Anionic Guests Research Articles

Intercalation of Fenoprofen into Layered Double Hydroxide for the Formation of Controlled Release Anti-Inflammatory Drug

Synthesis of a new hybrid nanocomposite materials, zinc-aluminium-fenoprofen, ZAF was successfully accomplished by self-assembly method with molar ratio of Zn to Al; R=2 at concentration of fenoprofen=0.3 M. As a result of the successful intercalation, the interlayer spacing expanded from 9.8 Å in the zinc-aluminium-layered double hydroxide, ZAL to 20.1 Å in the ZAF hybrid nanocomposite. The FTIR spectra of the ZAF show resemblance peaks of ZAL and fenoprofen indicating the inclusion of the organic compound into the LDH interlamellae. The percentage loading of the guest anion, fenoprofen in ZAL was estimated to be about 63.4% (w/w) calculated from the carbon content.

Guest-Induced Modulation of the Energy Transfer Process in Porphyrin-Based Artificial Light Harvesting Dendrimers.

A series of dendritic multiporphyrin arrays (PZnTz-nPFB; n = 2, 4, 8) comprising a triazole-bearing focal zinc porphyrin (PZn) with a different number of freebase porphyrin (PFB) wings has been synthesized, and their photoinduced energy transfer process has been evaluated. UV/vis absorption, emission, and time-resolved fluorescence measurements indicated that efficient excitation energy transfer takes place from the focal PZn to PFB wings in PZnTz-nPFB's. The triazole-bearing PZn effectively formed host-guest complexes with anionic species by means of axial coordination with the aid of multiple C-H hydrogen bonds. By addition of various anionic guests to PZnTz and PZnTz-nPFB's, strong bathochromic shifts of PZn absorption were observed, indicating the HOMO-LUMO gap (ΔEHOMO-LUMO) of PZn decreased by anion binding. Time-resolved fluorescence measurements revealed that the fluorescence emission predominantly takes place from PZn in PZnTz-nPFB's after the addition of CN-. This change was reversible because a treatment with a silver strip to remove CN- fully recovered the original energy transfer process from the focal PZn to PFB wings.

Synthesis, characterization and controlled release properties of zinc–aluminium-beta-naphthoxyacetate nanocomposite

An organic–inorganic nanohybrid nanocomposite was synthesized by co-precipitation method using beta-naphthoxyacetate (BNOA) as guest anion and zinc–aluminium layered double hydroxide (Zn–Al-LDH) as the inorganic host. A well-ordered nanohybrid nanocomposite was formed when the concentration of BNOA was 0.08 M and the molar ratio of Zn to Al, R = 2. Basal spacing of layered double hydroxide containing nitrate ions expanded from 8.9 to 19.5 A in resulting of Zn–Al-BNOA nanocomposite was obtained indicates that beta-naphthoxyacetate was successfully intercalated into interlayer spaces of layered double hydroxide. It was also found out the BET surface area increased from 1.13 to 42.79 m2 g−1 for Zn–Al-LDH and Zn–Al-BNOA nanocomposite, respectively. The BJH average pore diameter of the synthesized nanocomposite is 199 A which shows mesoporous-type of material. CHNS analysis shows the Zn–Al-BNOA nanocomposite material contains 36.2 % (w/w) of BNOA calculated based on the percentage of carbon in the sample. Release of BNOA from the lamella of Zn–Al-BNOA was controlled by the zeroth and first order kinetics at the beginning of the deintercalation process up to 200 min and controlled by pseudo-second order kinetics for the whole process. This study suggests that layered double hydroxide can be used as a carrier for organic acid herbicide controlled release formulation of BNOA.

Anion Recognition by Aliphatic Helical Oligoureas

AbstractInvited for the cover of this issue is the group of Gilles Guichard at the University of Bordeaux. The image depicts the interaction between a 2.5‐helical oligourea foldamer and an anionic guest symbolized as a soccer ball. Read the full text of the article at 10.1002/chem.201602481.

Pathway-Dependent Post-assembly Modification of an Anthracene-Edged M(II)4L6 Tetrahedron.

