Showing papers by "Susumu Kitagawa published in 2017"
TL;DR: This review article focuses on the methodology for hybridization of MOFs and polymers, as well as the intriguing functions of hybrid materials.
Abstract: Metal–organic frameworks (MOFs) have received much attention because of their attractive properties. They show great potential applications in many fields. An emerging trend in MOF research is hybridization with flexible materials, which is the subject of this review. Polymers possess a variety of unique attributes, such as softness, thermal and chemical stability, and optoelectrical properties that can be integrated with MOFs to make hybrids with sophisticated architectures. Hybridization of MOFs and polymers is producing new and versatile materials that exhibit peculiar properties hard to realize with the individual components. This review article focuses on the methodology for hybridization of MOFs and polymers, as well as the intriguing functions of hybrid materials.
611 citations
TL;DR: In this article, the authors report substantial selectivity enhancements within high-permeability polymers as a result of the efficient dispersion of amine-functionalized, nanosized metal-organic framework (MOF) additives.
Abstract: Mixed matrix membranes (MMMs) for gas separation applications have enhanced selectivity when compared with the pure polymer matrix, but are commonly reported with low intrinsic permeability, which has major cost implications for implementation of membrane technologies in large-scale carbon capture projects. High-permeability polymers rarely generate sufficient selectivity for energy-efficient CO2 capture. Here we report substantial selectivity enhancements within high-permeability polymers as a result of the efficient dispersion of amine-functionalized, nanosized metal–organic framework (MOF) additives. The enhancement effects under optimal mixing conditions occur with minimal loss in overall permeability. Nanosizing of the MOF enhances its dispersion within the polymer matrix to minimize non-selective microvoid formation around the particles. Amination of such MOFs increases their interaction with thepolymer matrix, resulting in a measured rigidification and enhanced selectivity of the overall composite. The optimal MOF MMM performance was verified in three different polymer systems, and also over pressure and temperature ranges suitable for carbon capture. Mixed matrix membranes can separate CO2 from flue gas mixtures but increasing selectivity without sacrificing permeability remains challenging. Selectivity can be increased with little loss in permeability by using nanoparticulate, amine-functionalized metal–organic framework fillers.
381 citations
TL;DR: In this paper, a review of water-resistant porous coordination polymers is presented with an emphasis on their adsorptive-and membrane-based gas separations, which is intended to be useful for researchers who are interested in designing water resistant PCPs and exploring promising applications for gas separation.
305 citations
TL;DR: A general strategy, called internal extended growth method (IEGM), is demonstrated for the feasible assembly of MOFs with distinct crystallographic parameters in an MOF matrix to form 3D core-satellite pluralistic hybrid system.
Abstract: Fabrication of hybrid MOF-on-MOF heteroarchitectures can create novel and multifunctional platforms to achieve desired properties. However, only MOFs with similar crystallographic parameters can be hybridized by the classical epitaxial growth method (EGM), which largely suppressed its applications. A general strategy, called internal extended growth method (IEGM), is demonstrated for the feasible assembly of MOFs with distinct crystallographic parameters in an MOF matrix. Various MOFs with diverse functions could be introduced in a modular MOF matrix to form 3D core-satellite pluralistic hybrid system. The number of different MOF crystals interspersed could be varied on demand. More importantly, the different MOF crystals distributed in individual domains could be used to further incorporate functional units or enhance target functions.
212 citations
TL;DR: Developing science and technology of porous materials provides fuels and useful substances from ubiquitous gaseous substances such as air.
Abstract: Developing science and technology of porous materials provides fuels and useful substances from ubiquitous gaseous substances such as air.
120 citations
TL;DR: A rational design of stabilized high-porosity meso-PCPs is proposed, employing a low-symmetry ligand in combination with the shortest linker, formic acid, enabling highly selective and effective separation of C2H2 from C2h2/CO2 mixtures at 298 K, as verified by binding energy (BE) and electrostatic potentials (ESP) calculations.
