RESUMO
Deuteration of amine compounds has been widely of concern because of its practical role in organic reaction mechanisms and drug research; however, only limited deuteration label methods are accessible with D2O as a deuterium source. Herein, we propose a convenient deuteration protocol, including preparing D2 by the AlGa activation method, using PtRu nanowires as catalysts, and utilizing the elementary step in the couple reaction involving an imine unit, to realize the rapid preparation of a secondary amine with a diversified deuteration label. The self-coupling between nitriles not only provides a symmetric secondary amine with four α-D atoms but also produces high-valued ND3 in an atomic-economic way.
RESUMO
With the aim of producing a photomechanical material for incorporation in soft microrobots, a one-dimensional diene coordination polymer (CP) [Cd(F-bpeb)(3-CBA)2]n (CP1, F-bpeb=4,4'-((1E,1'E)-(2,5-difluoro-1,4-phenylene)bis(ethene-2,1-diyl))dipyridine, 3-HCBA=3-chlorobenzoic acid) was synthesized and characterized. Irradiation of CP1 with ultraviolet (UV) or visible light causes [2+2] photocycloaddition reactions resulting in the introduction of crystal strain which triggers various types of crystal movements. Composite films of CP1-PVA (SC) fabricated by dispersing CP1 crystals into polyvinyl alcohol (PVA) solution allow amplification of the crystal movement so that the film strips exhibit fast and flexible curling upon photoirradiation. The composite films may be cut into long rectangular strips and folded to simulate soft microrobots which exhibit a variety of fast, flexible and continuous photomechanical movements resembling a human performing various gymnastic exercises.
RESUMO
Molecular crystals with the ability to transform light energy into macroscopic mechanical motions are a promising class of materials with potential applications in actuating and photonic devices. In regard to such materials, coordination polymers that exhibit dynamic photomechanical motion, associated with a phase transition, are unknown. Herein, we report an intriguing photoactive, one-dimensional ZnII coordination polymer, 1, derived from 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene and 3,5-difluorobenzoate. Single crystals of 1 under UV light irradiation exhibit rapid shrinking and bending, violent bursting-jumping, splitting, and cracking behavior. Single-crystal X-ray diffraction analysis and 1 Hâ NMR spectroscopy reveal an unusual photoinduced phase transition involving a single-crystal-to-single-crystal [2+2] cycloaddition reaction that results in photomechanical responses. Interestingly, crystals of 1, which are triclinic with space group P 1 â¾ ${P\bar{1}}$ , are transformed into a higher symmetry, monoclinic cell with space group C2/c. This process represents a rare example of symmetry enhancement upon photoirradiation. The photomechanical activity is likely due to the sudden release of stress associated with strained molecular geometries and significant solid-state molecular movement arising from cleavage and formation of chemical bonds. A composite membrane fabricated from 1 and polyvinyl alcohol (PVA) also displays interesting photomechanical behavior under UV light illumination, indicating the material's potential as a photoactuator.
RESUMO
We report a unique vinyl coordination polymer (CP), [Zn(4-Fb)2 (tkpvb)]n (1, 4-HFb=4-fluorobenzoic acid, tkpvb=1,2,4,5-tetrakis(4-pyridylvinyl)benzene) that undergoes a rare photopolymerization reaction to form a two-dimensional CP integrated with a one-dimensional linear organic polymer. Upon light irradiation at different wavelengths, 1 exhibits an unprecedented phenomenon of photoinduced nonlinear lattice expansion. 1 can be uniformly dispersed in polyvinyl alcohol (PVA) to form the composite film of 1-PVA. When this film is exposed to UV light, internal minute stresses within crystallites are released by lattice expansion, resulting in a variety of photopolymerization-driven macroscopic mechanical motions. The findings provide new insights into the conversion of small lattice expansions of CPs into macroscopic mechanical motions based on photopolymerization reactions, which can promote the development of CPs-based smart photoactuators in the burgeoning field of microrobotics.