Fe(II)4L6 tetrahedral cage 1 undergoes post-assembly modification (PAM) via a Diels-Alder cycloaddition of the anthracene panels of the cage with tetracyanoethylene (TCNE). The modified cage 2 possesses an enclosed cavity suitable for encapsulation of the fullerene C60, whereas original cage 1 forms a unique covalent adduct through a Diels-Alder cycloaddition of three of its anthracene ligands with C60. This adduct undergoes further PAM via reaction of the remaining three ligands with TCNE, enabling the isolation of two distinct products depending on the order of addition of C60 and TCNE. Modified cage 2 was also able to bind an anionic guest, [Co(C2B9H11)2](-), which was not encapsulated by the original cage, demonstrating the potential of PAM for tuning the binding properties of supramolecular hosts.

Diamidonaphthalenodipyrrole-derived fluorescent sensors for anions

We describe the synthesis and properties of bisamide derivatives of naphthalenedipyrrole, which represent a convenient platform for the construction of fluorescent anion sensors. As we show, the spectroscopic properties of such sensors can be fine-tuned through small modifications of the structure at the sensor periphery. The strong fluorescence of these compounds is perturbed through the binding of anionic species in the binding pocket through four hydrogen bonds. Importantly, these effects depend on the nature of the anionic guest, its concentration, and the specific structure of the receptor host. For instance, in the case of one derivative (2a) the fluorescence is selectively quenched upon addition of PhCO2−, while other anions do not have an effect on its spectral properties. In another case (2b), only H2PO4− triggers a spectacular enhancement of fluorescence (more than five times higher intensity), while other anions do not change its spectral properties. Such selective responses are related to the selectivity of the anionic species binding, which can be controlled with the structure of the binding pocket. Overall, the study demonstrates that a diamidonaphthalenedipyrrole platform can be used to construct selective sensors for anions that allow for fast and efficient identification of the desired anion present in the analytical samples.

Guest‐Induced, Self‐Assembled Supramolecular Capsule: Effect of Guest and Counter Anions

AbstractMolecular capsules form due to various interactions between molecules. Cyclotricatechylene (CTC) is a poly‐phenolic macrocycle that has been shown to form capsule under highly basic conditions. Here, we describe the formation of a molecular capsule under ambient conditions, from CTC by addition of a guest molecule. The capsule is most probably forming through pure electrostatic interaction between the guest and CTC. The capsule formation has been studied using solution techniques such as NMR and Mass spectroscopy. The information about capsule formation is also obtained from the solid state structure using single crystal X‐ray diffraction studies, which corroborates well with the findings in solution state. Upon changing the cation to a larger one, both capsule formation and the encapsulation are hindered. However, change of anions keeping the cation unchanged does not affect the assembly process.

Cofactor-Controlled Chirality of Tropoisomeric Ligand

A new tropos ligand with an integrated anion receptor site has been prepared. Chiral carboxylate and phosphate anions that bind in the anion receptor unit proved capable of stabilizing chiral conformations of the achiral flexible bidentate biaryl phosphite ligand, as shown by variable temperature 1H and 31P NMR spectroscopical studies of palladium(0) olefin complexes. Palladium allyl complexes of the supramolecular ligand-chiral cofactor assemblies catalyzed asymmetric allylic substitutions of rac-(E)-1,3-diphenyl-2-propenyl carbonate and rac-3-cyclohexenyl carbonate with malonate and benzylamine as nucleophiles to provide nonracemic products. Although moderate enantioselectivities were observed, (ee:s up to 66%), the results confirm the ability of the anionic guests to affect the conformation of the ligand.

Development of a novel nanocomposite consisting of 3-(4-methoxyphenyl)propionic acid and magnesium layered hydroxide for controlled-release formulation

ABSTRACTMagnesium layered hydroxide (MLH) intercalated with anionic 3-(4-methoxyphenyl)propionic acid (MPP) was synthesised by a direct reaction method using magnesium oxide and MPP as precursors. A further coating of chitosan was applied on the external surface of MLH–MPP nanocomposite to form a new material, named MLH–MPP/chitosan nanocomposite. The XRD pattern showed an intense and sharp peak at basal spacing 18.9 Å, proving that MPP anions were successfully intercalated into the interlayer gallery of MLH in a monolayer arrangement. The XRD pattern of the MLH–MPP/chitosan nanocomposite shows similar peaks with the MLH–MPP nanocomposite. The result was also supported by FTIR spectra and elemental analysis. TGA/DTG spectra showed that the thermal stabilities of the guest anion in the both nanocomposites were markedly enhanced. A controlled-release study of the MPP ion from the MLH–MPP/chitosan nanocomposite showed a slower release compared to MLH–MPP nanocomposite with an initial rapid release and slow release thereafter. Meanwhile, the release behaviours of MPP ions from both nanocomposites were governed by pseudo-second order kinetics. This result highlights the potential of the nanocomposite as an encapsulated material for the controlled-release formulation of MPP anions.

