, which was comparable to the device prepared with Pt-based CE (PCE of 5.15percent). The addition of GO is found to increase the Jsc to 12.91 mA/cm2 and the fill factor to 67percent in CE containing 0.45 wtpercent of GO (in respect to aniline during synthesis) where the PCE is boosted to 6.12percent, which is about 20percent higher than Pt-based CE. The investigation of both morphological features and spectroscopic properties showed that PANI-GO nanocomposites prepared by in situ route have dissimilar protonation and oxidation states when compared with those prepared by physical mixture route. These results give insights into the role of GO in tuning PANI chemical and physical properties. Also offers a simpler and more efficient methodology for the synthesis of new CEs for DSSCs.
The application of solid electrolyte reactors for methane oxidation to co-generation of power and chemicals could be interesting, mainly with the use of materials that could come from renewable sources and abundant metals, such as the [6,6?- (2, 2?-bipyridine-6, 6?-diyl)bis (1,3,5-triazine-2, 4-diamine)](nitrate-O)copper (II) complex. In this study, we investigated the optimal ratio between this complex and carbon to obtain a stable, conductive, and functional reagent diffusion electrode. The most active Cu-complex compositions were 2.5 and 5% carbon, which were measured with higher values of open circuit and electric current, in addition to the higher methanol production with reaction rates of 1.85 mol L-1 h-1 close to the short circuit potential and 1.65 mol L-1 h-1 close to the open circuit potential, respectively. This activity was attributed to the ability of these compositions to activate water due to better distribution of the Cu complex in the carbon matrix as observed in the rotating ring disk electrode experiments.
By examining the crystal structures of the self-assemblies of 1H,1?H-[3,3?]bipyridinyl-6,6?-dione 1 and its coordination structure with Co(ii), to form novel CP-671, our study demonstrates the tendency of dipyridones to generate predictable patterns by hydrogen bonding depending on the crystallization conditions and the potential of pyridone ligating groups to design novel coordination polymers with structural diversity. The two structures of 1 elucidated by single-crystal X-ray diffraction show a cyclic dimer and zigzag chain to generate fascinating hydrogen bond frameworks. A two-dimensional coordination polymer structure (CP-671) is obtained by the linkage of 1 with a cobalt cation according to a known coordination mode of the 2-pyridone ligating group.
Sixfold phenyl embraces are well-established aromatic interactions that are strong and directional. In addition, functional groups that are able to participate, such as triphenylmethyl (trityl), are easily incorporated in molecular structures. As a result, embraces offer a possible way to control molecular organization in materials. To test this notion, we used a hybrid organic-inorganic strategy to make compounds with multiple trityl groups. Trityl-substituted alkynylpyridines 3-5 react with Pd(II) to form square-planar 4:1 complexes with multiple divergent trityl groups poised to engage in embraces. The complexes were crystallized, and their structures were determined by X-ray diffraction. Surprisingly, few structures in this set of compounds were found to incorporate sixfold embraces. Our observations suggest that predictable molecular organization cannot normally be achieved using these embraces, which must compete with alternative aromatic interactions of similar energy.
The synthetic difficulties associated with quaterpyridine (qtpy) complexes have limited their use in the formation of various metallosupramolecular architectures in spite of their diverse structural and physicochemical properties. Providing a new facile synthetic route to the synthesis of functionalised qtpy mimics, we herein report the synthesis of three novel -NH2 functionalized qtpy-like complexes 12-14 with the general formula M(C16H14N12)(NO3)2 (M = Co(ii), Ni(ii) and Cu(ii)) in high yield and purity. Characterization of these complexes has been done by single crystal X-ray diffraction (SCXRD), thermogravimetric analysis, UV-Vis, infrared, mass spectrometry and cyclic voltammetry. As indicated by SCXRD, in all the synthesized complexes, the metal ions show a strongly distorted octahedral coordination geometry and typical hydrogen bonding networks involving DAT groups. In addition, complexes 12-14 have been analyzed as potential photocatalysts for hydrogen evolution reaction (HER) displaying good turnover numbers (TONs). Hydrogen produced from these photocatalysts can serve as the possible alternative for fossil fuels. To the best of our knowledge, this is the only study showcasing -NH2 functionalized qtpy-like complexes of Co(ii), Ni(ii) and Cu(ii) and employing them as photocatalysts for HER. Thus, a single proposed strategy solves two purposes-one related to synthesis while second is related to our environment.
