Synthesis and crystal structures of Ag and Hg complexes of bis(N-heterocyclic carbenes) on p-tert-butylcalix[4]arene platform

A series of p-tert-butylcalix[4]arene 1,3-diimidazolium salts were successfully prepared by the alkylation of p-tert-butylcalix[4]arene with dibromoalkanes, and sequential substitution reaction with 1-alkylimidazole. Furthermore, coordination reactions of p-tert-butylcalix[4]arene 1,3-diimidazolium salts with silver oxide and mercury acetate gave novel Ag and Hg complexes of bis(N-heterocyclic carbenes) on p-tert-butylcalix[4]arene platform. The single-crystal structures of four p-tert-butylcalix[4]arene 1,3-diimidazolium salts and three metal complexes were successfully determined by X-ray diffraction. An Ag–Ag argentophilic interaction (Ag–Ag bond length is 3.1599(6) Å) is formed between the two Ag–NHC complexes and a dimetallic coordination mode exists in Hg–NHC complexes.     

共价键链杯芳烃-四硫富瓦烯超分子体系研究进展

综述了共价键链的杯芳烃-四硫富瓦烯超分子主体化合物的设计合成及其在电化学调控的分子识别、离子调节的电子转移行为和分子组装等领域的研究进展.     

通过杯芳烃片段桥联合成杯[4]冠4齐聚物及其络合性能研究

通过杯芳烃片段桥联合成杯[4]冠4齐聚物,并通过两相萃取实验评估其络合性能。络合研究表明,酰胺型杯[4]冠4齐聚物（TCA[4]-III）对软金属银、铅离子和氨基酸具有选择性络合。其对色氨酸和组氨酸的萃取率分别高达87.9% 和 91.5%。     

Recognition in water of bioactive substrates by a sulphonato p-tert-butylcalix[5]arene

The molecular recognition in water of neurotransmitter monoamine and trace amine hydrochlorides by p-tert-butylcalix[5]-arene 1 – bearing 4-sulphonatobutoxy groups at the lower rim – has been investigated. According to ¹H NMR measurements, the hydrophobic cavity of receptor 1 best binds tyramine hydrochloride, K_a = 5370 ± 870 M^? 1.     

Sensitive fluorescence probes for dihydrogen phosphonate anion based on calix[4]arene bearing naphthol-hydrazone groups

t-Butyl and t-pentylcalix[4]arenes bearing two 2-naphthol-1-hydrazone groups at the lower rim were synthesized,and showed excited-state intermolecular proton transfer fluorescent signal with basic anion.They are more sensitive to dihydrogen phosphate anion than to fluoride anion,although the latter has stronger basicity.Compared with t-butylcalix[4]arene bearing two 2-naphthol-1-hydrazone groups,t-pentylcalix[4]arenes derivative has a larger fluorescent difference between dihydrogen phosphate and fluoride a...     

Intramolecular hydrogen bonding and calixarene-like structures in p-cresol/formaldehyde resins

The nature of the strong hydrogen bonds found in p-cresol/formaldehyde (PCF) resins, compared to ordinary phenolic compounds, is studied. The evidence from FTIR spectroscopy indicates that this strong interaction is due to intramolecular hydrogen bonding from “calixarene-like” structures. The formation of this structure in PCF is enabled by its “linear” (all-ortho-linkage) structure, which is not present in branched resins. Additionally, a transition is observed at around 175 to 200°C where the intramolecular hydrogen bonded structure is lost. This structure cannot be recovered upon cooling or annealing due to restrictions on conformational rotations that are coupled to a new pattern of intermolecular hydrogen bonding. However, the structure is reformed by dissolving the resin in solution and casting new films.     

