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The envisaged shift in the interest of crystal engineering researchers from crystal structure to mechanical property has sown the seeds of analogous understanding and interpretation of the molecula...

Tuning the mechanical properties of crystalline materials is alluring and has captivated the interest of material scientists. Here, we have demonstrated a crystal engineering approach to introduce ...

Proton-conducting materials have been gaining significant attention due to their applicability as solid electrolytes in proton exchange membrane fuel cells (PEMFCs). The confined architectural design and open space in metal organic frameworks (MOFs) and covalent organic frameworks (COFs) makes them attractive as proton-conducting materials for PEMFCs applications. They offer a high degree of structural tunability, well-defined accessible pores, good crystallinity, thermo/chemical stability, etc., which make them ideal proton conductors at various temperatures under hydrous and anhydrous conditions. In this article, we are reviewing the reported state-of-the-art porous crystalline proton-conducting materials (MOFs and COFs) with detailed insights into their conduction pathway/mechanism in relation to their unique structural features. Further, the design and synthetic principle of many well-known proton-conducting MOFs and COFs, including their operation under various conditions, will be discussed. At the end, a dedicated perspective section will be presented based on our learning experiences, which will definitely add a new dimension in the design of potential porous crystalline materials for conduction-related applications in the future.

The advancement of our understanding of stimuli-responsive molecular crystals has led to the realization that they hold great yet unexplored potential as adaptive materials. Although molecular crystals that exhibit a single mechanical response to a single input stimulus are now abundant, crystals that are capable of response to multiple stimuli are rather scarce. Here we report two photoswitchable acylhydrazone derivatives, Ac-1 and Ac-2, which respond to light as well as to mechanical force. Upon application of localized mechanical stress, the anhydrous (Ac-1a) and monohydrate (Ac-1h) crystals of Ac-1 undergo plastic shearing deformation and bending, whereas monohydrate crystals of Ac-2 undergo elastic deformation. When they are exposed to UV light, crystals of Ac-1h and Ac-2 undergo photoinduced bending; on the other hand, crystals of Ac-1a and thicker crystals of Ac-2 exhibit photosalient effect (light-induced leaping). It is demonstrated that the synergistic action of multiple stimuli (UV light and fo...

New Y-shaped ferrocene conjugated imidazole chromophores were prepared and fully characterized. The Y-shaped structure was confirmed by the single crystal X-ray diffraction technique. The chromophores show interesting second-order nonlinear optical (NLO) properties in solution, as determined by the Electric-Field Induced Second Harmonic generation (EFISH) technique. Remarkably, the trifluoro substituted compound 3 is characterized by a high mu beta(EFISH) value and has good potential as a molecular building block for composite films with Second Harmonic Generation (SHG) properties. For all compounds, the dipole moments and frontier orbital energies were calculated by the Density Functional Theoretical method.

In this study, we report a synthetically simple donor-acceptor (D-A)-type organic solid-state emitter 1 that displays unique fluorescence switching under mechanical stimuli. Orange and yellow emissive crystals of 1 (1O, 1Y) exhibit an unusual "back and forth" fluorescence response to mechanical force. Gentle crushing (mild pressure) of the orange or yellow emissive crystal results in hypsochromic shift to cyan emissive fragments (lambda(em) = 498-501 nm) with a large wavelength shift Delta lambda(em) = -71 to -96 nm, while further grinding results in bathochromic swing to green emissive powder lambda(em) = 540-550 nm, Delta lambda(em) = + 40 to 58 nm. Single-crystal X-ray diffraction study reveals that molecules are packed by weak interactions, such as C-H center dot center dot center dot pi, C-H center dot center dot center dot N, and C-H center dot center dot center dot F, which facilitate intermolecular charge transfer in the crystal. With the aid of structural, spectroscopic, and morphological studies, we established the interplay between intermolecular and intramolecular charge-transfer interaction that is responsible for this elusive mechanochromic luminescence. Moreover, we have also demonstrated the application of this organic material for chlorine gas sensing in solid state.

The time course of photochemical solid-state reactions is routinely monitored by using spectroscopic methods such as NMR or IR spectroscopies, but is comparatively less investigated with thermal methods. In this work, a combination of thermal methods (thermogravimetric analysis and differential scanning calorimetry) was applied together with irradiation with UV light to quantify the conversion and monitor the progress of a well-known photochemical reaction, the [2 + 2] dimerization of trans-cinnamic acid, and the results are compared with the conversion determined by using 1H NMR spectroscopy. The conversion was correlated with thermodynamic parameters for the reactant such as molar enthalpy, entropy, and melting temperature.

