para‐Sulfonated Calixarenes Used as Synthetic Receptors for Complexing Photolabile Cholinergic Ligand

The water‐soluble tetra‐, hexa‐ and octasulfonated calix[4]arenes, calix[6]arenes, and calix[8]arenes 1 – 3 , respectively, were investigated as potential synthetic receptors for photolabile cholinergic ligand A , a photolytic precursor of choline. Ligand A is a bifunctional molecule carrying a photolabile 2‐nitrobenzyl group at one end and a choline moiety at the other end. Results from NMR studies have shown that calixarenes 1 – 3 form stable 1 : 1 complexes with A , having similar binding potential to that observed with the cholinergic enzymes acetylcholinesterase and butyrylcholinesterase. Further studies have suggested that calix[8]arene forms a ditopic complex by binding concomitantly to both the cationic choline moiety and the aromatic photolabile group of A , whereas calix[4]arene and calix[6]arene form monotopic complexes with A . The ditopic complex between calix[8]arene and A results from mutually induced fitting process, while the monotopic complexes between calix[4]arene and A can be regulated by pH: at neutral pH, calix[4]arene specifically binds the cationic choline moiety, while, at acidic pH, it complexes unselectively both the cationic choline moiety and the aromatic group of A . Our results show that para‐sulfonated calixarenes are versatile artificial receptors which bind in various ways to the bifunctional photolabile cholinergic ligand A , depending on their size, geometry, and state of protonation.     

Water‐Soluble Molecular Capsules: Self‐Assembly and Binding Properties

The self‐assembly and characterization of water‐soluble calix[4]arene‐based molecular capsules ( 1?2 ) is reported. The assemblies are the result of ionic interactions between negatively charged calix[4]arenes 1 a and 1 b , functionalized at the upper rim with amino acid moieties, and a positively charged tetraamidiniumcalix[4]arene 2 . The formation of the molecular capsules is studied by ¹H NMR spectroscopy, ESI mass spectrometry (ESI‐MS), and isothermal titration calorimetry (ITC). A molecular docking protocol was used to identify potential guest molecules for the self‐assembled capsule 1 a?2 . Experimental guest encapsulation studies indicate that capsule 1 a?2 is an effective host for both charged (N‐methylquinuclidinium cation) and neutral molecules (6‐amino‐2‐methylquinoline) in water.     

Potentiometric Ag+ Sensors Based on Conducting Polymers: A Comparison between Poly(3,4‐ethylenedioxythiophene) and Polypyrrole Doped with Sulfonated Calixarenes

Potentiometric Ag⁺ sensors were prepared by galvanostatic electropolymerization of 3,4‐ethylenedioxythiophene (EDOT) and pyrrole (Py) on glassy carbon electrodes by using sulfonated calixarenes as doping ions. Poly(3,4‐ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) doped with p‐sulfonic calix[4]arene (C4S), p‐sulfonic calix[6]arene (C6S) and p‐sulfonic calix[8]arene (C8S) were compared. PEDOT and PPy doped with poly(styrene sulfonate) (PSS) were also included for comparison. The analytical performance of the conducting polymer‐based Ag⁺ sensors was studied by potentiometric measurements. All conducting polymer and dopant combinations showed sensitivity and selectivity to Ag⁺ compared to several alkali, alkaline‐earth, and transition‐metal cations. The type of the conducting polymer used for the fabrication of the electrodes was found to have a more significant effect on the selectivity of the electrodes to Ag⁺ than the ring size of the sulfonated calixarenes used as dopants. Selected conducting polymer‐based sensors were studied by cyclic voltammetry (CV) and energy dispersive analysis of X‐rays (EDAX) measurements. Results from the EDAX measurements show that both PEDOT‐ and PPy‐based membranes accumulate silver.     