Structures and properties of solvated and unsolvated isopropyl functionalised calix[4]arenes

The tetra-isopropyl ethers of calix[4]arene and p-t-butylcalix[4]arene have been isolated in the cone conformation, and structurally characterised as chloroform solvates. Thermogravimetric analysis demonstrated that the parent isopropylcalix[4]arene solvate is significantly more stable than the p-t-butylcalix[4]arene analogue, retaining the solvent up to a temperature of 125°C. It was found that the calix[4]arene ether sublimes at atmospheric pressure, and solvent-free crystals appropriate for structure determination were produced at reduced pressure. The p-t-butylcalix[4]arene ether was also isolated without solvent in the lattice, but in this case the calixarene was crystallised from acetone, as sublimation did not produce crystals of sufficient quality.     

Complexation of M3+ Lanthanide Cations by Calix[4]arene-CMPO Ligands: A Molecular Dynamics Study in Methanol Solution and at a Water/Chloroform Interface

Abstract

We report a molecular dynamics study on the 1:1 M³⁺ lanthanide (La³⁺, Eu³⁺ and Yb³⁺) inclusion complexes of an important extractant molecule L: a calix[4]arene-tetraalkyl ether substituted at the wide rim by four NH-C(O)-CH₂-P(O)Ph₂ arms. The M(NO₃)₃ and MCl₃ complexes of L are compared in methanol solution and at a water / chloroform interface. In the different environments the coordination sphere of M³⁺ involves the four phosphoryl oxygens and three to four loosely bound carbonyl oxygens of the CMPO-like arms. Based on free energy simulations, we address the question of ion binding selectivity in pure liquid phases and at the liquid-liquid interface where L and the complexes are found to adsorb. According to the simulations, the enhancement of M³⁺ cation extraction in the presence of the calixarene platform, examined by comparing L to the (CMPO)₄ “ligand” at the interface, is related to the fact that (i) the (CMPO)₄Eu(NO₃)₃ complex is more hydrophilic than the LEu(NO₃) one and (ii) the free CMPO ligands spread at the interface, and are therefore less organized for cation capture than L.     

Synthesis and photoinduced deprotection of calixarene derivatives containing certain protective groups

Calixarene derivatives 1a , 1b , and 1c containing pendant tert‐butoxycarbonyl (t‐BOC) groups were synthesized in 81, 93, and 83% yields, respectively, by the reaction of C‐methylcalix[4]resorcinarene (CRA), p‐methylcalix[6]arene (MCA), and p‐tert‐butylcalix[8]arene (BCA) with di‐tert‐butyl dicarbonate using triethylamine as a base in pyridine. Calixarene derivatives 2a , 2b , and 2c containing pendant trimethylsilyl ether (TMSE) groups were obtained in 58, 50, and 82% yields, respectively, by the reaction of CRA, MCA, and BCA with 1,1,1,3,3,3‐hexamethyldisilazane using chlorotrimethylsilane as an accelerator in tetrahydrofuran. Calixarene derivatives 3a , 3b , and 3c containing pendant cyclohexenyl ether (CHE) groups were also prepared in 65, 78, and 84% yields, respectively, by the reaction of CRA, MCA, and BCA with 3‐bromocyclohexene using potassium hydroxide as a base as well as tetrabutylammonium bromide as a phase‐transfer catalyst in N‐methyl‐2‐pyrolidone. The photoinduced deprotection of calixarene derivatives 1a – c was examined with bis‐[4‐(diphenylsulfonio)phenyl]sulfide bis(hexafluorophosphate) as a photoacid generator on UV irradiation followed by heating in the film state, and it was found that the deprotection of the t‐BOC groups of 1a proceeded smoothly in high conversion. The deprotection rates of the t‐BOC groups of 1b and 1c were much lower than that of 1a under the same irradiation conditions. The photoinduced deprotection of calixarenes 2b – c containing tetramethylsilane groups as well as 3a – c containing CHE groups were also examined under similar reaction conditions in the film state, and it was found that the deprotection rates of calixarenes 2b – c and 3a – c were lower than those of the corresponding 1a – c calixarenes. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1481–1494, 2001