Abstract: The prevalence of the condensed phase, interpenetration, and fragility of mesoporous coordination polymers (meso-PCPs) featuring dense open metal sites (OMSs) place strict limitations on their preparation, as revealed by experimental and theoretical reticular chemistry investigations. Herein, we propose a rational design of stabilized high-porosity meso-PCPs, employing a low-symmetry ligand in combination with the shortest linker, formic acid. The resulting dimeric clusters (PCP-31 and PCP-32) exhibit high surface areas, ultrahigh porosities, and high OMS densities (3.76 and 3.29 mmol g–1, respectively), enabling highly selective and effective separation of C2H2 from C2H2/CO2 mixtures at 298 K, as verified by binding energy (BE) and electrostatic potentials (ESP) calculations.
106 citations
TL;DR: A new opportunity to use MOFs as macromolecular scaffolds towards CO-releasing materials and the advantage of MOFs for high CO payloads, which is essential in future therapeutic applications is demonstrated.
Abstract: A new carbon monoxide (CO)-releasing material has been developed by embedding a manganese carbonyl complex, MnBr(bpydc)(CO)3 (bpydc = 5,5′-dicarboxylate-2,2′-bipyridine) into a highly robust Zr(IV)-based metal–organic framework (MOF). Efficient and controllable CO-release was achieved under exposure to low intensity visible light. Size-controllable nanocrystals of the photoactive MOF were obtained and their CO-releasing properties were correlated with their crystal sizes. The photoactive crystals were processed into cellular substrates with a biocompatible polymer matrix, and the light-induced delivery of CO and its subsequent cellular uptake were monitored using a fluorescent CO-probe. The results discussed here demonstrate a new opportunity to use MOFs as macromolecular scaffolds towards CO-releasing materials and the advantage of MOFs for high CO payloads, which is essential in future therapeutic applications.
91 citations
TL;DR: A flexible metal-organic framework is exploited to achieve quantitative and reversible photoisomerization in a porous crystalline solid by introducing structural flexibility into crystalline porous frameworks with a twofold interpenetration composed of a diarylethene-based ligand.
Abstract: Photochromic molecules have shown much promise as molecular components of stimuli-responsive materials, but despite recent achievements in various photoresponsive materials, quantitative conversion in photochemical reactions in solids is hampered by the lack of intrinsic structural flexibility available to release stress and strain upon photochemical events. This issue remains one of the challenges in developing solid-state photoresponsive materials. Here, we report a strategy to realize photoresponsive crystalline materials showing quantitative reversible photochemical reactions upon ultraviolet and visible light irradiation by introducing structural flexibility into crystalline porous frameworks with a twofold interpenetration composed of a diarylethene-based ligand. The structural flexibility of the porous framework enables highly efficient photochemical electrocyclization in a single-crystal-to-single-crystal manner. CO2 sorption on the porous crystal at 195 K is reversibly modulated by light irradiation, and coincident X-ray powder diffraction/sorption measurements clearly demonstrate the flexible nature of the twofold interpenetrated frameworks. Organizing photochromic molecules into 3D networks is a key strategy to access photoresponsive materials, but framework rigidity typically limits conversion efficiency. Here, the authors exploit a flexible metal-organic framework to achieve quantitative and reversible photoisomerization in a porous crystalline solid.
87 citations
TL;DR: Utilization of CP crystal in liquid state enables to be a novel route to incorporate functional molecules and defects, and it provides a tool to control the bulk properties of the CP material.
Abstract: The melting behavior of a coordination polymer (CP) crystal was utilized to achieve enhanced and optically switchable proton conductivity in the solid state. The strong acid molecules (triflic acid) were doped in one-dimensional (1D) CP, [Zn(HPO4 )(H2 PO4 )2 ](ImH2 )2 (ImH2 =monoprotonated imidazole) in the melt state, and overall enhancement in the proton conductivity was obtained. The enhanced proton conductivity is assigned to increased number of mobile protons and defects created by acid doping. Optical control over proton conductivity in the CP is achieved by doping of the photo acid molecule pyranine into the melted CP. The pyranine reversibly generates the mobile acidic protons and local defects in the glassy state of CP resulting in the bulk switchable conductivity mediated by light irradiation. Utilization of CP crystal in liquid state enables to be a novel route to incorporate functional molecules and defects, and it provides a tool to control the bulk properties of the CP material.