RESUMO
Due to its high reactivity and oxidative strength, singlet oxygen (1 O2 ) is used in a variety of fields including organic synthesis, biomedicine, photodynamic therapy and materials science. Despite its importance, the controlled trapping and release of 1 O2 is extremely challenging. Herein, we describe a one-dimensional coordination polymer, CP1, which upon irradiation with visible light, transforms 3 O2 (triplet oxygen) to 1 O2 . CP1 consists of CdII centers bridged by 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene ligands which undergo a [4+2] cycloaddition reaction with 1 O2 , resulting in the generation of CP1-1 O2 . Using microwave irradiation, CP1-1 O2 displays efficient release of 1 O2 , over a period of 30â s. In addition, CP1 exhibits enhanced fluorescence and has an oxygen detection limit of 97.4â ppm. Theoretical calculations reveal that the fluorescence behaviour is dominated by unique through-space conjugation. In addition to describing a highly efficient approach for the trapping and controlled release of 1 O2 , using coordination polymers, this work also provides encouragement for the development of efficient fluorescent oxygen sensors.
RESUMO
The two-dimensional (2-D) framework, [Cu(BTDAT)(MeOH)] {BTDAT = bis-[1,2,5]-thiadiazolo-tetracyanoquinodimethane}, possesses remarkable multi-step redox properties, with electrochemical studies revealing six quasi-stable redox states in the solid state. In situ electron paramagnetic resonance and visible-near infrared spectroelectrochemistry elucidated the mechanism for these multi-step redox processes, as well as the optical and electrochromic behavior of the BTDAT ligand and framework. In studying the structural, spectroscopic, and electronic properties of [Cu(BTDAT)(MeOH)], the as-synthesized framework was found to exist in a mixed-valence state with thermally-activated semiconducting behavior. In addition to pressed pellet conductivity measurements, single-crystal conductivity measurements using a pre-patterned polydimethylsiloxane layer on a silicon substrate provide important insights into the anisotropic conduction pathways. As an avenue to further understand the electronic state of [Cu(BTDAT)(MeOH)], computational band structure calculations predicted delocalized electronic transport in the framework. On the balance of probabilities, we propose that [Cu(BTDAT)(MeOH)] is a Mott insulator (i.e., electron correlations cause a metal-insulator transition). This implies that the conductivity is incoherent. However, we are unable to distinguish between activated transport due to Coulombically bound electron-hole pairs and a hopping mechanism. The combined electrochemical, electronic, and optical properties of [Cu(BTDAT)(MeOH)] shine a new light on the experimental and theoretical challenges for electroactive framework materials, which are implicated as the basis of advanced optoelectronic and electrochromic devices.
RESUMO
A remarkably flexible, multifunctional, 2D coordination polymer exhibiting an unprecedented mode of reversible mechanical motion, enabling pores to open and close, is reported. Such multifunctional materials are highly sought after, owing to the potential to exploit coexisting electronic and mechanical functionalities that underpin useful technological applications such as actuators and ultrasensitive detectors. The coordination polymer, of composition Mn(F4TCNQ)(py)2 (F4TCNQ = 2,3,5,6-tetrafluoro-7,7,8,8-tetracycanoquinodimethane; py = pyridine), consists of Mn(II) centers bridged by F4TCNQ dianions and coordinated by py molecules that extend above and below the 2D network. Exposure of Mn(F4TCNQ)(py)2, in its collapsed state, to carbon dioxide results in a pore-opening process at a threshold pressure for a given temperature. In addition to carbon dioxide, a variety of volatile guests may be incorporated into the pores, which are lined with electron-rich F4TCNQ dianions. The inclusion of electron-deficient guests such as 1,4-benzoquinone, nitrobenzene, maleic anhydride, and iodine into the pores is accompanied by a striking color change associated with a new host-guest charge-transfer interaction and an improvement in the semiconductor behavior, with the iodine adduct showing an increase in conductivity of almost 5 orders of magnitude. Experimental and density functional theory calculations on this remarkable multifunctional material demonstrate a reduction in the optical band gap with increasing electron affinity of the guest.
