Calix[4]arene-based ditopic receptor for dicarboxylates

Shape-selective recognition for the dicarboxylates in DMSO can be attained by a new calix[4]arene-based receptor 1 having two urea groups. Biologically active chorismate selectively bound in 1 over its dehydrated derivative. Molecular mechanics calculations gave a plausible explanation for the selective binding.     

Calix[4]arene-based ligands as endotoxin receptors

Three new calix[4]arene-based receptors as potential antimicrobial agents have been synthesized. Their recognition ability towards lipopolysaccharides of Gram-negative bacteria has been studied by NMR and UV titrations.     

Calix[4]- and calix[5]arene-based multicavity macrocycles

Synthesis and single-crystal X-ray structures of mixed triple and double calixarenes 6 and 7, obtained from the base-catalyzed condensation of calix[5]arene 1 with cone pertosylated calix[4]arene 2, are reported. VT-NMR studies on 7 are consistent with a molecular motion arising from the anti-gauche conformational interconversion of its ethylene linkages.     

Calix[4]arene-based bis[2]catenanes: synthesis and chiral resolution

The exclusive formation of hydrogen-bonded dimers between tetraaryl and tetratosylurea calix[4]arenes has been used to prepare a series of ten "bisloop" tetraurea calix[4]arenes 3, in which adjacent phenylurea groups are covalently linked through alpha,omega-dioxyalkane chains. This dimerization with tetratosylurea 2 as template preorganizes the alkenyl residues of tetra(m-alkenyloxyphenyl) ureas 1 and enables their selective connection in high yield (up to 95 %) by olefin metathesis followed by hydrogenation. The "bisloop" calixarenes 3 also exclusively form heterodimers with 1. Thus, in a separated metathesis/hydrogenation sequence, a series of 14 cyclic bis[2]catenanes 4, in which two calix[4]arenes are connected through their wide rims by two pairs of interlocked rings (total size 29 to 41 atoms), were prepared in yields of up to 97 %. Optical resolution of these chiral bis[2]catenanes was studied by HPLC on chiral stationary phases. The single-crystal X-ray structure of one example (4(P,10)) confirmed the interlocking rings and revealed that the hydrogen-bonded dimeric capsule of the calix[4]arene can be "completely" opened.     

Calix[4]arene-based metal-organic frameworks: towards hierarchically porous materials

An upper rim-functionalised calix[4]arene dicarboxylic acid (H(2)caldc) has been used to prepare four metal-organic frameworks, three of which have been structurally characterised and shown to form two- or three-dimensional network structures. Simulations suggest that such networks are likely to display interesting selectivity to guest molecules.     

Calix[8]arene-based glycoconjugates as multivalent carbohydrate-presenting systems

An efficient approach for the introduction of eight mono- or disaccharide sugar moieties (d-glucose, N-acetyl-d-glucosamine, d-galactose, l-fucose, d-maltose and d-cellobiose) at the upper rim of calix[8]arene 1, using thioureido linkers, is reported. The obtained water-soluble, nanosized glycocalix[8]arenes 5b-10b may act as biomimetic carbohydrate systems and as hosts for highly polar organic molecules. Preliminary ¹H NMR complexation experiments of octaglycosyl derivative 7b and 10b with ionic guests are also reported.     

Calix[4]arene-based ditopic receptors for simultaneous recognition of fluoride and cobalt(II) ions

A series of calix[4]arene based ditopic receptors possessing bipyridyl and hydrazone units have been synthesized and evaluated for ionic recognition. It has been observed that the synthesized derivatives function as allosteric receptors for simultaneous recognition of Co²⁺and F^? ions through non-covalent interactions. Significant bathochromic shifts in the UV–visible spectrum with a profound colour change promise their use to engineer novel applications.     

Calix[4]arene-based Zn2+ complexes as shape- and size-selective catalysts of ester cleavage

[structures: see text] The kinetics of methanolysis of a number of esters endowed with a carboxylate anchoring group have been investigated in the presence of di- and trinuclear Zn2+ complexes of calix[4]arenes functionalized at the upper rim with nitrogen ligands. The results (i) emphasize the importance of a good match between ester size and intermetal distance, (ii) reveal a substrate independent superiority of the 1,2-vicinal dinuclear catalyst 1-Zn2 to its 1,3-distal regioisomer 2-Zn2, and (iii) provide further evidence for the concurrence of the three metal ions of 3-Zn3 in the catalytic mechanism.     

4-tert-butylcalix[4]arene-based porous structures

Microporous material with a large surface area is obtained through the controlled desolvation of 4-tert-butylcalix[4]arene complex with acetonitrile.     

Calix[4]arene-based, Hg2+ -induced intramolecular fluorescence resonance energy transfer chemosensor

A novel calix[4]arene-based chemosensor 1 based on Hg2+-induced fluorescence resonance energy transfer (FRET) was synthesized, and its sensing behavior toward metal ions was investigated by UV/vis and fluorescence spectroscopies. Addition of Hg2+ to a CH3CN solution of 1 gave a significantly enhanced fluorescence at approximately 575 nm via energy transfer (FRET-ON) from the pyrenyl excimer to a ring-opened rhodamine moiety. In contrast, addition of Al3+ induced a distinct increase of pyrenyl excimer emission ( approximately 475 nm), while no obvious FRET-ON phenomenon was observed. Different binding behaviors of 1 toward Hg2+ and Al3+ were also proposed for the interesting observation.     