单氧代-二硒烷基-1, w-二氧取代杯[4]衍生物的合成,结构及萃取性能研究

Novel macrocyclic monooxa-diselkylene-1,ω-dioxy substituted calix[4]arene derivatives 1a-5a were synthesized by the reaction of calix[4]arene dibromides 1-5 with the disodium salt of bis（2-selenylethyl）ether in the yields between 28% and 64%. Their structures were characterized by proton and carbon NMR spectra. X-Ray structure analysis of la further confirmed the cone conformation of compounds 1a-5a. An interesting host-guest complex of la with dichloromethane via CH/π and C1/π interactions was elucidated. Extraction experiments showed that these novel monooxa-diselkylene-1,ω-dioxy substituted calix[4]arene derivatives 1a-5a had strong extraction ability towards mercury ion. The interaction of Hg^2＋with the calix ligand has also been investigated by 1^H NMR titration.     

Complexation Between (O‐Methyl)6‐2,6‐Helic[6]arene and Tertiary Ammonium Salts: Acid/Base‐ or Chloride‐Ion‐Responsive Host–Guest Systems and Synthesis of [2]Rotaxane

Complexation between (O ‐methyl)₆‐2,6‐helic[6]arene and a series of tertiary ammonium salts was described. It was found that the macrocycle could form stable complexes with the tested aromatic and aliphatic tertiary ammonium salts, which were evidenced by ¹H NMR spectra, ESI mass spectra, and DFT calculations. In particular, the binding and release process of the guests in the complexes could be efficiently controlled by acid/base or chloride ions, which represents the first acid/base‐ and chloride‐ion‐responsive host–guest systems based on macrocyclic arenes and protonated tertiary ammonium salts. Moreover, the first 2,6‐helic[6]arene‐based [2]rotaxane was also synthesized from the condensation between the host–guest complex and isocyanate.     

Synthesis of p‐tert‐Butyl‐calix[6] ‐biscrown‐3 via Intramolecular Ring‐closure of 1,4‐Bis (2‐(2‐chloroethoxy) ethoxy) ‐p‐tert‐butyl‐calix[6]arene

With a variation in reaction conditions, 1, 4‐bis (2‐(2‐chloroethoxy)ethoxy)‐calix[6]arene (3) and l,3,5‐tris(2‐(2‐chloroethoxy) ethoxy)‐calix [6] arene (4) or 4 and 4‐chloroethoxyethoxy‐calix[6]crown‐3 (5) were selectively synthesized from p‐tert‐butyl‐calix [6] arene and 2‐(2‐chloroethoxy)ethyltosylate. l,3–4,6‐p‐tert‐butylcalix[6]‐bis‐crown‐3 (6) with (u,u,u,d,d,d) conformation and 1,3–4,5‐p‐tert‐butylcalix[6]‐biscrown‐3 (7) with self‐anchored (u,u, u, u, u, d) conformation were synthesized through an intramolecularly ring‐closing condensation of 1, 4‐bis (2‐(2‐chloroethoxy)ethoxy)‐p‐tert‐butyl‐calix[6]arene (3) in 25% and 15% yield, respectively. Using 5 instead of 3, only 7 was obtained in 65% high yield. 6 and 7 show different complexation properties toward alkali metal and ammonium ions.     

Studies on Properties of p—Nitrophenylazo Calix[4]arene Derivatives

The p-nitrophenylazo calix[4] arene derivatives la-ld with nonlinear optical(NLO)properties were prepared by the diazo-coupling reaction of calix[4]arene with p-nitrophenyl diazonium.The diazotization reaction of p-nltroaniline was caried out with isoamyl nitrite as a source of nitrous acid in EtONa/EtOH under refluxing conditon.X-Ray crystallographic analysis and ^1H NMR sptectra reveal that they exist as cone conformation in crystal state or in soution.HRS measurements at 1064 nm in THF indicate that p-nitrophenylazo calix[4]arenes have higher hyperpolarizability βz values than the corresponding reference compound 4-(4-nitrophenylazo)-2,6-dimethyl-phenol,without red shift of the charge transfer band.The tetrakis p-nitropheylazo calix[4]arene(2)with longer alkyl chains can form monolayer aht the air/water interface.     