RESUMO
A 2-D coordination framework, (NEt4)2[Fe2(fan)3] (1·5(acetone); H2fan = 3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone), was synthesized and structurally characterized. The compound is structurally analogous to a formerly elucidated framework, (NEt4)2[Fe2(can)3] (H2can = 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone), and adopts a 2-D (6,3) topology with the symmetrical stacking of [Fe2(fan)3]2- sheets that are held in position by the NEt4+ cations between the sheets. The investigation of the dc and ac magnetic properties of 1·5(acetone) revealed ferromagnetic ordering behavior and slow magnetization relaxation, as evinced from ac susceptibility measurements. Furthermore, the exposure of 1·5(acetone) to air led to the formation of a heptahydrate 1·7H2O which displayed distinct magnetic properties. The study of the redox state and extent of delocalization in 1·5(acetone) was undertaken via crystallography, in combination with Mössbauer and vis-NIR spectroscopy, to reveal the mixed-valence and delocalized nature of the as-synthesized material. As a result, the conductivity studies conducted on a pressed pellet showed a relatively high conductivity of 1.8 × 10-2 S cm-1 (300 K). In order to compare structurally related anilate-based structures, a relationship among the redox state, spectroscopic properties, and electronic properties was elucidated in this work. A preliminary investigation of 1·5(acetone) as a candidate anode material in lithium ion batteries revealed a high reversible capacity of 676.6 mAh g-1 and high capacity retention.
RESUMO
An investigation of the adsorption properties of two structurally related, 3D coordination polymers of composition Zn(2-Mehba) and Zn(2,6-Me2hba) (2-Mehba = the dianion of 2-methyl-4-hydroxybenzoic acid and 2,6-Me2hba = the dianion of 2,6-dimethyl-4-hydroxybenzoic acid) is presented. A common feature of these structures are parallel channels that are able to accommodate appropriately sized guest molecules. The structures differ with respect to the steric congestion within the channels arising from methyl groups appended to the bridging ligands of the network. The host network, Zn(2-Mehba), is able to take up appreciable quantities of H2 (77 K) and CO2 and CH4 (298 K) in a reversible manner. In regard to the adsorption of N2 by Zn(2-Mehba), there appears to be an unusual temperature dependence for the uptake of the gas such that when the temperature is increased from 77 to 298 K the uptake of N2 increases. The relatively narrow channels of Zn(2,6-Me2hba) are too small to allow the uptake of N2 and CH4, but H2 molecules can be adsorbed. A pronounced step at elevated pressures in CO2 and N2O isotherms for Zn(2,6-Me2hba) is noted. Calculations indicate that rotation of phenolate rings leads to a change in the available intraframework space during CO2 dosing.
RESUMO
Reaction of the chloranilate dianion with Y(NO3 )3 in the presence of Et4 N+ in the appropriate proportions results in the formation of (Et4 N)[Y(can)2 ], which consists of anionic square-grid coordination polymer sheets with interleaved layers of counter-cations. These counter-cations, which serve as squat pillars between [Y(can)2 ] sheets, lead to alignment of the square grid sheets and the subsequent generation of square channels running perpendicular to the sheets. The crystals are found to be porous and retain crystallinity following cycles of adsorption and desorption. This compound exhibits a high affinity for volatile guest molecules, which could be identified within the framework by crystallographic methods. In situ neutron powder diffraction indicates a size-shape complementarity leading to a strong interaction between host and guest for CO2 and CH4 . Single-crystal X-ray diffraction experiments indicate significant interactions between the host framework and discrete I2 or Br2 molecules. A series of isostructural compounds (cat)[MIII (X-an)2 ] with M=Sc, Gd, Tb, Dy, Ho, Er, Yb, Lu, Bi or In, cat=Et4 N, Me4 N and X-an=chloranilate, bromanilate or cyanochloranilate bridging ligands have been generated. The magnetic properties of representative examples (Et4 N)[Gd(can)2 ] and (Et4 N)[Dy(can)2 ] are reported with normal DC susceptibility but unusual AC susceptibility data noted for (Et4 N)[Gd(can)2 ].
RESUMO
A chiral, octahedral M12 L12 cage, which is charge neutral and contains an internal void of about 2000â Å3 , is reported. The cage was synthesised as an enantiopure complex by virtue of amino-acid-based dicarboxylate ligands, which assemble around copper paddlewheels at the vertices of the octahedron. The cage persists in solution with retention of the fluorescence properties of the parent acid. The solid-state structure contains large pores both within and between the cages, and displays permanent porosity for the sorption of gases with retention of crystallinity. Initial tests show some enantioselectivity of the cage towards guests in solution.
RESUMO
Photoreactive olefinic species are incorporated into a metal-organic framework (MOF), [Zn(bdc)(3-F-spy)] (1). Single crystals of 1 are shown to undergo three types of photomechanical macroscopic deformation upon illumination by UV light. To demonstrate the practical potential of this system, the inclusion of 1 in a PVA (polyvinyl alcohol) composite membrane, by exploiting hydrogen-bonding interactions, is presented. Using this composite membrane, the amplification of mechanical stress to achieve macroscopic actuation behavior is demonstrated. These results pave the way for the generation of MOF-based soft photoactuators that produce clearly defined mechanical responses upon irradiation with light. Such systems are anticipated to have considerable potential in photomechanical energy harvesting and conversion systems.