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.

The artist Sir Anthony van Dyck spent his life illustrating the English royalty in the early to mid-17th century, and during his career he became famous for his relaxed elegance and use of a particular hue of brown. The brown pigment would eventually be named after him, ‘van Dyck brown’, and can still be found today. However, another pigment became commercially available much later after his death, and it is commercially available as ‘van Dyck crystals’. In practice the two terms are used interchangeably, as they both are made from organic material. Here we investigate the complex chemical composition of ‘van Dyck crystals’, and we show that the two pigments are distinctly different, both in composition and in origin. We show that the colored component of the ‘van Dyck crystals’ is not crystalline and should not be confused with the original pigment.

The effect of dimensionality (1D to 2D) on charge carrier mobility have been studied thoroughly on three In(III)-isophthalate based MOFs [In-IA-1D, In-IA-2D-1 and -2]. In-IA-1D possess 1D nanotubular architecture with [(CH3)2NH2]+. In-IA-2D-1 have 2D layers containing only [(CH3)2NH2]+ cations. Whereas, In-IA-2D-2 have [(CH3)2NH2]+ cations as well as solvent DMF molecule inside the crystal structure. Due to presence of the π–π stacking arrangement among the phenyl rings of IA moieties facilitates the high charge carrier mobility (4.6 × 10−3 cm2 V−1 s−1 at VG = −40 V) in In-IA-2D-2. However, In-IA-1D and In-IA-2D-1 does not show any charge carrier mobility due to absence of π–π stacking arrangement.

Three Co based Zeolitic Imidazolate Frameworks (Co-ZIF-68, -69 and -81) which adopt a GME topology with high porosity have been synthesized. These Co-ZIFs show high CO2 (273 K/298 K) uptake compared to their isostructural Zn based analogues, which has been proved experimentally as well as by ab initio calculations.

Seven new partially fluorinated metal−organic frameworks (F-MOFs) have been synthesized under different solvothermal conditions (H2O or N,N-dimethylformamide (DMF)) from transition metal cations [Zn(II), Co(II), and Mn(II)], 1,10-phenanthroline (phen), and 4,4′-(hexafluoroisopropylidene) bis(benzoic acid) (C17H10F6O4, H2hfbba) to determine the influence of reaction conditions on the formation of metal−organic frameworks. This family of materials displays a striking degree of structural similarity depending on the solvent of synthesis. Of the seven materials, two contain three-dimensional connectivity: Co3(hfbba)6(phen)2 (F-MOF-6) and Mn3(hfbba)6(phen)2 (F-MOF-10). Three materials are one-dimensional structures: Zn(hfbba)0.5(phen)(HCO2) (F-MOF-8), Mn(Hhfbba)2(phen) (F-MOF-11), and [Mn(hfbba)2(dm-phen)]·(H2O) (F-MOF-11A). Lastly, Co(hfbba)(phen)2·2(H2hfbba)(H2O)(HCO2) (F-MOF-7) and Zn(hfbba)(phen)2·2(H2hfbba) (H2O)(HCO2) (F-MOF-9) are discrete zero-dimensional molecular complexes. F-MOF-6 and -10, which fea...

A three dimensional -NH(2) functionalized Zeolitic Tetrazolate Framework (ZTF-1) has been reported. The framework adopts a dia topology (M-L-M angle is close to 156°). ZTF-1 shows high CO(2) (273 K) and H(2) (77 K) uptake due to the presence of the free -NH(2) group and uncoordinated tetrazolate nitrogen.

Proton conductivity has been studied thoroughly in two isomeric In(III)-isophthalate based MOFs. In-IA-2D-1 is capable of showing proton conductivity (3.4 × 10(-3) S cm(-1)) under humidified conditions (98% RH), whereas In-IA-2D-2 can conduct protons (2.6 × 10(-5) S cm(-1)) under humidified as well as anhydrous conditions.