Synthesis of Water-Soluble Cyclophane Hexamers Having a Triphenylene Core and Their Enhanced Guest-Binding Behavior.

A key compound, a precursor of water-soluble cyclophane hexamer, was prepared via Williamson ether synthesis of tetraaza[6.1.6.1]paracyclophane derivatives bearing a bromoacetamide moiety with triphenylene-2,3,6,7,10,11-hexaol as a core. A cationic cyclophane hexamer (1) was obtained by removing the protecting groups from the precursor. Fluorescence titration experiments proved that cationic cyclophane hexamer 1 showed macrocyclic multivalency effects; i.e., 1:1 host/guest binding constants (K) of 1 with anionic guests, 6-anilinonaphthalene-2-sulfonate and 6-p-toluidinonaphthalene-2-sulfonate, were increased about 63- and 62-fold, respectively, relative to those of monomeric cyclophane. Similarly, anionic cyclophane hexamer 2, which was easily prepared from 1, showed macrocyclic multivalency effects in K values with cationic guests such as hydrochlorides of doxorubicin and daunorubicin as an anticancer drug.

Double‐Decker Coordination Cages

Bis(pyridin‐3‐ylmethyl) pyridine‐3,5‐dicarboxylate (L) possessing one internal and two terminal pyridine moieties displayed differential coordination ability when combined with suitable PdII components. The compound L acted as a bidentate chelating ligand to form mononuclear complexes when combined with cis‐[Pd(tmeda)(NO3)2] or Pd(NO3)2 in calculated ratios. The combination of Pd(NO3)2 with L in a ratio of 3:4, however, afforded the trinuclear “double‐decker” cage [(NO3)2⊂Pd3(L)4](NO3)4, in which L acts as a nonchelating tridentate ligand and the counter anion (i.e., NO3–) acts as template. The encapsulated NO3– can be replaced by F–, Cl–, or Br– but not by I–. The F–‐encapsulated cage could not be isolated due to its reactivity, whereas the Cl– or Br– encapsulated cages could be isolated. Although anionic guests such as NO3–, Cl–, or Br– stabilized the cages, the presence of excess Cl– or Br– (not NO3–) facilitated decomplexation reactions releasing the ligand. The complexation of Pd(Y)2 (Y = BF4–, PF6–, CF3SO3–, or ClO4–) with L afforded the corresponding mononuclear complexes under appropriate conditions. However, these counter anions could not act as templates for the construction of double‐decker cages.

A Room‐Temperature Luminescent AgCF3COO Complex Consisting of Cationic Complex Chains and Anionic Guests

AbstractReaction of p‐phenylenediacetonitrile (p‐phda) with AgCF3COO afforded the coordination polymer, {[Ag2(p‐phda)2] [Ag4(CF3COO)6]}n (1), where the 1D cationic [Ag2(p‐phda)2]2+ chain acts as host and the anionic [Ag4(CF3COO)6]2– as guest molecules occupy the channel between neighboring host chains. This is a rare crystal example of AgCF3COO complex consisting of cationic complex chains and anionic guests. In addition, complex 1 exhibits luminescence at room temperature in solid state.

1,3-Alternate Tetraamido-Azacalix[4]arenes as Selective Anion Receptors.

Six tetraaza[1.1.1.1]cyclophane derivatives bearing peripheral amide groups were prepared according to two distinct synthetic strategies that depend on the connection pattern between the aryl units. NMR experiments combined with the X-ray structures of two tetraamide derivatives 4 b and 10 show that these cavitands adopt a 1,3-alternate conformation both in solution and in the solid state. Consequently, the four amide groups of the aza[1.1.1.1]-m,m,m,m-cyclophane isomer 10 can contribute to the same recognition process towards neutral water molecules or anion guests. NMR experiments, mass spectrometry analyses and single-crystal X-ray structures confirm the anion-binding ability of this receptor. Absorption spectrophotometric titrations in nonpolar solvents provided evidence for the selectivity of 10 to chloride anions in the halide series, with a corresponding association constant Ka reaching 2.5 × 10(6) m(-1).

