Encapsulated Complex Research Articles

Structure, Stability, and Properties of Boron Encapsulated Complexes of C60, C59B, and C59N.

Density functional studies are performed for the boron atom encapsulated complexes of C60, C59B, and C59N using B3LYP and B3LYP-GD2 functionals with 6-311G* basis set. The study shows that the complexes B@C59B and B@C59N can exist in different forms which differ in their structure as well as electronic and magnetic properties. The nature of interaction between the guest and the host is analyzed based on the stabilization energies of complexes for their different spin states. The electronic properties such as vertical electron affinity (VEA), vertical ionization energy (VIE), and energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the complexes are calculated. The transfer of electron spin density and spin-spin coupling of electrons between the guest and the host are examined. The study reveals that ferromagnetic core@shell spin coupling occurs between the host and the guest species of the complexes B@C59B and B@C59N in their triplet state without any transfer of spin density. The values of hyperfine coupling constant (hfcc) for the heteroatom of the cage and for the encapsulated boron atom of the complexes are analyzed, and it indicates that the value of hfcc for the encapsulated boron decreases significantly due to confinement.

Tetramethylcucurbit[6]uril-triggered fluorescence emission and its application for recognition of rare earth cations

The host–guest interaction between tetramethylcucurbit[6]uril (TMeQ[6]) and 2-(4-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline hydrochloride salt (guest 1) has been investigated. 1H NMR results have confirmed the formation of an encapsulated complex, and fluorescence titration implies an interaction ratio of 1:1 with a moderate association constant of Ka=4.0×106Lmol−1. The triggered fluorescence emission of guest 1 by TMeQ[6] has been developed to achieve a supramolecular probe capable of recognizing La3+ and Ce3+ through a dramatic decrease in fluorescence intensity, whereas there is minimal difference upon the introduction of Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Er3+, or Tm3+. Combined evidence from 1H NMR, IR, and fluorescence titration supports coordination of the inclusion complex to La3+ and Ce3+, with association constants of 1.1×104Lmol−1 and 1.0×104Lmol−1, respectively. The linear decrease in fluorescence intensity in response to different concentrations of La3+ or Ce3+ gives a low limit of detection (LOD) of 1.1×10−8molL−1.

Encapsulation of Cu(II)[2-(2′-hydroxyphenyl)benzimidazole]2 within zeolite nano-cavity: Structural properties and its catalytic activity towards phenol and styrene oxidation

The Cu(opbmzl)2 [ohpbmzl=2-(2′-hydroxyphenyl)benzimidazole] was encapsulated within the super-cage of zeolite-Na-Y through a facile ligand approach and characterized by various analytical techniques such as elemental analysis, X-ray diffraction, inductively coupled plasma-atomic emission, FT-IR, UV–vis-DRS and EPR spectroscopy, thermogravimetric analysis (TGA), BET surface area measurements, pore volume by Horvath-Kawazoe (HK) method and cyclic voltammetry (CV). The shifting of the absorption bands and changes in redox properties of intra-zeolite complex compared to non-encapsulated complex implicated that the zeolite matrix remarkably influenced the structure-electronic properties. The peak potentials of Cu(opbmzl)2-Y in cyclic voltammogram were independent of scan rates, further corroborating the intrazeolite mechanism for electron-transfer-pathway in the zeolite-Y. The catalytic activity of Cu-Y, non-encapsulated and encapsulated complex was evaluated for phenol and styrene oxidation. As very low selectivity and formation of tarry products (for phenol oxidation) prevailed with t-butyl hydroperoxide (TBHP), H2O2 was reported to be the reasonable oxidant for the probe reactions. The influence of reaction parameters such as catalyst dosage, substrate concentration, substrate: H2O2 mole-ratio, temperature, time and solvent effects were investigated in detail. All the reaction parameters investigated were very crucial in tuning the product selectivity and conversion efficiency. The encapsulated complex exhibited better catalytic activity and selectivity than the non-encapsulated complex for the probe reactions, associated with exceptional structural stability during the recycling process. From the results, it was derived that the reactions proceeded without the involvement of free radicals and the probable mechanistic pathways based on the intermediate complexes associated with Cu-O species were proposed tentatively.