El pdf del artículo es la versión de autor.-- et al., The synthesis, structure, gas adsorption and catalytic properties of a new 3D porous, crystalline metal-organic framework (Ca-5TIA-MOF) as well as stable viscoelastic metallogels (Ca-5TIA-Gel) are reported. Remarkably, the preparation of both types of materials can be carried out starting from the same organic ligand (i.e. 5-(1,2,4-triazoleyl)isophthalic acid (5TIA)), divalent metal ion (i.e. Ca(ii)) and organic solvent (i.e. DMF). In this particular case, the presence of water in the solvent system favors the formation of a crystalline MOF, whereas a pure organic solvent induces gelation. The characterization of the materials was carried out using a series of techniques including XRD, FT-IR, TGA, TEM, SEM, SAXS and dynamic rheology. Experimental PXRD peaks of both Ca-5TIA-xerogel and Ca-5TIA-MOF matched reasonably well with simulated PXRD, suggesting the presence of, at least, some common structural elements in the 3D networks of both xerogel and crystalline phases. Moreover, the nature of the metal counteranion was found to have a critical influence on the gelation phenomenon. To the best of our knowledge, this report describes unprecedented Ca-based LMW-metallogels, as well as the first porous Ca-based MOF, which shows adsorption capacity for CO 2 at 1 atm pressure. Interestingly, Ca-5TIA-xerogel presented 20% higher CO 2-uptake than the crystalline Ca-5TIA-MOF at 1 atm and 298 K. Both Ca-5TIA-MOF and Ca-5TIA-Gel also displayed a modest catalytic activity towards the hydrosilylation of benzaldehyde, with slightly better performance for the gel phase material. This journal is © The Royal Society of Chemistry 2012., A. M. and T. P. acknowledge CSIR for a Junior Research Fellowship. R. B. acknowledges NCL Director, for in-house project (MLP020626) and CSIR’s XIth Five Year Plan Project (NWP0022-H) and Clean Coal Technology Project (NWP0021- A). Financial support from DST (SR/S1/IC-22/2009), UR (Anschubfinanzierung von Wissenschaftlichen Projekten-2011) and CSIC (PIE 200980I059) is also acknowledged.

Three new metal-organic framework isomers have been synthesized by using the organic linker 5-triazole isophthalic acid and Mn(NO(3))(2)·xH(2)O. Structural conversions from non-porous to porous MOFs due to the template effect have been observed. The cross-sectional pore apertures of the resulting Mn-MOFs are comparable to the molecular dimensions of the template (pyrazine and 4,4'-bipyridine). The periodic increased porosity in Mn-MOFs depending on the size of the template used has been further confirmed by the CO(2) adsorption isotherms.

The catalytic activity of the N-tailed ("biuret") TAML (tetraamido macrocyclic ligand) activators [Fe{4-XC6 H3 -1,2-(NCOCMe2 NCO)2 NR}Cl](2-) (3; N atoms in boldface are coordinated to the central iron atom; the same nomenclature is used in for compounds 1 and 2 below), [X, R=H, Me (a); NO2 , Me (b); H, Ph (c)] in the oxidative bleaching of Orange II dye by H2 O2 in aqueous solution is mechanistically compared with the previously investigated activator [Fe{4-XC6 H3 -1,2-(NCOCMe2 NCO)2 CMe2 }OH2 ](-) (1) and the more aggressive analogue [Fe(Me2 C{CON(1,2-C6 H3 -4-X)NCO}2 )OH2 ](-) (2). Catalysis by 3 of the reaction between H2 O2 and Orange II (S) occurs according to the rate law found generally for TAML activators (v=kI kII [Fe(III) ][S][H2 O2 ]/(kI [H2 O2 ]+kII [S]) and the rate constants kI and kII at pH 7 both decrease within the series 3 b>3 a>3 c. The pH dependency of kI and kII was investigated for 3 a. As with all TAML activators studied to-date, bell-shaped profiles were found for both rate constants. For kI , the maximal activity was found at pH 10.7 marking it as having similar reactivity to 1 a. For kII , the broad bell pH profile exhibits a maximum at pH about 10.5. The condition kI ≪kII holds across the entire pH range studied. Activator 3 b exhibits pronounced activity in neutral to slightly basic aqueous solutions making it worthy of consideration on a technical performance basis for water treatment. The rate constants ki for suicidal inactivation of the active forms of complexes 3 a-c were calculated using the general formula ln([S0 ]/[S∞ ])=(kII /ki )[Fe(III) ]; here [Fe(III) ], [S0 ], and [S∞ ] are the total catalyst concentration and substrate concentration at time zero and infinity, respectively. The synthesis and X-ray characterization of 3 c are also described.