Mono‐ and Binuclear Rhodium and Platinum Complexes of 1, 3, 5‐Trimethyl‐1, 3, 5‐triaza‐2σ3λ3‐phosphorin‐4, 6‐dionyloxy‐substituted Calix[4]arenes

The reaction behaviour of 1, 3, 5‐triaza‐2σ³λ³‐phosphorin‐4, 6‐dionyloxy‐substituted calix[4]arenes towards mono‐ and binuclear rhodium and platinum complexes was investigated. Special attention was directed to structure and dynamic behaviour of the products in solution and in the solid state. Depending on the molar ratio of the reactands, the reaction of the tetrakis(triazaphosphorindionyloxy)‐substituted calix[4]arene ( 4 ) and its tert‐butyl‐derivative ( 1 ) with [(cod)RhCl]₂ yielded the mono‐ and disubstituted binuclear rhodium complexes 2 , 3 , and 5 . In all cases, a C₂‐symmetrical structure was proved in solution, apparently caused by a fast intramolecular exchange process between cone conformation and 1, 3‐alternating conformation. The X‐ray crystal structure determination of 5 confirmed [(calixarene)RhCl]₂‐coordination through two opposite phosphorus atoms with a P ⃜P separation of 345 pm. The complex displays crystallographic inversion symmetry, and the Rh₂Cl₂ core is thus exactly planar. Reaction of 1 and of the bis(triazaphosphorindionyloxy)‐bis(methoxy)‐substituted tert‐butyl‐calix‐[4]arene ( 7 ) with (cod)Rh(acac) in equimolar ratio and subsequent reaction with HBF₄ led to the expected cationic monorhodium complexes 5 and 8 , involving 1, 3‐alternating P‐Rh‐P‐coordination. The cone conformation in solution was proved by NMR spectroscopy and characteristic values of the ¹J(PRh) coupling constants in the ³¹P‐NMR‐spectra. Reaction of equimolar amounts of 4 with (cod)Rh(acac) or (nbd)Rh(acac) led, by substitution of the labile coordinated acetylacetonato and after addition of HBF₄, to the corresponding mononuclear cationic complexes 9 and 10 . Only two of the four phosphorus atoms in 9 and 10 are coordinated to the central metal atom. Displacement of either cycloocta‐1, 5‐diene or norbornadiene was not observed. For both compounds, the cone conformation was proved by NMR spectroscopy. Reaction of 4 with (cod)PtCl₂ led to the PtCl₂‐complex ( 11 ). As for all compounds mentioned above, only two phosphorus atoms of the ligand coordinate to platinum, while two phosphorus atoms remain uncoordinated (proved by δ³¹P and characteristic values of ¹J(PPt)). NMR‐spectroscopic evidence was found for the existence of the cone conformation in the cis‐configuration of 11 .     

Application of bromoacetate‐substituted β‐CD‐bonded silica particles as chiral stationary phase for HPLC

Bromoacetate‐substituted [3‐(2‐O‐β‐cyclodextrin)‐2‐hydroxypropoxy]propylsilyl‐appended silica particles (BACD‐HPS), an important and useful synthetic intermediate for preparation of novel types of macrocycles‐capped β‐CD‐bonded silica particles including crown ether/cyclam/calix[4]arene‐capped β‐CD‐bonded silica particles, have been prepared and used as chiral stationary phase for HPLC. This synthetic stationary phase is characterized by means of elemental analysis. For the first time, the chromatographic behavior of BACD‐HPS was systematically evaluated with several disubstituted benzenes and some chiral drug compounds under both normal and RP conditions in HPLC. The results show that BACD‐HPS has excellent selectivity for the separation of aromatic positional isomers and chiral isomers of some drug compounds when used as stationary phase in HPLC.     