77 citations
TL;DR: Two distinct ion conductance states are demonstrated by embedding a single metal-organic porous molecule with the geometry of an Archimedean cuboctahedron into an artificially reconstructed lipid bilayer membrane in which triangular and square apertures in the cuboct ahedron work independently as ion-transporting pathways.
75 citations
TL;DR: The capability of MOFs to act as platform materials for studying single-site catalysis in heterogeneous systems is highlighted and structural insights explain why the Rh metalated MOF is catalytically competent toward the carbonylation of MeBr but only affords stoichiometric turn-over in the case of MeI.
Abstract: Single-crystal X-ray crystallography is employed to characterize the reaction species of a full catalytic carbonylation cycle within a MnII-based metal–organic framework (MOF) material. The structural insights explain why the Rh metalated MOF is catalytically competent toward the carbonylation of MeBr but only affords stoichiometric turn-over in the case of MeI. This work highlights the capability of MOFs to act as platform materials for studying single-site catalysis in heterogeneous systems.
TL;DR: A soft porous crystal possessing hemilabile cross-links in its framework that exhibits exclusive gate opening for ethylene, enabling the discriminatory adsorption of ethylene over ethane is reported, demonstrating the potential of the "gate-locking/unlocking" mechanism that exploits the hemilabsili cross-linking in soft porous crystals.
Abstract: Here we report a soft porous crystal possessing hemilabile cross-links in its framework that exhibits exclusive gate opening for ethylene, enabling the discriminatory adsorption of ethylene over ethane. A Co-based porous coordination polymer (PCP) bearing vinylogous tetrathiafulvalene (VTTF) ligands, [Co(VTTF)], forms Co–S bonds as intermolecular cross-links in its framework in the evacuated closed state. The PCP recognizes ethylene via d−π complexation on the accessible metal site that displaces and cleaves the Co–S bond to “unlock” the closed structure. This ethylene-triggered unlocking event facilitates remarkable nonporous-to-porous transformations that open up accessible void space. This structural transformation follows a two-step gate-opening process. Each phase, including the intermediate structure, was successfully characterized by single-crystal X-ray diffraction analysis, which revealed an intriguing “half-open” structure suggestive of a disproportionate gate-opening phenomenon. The gate-openin...
TL;DR: By limiting the accessible configurations for the framework and forbidding the formation of a reactive intermediate, the polymeric guest prevented the thermal degradation of the host MOF even at very low loading and increased its stability domain by more than 200 °C.
Abstract: The development of highly porous metal–organic frameworks (MOFs) is greatly sought after, due to their wide range of applications. As an alternative to the development of new structures, we propose to obtain new stable configurations for flexible MOFs by insertion of polymeric guests. The guests prevent the otherwise spontaneous closing of the host frameworks and result in stable opened forms. Introduced at a fraction of the maximal capacity, polymer chains cause an opening of the occupied nanochannels, and because of the MOF reticular stiffness, this opening is propagated to the neighboring nanochannels that become accessible for adsorption. Composites were obtained by in situ polymerization of vinyl monomers in the nanochannels of an otherwise nonporous MOF, resulting in homogeneously loaded materials with a significant increase of porosity (SBET = 920 m2/g). In addition, by limiting the accessible configurations for the framework and forbidding the formation of a reactive intermediate, the polymeric gu...
TL;DR: It is reported that polyhedra, a natural crystalline protein assembly of polyhedrin monomer produced in insect cells infected by cypovirus, can be engineered to extend porous networks by deleting selected amino acid residues located on the intermolecular contact region of PhM.