Polypyridyl-imidazole based smart Ru(II) complex mimicking advanced Boolean and Fuzzy logic functions

A terpyridyl-imidazole based heteroditopic Ru(II) complex of composition [(phen)2Ru(tpy-Hbzim-dipy)](ClO4)2] (1), where tpy-Hbzim-dipy=4′-[4-(4,5-Di-pyridin-2-yl-1H-imidazol-2-yl)-phenyl]-[2,2′;6′,2″] terpyridine and phen=1,10-phenanthroline is designed and structurally characterized in this work for the construction of multifunctional Boolean and Fuzzy logic devices. The designed complex acts as a red-color emitter and has a free terpyridine moiety which can be coordinated to a cationic guest and an imidazole motif capable of interacting with selective anionic guests through hydrogen bonding. Consequently, modulation of physicochemical properties of the complex by the anionic and cationic guests was examined through different optical channels. The metalloreceptor acts as a chromogenic sensor for F−, AcO−, CN−, and H2PO4− among the anions, while for Fe2+ among bivalent 3d cations in acetonitrile. Based on various output signals with a particular set of anionic and cationic inputs, the complex mimics the functions of four-inputs NOR logic gate and complicated function of memory device. More importantly, we also report the implementation of Fuzzy logic approach to develop an infinite-valued logic system based on either the absorbance or luminescence dependence of the complex upon concentration of different ionic inputs. In conjunction with the experimental investigation, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) studies were also carried out to investigate the structural and electronic properties of the receptor.

Low‐Overpotential Li–O2 Batteries Based on TFSI Intercalated Co–Ti Layered Double Oxides

Lithium–oxygen batteries with an exceptionally high theoretical energy density have triggered worldwide interest in energy storage system. The research focus of lithium–oxygen batteries lies in the development of catalytic materials with excellent cycling stability and high bifunctional catalytic activity in oxygen reduction and oxygen evolution reactions. Here, a hierarchically porous flower‐like cobalt–titanium layered double oxide on nickel foam with intercalated anions of bistrifluoromethane sulfonamide (TFSI) is designed and prepared. When used as a binder‐free cathode for lithium–oxygen batteries, this material exhibits low polarization (initial polarization of 0.45 V) and superior cycling stability (80 cycles at a current density of 100 mA g−1 at full discharge/charge). The high electrochemical performance of the cathode material is attributed to the good dispersion of binary elements in its host layer and good compatibility with lithium bistrifluoromethane sulfonamide electrolyte induced by intercalated guest anions of TFSI within its interlayer. This work provides a novel strategy for the fabrication of binder‐free cathodes based on layered double oxides for high‐performance lithium–oxygen batteries.

Biasing hydrogen bond donating host systems towards chemical warfare agent recognition.

A series of neutral ditopic and negatively charged, monotopic host molecules have been evaluated for their ability to bind chloride and dihydrogen phosphate anions, and neutral organophosphorus species dimethyl methylphosphonate (DMMP), pinacolyl methylphosphonate (PMP) and the chemical warfare agent (CWA) pinacolyl methylphosphonofluoridate (GD, soman) in organic solvent via hydrogen bonding. Urea, thiourea and boronic acid groups are shown to bind anions and neutral guests through the formation of hydrogen bonds, with the urea and thiourea groups typically exhibiting higher affinity interactions. The introduction of a negative charge on the host structure is shown to decrease anion affinity, whilst still allowing for high stability host-GD complex formation. Importantly, the affinity of the host for the neutral CWA GD is greater than for anionic guests, thus demonstrating the potential for selectivity reversal based on charge repulsion.

Tris-ureas as transmembrane anion transporters.

Nine tris-urea receptors (L(1)-L(9)) have been synthesised and shown to coordinate to a range of anionic guests both by (1)H NMR titration techniques and single crystal X-ray structural analysis. The compounds have been shown to be capable of mediating the exchange of chloride and nitrate and also chloride and bicarbonate across POPC or POPC : cholesterol 7 : 3 vesicle bilayer membranes at low transporter loadings. An interesting dependency of anion transport on the nature of the cation is evidence to suggest that a M(+)/Cl(-) cotransport process may also contribute to the release of chloride from the vesicles.

