A Hexahomotrioxacalix[3]arene-Based Ditopic Receptor for Alkylammonium Ions Controlled by Ag⁺ Ions.

A receptor cone-1 based on a hexahomotrioxacalix[3]arene bearing three pyridyl groups was successfully synthesized, which has a C3-symmetric conformation and is capable of binding alkylammonium and metal ions simultaneously in a cooperative fashion. It can bind alkylammonium ions through the -cavity formed by three aryl rings. This behaviour is consistent with the cone-in/cone-out conformational rearrangement needed to reorganize the cavity for endo-complexation. As a C3-symmetrical pyridyl-substituted calixarene, receptor cone-1 can also bind an Ag⁺ ion, and the nitrogen atoms are turned towards the inside of the cavity and interact with Ag⁺. After complexation of tris(2-pyridylamide) derivative receptor cone-1 with Ag⁺, the original C3-symmetry was retained and higher complexation selectivity for n-BuNH3⁺ versus t-BuNH3⁺ was observed. Thus, it is believed that this receptor will have a role to play in the sensing, detection, and recognition of Ag⁺ and n-BuNH3+ ions.

A novel fluorescence "on-off-on" chemosensor for Hg(2+)via a water-assistant blocking heavy atom effect.

Upper rim pyrene-functionalized hexahomotrioxacalix[3]arene L was synthesized via Click chemistry, and its fluorescence behaviors toward several common metal cations were investigated. L exhibited a significant fluorescence quenching response to Hg(2+) in CH3CN solution, which was unaffected by the coexistence of other competitive metal cations. Thus, L can be utilized as a highly selective and sensitive fluorescent chemosensor for Hg(2+) with a detection limit in the nM level. Interestingly, the quenched fluorescence emission can be successfully revived upon the addition of water. In this process, the heavy atom effect of Hg(2+) can be blocked by further coordination of a water molecule and resulted in the revival of the fluorescence emission of L/Hg(2+) complex. Particularly, other polar solvents such as CH3OH and CH3CH2OH also have the ability to revive the fluorescence emission of the L/Hg(2+) complex, but on a much smaller scale than observed for H2O. The heavy atom effect and blocking thereof were demonstrated within the same system by the use of a C3-symmetric homooxacalix[3]arene scaffold. The present studies provided further evidence for the blocking heavy atom effect.

Click-modified hexahomotrioxacalix[3]arenes as fluorometric and colorimetric dual-modal chemosensors for 2,4,6-trinitrophenol.

A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV-vis and fluorescence spectroscopy studies. (1)H NMR titration analysis verified that CH⋯O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer.

An Unprecedented Photochemical Reaction for Anthracene-Containing Derivatives.

A series of anthracene-containing derivatives have been synthesised and characterised. The photochemical behaviour of these derivatives have been investigated by 1 H NMR spectroscopy. An unprecedented photolysis reaction for anthracene-containing derivatives was observed in the case of anthracenes directly armed with a -CH2 O-R group upon UV irradiation. The photolysis reaction process has been demonstrated to occur in three steps. Firstly, the anthracene-containing derivatives are converted into the corresponding endoperoxide intermediate upon UV irradiation in the presence of air; then, the endoperoxide intermediate is decomposed to the corresponding starting compound and 9-anthraldehyde; finally, 9-anthraldehyde is further oxidised to anthraquinone. Additionally, the photolysis reaction of anthracene-containing derivatives is significantly promoted in the presence of a thiacalix[4]arene platform.

Tri-substituted hexahomotrioxacalix[3]arene derivatives bearing imidazole units: synthesis and extraction properties for cations and chromate anions.

The article describes the synthesis and extraction properties of the new hexahomotrioxacalix[3]arenebased derivatives cone- and partial-cone-2 bearing 1-methyl-1H-imidazole moieties at the lower rim. It has been demonstrated that O-alkylation of the flexible macrocycle 1 with 2-(chloromethyl)-1-methyl-1Himidazole hydrochloride affords tri-O-alkylated products with a cone or partial-cone conformation. Alkali metal salts such as NaH and Cs2CO3 can play an important role in the conformer distribution via a template effect. The conformation of receptors 2 has been confirmed by X-ray crystallographic analysis. Furthermore, the complexation properties of receptors 2 toward selected alkali/transition metal cations and alkylammonium ions are reported. The new 1-methyl-1H-imidazole-substituted hexahomotrioxacalix[3] arene frameworks are also efficient extractors of HCr2O7(-)/Cr2O7(2-) anions at low pH.