Abstract: Crystalline porous materials have been investigated for development of important applications in molecular storage, separations, and catalysis. The potential of protein crystals is increasing as they become better understood. Protein crystals have been regarded as porous materials because they present highly ordered 3D arrangements of protein molecules with high porosity and wide range of pore sizes. However, it remains difficult to functionalize protein crystals in living cells. Here, we report that polyhedra, a natural crystalline protein assembly of polyhedrin monomer (PhM) produced in insect cells infected by cypovirus, can be engineered to extend porous networks by deleting selected amino acid residues located on the intermolecular contact region of PhM. The adsorption rates and quantities of fluorescent dyes stored within the mutant crystals are increased relative to those of the wild-type polyhedra crystal (WTPhC) under both in vitro and in vivo conditions. These results provide a strategy for desi...
TL;DR: X-ray and STEM-EDX studies revealed that performing mechanical milling under an Ar atmosphere promotes the high diffusivity of each metal ion in an amorphous solid matrix, which turns into the porous crystalline structure by vapor exposure treatment to form a new phase of a MOF solid solution.
Abstract: The solvent-free mechanical milling process for two distinct metal–organic framework (MOF) crystals induced the formation of a solid solution, which is not feasible by conventional solution-based syntheses. X-ray and STEM-EDX studies revealed that performing mechanical milling under an Ar atmosphere promotes the high diffusivity of each metal ion in an amorphous solid matrix; the amorphous state turns into the porous crystalline structure by vapor exposure treatment to form a new phase of a MOF solid solution.
TL;DR: In this article, the highly ordered chain alignment of unsubstituted polythiophene, an unprocessable polymer, has been achieved using a porous coordination polymer (PCP) as a template.
TL;DR: In this paper, coordination modulation is employed in the LPE fabrication of thin films composed of the Zn4O(L)3 structure type (L2− = 3,5-dialkyl-4-carboxyrazolate).
Abstract: One of the primary challenges facing the integration of metal–organic frameworks (MOFs) with real-world technologies is the development of enhanced fabrication processes that maximize compatibility with specific device configurations, while maintaining or even improving the performance profile relative to bulk MOF materials. Stepwise liquid-phase epitaxy (LPE) has emerged as an important method for depositing MOF thin films on a variety of substrate types, although current limitations include challenges in obtaining well-oriented and highly crystalline thin films, and the applicability of the technique beyond the most common MOF structure types (e.g. paddlewheel-based MOFs). Coordination modulation is a method often employed for controlling MOF crystal growth processes within bulk crystallization solutions and presents a potentially powerful route for manipulation of the properties of MOF thin films via integration into a LPE-based process. In this work, coordination modulation is employed in the LPE fabrication of thin films composed of the Zn4O(L)3 structure type (L2− = 3,5-dialkyl-4-carboxypyrazolate). The films are grown on Au-coated quartz crystal microbalance (QCM) substrates, allowing both film deposition and molecular adsorption to be precisely probed. Addition of a modulator during the LPE process leads to enhanced orientation and crystallinity that offers a boost to the adsorption capacities of polar adsorbates when using a small molar ratio of the modulator. Closer inspection of the QCM data reflects a change in growth kinetics, which influences the quantity of MOF deposited per growth cycle and the overall growth rate. In all, this integrated fabrication process could provide a potentially versatile route for the fabrication of a wide range of MOF thin films with enhanced characteristics.
TL;DR: In this paper, the position and length of the shortest two alkyl groups in the channels were optimized to achieve improved surface area, gas uptake, gas selectivity, thermal stability and chemical stability of nano-porous coordination polymers.
Abstract: Nano-porous coordination polymers (nano-PCPs), as a new class of crystalline material, have become a lucrative topic in coordination chemistry due to the facile tunability of their functional pore environments. However, elucidating the pathways for the rational design and preparation of nano-PCPs with various integrated properties for feasible gas separation remains a great challenge. Here, we demonstrate a new route to achieve nano-PCPs with an integrated pore system and physical properties using a reticular chemistry strategy. By optimizing the position and length of the shortest two alkyl groups in the channels, unprecedented phenomena of improved surface area, gas uptake, gas selectivity, thermal stability and chemical stability were observed in the PCPs, especially in NTU-14, the structure with a pendant ethyl group. Furthermore, the high performance of adsorption- and membrane-based separation makes NTU-14 a promising medium for CH4 purification from a mixture at room temperature.