Highly selective binding of methyl orange dye by cationic water-soluble pillar[5]arenes.

A new water-soluble pillar[5]arene with an amide fragment and triethylammonium groups was synthesized by our original method of aminolysis of the ester groups. Using UV-spectroscopy, it is shown that cationic pillar[5]arenes are able to selectively form 1 : 1 complexes with some hydrophobic anions: the guests with bulky uncharged or negatively charged substituents hindering entry into the macrocycle cavity. Highly selective binding of the most lipophilic guest, methyl orange dye, in the form of organic anion salts by positively charged water-soluble pillar[5]arenes was detected. In the case of the azo dye the appropriate Kass values were 10-100-fold higher than those calculated for the other sulfonic acid derivatives studied. The 2D NMR NOESY (1)H-(1)H spectroscopy confirms the formation of the inclusion complex: negative charge sulfonate head is outside the cavity of pillar[5]arenes and the hydrophobic fragment of the guest is located in the cavity.

Polypyridyl-imidazole based Os(II) complex as optical chemosensor for anions and cations and multi-readout molecular logic gates and memory device: Experimental and DFT/TDDFT study

A monometallic Os(II) complex of composition, [(bpy)2OsII(phen-Hbzim-tpy)](ClO4)2, where phen-Hbzim-tpy=2-(4-(2,6-di(pyridin-2-yl)pyridine-4-yl)phenyl)-1H-imidazole[4,5-f] [1,10]phenanthroline and bpy=2,2′-bipyridine, containing a free terpyridine site for cationic guest and an imidazole moiety for the anionic guest, has been designed for the fabrication of multifunctional logic circuits. This complex acts a red-color emitter and effective bifunctional optical chemosensor for F− and CN− as well as Fe2+ and Cu2+ ions. The anion and cation sensing properties of the metalloreceptor have been thoroughly investigated in solution through different channels such as absorption, steady state and time-resolved emission spectroscopic methods and by square wave voltammetric technique. On the basis of the absorption, emission and electrochemical responses with specific set of anionic and cationic inputs, the present metalloreceptor finds its ability to mimic the logic functions of two-inputs INHIBIT, IMPLICATION, and OR logic gate as well as four inputs NOR logic behavior. Moreover, the complex can mimic sequential Boolean logic functions capable of integrating into “Writing–Reading–Erasing–Reading” combinational circuit for molecular-level information processing. To gain a deeper insights about the structural as well as spectral aspects of the complex, theoretical calculations have also been performed employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT).

Comparison of the selectivity of [M(12-Crown-4)]+ (M=Li+, Na+, K+) complexes for halide anions and some neutral molecules; a computational study

A theoretical study on the selectivity of a series of [M(12C4)][Formula: see text] (M = Li[Formula: see text], Na[Formula: see text], K[Formula: see text], 12C4 = 12-crown-4) complexes for F[Formula: see text], Cl[Formula: see text] and Br[Formula: see text] anions and a number of neutral molecules (CH3CN, CH3OH, NH3, H2O, py, and 12C4) is reported. At first, it was shown that in the gas phase among all studied halide anions and neutral molecules, halides have much more bonding interaction with all [M(12C4)][Formula: see text] cations. Calculated interaction energies of above anions and [M(12C4)][Formula: see text] cations decrease from F[Formula: see text] to Br[Formula: see text]. Also the interaction energy of halide anions with [M(12C4)][Formula: see text] complexes, decreases from [Li(12C4)][Formula: see text] to [K(12C4)][Formula: see text]. The electron decomposition analysis showed that the bond between [M(12C4)][Formula: see text] complexes and both the neutral and anion guests is mainly electrostatic in nature. Then the selectivity of [M(12C4)][Formula: see text] complexes for studied anions and neutral molecules are compared in methanol, acetone, acetonitrile, and nitromethane solutions. It was shown that both the desolvation process of reactants and the strength of host–guest interactions have significant effect on the selectivities. Thus the selectivity of [Li(12C4)][Formula: see text] cation for NH3and H2O neutral molecules in solution, in contrast to the gas phase, is higher than that for bromide anion. The results of calculations showed that all [M(12C4)][Formula: see text] complexes, specially [Li(12C4)][Formula: see text], have high selectivity for F[Formula: see text] over other halide anions and neutral molecules.