Tert-butyl Calix Research Articles

Theoretical studies of calixarene derivatives as receptors for transition metals

The behavior of a calixarene derivative – p–tert butyl calix[4]arene (TBC4) – as receptor for transition metals (Cr, Ni, Cd) has been investigated by density functional calculations. Particular attention has been paid to the energetics and the nature of the metal–TBC4 interactions. Our results predict, that TBC4 should be a good receptor for the extraction of Ni, due to the strong interactions between Ni and the cone-shaped part of the organic molecule in comparison with Cd and Cr.

Design, Preparation, and Characterization of Novel Calix[4]arene Bioactive Carrier for Antitumor Drug Delivery.

An amphiphilic and bioactive calix[4]arene derivative 8 (CA) is designed and successfully synthesized from tert-butyl calix[4] arene 1 by sequential inverse F-C alkylation, nitration, O-alkylation, esterification, aminolysis, reduction, and acylation reaction. The blank micelles of FA-CA and doxorubicin (DOX) loaded micelles FA-CA-DOX are prepared subsequently undergoing self-assembly and dialysis of CA and DSPE-PEG2000-FA. The drug release kinetics curve of the encapsulated-DOX micelle demonstrates a rapid release under mild conditions, indicating the good pH-responsive ability. Furthermore, the cytotoxicity of DOX-loaded micelle respect to the blank micelle against seven different human carcinoma (A549, HeLa, HepG2, HCT116, MCF-7, MDA-MB231, and SW480) cells has been also investigated. The results confirm the more significant inhibitory effect of DOX-loaded micelle than those of DOX and the blank micelles. The CDI calculations show a synergistic effect between blank micelles and DOX in inducing tumor cell death. In conclusion, FA-CA micelles reported in this work was a promising drug delivery vehicle for tumor targeting therapy.

Synthesis and Characterization of Functionalized Calix[4]arene Derivatives and Preparation of Rigid Polyurethane Foams by the Incorporation of Calixarene

SummaryCalix[4]arenes namely, 5,11,17,23 tetra tert butyl calix[4]arene and 5,11,17,23 tetra chlorosulfonyl calix[4]arene were synthesized to produce octakis (hydroxyl ethyl) sulfonamide calix[4]arene which was used in polyurethane‐calixarene rigid foam composite formulation. The effect of calixarene ratio on mechanical properties of synthesized composites was studied at three calixarene ratios including 1.5, 2, and 3 % (w/w). The obtained data indicate that the tensile strength and modulus are increased as the calixarene ratio increases while the fracture strain is decreased. Quantitatively, addition of 3% (w/w) of calixarene to the polyurethane resulted in 30.99% and 30.01% improvements in modulus and tensile strength, respectively. Contrarily, a decrease of about 13.1% was observed in fracture strain when compared to the properties of the pristine polyurethane rigid foam. The effect of Calixarene on thermal stability of Calixarene‐ polyurethane composite indicating that Calixarene component strictly enhances the thermal stability of composite.

Thermal Behaviors of Bisazocalix[4]arene Derivatives

ABSTRACTIn this article, calix[4]arene (4) was prepared by debutylation and hydrolyses reacting from 25,27-dibenzoyl-26,28-dihydroxy-5,11,17,23-tetra(tert-butyl)calix[4]arene (2). Azocalix[4]arenes (6a-c) were coupled by linking 4-methoxy, 4-ethyl, and 4-nitroaniline to calix[4]arene (4) through a diazo-coupling reaction. Thermal behavior characteristics and decomposition routes of 25,26,27,28-tetrahydroxy-11,23-di(tert-butyl)-5,17-(p-substitue phenyl)azocalix[4]arene (6a-c) were investigated in air atmosphere by means of thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermal analysis (DTA) analyses. It was found that the decomposition of all compounds complete with two exothermic stages which corresponded to removal of substitute groups (methoxy-, ethyl-, nitro-) and second stage rest of structure decomposition.