A new series of hydrogen-bonded metallotecton networks 6-9 of the general formula [M(2)2(NO3)2] were obtained from the reaction of 6-pyridin-2-yl-[1,3,5]-triazine-2,4-diamine 2 with transition-metal ions [M: Co(II), Ni(II), Cu(II), and Zn(II)]. Their supramolecular networks and associated properties were characterized by single-crystal and powder X-ray diffraction, IR, solid-state UV-vis spectroscopy, and thermogravimetric analysis associated with differential scanning calorimetry. On the basis of standard patterns of coordination involving 2,2?-bipyridine and simple derivatives, compound 2 binds transition-metal ions with predictable constitution and the diaminotriazinyl (DAT) groups serve orthogonally to ensure the intermetallotecton interactions by hydrogen bonding according to well-established motifs I-III. As expected, compound 2 formed octahedral 2:1 metallotectons with M(NO3)2, and further self-assembled by hydrogen bonding of the DAT groups to produce pure, crystalline, homogeneous, and thermally stable materials. In these structures, nitrate counterions also play an important role in the cohesion of intermetallotectons to form two-dimensional and three-dimensional networks. These results illustrated the effectiveness of the synthetic approach to create a wide range of novel ordered materials with controllable architectures and tunable properties achieved by varying the central metal ion. Crystal morphologies of 6-9 were also investigated by scanning electron microscopy and calculation using Bravais-Friedel-Donnay-Harker method from their single-crystal structure.
Ordered coordination polymers (CPs) have been an interesting class of materials for scientific and industrial research for the last few decades. However, their availability as well as certain economic and environmental limitations could slow down their use in many applications. Herein, we present room temperature synthesis in water of a series of CPs (four metal-organic polymers MOPs-(1-4) and three mixed metal-organic polymers MMOPs-(5-7)). All MMOPs were found to be isostructural to MOPs as determined by XRD. Remarkably, MOPs-(2 and 3) and MMOPs-(5-7) exhibit switchable chromic behaviour associated with reversible structural transformation which was facilitated by dehydration/rehydration or solvent exchange (MeOH/H2O) processes. Chromic behaviour and its mechanism were investigated using IR, solid-state UV-Vis, XRD, PXRD and TGA indicating the coordination/de-coordination of water molecules to be the key factor that influences the colour changes. These results render the potential application of MOPs and MMOPs as sensor materials.
The bis(diaminotriazinyl)-substituted derivatives of benzene, pyridine, and pyrazine 1-6 were made to test the ability of the 4,6-diamino-1,3,5-triazinyl group (DAT) to direct molecular organization by hydrogen bonding. Analysis of the structures of compounds 1-6 by X-ray crystallography revealed that the DAT groups control association by forming hydrogen bonds according to the well-established motifs I-III. The resulting association normally produces complex networks consisting of tapes, rings, and sheets. 1,2-Disubstituted compounds 1-3 have structures in which the DAT groups do not lie close to the plane of the aryl or heteroaryl core, whereas 1,3-disubstituted compounds 4-6 adopt flattened conformations. The observed structures of compounds 1-6, which include novel embraces and rings held together by hydrogen bonds, highlight the special ability of motifs based on DAT groups to direct molecular association.
Various symmetric isomers of [2, 2?-bipyridine]dicarbonitrile and [1, 10-phenanthroline]dicarbonitrile were crystallized from solution and also deposited as monolayers adsorbed on graphite. The resulting three- and twodimensional (3D and 2D) structures were studied by single-crystal X-ray diffraction and scanning tunneling microscopy, respectively. Previous comparisons of 3D and 2D structures have provided new understanding of molecular organization and have revealed that crystals and adlayers can have closely analogous structures despite the effects of the underlying surface, especially when organization is dominated by strong intermolecular interactions within a single plane. The present study extends previous work by showing that analogous 3D and 2D structures can be formed even when association is directed by weaker intermolecular forces, as exemplified by C- H ? N interactions of nitriles.
Heteroleptic complexes of Ru(II) with tridentate ligand Py-DAT2 (2,6-bis(4,6-diamino-1,3,5-triazin-2-yl)pyridine) and with derivatives of tridentate ligands tpy (2,2?:6?,2?-terpyridine) or dpt (2,6-dipyridyltriazine) have been synthesized and characterized. Changing the second ligand from tpy to dpt was found to profoundly alter the electronic and photophysical properties of the complexes. Structural analysis of the Py-DAT2/tpy complex by single-crystal XRD revealed the presence of a 2D terpyridyl embrace and an extended array of hydrogen bonds involving water of crystallization and the amino groups of Py-DAT2.