RESUMO
Coordination frameworks containing DCNQI2- (DCNQI = N, N'-dicyanoquinonediimine ligand) are produced by deprotonation of DCNQIH2 in the presence of a metal center and a co-ligand. This approach has yielded two-dimensional (2D) sheet compounds [Cd(DCNQI)(L)2] (where L = pyridine (py) or isoquinoline (isoquin)) that can be partially oxidized via solid-state electrochemical and in situ spectroelectrochemical methods to materials that contain DCNQI as its radical monoanion. The new frameworks display charge-transfer bands that are indicative of interligand charge-transfer interactions as supported by TD-DFT computational calculations. The redox-state dependent spectral properties of the frameworks have been probed using a newly developed solid-state spectroelectrochemical cell. Coupled with computational calculations, the experimental data provide an understanding of the fundamental charge-transfer processes that may underpin long-range functional properties such as conductivity in framework materials.
RESUMO
Regioselective photodimerization of trans-4-styrylpyridine (4-spy) derivatives is performed using pseudorotaxane-like Zn-based metal organic frameworks MOFs as templates. The formation of rctt-HT (head-to-tail) dimers is achieved by confining pairs of coordinated 4-spy derivative ligands within hexagonal windows and then irradiating them with UV light. It is also possible to achieve a photodimerization reaction where two different substituted 4-spy ligands are included in such a MOF material. The ether bond formation is employed to protect the sensitive -OH group of HO-spy and the methyl group of CH3 O-spy is subsequently removed after the formation of cyclobutane derivative in the CH3 O-spy-based MOF. Introducing substituents at the 2- or 3-position of the phenyl group of 4-spy does not significantly affect the rate of the dimerization process except in the case of the strongly electron-withdrawing nitro group where the rate is significantly decreased. These results are in striking contrast to the mixtures of photoproducts and low yields obtained by untemplated photodimerization in organic solvents.
RESUMO
The need for effective CO2 capture systems remains high, and due to their tunability, metallosupramolecular architectures are an attractive option for gas sorption. While the use of extended metal organic frameworks for gas adsorption has been extensively explored, the exploitation of discrete metallocage architectures to bind gases remains in its infancy. Herein the solid state gas adsorption properties of a series of [Pd2 (L)4 ]4+ lantern shaped coordination cages (L = variants of 2,6-bis(pyridin-3-ylethynyl)pyridine), which had solvent accessible internal cavities suitable for gas binding, have been investigated. The cages showed little interaction with dinitrogen gas but were able to take up CO2 . The best performing cage reversibly sorbed 1.4â mol CO2 per mol cage at 298â K, and 2.3â mol CO2 per mol cage at 258â K (1â bar). The enthalpy of binding was calculated to be 25-35â kJ mol-1 , across the number of equivalents bound, while DFT calculations on the CO2 binding in the cage gave ΔE for the cage-CO2 interaction of 23-28â kJ mol-1 , across the same range. DFT modelling suggested that the binding mode is a hydrogen bond between the carbonyl oxygen of CO2 and the internally directed hydrogen atoms of the cage.
RESUMO
The uptake of inhalation anesthetics by three topologically identical frameworks is described. The 3D network materials, which possess square channels of different dimensions, are formed from the relatively simple combination of ZnII centres and dianionic ligands that contain a phenolate and a carboxylate group at opposite ends. All three framework materials are able to adsorb N2 O, Xe and isoflurane. Whereas the framework with the widest channels is able to adsorb large quantities of the various guests from the gas phase, the frameworks with the narrower channels have superior binding enthalpies and exhibit higher levels of retention. The use of ligands in which substituents are bound to the aromatic rings of the bridging ligands offers great scope for tuning the adsorption properties of the framework materials.