Zeolite-Y encapsulated VO[2-(2′-hydroxyphenyl)benzimidazole] complex: investigation of its catalytic activity towards oxidation of organic substrates

Zeolite-Y encapsulated VO(IV)2-(2′-hydroxyphenyl)benzimidazole (ohpbmzl) was synthesized by flexible ligand approach and characterized using various physico-chemical techniques such as elemental analysis, XRD, inductively coupled plasma-atomic emission, fourier transform infrared spectroscopy, UV–vis-diffuse reflectance and electron paramagnetic resonance spectroscopy, thermogravimetric analysis, BET surface area and cyclic voltammetry (CV). Based on the results a square pyramidal structure was suggested for the encapsulated complex. Shift in UV absorbance to higher wavelength and variations in the redox potential values compared to the non-encapsulated complex in CV confirmed the successful encapsulation of the complex in the zeolite matrix. The catalytic efficacy was investigated towards oxidation of phenol, styrene, cyclohexane and ethyl benzene in acetonitrile using H2O2 as oxidant. Influence of reaction parameters like catalyst and substrate concentration, substrate/H2O2 molar ratio, and temperature were investigated to optimize the reaction conditions for maximum substrate conversion and selectivity towards desired products using the encapsulated complex. The catalytic activity was compared with vanadyl exchanged zeolite-Y (VO-Y) and non-encapsulated complex. The encapsulated complex retained its stability up to 3 runs as confirmed by recycling studies. Mechanistic pathways were proposed for all the probe reactions.

Novel Polymeric Nanoformulation of Mancozeb – An Eco-Friendly Nanomaterial

The best alternative to conventional pesticides is nanopesticide. Severe pollution is caused due to the rapid degradation and uncontrolled, unconstrained utilization of conventional pesticides. Nanopesticides can provide better penetration through the plants and control different diseases. Nanoformulation of pesticide certainly protects the premature degradation in the environment and delivers high impact on target species. Less environmental contamination and safe handling are the advantages of nanopesticides. In this paper, we reported the novel nano-mancozeb pesticide for plant disease control. Our study provides a novel nanoformulation of mancozeb pesticide by using Polyethylene glycol as a capping agent. Nanoparticles of the encapsulated complex were characterized by UV-Vis, Dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), and transmission electron microscopy (TEM). Biological evaluation was conducted against Candida albicans and Staphylococcus aureus. The developed method is useful to farmers and it is an eco-friendly pesticide formulation.

Characteristics of menthone encapsulated complex by mungbean, tapioca, and rice starches

ABSTRACTIn order to use commercial starch for flavor encapsulation, three starches (mungbean, rice, and tapioca) were selected to determine their ability to form inclusion complex with menthone. Mungbean starch had the highest amylose content, followed by rice starch and tapioca starch, respectively. After complexation, appearance and microstructure changes were observed for all starches. Mungbean and tapioca complexes with well-organized V7 crystalline pattern gave similar menthone entrapment (around 4%) which was higher than that of the rice sample (<1%). Molecular size distribution of the complexes revealed the role of amylose fractions for both mungbean and tapioca complexes. According to differential scanning calorimetric analysis, menthone complexes formation was confirmed by a thermoreversible event. Regarding the high yield of starch precipitate and menthone entrapment, mungbean starch is considered a more suitable material for menthone encapsulation rather than tapioca and rice starches.