Exploring the structural landscape of 2‐(thiophen‐2‐yl)‐1,3‐benzothiazole: high‐Z′ packing polymorphism and cocrystallization with calix[4]tube

We report here for the first time a cocrystal of the so‐called neutral calix[4]tube, which is two tail‐to‐tail‐arranged and partially deprotonated tetrakis(carboxymethoxy)calix[4]arenes, including three sodium ions, with 2‐(thiophen‐2‐yl)‐1,3‐benzothiazole, namely trisodium bis(carboxymethoxy)bis(carboxylatomethoxy)calix[4]arene tris(carboxymethoxy)(carboxylatomethoxy)calix[4]arene–2‐(thiophen‐2‐yl)‐1,3‐benzothiazole–dimethyl sulfoxide–water (1/1/2/2), 3Na⁺·C₃₆H₃₀O₁₂^2?·C₃₆H₃₁O₁₂^?·C₁₁H₇NS₂·2C₂H₆OS·2H₂O, which provides a new approach into the host–guest chemistry of inclusion complexes. Three packing polymorphs of the same benzothiazole with high Z′ (one with Z′ = 8 and two with Z′ = 4) were also discovered in the course of our desired cocrystallization. The inspection of these polymorphs and a previously known polymorph with Z′ = 2 revealed that Z′ increases as the strength of intermolecular contacts decreases. Also, these results expand the frontier of invoking calixarenes as a host for nonsolvent small molecules, besides providing knowledge on the rare formation of high‐Z′ packing polymorphs of simple molecules, such as the target benzothiazole.     

Calix[4]arene‐based Bis‐phosphonites,Bis‐phosphites,and Bis‐O‐acyl‐phosphites as Ligands in the Rhodium(I)‐catalyzed Hydroformylation of 1‐Octene

New calix[4]arene‐based bis‐phosphonites, bis‐phosphites and bis‐O‐acylphosphites were synthesized and characterized. Treatment of these P‐ligands with selected rhodium and platinum precursors led to mononuclear complexes that were satisfactorily characterized. The solid state structure of the dirhodium(I) complex 14 has been determined by X‐ray diffraction. The two rhodium centres are bridged by two chloro ligands; one rhodium atom is further coordinated by calix[4]arene phosphorus atoms and the other by cyclooctadiene. The new calix[4]arene P‐ligands were tested in the Rh(I) catalyzed hydroformylation of 1‐octene. All Rh(I) complexes catalyzed the reaction leading to high chemoselectivity with regard to the formation of aldehydes. Yields and n/iso‐selectivities depended on the reaction conditions. Average yields of 80 % and n/iso‐ratios of about 1.3 to 1.5 were observed. High yields of aldehydes can be achieved using the methoxy substituted P‐ligands at low Rh:ligand ratios.     

Synthesis of fully lower‐rim,carbonate‐bridged calix[8]arenes and their curing behavior

Novel fully lower‐rim, carbonate‐bridged calix[8]arene derivatives were successfully synthesized in high yield by the condensation of p‐alkyl substituted calix[8]arenes with triphosgene. Different bases and catalysts were used for the preparation depending on the p‐alkyl substituted groups of the calix[8]arenes. The conformational features of the derivatives were examined by ¹H NMR analysis. Thermosetting formulations were prepared from a mixture of bisphenol A polycarbonate with calix[8]arene carbonate derivatives using sodium benzoate as a catalyst. Their crosslinking behaviors were studied using differential thermal/thermogravimetric analysis. No glass‐transition temperatures were observed after annealing at 280–300 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1149–1155, 2001     

Synthesis of Flavin–Calix[4]arene Conjugate Derivatives

The synthesis of two new flavin substituted calix[4]arene derivatives, 9 and 10 , is described. The first flavin substituted calix[4]arene derivative 9 was synthesized by the reaction of 3‐methylalloxazine ( 5 ) with 25,27‐bis(3‐bromopropoxy)‐26,28‐dihydroxy‐5,11,17,23‐tetra(tert‐butyl)calix[4]arene ( 4 ) in high yield (92%). The other derivative 10 was prepared from 3‐methylalloxazine‐1‐acetic acid ( 7 ) and 25,27‐bis(3‐cyanopropoxy)calix[4]arene ( 3 ). All new compounds were characterized by a combination of FT‐IR and ¹H‐NMR spectroscopy, and elemental‐analysis techniques.     