Design, construction and investigating functionality of a nickel (II) ion selective electrode

Ni2+ ion–selective electrode (Ni-ISE) based on plasticized poly(vinyl chloride) (PVC) membrane with 25, 26, 27 tri propoxy 28, Amino 5, 11, 17, 23–tetra–tert–butyl–calix[4]arene as ionophore and dibutyl phthalate (DBP) as plasticizer was designed and constructed. The Ni-ISE showed a linear reply in the concentration range of 1.0 × 10-1 to 1.0 × 10-4 M with slope of 29.3 ± 0.5 mV/decad. The Ni-ISE response time was ≤ 6 s and was used for two months with no deviation in the pH range 4 to 9. The best performance was obtained with a membrane composition of 30% PVC, 62% DBP, 3% 25, 26, 27–tripropoxy–28, amino 5, 11, 17, 23–tetra–tert–butyl-calix[4]arene and 5% potassium tetrakis[p–cholorophenyl]borate (KTpClPB). Its detection limit was 1.0 × 10-5 M. The selectivity coefficients for different cations were calculated by the matched potential method (MPM). The scanning electron microscopy (SEM) of the Ni-ISE’s membranes showed some morphological changes during its life span, probably due to both the reaction between the Ni2+ ion and / or less of the membrane parts by permeation. Key words: Ni2+ ion–selective electrode, 25, 26, 27 tri propoxy 28, amino 5, 11, 17, 23–tetra–tert–butyl–calix[4]arene; scanning electron microscopy (SEM).

Spectroscopic and theoretical investigations on effective and selective complexation between fullerenes (C 60 and C 70) and calix[5]arene

Ground state interactions between a macrocyclic calixarene receptor, namely, 4- tert-butyl calix[5]arene ( 1) with fullerenes C 60 and C 70, were studied by absorption spectrophotometric method in toluene medium. Well defined charge transfer (CT) absorption bands were located for the complexes of C 60 and C 70 with 1. Utilizing the CT absorption bands, various important physico-chemical parameters like oscillator strength, resonance energy and electronic coupling elements were determined for fullerene- 1 complexes. It was observed that 1 binds preferentially C 70 compared to C 60 as obtained from binding constant ( K) data, i.e., K C 60 - 1 = 23600 dm 3 mol −1 and K C 70 - 1 = 94460 dm 3 mol −1. Proton NMR investigations also provided a very good support in favor of strong complexation between C 70 and 1. PM3 calculations established that binding pattern of C 70 towards 1 was end-on rather than side-on as C 70/ 1 complex gained 2.43 kJ mol −1 of extra stabilization energy in case of its end-on orientation rather than traditional side-on approach.

Transport kinetics of chromium(VI) ions through a bulk liquid membrane containing p- tert-butyl calix[4]arene 3-morpholino propyl diamide derivative

The transport of chromate ions (Cr 2O 7 2−) from an aqueous solution into an aqueous receiving solution through a bulk liquid membrane containing p- tert-butyl calix[4]arene 3-morpholino propyl diamide as a carrier was examined. The influence of pH on donor and acceptor phase, effect of chromate and carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters ( k 1 , k 2 , t max , R m max , J d max , J a max ) were calculated for the interface reactions assuming two consecutive, irreversible first order reactions. The activation energy values are 24.83 kJ mol −1 for extraction and 5.14 kJ mol −1 for reextraction. These values indicate that the process is diffusionally controlled by chromate ions. The experiments demonstrated that calix[4]arene diamide derivative is a good carrier for Cr(VI) transport through liquid membranes in this study.