Investigation of different methods for cisplatin loading using single-walled carbon nanotube

Cisplatin as an anticancer drug is frequently used in cancer treatment, but with a lot of side effects. In this study, we investigated three different protocols of cisplatin drug loading inside and outside of single-walled carbon nanotube as a nano-platform. The drug encapsulation, electrostatic interactions, and covalent binding of cisplatin were utilized in these complexes to evaluate the capability of drug–carrier interaction in each method. All nanotube samples were dialyzed after preparation in phosphate buffer saline at acidic and neutral conditions for better simulation of tumor environments and then, the rate of drug release was determined using drug concentrations from the inside and outside of dialysis bags in the samples. Cisplatin showed the maximum and minimum rate of release for covalent and encapsulated complexes, respectively. Also, the amount of cisplatin drug release was quite different for two compounds at the beginning and at the end of dialysis. These trends of drug release in each of these drug loading approaches in different pH environments can help us to manage the optimized circulation time of cisplatin in the human body and the maximum release of drug at the target position.

A low-temperature fast curing latent catalyst microencapsulated in a porous resin structure

Low-temperature, fast curing latent catalysts for epoxides were prepared by microencapsulation of aluminum complexes through interfacial and radical polymerization. The resulting resin microcapsules were thermally responsive. Moreover, because the inside of the capsule had a porous structure, a highly active aluminum complex could be forced into the capsule by solvent penetration. The differential scanning calorimetric curve of the encapsulated complex showed an exothermic peak at 100°C or less. In addition, after a mixture of bisphenol A epoxy resin, the curing catalyst, and triphenyl silanol was stored for 5000h at 30°C, the viscosity was only 1.6 times greater than the viscosity just after blending.

Highly efficient heterogeneous catalysts for phenol oxidation: Binuclear pyrrolyl-azine metal complexes encapsulated in NaY zeolite

Phenol was successfully oxidized by the heterogeneous catalysts based on iron(II) or copper(II) pyrrolyl-azine complexes encapsulated into NaY zeolite, under mild conditions. The heterogeneous catalysts were prepared using two different methods and characterized by different spectroscopic techniques and chemical analysis. The pyrrolyl-azine complexes are formed with a metal/ligand molar ratio of 2:1. Their structures were further confirmed by DFT calculations. The catalytic experimental conditions (e.g., amount of catalyst, presence or absence of the oxidant, PhOH:tBuOOH molar ratio) were optimized. The presence of the encapsulated metal pyrrolyl-azine complexes in NaY zeolite enhances higher conversion of phenol to catechol. The catalytic activities of the encapsulated metal complexes in NaY zeolite were compared with the homogeneous counterpart, and the catalysts were easily recovered and reused.

Combined experimental and theoretical investigations on the encapsulation of nickel(ii)tet-a complex in zeolite Y and its photocatalytic activity

Photocatalytic mechanism of the 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane [tet-a] nickel(ii) encapsulated in zeolite Y.

Qualitative/Chemical Analyses of Ankaferd Hemostat and Its Antioxidant Content in Synthetic Gastric Fluids.

Introduction. Ankaferd hemostat (ABS) is the first topical haemostatic agent involving the red blood cell-fibrinogen interactions. The antihemorrhagic efficacy of ABS has been tested in controlled clinical trials. The drug induces the formation of an encapsulated complex protein web with vital erythroid aggregation. The aim of this study is to detect the essential toxicity profile and the antioxidant molecules inside ABS. Methods. The pesticides were analyzed by GC-MS and LC-MS. The determination by ICP-MS after pressure digestion was performed for the heavy metals. HPLC was used for the detection of mycotoxins. Dioxin Response Chemically Activated Luciferase Gene Expression method was used for the dioxin evaluation. TOF-MS and spectra data were evaluated to detect the antioxidants and other molecules. Results. TOF-MS spectra revealed the presence of several antioxidant molecules (including tocotrienols, vitamin E, tryptophan, estriol, galangin, apigenin, oenin, 3,4-divanillyltetrahydrofuran, TBHQ, thymol, BHA, BHT, lycopene, glycyrrhetinic acid, and tomatine), which may have clinical implications in the pharmacobiological actions of ABS. Conclusion. The safety of ABS regarding the presence of heavy metals, pesticides, mycotoxins, GMO and dioxins, and PCBs was demonstrated. Thus the present toxicological results indicated the safety of ABS. The antioxidant content of ABS should be investigated in future studies.