Synthesis of （p-Formylphenyl）azo Calix[4]arenes

Five novel azo calix[4]arenes were reported. The p-aminobenzaldehyde was diazotized with sodium nitrite in aqueous hydrochloride solution. Mono-, bis-, tris- and tetrakis(p-formylphenyl)azo calix[4]arenes (including proximal and distal isomers) were obtained respectively by diazo-coupling in different molar ratio to calix[4]arene(1) under pH=7.5--8.5 at 0-5℃. All (p-formylphenyl)azo calix[4]arenes were characterized by ^1H NMR, ^13C NMR, IR, MS (ESIMS) spectroscopies and elemental analysis.     

Calix[6]arene‐Based Cascade Complexes of Organic Ion Triplets Stable in a Protic Solvent

Herein we report a D_3h‐symmetric tail‐to‐tail bis‐calix[6]arene 3 featuring two divergent cavities triply connected by ureido linkages. This calix[6]tube was synthesized by a domino Staudinger/aza‐Wittig reaction followed by a macrocyclization reaction. This process also afforded a C_2h‐symmetric isomer that represents a rare example of a self‐threaded rotaxane based on calix[6]arene subunits. The binding properties of 3 have been evaluated by NMR studies. Thus, bis‐calix[6]arene 3 is able to bind simultaneously two neutral ureido guests through an induced‐fit process. The guests are located in the cavities and are recognized through multiple hydrogen‐bonding interactions with the ureido bridges. Host 3 can also simultaneously bind multiple ions and is especially efficient for the complexation of organic ion triplets. The anion is recognized through hydrogen‐bonding interactions at the ureido binding site and is thus located between the two ammonium ions accommodated in the cavities. The resulting [1+1+2] quaternary complexes represent rare examples of cascade complexes with organic cations. These complexes are unique: 1) They are stable even in a markedly protic solvent, 2) the recognition of the ion triplets proceeds in a cooperative way through an induced‐fit process and with a high selectivity, linear cations and doubly charged anions being particularly well recognized, 3) the ions are bound as contact ion triplets thanks to the closeness of the three binding sites, 4) the cationic guests can be exchanged and thus mixed [1+1+1+1] complexes can be obtained, 5) the ureido linkers wrapped around the anion adopt a helical shape and the resulting chirality is sensed by the cations. In other words, bis‐calix[6]arene 3 presents a selective inner tunnel in which multiple guests such as organic ion triplets can be aligned in a cooperative way through induced‐fit processes.     

Supramolecular Detoxification of Colchicine through Electrochemical Recognition

The complex characteristics of p-sulfonated calix[n]arene and colchicine were examined using various techniques. Cyclic voltammetry indicated that the structural matching and electrostatic interactions were the dominant stabilizing factors for the host–guest complexes. The method showed a long linear voltammetric range for p-sulfonated calix[4]arene from 1?×?10^?8 to 1?×?10^?6?mol?L^?1 with a detection limit of 3?×?10^?9?mol?L^?1. Ultraviolet absorption spectroscopy confirmed that a 1:1 ratio complex was formed. Molecular mechanics showed that the benzene ring of colchicine entered the p-sulfonated calix[4]arene cavity. The solubility of colchicine increased with the p-sulfonated calix[4]arene concentration 50-fold from 0.13 to 6.4?mol?L^?1. The simulation of cell membrane permeability indicated that colchicine was released from the colchicine-p-sulfonated calix[4]arene complex and entered the hydrophobic micelles. These results show that p-sulfonated calix[4]arene is suitable as a drug carrier for colchicine. This work has expanded applications of drug loading, transport, and targeted release for the treatment of gout.     

Fluorescence Spectral Studies on the Coordination of Calix[4]‐arenes Bearing Boronic Acid Moieties with Monosaccharides

Coordination of ten calix[4]arenes bearing boronic acid moieties with five monosaccharides was studied by fluorescence spectrometry. The stability constants (K₂) of the complexes and Gibbs free energy change ( ‐ ΔG⁰) of the coordination reactions were calculated according to the modified Hilderbrand‐Benesi equation. The results obtained indicated that the coordination ability of D‐( ‐ )‐fructose with calix[4] arenes bearing boronic acid moieties was stronger than that of the other monosaccharides. And these calix[4]arene derivatives might be used for identification of L‐( ‐ )‐sorbose.     