Calix[4]arene-porphyrin molecular receptors for selective binding of ethylenediamines

A new zinc calix[4]arene-bis-porphyrinate was synthesized and its 1 : 1 and 1 : 2 complexation reaction with ehtylenediamine, diethylenediamine, and triethylenediamine in toluene at 298 K was studied by spectrophotometric titration and ¹H NMR.     

Hydrazide as a new hydrogen-bonding motif for resorcin[4]arene-based molecular capsules

The resorcin[4]arene-based benzoylhydrazide cavitands formed stable molecular capsules in nonpolar solvents by the eight intermolecular N-H...O=C hydrogen bondings, two from each four paired hydrazides, and the four intramolecular O-H2C-O...H-N hydrogen bondings on each cavitand. The stability of these molecular capsules depends on the encapsulated guest in the following order: CH3SO3(-) > CH3CO2(-) > CH3CH2NH2 x HCl approximately = CH3NH2 x HCl > (CH3)4N(+) > toluene > C2D2Cl4.     

Sulfonylcalix[4]arene-based Coordination Supercontainers

Sulfonylcalix[4]arenes-based coordination containers, namely metal-organic supercontainers(MOSCs), are a new class of coordination containers constructed from the self-assembly of divalent metal ions, suitable carboxylate linkers, and sulfonylcalix[4]arenes container precursor. MOSCs feature both endo cavity surrounded by carboxylate linkers and exo cavities originated from the upper rim of sulfonylcalix[4]arenes. The molecular topologies and endo cavity of MOSCs are tuneable via judicious design of carboxylate linkers, while the modulation of endo cavity are accessible by chemical modification on the para substituent group of the sulfonylcalix[4]arenes. In this paper, recent advances and typical examples of design and functionalization of MOSCs are presented.     

Calix[4]azulene

Azulene reacts with paraformaldehyde in the presence of florisil to give excellent yields of calix[4]azulene.     

Calix[4]arene based molecular probe for sensing copper ions

A novel calix[4]arene based molecular probe for metal ions has been designed, synthesized and evaluated. Studies on its binding with different metal ions reveal a noticeable naked eye color change, bathochromic shift in absorption spectrum and remarkable enhancement in fluorescence emission in the presence of Cu²⁺ only. The role of calix[4]arene scaffold for selective recognition of Cu²⁺ has been demonstrated by repeat evaluation and analysis of an appropriate reference molecule. A rational explanation for fluorescence enhancement in 3 on interaction with copper has been suggested.     

Pi-dimer formation as the driving force for calix[4]arene-based molecular actuators

Stable pi-dimers are formed upon oxidation of the model units of proposed calix[4]arene-based molecular actuators in a solvent of low dielectric constant (CH 2Cl 2) at room temperature. Evidence from UV-vis, EPR, and DPV are all in agreement with the pi-dimer formation. In addition, pi-dimer formation is dependent upon the conformational flexibility of the calix[4]arene hinge.     

Calix[4]arene-porphyrin conjugates as versatile molecular receptors for anions

[structure: see text] Appending tetraphenylporphyrin units to the calix[4]arene skeleton via the ureido function leads to novel anion receptors designed for anion and/or cation detection by UV-vis spectroscopy. Calixarenes in the cone or 1,3-alternate conformations bearing two ureido moieties on the upper rim represent well-preorganized cavities where the anion can be held by synchronous hydrogen bonding interaction with the NH groups.     

Calix[4]arene-based Mannich and Schiff bases as versatile receptors for dichromate anion extraction: synthesis and comparative studies

A series of novel calix[4]arene-based Mannich (5 and 6) and Schiff base (9–11) receptors have been synthesized and characterized by various analytical techniques. Competitive two-phase extraction experiments of these novel calix[4]arene amine- and imine-containing derivatives revealed a strong affinity for dichromate anions $\left({\text{Cr}}_2{\text{O}}_7^{2?}/{\text{HCr}}_2{\text{O}}_7^{?}\right)$. The protonated alkylinium form of 5, 6 and 9–11 proved to be effective extractants for transferring the dichromate anions from an aqueous into an organic phase. Moreover, the extraction of dichromate anions by 5 and 9 in the presence of competitive anions such as F^?, Cl^?, Br^?, ${\text{NO}}_3^{?}$, ${\text{NO}}_2^{?}$, ${\text{PO}}_4^{3?}$ and ${\text{SO}}_4^{2?}$ showed that 5 and 9 could be selective anion receptors for dichromate anions in the presence of those anions.     

N-硫脲基套索杯[4]冠醚与四硫脲基杯[4]芳烃的合成

控制反应物的物质的量比, 杯式对叔丁基杯[4]-1,3-二乙酸乙酯衍生物1与5或50倍二乙烯三胺反应, 分别得到杯[4]氮杂冠醚2和开链的氮杂杯[4]芳烃衍生物3. 化合物2和3进一步与异硫氰酸苯酯反应得到首例侧链含硫脲基的套索杯[4]氮杂冠醚4和含4个硫脲基的杯[4]芳烃衍生物5, 产率为92%和87%. 新化合物的结构与构象经元素分析、红外、质谱、核磁共振谱等表征证实.