TL;DR: A new porous coordination polymer based on a ligand with a unique bent angle bearing a thiophene-bridged bent carboxylate ligand and the Cu2+ ion was synthesized and structurally characterized.
Abstract: A new porous coordination polymer (PCP) based on a ligand with a unique bent angle bearing a thiophene-bridged bent carboxylate ligand and the Cu2+ ion was synthesized and structurally characterized. The structure has a pillared-layer framework based on a kagome-like layer with aromatic partition groups. It exhibits a high CO2 uptake of 180 mL(STP)/g at 1 bar, and 400 mL(STP)/g at 30 bar at 273 K. The uptakes of C2H2 and C2H4 reach 164 and 160 mL(STP)/g at 298 K and 1 bar, with good selectivity of C2H2 and C2H4 over CH4, both of which are among the highest levels of reported PCPs.
TL;DR: The structure contains rare Mn2+-4N tetrahedral geometry and has larger cell parameters, resulting in 20% larger amounts of gas uptake compared with [Zn(2-methylimidazolate)2]; a kinetically favored reaction using a reactive metal borohydride precursor is key for the construction of new metal-organic framework systems.
Abstract: Cubic and highly porous [Mn(2-methylimidazolate)2] (Mn-ZIF-8) was synthesized from [Mn(BH4)2·3THF]·NaBH4 under an Ar atmosphere. The structure contains rare Mn2+-4N tetrahedral geometry and has larger cell parameters, resulting in 20% larger amounts of gas uptake compared with [Zn(2-methylimidazolate)2]. A kinetically favored reaction using a reactive metal borohydride precursor is key for the construction of new metal–organic framework systems.
TL;DR: In this article, a novel type of network polymer is synthesized via conversion of a highly ordered metal-organic framework (MOF) template into a polymer gel, performed using light-induced and metal-free thiol-ene click chemistry.
Abstract: The ability to control the structure and topology of polymer networks, both on macroscopic and molecular levels, is crucial for optimizing their performance. Here we describe a novel type of network polymer, which is synthesized via conversion of a highly ordered metal–organic framework (MOF) template into a polymer gel. The synthesis is performed using light-induced and metal-free thiol–ene click chemistry. The use of light-triggered reactions in combination with photomasks or other photopatterning techniques allows the reaction to be locally confined and thereby structuring the network polymer on a macroscopic level. The potential to vary and exactly adjust the parameters within the polymer network (including exact network topology on the nanometer scale as well as the macroscopic morphology) combined with the ability to further functionalize their surfaces or incorporate guest molecules allows their targeted design for potential applications in catalysis and optoelectronics as well as their use as a no...
TL;DR: Diffraction and simulation studies reveal the presence of significant porosity in both the glass and liquid phases of a metal–organic framework.
Abstract: Diffraction and simulation studies reveal the presence of significant porosity in both the glass and liquid phases of a metal–organic framework.
TL;DR: An efficient synthetic methodology for the preparation of polysaccharides with controllable mesoporosity in the structure is disclosed, utilizing [Cu3(benzene-1,3,5-tricarboxylate)]n (HKUST-1; 1) as templates.
Abstract: Polymerization of monosaccharide monomers usually suffers from the production of polysaccharides with ill-defined structures because of the uncontrolled random reactions among many reactive hydroxyl groups on saccharide monomers. In particular, rational synthesis of polysaccharides with porosity approximating molecular dimensions is still in its infancy, despite their usefulness as drug carriers. Here, we disclose an efficient synthetic methodology for the preparation of polysaccharides with controllable mesoporosity in the structure, utilizing [Cu3(benzene-1,3,5-tricarboxylate)]n (HKUST-1; 1) as templates. Cationic ring-opening polymerization of 1,6-anhydro glucose was performed in nanochannels of 1, followed by removal of the host frameworks, giving polysaccharide particles as replicas of the original molds. Nitrogen adsorption measurement revealed that the obtained polysaccharide particles contained high mesoporosity in the structure, which could be controlled systematically depending on the polymeriza...