5,11,17,23-Tetrakis[(p-carboxyphenyl)azo]-25,26,27,28-tetra-hydroxy Calix[4]arene: Crystal Structure and pH Sensing Properties

Treatment of 5,11,17,23‐tetrakis[(p‐carboxyphenyl)azo]‐25,26,27,28‐tetrahydroxy calix[4]arene ( 2 ) with HCl in DMF or NaOH in MeOH produced 5,11,17,23‐tetrakis[(p‐carboxyphenyl)azo]‐25,26,27,28‐tetrahydroxycalix[4]‐arene·4DMF (2·4DMF) and 5,11,17,23‐tetrakis[(p‐carboxyphenylsodium)azo]‐25,26,27,28‐tetrahydroxycalix[4]‐ arene ( 3 ), respectively, which were characterized by elemental analysis, IR, UV‐vis, ¹H NMR and ¹³C NMR. An X‐ray analysis of 2·4DMF revealed that its calix[4]arene core adopts a flattened cone conformation in which opposed phenyl groups take parallel or sharply inclined positions. The intra‐ and intermolecular hydrogen‐bonding interactions and the π···π interactions form a 2D hydrogen‐bonded wavelike network. Compound 2 had a unique reversible color change in a wide pH range from 1 to 13.5 and showed interesting pH sensing properties.     

Highly Efficient Chirality Transfer from Diamines Encapsulated within a Self‐Assembled Calixarene–Salen Host

A calix[4]arene host equipped with two bis‐[Zn(salphen)] complexes self‐assembles into a capsular complex in the presence of a chiral diamine guest with an unexpected 2:1 ratio between the host and the guest. Effective chirality transfer from the diamine to the calix–salen hybrid host is observed by circular dichroism (CD) spectroscopy, and a high stability constant K_2,1 of 1.59×10¹¹ M ^?2 for the assembled host–guest ensemble has been determined with a substantial cooperativity factor α of 6.4. Density functional calculations are used to investigate the origin of the stability of the host–guest system and the experimental CD spectrum compared with those calculated for both possible diastereoisomers showing that the M,M isomer is the one that is preferentially formed. The current system holds promise for the chirality determination of diamines, as evidenced by the investigated substrate scope and the linear relationship between the ee of the diamine and the amplitude of the observed Cotton effects.     

Synthesis and photochemical reaction of cyclic oligomers: Synthesis and photopolymerization of novel C‐methylcalix[4]resorcinarene and p‐alkylcalix[n]arene derivatives containing spiro ortho ether groups

New photoreactive calixarene derivatives containing spiro ortho ester groups (calixarenes 3a–3c ) were synthesized by the reaction of 2‐bromomethyl‐1,4,6‐trioxaspiro[4.4]nonane with 2,8,14,20‐tetramethyl‐4,6,10,12,16,18,22,24‐octakis(carboxymethoxy)calix[4]resorcinarene, 5,11,17,23,29,35‐hexamethyl‐37,38,39,40,41,42‐hexakis(carboxymethoxy)calix[6]arene, and 5,11,17,23,29,35,41,47‐octa‐tert‐butyl‐49,50,51,52, 53,54,55,56‐octakis‐(carboxymethoxy)calix[8]arene, which were prepared by the reaction of C‐methylcalix[4]resorcinarene, p‐methylcalix[6]arene, and p‐tert‐butylcalix[8]arene, respectively. The thermal stability of the obtained calixarene derivatives containing spiro ortho ester groups was examined with thermogravimetric analysis, and it was found that these calixarene derivatives had good thermal stability. The photoinitiated cationic polymerization of spiro ortho ester groups in calixarene derivatives 3a–3c was examined with certain photoacid generators in the film state. Interestingly enough, the reaction of calixarene derivatives did not proceed with only photoirradiation; however, the reaction proceeded smoothly when the photoirradiation was followed by heating. Furthermore, calixarene 3a , composed of a C‐methylcalix[4]resorcinarene structure, showed the highest photochemical reactivity in this reaction system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1293–1302, 2002