Light driven mesoscale assembly of a coordination polymeric gelator into flowers and stars with distinct properties

Control over the self-assembly process of porous organic–inorganic hybrids often leads to unprecedented polymorphism and properties. Herein we demonstrate how light can be a powerful tool to intervene in the kinetically controlled mesoscale self-assembly of a coordination polymeric gelator. Ultraviolet light induced coordination modulation via photoisomerisation of an azobenzene based dicarboxylate linker followed by aggregation mediated crystal growth resulted in two distinct morphological forms (flowers and stars), which show subtle differences in their physical properties

対流圏に見られる鉛直微細構造

We report the design, synthesis, detailed characterization, and analysis of a new multifunctional pi-conjugated bola-amphiphilic chromophore: oligo-(p-phenyleneethynylene)-dicarboxylic acid with dialkoxyoctadecyl side chains (OPE-C-18-1). OPE-C-18-1 shows two polymorphs at 123 K (OPE-C-18-1') and 373 K (OPE-C-18-1 `'), whose crystal structures were characterized via single crystal X-ray diffraction. OPE-C-18-1 also exhibits thermotropic liquid crystalline property revealing a columnar phase. The inherent pi-conjugation of OPE-C-18-1 imparts luminescence to the system. Photoluminescence measurements on the mesophase also reveal similar luminescence as in the crystalline state. Additionally, OPE-C-18-1 shows mechano-hypsochromic luminescence behavior. Density functional theory (DFT)-based calculations unravel the origins behind the simultaneous existence of all these properties. Nanoindentation experiments on the single crystal reveal its mechanical strength and accurately correlate the molecular arrangement with the liquid crystalline and mechanochromic luminescence behavior

Charge-assisted soft supramolecular porous frameworks: effect of external stimuli on structural transformation and adsorption properties

Four novel supramolecular frameworks {(H2–bpee)4[Fe(CN)6]2·9H2O} (1), {(H2–bpee)(H3O)2[Fe(CN)6]·2H2O} (2), {[(H2-bpee)(H-bpee)]2[Fe(CN)6]2·5H2O} (3), and {[(H1.5–bpee)2][Fe(CN)6]·6H2O}, (4) [bpee = 1,2-bis(4–pyridyl)ethylene] have been synthesized by the reaction of bpee and K4[Fe(CN)6] (for 1 and 2) or K3[Fe(CN)6] (for 3 and 4) in aqueous medium. The supramolecular structures are constructed by cooperative noncovalent hydrogen bonding and π···π interactions between protonated bpee, [Fe(CN)6]3/4–, and crystalline water molecules. All the supramolecular soft hosts transformed to two different states depending upon the dehydration condition, as observed from the PXRD patterns. When the compounds were activated under vacuum at 373 K (1′–4′), they exhibit different adsorption behavior with different adsorbates like H2O, MeOH, and EtOH compared to when they were activated under high vacuum at room temperature for 24 h (1″–4″). Desolvated compounds 1′–4′ show gradual uptake of water, while multistep water adsorption profiles were observed with 1″–4″, suggesting a difference in hydrophilicity in these two sets of compounds. Further, 1′–4′ and 1″–4″ unveil type I and double step MeOH (at 293 K) adsorption profiles, respectively, which have been correlated to guest-induced structural transformation in the desolvated soft frameworks obtained at two different activation conditions

High heat of hydrogen adsorption and guest-responsive magnetic modulation in a 3D porous pillared-layer coordination framework

A bimetallic pillared-layer coordination framework {[Mn<SUB>3</SUB>(bipy)<SUB>3</SUB>(H<SUB>2</SUB>O)<SUB>4</SUB>][Cr(CN)<SUB>6</SUB>]<SUB>2</SUB>·2(bipy)·4(H<SUB>2</SUB>O)}<SUB>n</SUB> has been constructed using a cyanometallate anion ([Cr(CN)<SUB>6</SUB>]<SUP>3−</SUP>) and an organic linker (4,4′-bipyridyl) that provides high heat of hydrogen adsorption (∼11.5 kJ mol<SUP>-1</SUP>) and shows guest dependent magnetic modulation

A bimodal anionic MOF: turn-off sensing of Cu<SUP>II</SUP> and specific sensitization of Eu<SUP>III</SUP>

A novel porous anionic MOF {[Mg<SUB>3</SUB>(ndc)<SUB>2.5</SUB>(HCO<SUB>2</SUB>)<SUB>2</SUB>(H<SUB>2</SUB>O)][NH<SUB>2</SUB>Me<SUB>2</SUB>]·2H<SUB>2</SUB>O·DMF} (1) having exchangeable dimethyl amine cations in 1D channels has been synthesized and characterized. Through cation exchange, 1 manifests bimodal functionality, being a turn-off sensor of Cu<SUP>II</SUP> on one hand, and a selective sensitizer of Eu<SUP>III</SUP> emitting intense pure red emission on the other

Stoichiometry-Controlled Two Flexible Interpenetrated Frameworks: Higher CO₂ Uptake in a Nanoscale Counterpart Supported by Accelerated Adsorption Kinetics