Encapsulation of monomers, homodimers and heterodimers of amides and carboxylic acids in three non-covalent assemblies

A structural study has been carried out involving geometry optimization of different capsules and encapsulated complexes of single monomers, homodimers and heterodimers of benzoic acid and benzamide and substituted dimers, as well as hydrogen-bonded networks of benzamide addressing experimental observation, where cages offering similar cavities but made up of slightly different cavitands result in strikingly different dimer distributions. This is attributed, according to the present results, mainly to the fact that the two cages have different formation energy and different dimer encapsulation energy. The generation of hydrogen-bonded networks of the amide in solution acts competitively to encapsulation. In addition, the trends of the different quantities associated with encapsulation such as dimerization energy, % dimer distribution and encapsulation energies, as the size of the dimers is increased, are examined. Furthermore, the efficacy of the ONIOM(DFT or MP2 and CCSD:PM6) method with respect to the calculation of % distribution of encapsulated dimers in limited cavities is studied. The results show that when the interaction of the guests with the cage is significant, the ONIOM % distributions do not agree with the experimental finding, as full DFT does, due to PM6 method, where the use of semi-empirical PM6 method changes the ordering of the low in energy encapsulated complexes.

Self-Assembly of a Tris(Urea) Receptor as Tetrahedral Cage for the Encapsulation of a Discrete Tetrameric Mixed Phosphate Cluster (H2PO4–•HPO42–)2

A tris(2-aminoethyl)amine-based tris(urea) receptor L, in the presence of excess TBA(H2PO4) self-assembled into a tetrahedral molecular cage by encapsulation of a tetrameric tetrahedral mixed phosphate cluster (H2PO4–•HPO42–)2 via 24 −NH hydrogen bonds [complex (n-TBA)6{4L(H2PO4–•HPO42–)2}] (1). Further, in the presence of orthophosphoric acid the receptor L has been observed to be self-assembled with side-cleft bonded tetrameric anion-acid cluster (H2PO4–•H3PO4)2 [complex {(LH)+(H2PO4–•H3PO4)DMSO•H 2O}] (2). In a proof of concept experiment, transformation of salt complex 2 into neutral phosphate encapsulated complex has been demonstrated in solution state by quantitative 1H NMR titration with (TBA)OH in DMSO-d6 (298 K). Extensive studies with receptor L have also been carried out with other halides in the solid state. Crystal structure elucidation revealed the formation of a pseudodimeric (2 + 2) capsular self-assembly with 1:1 host:guest ratio in fluoride encapsulated complex, (TEA)[L(F)] (3). 2D-NOESY NMR (DMSO-d6) experiments were carried out on the phosphate complexes (complexes 1 and 2) to study the binding discrepancies of phosphate anion with the neutral and charged host.

The deposition and imaging of silica sub-micron particles in dentine

ObjectivesSub-micron particles may assist in the delivery of compounds into dentine tubules. The surface interactions of the particles with dentine may prevent them from entering the tubules. The aim of this study is to investigate whether silica particles, treated with surfactants improves dentine tubules occlusion using both artificial and human tooth models MethodsSpherical silica particles (size 130–810nm) bearing an encapsulated ruthenium luminescent complex were coated with the following surfactants: Zonyl® FSA, Triton® X-100 and Tween20®. The particles were prepared as 0.004% w/v and 0.04% w/v solutions with deionized water and were applied to the surface of; (1) in vitro model of PET ThinCert™ cell culture inserts; (2) 0.1mm thick sections of human molar teeth. ResultsScanning electron and confocal fluorescence microscopy images show that particles without any coating and with TritonX-100 coating had the highest aggregation. Particles with Tween-20 are less aggregated on the surface and show inclusion in the tubules. Particles coated with fluorosurfactant Zonyl show a preference for aggregation at the tubule. With the ThinCert™ membranes high aggregation within the artificial tubules was increased by particle concentration. ConclusionsThe use of silica sub-micron particles on hard dental tissues is dependent on the modification of the surface chemistry of both the particle and the dentine and the employment of the fluorοsurfactant may improve tubule occlusion. The use of ThinCerts™ membrane is useful in vitro model to mimic dentinal tubules and observe the ability of particles to occlude small channels. Clinical significanceThe use of silica sub-micron particles on hard dentine tissues is dependent on the modification of the surface coating of the particles. This may influence how particles are incorporated in potential delivery vehicles applied to the dentine surface with the employment of a fluorosurfactant showing promise.