Assuntos
Anestésicos Inalatórios/química , Estruturas Metalorgânicas/química , Polímeros/química , Adsorção , Isoflurano/química , Óxido Nitroso/química , Porosidade , Xenônio/química , Zinco/químicaRESUMO
A pair of coordination polymers of composition (NBu4)2[M2(fan)3] (fan = fluoranilate; M = Fe and Zn) were synthesized and structurally characterized. In each case the compound consists of a pair of interpenetrating three-dimensional, (10,3)-a networks in which metal centers are linked by chelating/bridging fluoranilate ligands. Tetrabutylammonium cations are located in the spaces between the two networks. Despite the structural similarity, significant differences exist between (NBu4)2[Fe2(fan)3] and (NBu4)2[Zn2(fan)3] with respect to the oxidation states of the metal centers and ligands. For (NBu4)2[Fe2(fan)3] the structure determination as well as Mössbauer spectroscopy indicate the oxidation state for the Fe is close to +3, which contrasts with the +2 state for the Zn analogue. The differences between the two compounds extends to the ligands, with the Zn network involving only fluoranilate dianions, whereas the average oxidation state for the fluoranilate in the Fe network lies somewhere between -2 and -3. Magnetic studies on the Fe compound indicate short-range ordering. Electrochemical and spectro-electrochemical investigations indicate that the fluoranilate ligand is redox-active in both complexes; a reduced form of (NBu4)2[Fe2(fan)3] was generated by chemical reduction. Conductivity measurements indicate that (NBu4)2[Fe2(fan)3] is a semiconductor, which is attributed to the mixed valency of the fluoranilate ligands.
RESUMO
A ZnII complex of the dianionic tetradentate ligand formed by deprotonation of glyoxal-bis(4-phenyl-3-thiosemicarbazone) (H2 gtsp) is a [3+3] trinuclear triangular prism. Recrystallization of this complex in the presence of either CO2 , CS2 , or CH3 CN leads to the formation of [4+4] open-ended charge-neutral tetranuclear coordination nanotubes, approximately 2â nm in length and with internal dimensions large enough to accommodate linear guest molecules, which serve to template their formation. Upon removal of the templating molecules the nanotubes demonstrated reversible sorption of CO2 with an isosteric enthalpy of sorption of 28â kJ mol-1 at low loading.
RESUMO
A new divergent homopiperazine-derived ligand N,N'-bis(4-carboxyphenyl)-1,4-diazacycloheptane H2L has been prepared, containing a semirigid saturated heterocyclic core which is capable of providing multiple distinct bridging geometries. Reaction of H2L with zinc acetate in DMSO gives a two-dimensional parallel interpenetrated polyrotaxane structure 1 in which the loops and rods are formed by the bent cis-(eq,ax) twist boat and trans-(ax,ax) twist chair conformers, respectively. By matching the distances between the solvated metal sites in the structure of 1, a related material 2 can be prepared incorporating the pillaring ligand trans-1,2-bis(4-pyridyl)ethylene bpe. Compound 2 displays a similar polyrotaxane interpenetration mode, permitted by the presence of both cis and trans ligand conformers, but displays a three-dimensional 2.69 topology related to the dia diamondoid network. The guest exchange and gas adsorption properties of both materials were investigated; while compound 1 displays poor stability to guest exchange and negligible gas uptake, the higher connectivity microporous compound 2 shows facile guest exchange and a surprisingly high CO2 capacity of 12 wt % at 1 bar and 273 K, and a zero-loading enthalpy of adsorption of -32 kJ mol-1. High-pressure adsorption isotherms also show moderate physisorption of H2 and CH4 within the material.
RESUMO
The structure of Li(inox)â 2/3 DMF (inox(-) =the N-oxide of the isonicotinate anion) consists of a 3D framework with solvent-filled, square cross-section channels of approximate dimensions 5.5×5.5â Å. Unfortunately, the Li(inox) framework is unstable upon removal of DMF from the channels. When the structurally related 4-hydroxybenzoic acid (H2 hba) was used in place of Hinox, and Zn(2+) in place of the Li(+) , a structurally similar but more robust network, Zn(hba), was obtained; the isostructural compound, Co(hba), may also be prepared. Longer ligands with phenolate and carboxylate functional groups at opposite ends, such as the dianions of 4-coumaric acid (H2 cma) and 4'-hydroxy-4-biphenylcarboxylic acid (H2 hbpc), in combination with Zn(2+) yield Zn(cma) and Zn(hbpc) frameworks, respectively, with the same PtS topology but with larger channels. The coordination polymers remain intact after desolvation and exhibit microporosity, showing the ability to sorb significant quantities of CO2 , CH4 , and H2 .