Here we report a highly porous, water stable Co based ZIF [CoNIm (RHO)] and its solution mediated phase transformation to a less porous and water unstable ZIF [CoNIm (SOD)]. CoNIm (RHO) has high Langmuir surface area [2087 m(2) g(-1)] as well as high water adsorption [200 cm(3) (STP) g(-1)] capacity.

Two self-assembled isostructural functionalized metal-organic nanotubes have been synthesized using 5-triazole isophthalic acid (5-TIA) with In(III) and Cd(II). In- and Cd-5TIA possess one-dimensional (1D) nanotubular architecture and show proton conductivity along regular 1D channels, measured as 5.35 × 10(-5) and 3.61 × 10(-3) S cm(-1) respectively.

An Fe(III) complex of a biuret-amide based macrocyclic ligand that exhibits both excellent reactivity for the activation of H(2)O(2) and high stability, especially at low pH and high ionic strength, is reported.

A series of fluorinated metal–organic frameworks (F-MOFs) have been successfully synthesized under hydrothermal condition using 4,4′-(hexafluoroisopropylidene) bis(benzoic acid) (C17H10F6O4, H2hfbba) as a flexible dicarboxylate building block, Cu+2 and various heterocyclic co-ligands. These F-MOFs formulated as [Cu(hfbba)(phen)2]·2(H2hfbba)(H2O)(HCO2) (F-MOF-1), [Cu(hfbba)2(2,2′-bipy)2(H2O)] (F-MOF-2), [Cu(hfbba)(4,4′dime-2,2′-bipy)(HCO2)]·(hfbba)(H2O) (F-MOF-3), [Cu2(hfbba)2(3-mepy)2]·(DMF)2(3-mepy) (F-MOF-4), and [Cu(hfbba)2(phen)2]·0.5(DMF) (F-MOF-5) (hfbba = 4,4′-(Hexafluoroisopropylidene) bis(benzoate), phen = 1,10-phenanthroline; 2,2′-bipy = 2,2′-bipyridine; 4,4′dime-2,2′-bipy = 4,4′dimethyl 2,2′-bipyridine; 3-mepy = 3-methyl-pyridine and DMF = dimethyl formamide) display interesting H-bonded, 1D and 2D structural features. All these F-MOFs were structurally determined by single-crystal X-ray diffraction. F-MOF-1 and 5 form a distorted octahedral Cu+2 secondary building unit (SBU). F-MOF-5 forms a one-dimensional architecture constructed from Cu2+ ions bridged by phen anions and two types of 4 hfbba ligands while in F-MOF-1, two among the three acid co-ligands are not coordinated with Cu2+ ions. F-MOF-2 displays dinuclear SBUs within the three-dimensional frameworks whereas F-MOF-3 displays mononuclear SBUs and forms a one-dimensional chain. F-MOF-4 display a interesting 2D framework with conventional Cu2(CO2)4 paddle wheel SBU. In the crystal structures four hfbba ligands, each coordinated to a dicopper paddlewheel unit via one of their carboxylate groups. Solid-state properties such as UV-vis and thermal stability of F-MOF-1–5 have also been studied.

A series of flexible metal–organic frameworks (MOFs) have been successfully synthesized under hydrothermal condition using 1,3-adamantanediacetic acid (C14H20O4, H2ADA) as a flexible dicarboxylate building block, 4,4′-bipyridine and transition metal ions [Cd(II), Zn(II), and Mn(II)] as metal centers in DMF and aqueous media. These MOFs formulated as [Cd(ADA)(4,4′-bipy)0.5]·(DMF) (Cd-ADA-1), [Mn(ADA)(4,4′-bipy)0.5]·(DMF) (Mn-ADA-1), Zn(ADA)(4,4′-bipy)0.5 (Zn-ADA-1), and [Mn(HADA)2(4,4′-bipy)(H2O)2] (Mn-ADA-2) (ADA = 1,3-adamantanediacetate, 4,4′-bipy = 4,4′-bipyridine and DMF = N,N′-dimethyl formamide) display interesting 1D, 2D and 3D structural features depending on the solvent of synthesis. All these MOFs were structurally determined by single-crystal X-ray diffraction. The coordination modes of this ligand are discussed and in addition, thermal stability and hydrogen (H2) and carbon-dioxide (CO2) adsorption properties of Cd-ADA-1, Mn-ADA-1 and Zn-ADA-1 are also presented. Hydrogen sorption at 77 K and up to 1 atm is found to be 0.42, 0.72 and 1.36 wt% without saturation for Zn-ADA-1, Mn-ADA-1 and Cd-ADA-1 samples.