TL;DR: The generation of HCOO- via a catalytic hydride transfer from the NADH-type ligands of [1]2+ and [2]+ to CO2 was supported by the experimental results and a comparison with the reduction of CO2 catalyzed by [Ru(tpy)(bpy)(CO)]2+ under similar conditions.
Abstract: The catalytic performance of Ru-NAD-type complexes [Ru(tpy)(pbn)(CO)]2+ ([1]2+; tpy = 2,2′;6′,2″-terpyridine; pbn = 2-(pyridin-2-yl)benzo[b][1,5]naphthyridine) and the Ru-CO-bridged metallacycle [2]+ was investigated in the context of the electrochemical reduction of CO2 in H2O/CH3CN at room temperature. A controlled-potential electrolysis of [1]2+ and [2]+ afforded formate (HCOO–) as the main product, under concomitant formation of minor amounts of CO and H2. Metallacycle [2]+ showed a higher selectivity toward the formation of HCOO– than [1]2+ (HCOO–/CO for [1]2+, 2.7; HCOO–/CO for [2]+, 7). The generation of HCOO– via a catalytic hydride transfer from the NADH-type ligands of [1]2+ and [2]+ to CO2 was supported by the experimental results and a comparison with the reduction of CO2 catalyzed by [Ru(tpy)(bpy)(CO)]2+ under similar conditions. A mechanism for the catalytic reduction of CO2 by [1]2+ and [2]+ was proposed based on the experimental evidence. The thus-obtained results may help to expand the fi...
TL;DR: Microporous organically pillared layered silicates (MOPS) are found to be capable of discriminating two very similar gases by selective gate-opening solely through quenching pillar dynamics, and the shape of the slit-type micropores in MOPS can easily be fine-tuned by reducing the charge density.
Abstract: Microporous organically pillared layered silicates (MOPS) are a class of microporous hybrid materials that, by varying pillar density, allows for optimization of guest recognition without the need to explore different framework topologies. MOPS are found to be capable of discriminating two very similar gases, carbon dioxide and acetylene, by selective gate-opening solely through quenching pillar dynamics. Contrary to conventional gate-opening in metal organic frameworks, the additional adsorption capacity is realized without macroscopic volume changes, thus avoiding mechanical stress on the framework. Of the two gases studied, only CO2 can accomplish freezing of pillar dynamics. Moreover, the shape of the slit-type micropores in MOPS can easily be fine-tuned by reducing the charge density of the silicate layers. This concomitantly reduces the Coulomb attraction of cationic interlayer space and anionic host layers. Surprisingly, we found that reducing the charge density then alters the gate-opening mechani...
TL;DR: End-functionalized polymeric ligands (macroligands) and azobenzene-3,3'-dicarboxylic acid with Cu2+ self-sort into anisotropic coordination star polymers with polymeric chains on the arms, grafted from each polar position of the metal-organic polyhedral core.
TL;DR: Thermal ring-opening polymerization of the unsymmetrically substituted ferrocenophane was performed in one-dimensional nanochannels of porous coordination polymers (PCPs), and the tacticity of the resulting polymer was dependent on the pore size of PCPs.