Vanadium calixarene complexes as molecular models for supported vanadia

Reaction of dimethylated tert-butyl calix[4]arene, H 2 A Me2 , with O VCl 2(thf) 2 unexpectedly led to the isolation of Cl V IV A Me , 2, whose crystal structure was determined. Hence, one of the MeO–C bonds present in H 2 A Me2 has been cleaved and one equivalent of HCl eliminated leaving three phenolate and one phenolether function to coordinate at the V centre. 2 smoothly reacts with O 2 to give O V V A Me , B, i.e. the chloride ligand has been replaced by a terminal oxo ligand with concomitant oxidation of the vanadium atom to the oxidation state +5. B crystallises isostructurally with 2; crystallisation of a mixture of 2 and B even leads to crystals that contain both compounds beside each other. However, when B was co-crystallised together with H 2 A Me2 , from acetonitrile a different structure with a partial cone conformation was obtained. The mechanism by which B is formed from 2 is discussed. To obtain information concerning the fate of the chloride ligand in 2, a derivative, Ph 3SiO–V IV A Me , 3, has been synthesised and investigated with respect to its behaviour in the presence of O 2: it reacts the same way as 2.

Phosphoamide – modified p- tert-butyl calix[4]arene and its sodium complexes : Synthesis, coordination ability and structure

A new modified calix[4]arene, namely 5,11,17,23-tetra- tert-butyl-25,27-dihydroxy-26,28-bis[(tetramethyldiamidophosphinyl)oxy]calix[4]arene (L) has been prepared by reacting the parent calixarene with tetramethyldiamidophosphoric acid chloride, and its structure was solved by the X-ray diffraction method in the solid state and characterized in solution using 1H, 13C, 31P NMR and mass spectral (ES-MS and FAB-MS) data. The coordination ability of L towards Na + showed the formation of two different complex species, [NaL] +[AuCl 4] − · 4H 2O ( 1) and [Na 2L 2](ClO 4) 2 · (CH 3OH) 4 ( 2), depending on the reaction conditions and nature of the counter ion. Complex 1 is structurally characterized using NMR ( 1H, 13C, 31P) and mass spectral data. Complex 2 crystallizes with four molecules of methanol, two of them being bridges between two calixarene units and its structure was determined by X-ray analysis.

Surface Enhanced Vibrational (IR and Raman) Spectroscopy in the Design of Chemosensors Based on Ester Functionalized p-tert-Butylcalix[4]arene Hosts

Surface-enhanced IR (SEIR) and Raman scattering (SERS) have been employed to study the adsorption of ester functionalized tert-butyl calix[4]arenes on Ag and Au nanostructured surfaces as well as their complexes with pyrene. The influence of adsorption and complexation with pyrene on the host calixarene structure was tested for two different calixarene molecules bearing carboethoxy groups (CH(3)CH(2)COOCH(2)-) in the low rim at positions 1,3- and 1,2,3,4-. The results obtained with SEIR were compared to those obtained with SERS, to better understand the interaction mechanism of the studied calixarenes with the metallic surfaces and the ligand as well as to investigate the structure/selectivity relationship of these two surface techniques in the analysis of recognition problems in which these ester functionalized calixarene molecules are involved.

Lower Rim Substituted tert-Butyl calix[4]arene (part VII): Ionophoric Properties of Calix[4]arene-crown-6 Derivatives in Plasticized PVC-Membrane Electrodes and in Solution

The synthesis and characterization of p-tert-butylcalix[4]arene-crown-6 derivatives (compounds 2–9) are presented. Their ability to complex alkali, alkaline earth and some “softer” cations was investigated by using these compounds as ionophores in ion-selective membrane electrodes and determining the potentiometric selectivity coefficients and the complex stability constants in the membrane. The selectivities of these compounds depend on the size and nature of the substituents on the distal phenolic oxygens. The complexing properties of the two cone and partial cone conformers of compound 2 in the PVC membrane were compared with those in acetonitrile solution studied by UV absorption spectrophotometry and with alkali metal picrate liquid–liquid extraction.

Pulsed galvanostatic control of ionophore-based polymeric ion sensors.

