Synthesis, binding properties and theoretical studies of p-tert-butylhexahomotrioxacalix[3]arene tri(adamantyl)ketone with alkali, alkaline earth, transition, heavy metal and lanthanide cations

Synthesis of Mono-O-alkylated Homooxacalix[3]arene and a Protection-Deprotection Strategy for Homooxacalix[3]arene

The regioselective synthesis of mono-O-alkylated homooxacalix[3]arene is accomplished for the first time. The synthetic route relies on two key steps: (i) a facile protection of two OH groups at the lower rim of the homooxacalix[3]arene and (ii) the deprotection of 9-anthrylmethyl groups via the Pd/C-catalyzed hydrogenation under atmospheric hydrogen. An efficient protection-deprotection strategy for the functionalization of homooxacalix[3]arene is presented.

Synthesis, structure and properties of imidazolium-based energetic ionic liquids

Energetic ionic liquids bearing a wide liquid temperature range were easily synthesized, which display good thermal stabilities and energetic properties.

Co-existence of Distinct Supramolecular Assemblies in Solution and in the Solid State

The formation of distinct supramolecular assemblies, including a metastable species, is revealed for a lipophilic guanosine (G) derivative in solution and in the solid state. Structurally different G‐quartet‐based assemblies are formed in chloroform depending on the nature of the cation, anion and the salt concentration, as characterized by circular dichroism and time course diffusion‐ordered NMR spectroscopy data. Intriguingly, even the presence of potassium ions that stabilize G‐quartets in chloroform was insufficient to exclusively retain such assemblies in the solid state, leading to the formation of mixed quartet and ribbon‐like assemblies as revealed by fast magic‐angle spinning (MAS) NMR spectroscopy. Distinct N−H⋅⋅⋅N and N−H⋅⋅⋅O intermolecular hydrogen bonding interactions drive quartet and ribbon‐like self‐assembly resulting in markedly different 2D ¹H solid‐state NMR spectra, thus facilitating a direct identification of mixed assemblies. A dissolution NMR experiment confirmed that the quartet and ribbon interconversion is reversible–further demonstrating the changes that occur in the self‐assembly process of a lipophilic nucleoside upon a solid‐state to solution‐state transition and vice versa. A systematic study for complexation with different cations (K⁺, Sr²⁺) and anions (picrate, ethanoate and iodide) emphasizes that the existence of a stable solution or solid‐state structure may not reflect the stability of the same supramolecular entity in another phase.

Selective recognition of biogenic amine hydrochlorides by heteroditopic dihomooxacalix[4]arenes

New receptors for the selective binding of monoamine neurotransmitters and trace amine hydrochlorides, as ion pairs, are described.

Studies of aluminum (III) ion-selective optical sensor based on a chromogenic calix[4]arene derivative

An optical chemical sensor based on azo-calix[4]arene derivative is developed for the determination of aluminum (III) ions in aqueous solutions. The complex formation ability of azo-calix[4]arene toward metal cations such as Li(I), Cs(I), K(I), Sn(II), Pb(II), Cu(II), Eu(III), Er(III) and Al(III) is investigated by UV-vis spectroscopy. Assessments of results reveal that the azo-calix[4]arene derivative has high affinity to Al(III). The stoichiometric ratio and the association constant were determined as 1:1 and 1.24×10(4)M(-1), respectively for the complex between Al(3+) and the azo-calix[4]arene. The sensing film is fabricated by spin coating on glass plates. Under the optimized conditions, at pH 6.8, the proposed optical sensor displays a linear response to Al(3+) over 10(-7) to 10(-5)M range with response time of 12min. The optical sensor can be regenerated with HNO3 solution. In addition to its high stability and reproducibility, the sensor shows good selectivity for Al(3+) ion.

Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2':6',2''-terpyridine ligand: implications for actinide(III)/lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2' : 6',2''-terpyridine (CyMe(4)-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO(2)(2+)) ion were obtained by X-ray crystallographic analysis, and they showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. (1)H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligands.

Fifty years of oxacalix[3]arenes: A review

Hexahomotrioxacalix[3]arenes, commonly called oxacalix[3]arenes, were first reported in 1962. Since then, their chemistry has been expanded to include numerous derivatives and complexes. This review describes the syntheses of the parent compounds, their derivatives, and their complexation behaviour towards cations. Extraction data are presented, as are crystal structures of the macrocycles and their complexes with guest species. Applications in fields as diverse as ion selective electrode modifiers, fluorescence sensors, fullerene separations and biomimetic chemistry are described.

Ratiometric fluorescent receptors for both Zn2+ and H2PO4(-) ions based on a pyrenyl-linked triazole-modified homooxacalix[3]arene: a potential molecular traffic signal with an R-S latch logic circuit

A ratiometric fluorescent receptor with a C(3) symmetric structure based on a pyrene-linked triazole-modified homooxacalix[3]arene (L) was synthesized and characterized. This system exhibited an interesting ratiometric detection signal output for targeting cations and anions through switching the excimer emission of pyrene from the "on-off" to the "off-on" type in neutral solution. (1)H NMR titration results suggested that the Zn(2+) center of receptor L·Zn(2+) provided an excellent pathway of organizing anion binding groups for optimal host-guest interactions. It is thus believed that this receptor has potential application in sensing, detection, and recognition of both Zn(2+) and H(2)PO(4)(-) ions with different optical signals. In addition, the fluorescence emission changes by the inputs of Zn(2+) and H(2)PO(4)(-) ions can be viewed as a combinational R-S latch logic circuit at the molecular level.