Efficient Host‐Guest Complexation of a Bisporphyrin Host with Electron Deficient Guests: Synthesis, Structure, and Photoinduced Electron Transfer

AbstractThe encapsulation of 1,8‐naphthalic anhydride (NAN), 9‐dicyanomethylenefluorene (9‐DCF), acenaphthenequinone (ANQ), and 4‐chloro‐7‐nitrobenzofurazan (NBD‐Cl) by diethylpyrrole‐bridged bisporphyrin (H4DEP) and its dizinc(II) analogue (Zn2DEP) are employed to investigate the structural and spectroscopic changes within the bisporphyrin cavity upon substrate binding. Synthesis and X‐ray structures of all four encapsulated host‐guest complexes (H4DEP⋅NAN, H4DEP⋅9‐DCF, Zn2DEP⋅ANQ, and Zn2DEP⋅NBD‐Cl) are reported here. The binding constant calculations show strong 1 : 1 binding between the hosts (H4DEP and Zn2DEP) and the guests (NAN/9‐DCF/ANQ/NBD‐Cl). 1H‐NMR spectra also support the retention of the host‐guest assemblies in solution. Negative and positive shifts of the reduction and oxidation potentials, respectively, indicate that it is difficult to reduce/oxidize the encapsulated complexes. The emission intensities of the bisporphyrins (H4DEP and Zn2DEP) are substantially quenched in all the complexes, owing to photoinduced electron transfer from the excited state of the bisporphyrins to guest molecules. All the experimental evidence is further substantiated by DFT calculations. Such an efficient electron transfer is only possible when the donor and the acceptor moieties are in close propinquity to each other, which eventually lowers the reorganization energy.

Arene ruthenium dithiolato–carborane complexes for boron neutron capture therapy (BNCT)

We report the effect of low-energy thermal neutron irradiation on the antiproliferative activities of a highly hydrophobic organometallic arene ruthenium dithiolato–carborane complex [Ru(p-cymene) (1,2-dicarba-closo-dodecarborane-1,2-dithiolato)] (1), and of its formulation in Pluronic® triblock copolymer P123 core–shell micelles (RuMs). Complex 1 was highly active, with and without neutron irradiation, towards human ovarian cancer cells (A2780; IC50 0.14 μM and 0.17 μM, respectively) and cisplatin-resistant human ovarian cancer cells (A2780cisR; IC50 0.05 and 0.13 μM, respectively). Complex 1 was particularly sensitive to neutron irradiation in A2780cisR cells (2.6 × more potent after irradiation compared to non-irradiation). Although less potent, the encapsulated complex 1 as RuMs nanoparticles resulted in higher cellular accumulation (2.5×), and was sensitive to neutron irradiation in A2780 cells (1.4× more potent upon irradiation compared to non-irradiation).

Flexible ligand synthesis and characterization of a host (a copper(II) tetradentate Schiff base)/guest (zeolite NaY) nanocomposite material: an efficient and reusable catalyst for the selective hydroxylation of phenol

A copper(II) complex of 2,2′-(((butane-1,4-diylbis(oxy)) bis(2,1-phenylene))bis(azanylylidene)) bis(methanylylidene))diphenol (H2L) was successfully encapsulated in the supercages of zeolite NaY by the flexible ligand method. The structure of this compound was identified by physico-chemical and spectroscopic methods. The selective hydroxylation of phenol was catalyzed using the free and encapsulated complexes. The results illustrated that the catalytic activity and stability of the complex was increased by encapsulation. Furthermore, the optimum reaction conditions were obtained. The kinetics of the reaction was also studied at different temperatures. The encapsulated complex is stable enough and it could be reused several times.