This paper describes a pulsed galvanostatic technique to interrogate ion-selective electrodes (ISEs) with no intrinsic ion-exchange properties. Each applied current pulse is followed by a longer baseline potential pulse to regenerate the phase boundary region of the ion-selective membrane. The applied current fully controls the magnitude and sign of the ion flux into the membrane, thus offering instrumental control over an effect that has become very important in ion-selective electrode research in recent years. The resulting chronopotentiometric response curves essentially mimic traditional ISE behavior, with apparently Nernstian response slopes and selectivities that can be described with the Nicolsky equation. Additionally, the magnitude and sign of the current pulse may be used to tune sensor selectivity. Perhaps most important, however, appears to be the finding that the extent of concentration polarization near the membrane surface can be accurately controlled by this technique. A growing number of potentiometric techniques are starting to make use of nonequilibrium principles, and the method introduced here may prove to be very useful to advance these areas of research. The basic characteristics of this pulsed galvanostatic technique are here evaluated with plasticized poly(vinyl chloride) membranes containing the sodium-selective ionophore tert-butyl calix[4]arene tetramethyl ester and a lipophilic inert salt.

Silver ion-selective electrodes employing Schiff base p- tert-butyl calix[4]arene derivatives as neutral carriers

The potentiometric response characteristics and selectivity properties of poly(vinylchloride) (PVC) matrix membrane ion-selective electrodes for silver(I) ion, based on Schiff base p- tert-butyl calix[4]arene derivatives containing N and O as binding sites, were examined. These derivatives proves to work well with silver ions and corresponding electrodes display an excellent response to this ion. These electrodes works well over wide range of concentration ( 1.0×10 −5 to 1.0×10 −1 M) with a Nernstian slope. The electrodes have a fast response time of 20 s and operates in the wide pH range. These calix[4]arene derivatives, each showed excellent selectivities in ISE membrane electrodes with log K Ag, M pot around −4.5 against some of the alkali, alkaline and transition metals, even against the strongest interferent, Hg 2+ ions, the value was around −3.0. These silver(I) ion-selective electrodes were used as an indicator electrode for potentiometric titration of silver(I) using standard solution of sodium chloride, a sharp potential change occur at the end point. These ISEs were also used to determine low concentration of silver(I) ion in partially non-aqueous medium.

Use of some calixarenes as cleaning agents for low radioactive contaminated waters

In order to clean some low radioactive contaminated waters containing β+γ-active cations (55+59Fe3+, 60Co2+, 65Zn2+ and 137Cs+), calix[4]arene and p-(tert-butyl)calix[4]arene have been used. Experiments have been performed in the absence of ionic competition, at 4°C, 22°C and 40°C. Whatever the temperature and the sorbent used, the yield of retaining the β+γ-active cations varies as follows: 55+59Fe3+>60Co2+≥65Zn2+>137Cs+.

Metal complexes based on an upper-rim calix[4]arene phosphine ligand

A new upper-rim phosphacalix[4]arene 5,17-bis(diphenylphosphinomethyl)-25,26,27,28-tetrapropoxycalix[4]arene ( 4) has been prepared starting from commercially available tert-butyl calix[4]arene. Treatment of 4 with (COD)PdMeCl and (COD)PtCl 2 gives polymeric phosphine-coordinated Pd(II) and Pt(II) species, respectively. 4 reacts with [(COD)RhCl] 2 to give a di-rhodium complex that is an active catalyst for the hydroformylation of 1-octene and styrene.

Selectivity behavior and multianalyte detection capability of voltammetric ionophore-based plasticized polymeric membrane sensors.