Here, we report the synthesis, structural characterizations, and gas storage properties of two new 2-fold interpenetrated 3D frameworks, {[Zn₂(bpdc)₂(azpy)]·2H₂O·2DMF}_<i>n</i> (<b>1</b>) and {[Zn₃(bpdc)₃(azpy)]·4H₂O·2DEF}_<i>n</i> (<b>2</b>) [bpdc = 4,4′-biphenyldicarboxylate; azpy = 4,4′-azobipyridine], obtained from the same set of organic linkers. Furthermore, <b>1</b> has been successfully miniaturized to nanoscale (<b>MOF1N</b>) of spherical morphology to study size dependent adsorption properties through a coordination modulation method. The two different SBUs, dinuclear paddle-wheel {Zn₂(COO)₄} for <b>1</b> and trinuclear {Zn₃(μ₂-OCO)₂(COO)₄ }­for <b>2</b>, direct the different network topologies of the frameworks that render different adsorption characteristics into the systems. Both of the frameworks show guest induced structural transformations as supported by PXRD studies. Adsorption studies of <b>1</b> and <b>2</b> show CO₂ selectivity over several other gases (such as N₂, H₂, O₂, and Ar) under identical experimental conditions. Interestingly, <b>MOF1N</b> exhibits significantly higher CO₂ storage capacity compared to bulk crystals of <b>1</b> and that can be attributed to the smaller diffusion barrier at the nanoscale that is supported by studies of adsorption kinetics in both states. Kinetic measurement based on water vapor adsorption clearly distinguishes between the rate of diffusion of bulk (<b>1</b>) and nanospheres (<b>MOF1N</b>). The respective kinetic rate constant (<i>k</i>, s^–1) for <b>MOF1N</b> (<i>k</i> = 1.29 × 10^–2 s^–1) is found to be considerably higher than <b>1</b> (<i>k</i> = 7.1 × 10^–3 s^–1) as obtained from the linear driving force (LDF) model. This is the first account where a new interpenetrated MOF has been scaled down to nanoscale through a coordination modulation method, and their difference in gas uptake properties has been correlated through a higher rate of mass diffusion as obtained from kinetics of adsorption

Three-dimensional metal–organic framework with highly polar pore surface: H<SUB>2</SUB> and CO<SUB>2</SUB> storage characteristics

A three-dimensional (3D) pillared-layer metal–organic framework, [Cd(bipy)0.5(Himdc)](DMF)]n (1), (bipy =4,4′-bipyridine and Himdc = 4,5-imidazoledicarboxylate) has been synthesized and structurally characterized. The highly rigid and stable framework contains a 3D channel structure with highly polar pore surfaces decorated with pendant oxygen atoms of the Himdc linkers. The desolvated framework [Cd(bipy)0.5(Himdc)]n (1′) is found to exhibit permanent porosity with high H2 and CO2 storage capacities. Two H2 molecules occluded per unit formula of 1′ and the corresponding heat of H2 adsorption (&#x00394;HH2) is about ∼9.0 kJ/mol. The high value of &#x00394;HH2 stems from the preferential electrostatic interaction of H2 with the pendent oxygen atoms of Himdc and aromatic bipy linkers as determined from first-principles density functional theory (DFT) based calculations. Similarly, DFT studies indicate CO2 to preferentially interact electrostatically (C&#x003B4;+···O&#x003B4;-) with the uncoordinated pendent oxygen of Himdc. It also interacts with bipy through C–H···O bonding, thus rationalizing the high heat (&#x00394;HCO2 ∼ 35.4 kJ/mol) of CO2 uptake. Our work unveiled that better H2 or CO2 storage materials can be developed through the immobilization of reactive hetero atoms (O, N) at the pore surfaces in a metal–organic framework

Charge-Assisted Soft Supramolecular Porous Frameworks: Effect of External Stimuli on Structural Transformation and Adsorption Properties

Four novel supramolecular frameworks {(H₂–bpee)₄[Fe­(CN)₆]₂·9H₂O} (<b>1</b>), {(H₂–bpee)­(H₃O)₂[Fe­(CN)₆]·2H₂O} (<b>2</b>), {[(H₂-bpee)­(H-bpee)]₂[Fe­(CN)₆]₂·5H₂O} (<b>3</b>), and {[(H_1.5–bpee)₂]­[Fe­(CN)₆]·6H₂O}, (<b>4</b>) [bpee = 1,2-bis­(4–pyridyl)­ethylene] have been synthesized by the reaction of bpee and K₄[Fe­(CN)₆] (for <b>1</b> and <b>2</b>) or K₃[Fe­(CN)₆] (for <b>3</b> and <b>4</b>) in aqueous medium. The supramolecular structures are constructed by cooperative noncovalent hydrogen bonding and π···π interactions between protonated bpee, [Fe­(CN)₆]^3/4–, and crystalline water molecules. All the supramolecular soft hosts transformed to two different states depending upon the dehydration condition, as observed from the PXRD patterns. When the compounds were activated under vacuum at 373 K (<b>1</b>′–<b>4</b>′), they exhibit different adsorption behavior with different adsorbates like H₂O, MeOH, and EtOH compared to when they were activated under high vacuum at room temperature for 24 h (<b>1</b>″–<b>4</b>″). Desolvated compounds <b>1</b>′–<b>4</b>′ show gradual uptake of water, while multistep water adsorption profiles were observed with <b>1</b>″–<b>4</b>″, suggesting a difference in hydrophilicity in these two sets of compounds. Further, <b>1</b>′–<b>4</b>′ and <b>1</b>″–<b>4</b>″ unveil type I and double step MeOH (at 293 K) adsorption profiles, respectively, which have been correlated to guest-induced structural transformation in the desolvated soft frameworks obtained at two different activation conditions