TL;DR: Francesco Carraro, Karena Chapman, Zhijie Chen, Mircea Dincă, Timothy Easun, Mohamed Eddaoudi, Omar Farha, Ross Forgan, Laura Gagliardi, Frederik Haase, David Harris, Susumu Kitagawa, Jane Knichal, Carlo Lamberti, Jet-Sing M. Lee, Karen Leus, Jing Li, Wenbin Lin, Gareth Lloyd, Jeffrey R. Long, Connie Lu
Abstract: Francesco Carraro, Karena Chapman, Zhijie Chen, Mircea Dincă, Timothy Easun, Mohamed Eddaoudi, Omar Farha, Ross Forgan, Laura Gagliardi, Frederik Haase, David Harris, Susumu Kitagawa, Jane Knichal, Carlo Lamberti, Jet-Sing M. Lee, Karen Leus, Jing Li, Wenbin Lin, Gareth Lloyd, Jeffrey R. Long, Connie Lu, Shengqian Ma, Lauren McHugh, Jeffrey Paulo H. Perez, Marco Ranocchiari, Nathaniel Rosi, Matthew Rosseinsky, Matthew R. Ryder, Valeska Ting, Monique van der Veen, Pascal Van Der Voort, Dirk Volkmer, Aron Walsh, Duncan Woods and Omar M. Yaghi
TL;DR: In this article, the authors used a model system consisting of two [Cu2(O2CC6H4-R)4] units (R = H and Me), namely, dimer and monomer models.
Abstract: Adsorptions of CO, N2, NO, and CO2 in a paddle-wheel-type porous coordination polymer (PCP) [Cu(aip)]n (aip = 5-azidoisophthalate) were investigated with ONIOM[MP4(SDQ):ωB97XD] method using a model system consisting of two [Cu2(O2CC6H4-R)4] units (R = H and Me) and one [Cu2(O2CC6H4–R)4] unit, namely, dimer and monomer models. The experimental CO adsorption position was reproduced well by the present calculation with the dimer model. For adsorptions of CO, N2, NO, and CO2 in the dimer model, the position of gas molecule deviates from the normal one that is found in the monomer model and becomes more distant from the surrounding phenyl group(s) of the neighbor [Cu(aip)] unit. For all of these gas molecules, the calculated binding energy (BE) at the deviating adsorption position is larger than that at the normal one against our expectation that the normal position is the best for the gas adsorption. The deviation of gas adsorption position arises from the interaction between the organic linker (O2CC6H4–R moi...
TL;DR: A mechanism for the formation of a Ru-OCO-bridge complex was proposed here on the basis of H2O18 experiments, DDQ treatment and other experimental data, and these newly synthesized complexes appended with NAD-type ligands may have potential use as renewable hydride sources for organic reductions.
Abstract: A reaction of a ruthenium(II) NAD-type complex, [Ru(tpy)(pbn)(Cl)]+ (tpy = 2,2′:6′,2′′-terpyridine; pbn = 2-(pyridin-2-yl)benzo[b][1,5]naphthyridine), with pressurized CO (2 MPa) at 150 °C in H2O selectively produced a two-electron reduced ruthenium(II)-NADH-type carbonyl complex, [Ru(tpy)(pbnHH)(CO)]2+ (pbnHH = 2-(pyridin-2-yl)-5,10-dihydrobenzo[b][1,5]naphthyridine), rather than the oxidized [Ru(tpy)(pbn)(CO)]2+ complex. Indeed, [Ru(tpy)(pbnHH)(CO)]2+ was quantitatively oxidized to [Ru(tpy)(pbn)(CO)]2+ upon treatment with one equiv. of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). The reactivity of [Ru(tpy)(pbnHH)(CO)]2+ with various bases was studied herein. Treatment of [Ru(tpy)(pbnHH)(CO)]2+ with a suitable organic base, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), resulted in the formation of a new five-membered Ru–CO-bridge metallacycle quantitatively in acetonitrile under air at room temperature. A probable mechanism was proposed for this reaction based on UV-vis, NMR, and EPR spectral studies and other experimental data. Furthermore, a reaction of the five membered Ru–CO-bridge metallacycle with NH4PF6 in CH3CN : H2O (1 : 1) under air smoothly produced another new six-membered Ru-OCO-bridge complex. A mechanism for the formation of a Ru-OCO-bridge complex was also proposed here on the basis of H2O18 experiments, DDQ treatment and other experimental data. These newly synthesized complexes appended with NAD-type ligands may have potential use as renewable hydride sources for organic reductions.