The current response features ofvoltammetric ion-selective polymeric membranes doped with neutral ionophores in view of practical sensor development are elucidated. The membranes are designed to extract ions only under applied external potentials and interrogated by normal-pulse voltammetry and pulsed amperometry. They contain two polarizable interfaces to avoid loss of lipophilic ions at the sample side and to maximize the available potential window. A simple theoretical model is developed that describes the observed current at the end of an uptake pulse to the applied membrane potential, which is the sum of both boundary potentials (at the sample and inner electrolyte side) and the membrane internal iR drop. The results describe how the selectivity of the resulting sensor must be dependent on the applied potential. Evidently, the role of the applied potential is akin to incorporating lipophilic cationic and anionic sites with potentiometric ionophore-based membranes, which are well known to considerably affect membrane selectivity and to define the charge type of the assessed ions. This has important implications for sensor design, as the applied cell potential can be used to tune sensor selectivity. Theory also explains the role of the inner electrolyte on sensor behavior. A maximum measuring range is expected with ions in the inner electrolyte that are difficult to extract into the membrane. This corresponds to Kihara's experimental results and contrasts to common ion-selective electrode practice, where a salt of the analyte ion is normally present in the inner electrolyte. Separate and mixed solution experiments with membranes containing the sodium-selective ionophore tert-butyl calix[4]arene tetramethyl ester and the lithium ionophore ETH 1810 agree very well with theoretical expectations. Multianalyte detection capability with a single sensing membrane is demonstrated in a selectivity-modifying pulsed amperometric detection mode, where each applied voltage yields a different practical selectivity of the sensor. The sensor is altered from being sodium to potassium selective as the magnitude of the applied potential is repetitively varied within the pulse sequence. The sensors show high long-term stability under continuous measuring conditions over 15 h.

Novel approach of immobilization of calix[4]arene type ionophore in ‘self-plasticized’ polymeric membrane

The design of ion-selective membranes based on the immobilization of the calix[4]arene tetraethyl ester containing at their wider rim one polymerizable group in a linear isodecyl acrylate (IDA)/methyl methacrylate (MM) copolymer is reported. Preliminary studies were focused on an optimization of polymeric matrix based on IDA/MM copolymers to make them suitable for preparing ion-selective membranes. The effect of polymer composition (IDA:MM ratio), matrix features (glass transition temperature and molecular weight) and compatibility with electro-active components was examined. It was found that the copolymer of IDA:MM=3:7 ratio exhibited the best mechanical properties. The feasibility of the application of IDA/MM matrix for ion-selective membranes was examined using as a model ionophore, 4- tert-butyl calix[4]arene tetraethyl ester. Electrodes based on these membranes showed near theoretical sensitivity towards sodium concentration and selectivity similar to reported for classical plasticized PVC-based membranes. Methacrylamide derivative of calixarene was immobilized in IDA/MM polymer of optimized composition. Potentiometric measurements revealed that the selectivity and the slope of the response curve obtained for electrodes employing membranes with immobilized calixarene are essentially the same as for the membranes containing a free ionophore, while the lifetime was improved from 2 to 6 months.

An approach to calix[6]cryptands with bridgehead carbon atom: Stabilized in- and out- stereoisomers

A new approach to cap 1,3,5-trimethyloxy- p- tert-butyl calix[6]arene with 1,1,1-tri(tosyloxyethoxyethoxymethyl)propane to form a pair of separable stabilized in- and out- calix[6]cryptands was reported. After heating 5a or 5b at 280°C, the interconversion between them was not detected by TLC, which provides a direct and non-spectral methodology to obtain unambiguous evidence for the ring immobilization in calix[6]arenes with stereoisomers.

Tungsten(VI) p–tert–butylcalix arene diolato complexes. Crystal structure and reactions of [W(t–butylcalix)(eg)

Air- and moisture stable tungsten(VI) calixarene complex was prepared from [W(eg)3] (H2eg = 1,2–ethanediol) and H4tbcalix (p–tert–butylcalix[4]arene) by a ligand exchange reaction. X-ray structure of [W(tbcalix)(eg)] reveals that tungsten ion is octahedrally surrounded by six oxygen atoms. The reaction of the obtained complex with thionyl chloride or water leads to known dichloro and oxo complexes.

Novel ligands deriving from p- tert-butylcalix[4]arene O-substituted by diethyl malonate functions

The synthesis of calixarenes 1–6 combining a p- tert-butyl calix[4]arene unit and diethyl malonate functions is described. Preliminary complexing properties are given.