Encapsulation of a copper(II) tetradentate Schiff base complex in zeolite NaY: an efficient heterogeneous catalyst for the synthesis of benzimidazoles

A copper(II) complex of 2,2′-(((methylenebis(oxy))bis(2,1-phenylene))-bis(azanylylidene))bis(methanylylidene)) diphenol (H2L) was encapsulated in the supercages of zeolite NaY by the flexible ligand method. The resulting product was characterized by physicochemical and spectroscopic methods. The encapsulated complex and its corresponding free complex were used as catalysts for the synthesis of benzimidazoles. The results showed that the catalytic activity and stability of the complex were both increased by encapsulation. The effects of amount of catalyst, solvent, leaching and reusability of the heterogeneous catalyst were investigated.

Aluminum metal–organic framework as a new host for preparation of encapsulated metal complex catalysts

A facile strategy for encapsulation of metal complex guests into MOFs was proposed. This strategy involves pre-adsorbing metal salt on MOF, and then coordinating the metal ions with the organic ligand, as exemplified by encapsulation of tris(1,10-phenanthroline) Cu(II) complexes (CuPhen) in MIL-100(Al) (denoted as CuPhen/MIL). CuPhen encapsulated in MIL-100(Al) showed higher catalytic activity than the neat CuPhen and CuPhen encapsulated in zeolite-Y. The prepared CuPhen/MIL catalyst was stable and could be reused at least three times without significant loss in activity. This work is beneficial for the host–guest chemistry study and the development of new heterogeneous catalysts.

Photoprocess of molecules encapsulated in porous solids X: Photosensitization of zeolite-Y encapsulated tris(2,2′-bipyridine– nickel-(II)ion by phenosafranine adsorbed onto the external surface of the nanoporous host

Tris-(2,2′-bipyridine)-nickel-(II) complex ion encapsulated by zeolite-Y host has been synthesized by ship-in-a-bottle method. Photosensitization of nickel(II) complex (Ni(bpy)\(_{\mathrm {3}}^{\mathrm {2+}})\) in the zeolite host by surface adsorbed phenosafranine dye was investigated by time-resolved fluorescence and absorption spectral measurements. Formation of nickel (II)-complex in the super cage of the host was ascertained by XRD, FTIR, solid-state NMR, diffuse reflectance UV-visible absorption spectroscopic techniques and ICP-OES measurements. Phenosafranine dye adsorbed on the external surface of zeolite-Y shows a decrease in fluorescence intensity with increased loading of the nickel(II) complex in zeolite-Y. Time-resolved emission studies show two excited state lifetimes for the photoexcited phenosafranine dye. Average fluorescence lifetimes of the dye in this case do not change with increase in the loading of the nickel(II) complex. However, relative contribution of short lifetime component increases when the amount of encapsulated nickel(II) complex is increased. The zeolite-Y host containing only bipyridyl ligand shows a marked decrease in fluorescence intensity. Fluorescence lifetimes of the dye however do not change with increased loading of bipyridyl while relative contribution of short lifetime component increases with an increase in the loading of bipyridyl in the host. This observation is interpreted to be due to electron transfer from the excited state of phenosafranine dye to the bipyridine. Picosecond pump-probe investigations confirm that the photoinduced electron transfer occurs from the surface-adsorbed phenosafranine in the excited state to the nickel(II) complex within zeolite-Y cavity and also to the Ni(bpy)\(_{\mathrm {3}}^{\mathrm {2+ }}\)complex in contact with the phenosafranine dye co-adsorbed on the external surface of the host. Tris-(2,2′-bipyridine)-nickel(II)complex ion encapsulated zeolite-Y host has been synthesized via a ship-in-a-bottle method. Metal complexes and dye adsorptions were characterized by various spectroscopic methods. Photo-induced electron transfer between the surfaces adsorbed organic dye to encapsulated metal complexes have been investigated by picoseconds transient absorption spectroscopy.