•Calix[3]carbazole is a non-crown-ether based, C3-symmetrical, selective receptor for Ba2 +.•The marriage of cation–π and cation–dipole forces contribute to the interaction between calix[3]carbazole and Ba2 +.•The [1-Pb2 +] complex could serve as the “OFF-ON” sensor for Ba2 +.The binding ability of calix[3]carbazole (1) to metal ions has been investigated. It is found that 1 could serve as a non crown ether based, C3-symmetrical receptor for Ba2 + via the marriage of cation–π and cation–dipole interactions. FID assay further illustrates that 1 could selectively interact with Ba2 + over Pd2 +. A possible binding mechanism for [1-Ba2 +] complex is proposed.

Herein, we report a carbazolyl tubular macrocycle (3), which possesses a “π-tube” capable of encapsulating and sensing bisphenol F (BPF), which is a toxic industrial material. In this work, the synthesis of 3, its conformation in solution as well as its binding property to BPF have been investigated. Nuclear magnetic resonance (NMR), ultraviolet–visible light (UV-vis), fluorescence spectra, and molecular modeling studies reveal that the “π-tube” of 3 in 1,3-alternate conformation could encapsulate BPF with 1:1 binding stoichiometry in water, with its orthogonal tweezers sandwiching the two phenol units of BPF. Moreover, 3 could serve as a sensitive fluorescent probe for BPF (limitation of detection = 157 nM).

The one-step synthetic strategy for the preparation of the hitherto unknown calix[3]carbazole from readily available starting materials is described. Calix[3]carbazole is obtained in 20% yield, and it could selectively bind the N(C2H5)4+ cation (tetraethylammonium, TEA) via cation−π interactions. The experimental and modeling results indicate that calix[3]carbazole possesses a larger π-cavity as well as a better chromophoric property than the traditional phenol-based macrocycles, and thus is capable of binding to and optically responding to the relatively large guest TEA.

The synthesis of a novel methylene-bridged biscarbazole derivative 1 was described and the possible mechanism for its unexpectedly synthesized intermediate, compound A, was postulated. The binding properties of 1 to both Ct-DNA and nucleotides were investigated via fluorescent and UV–Vis spectra. The spectral investigations illustrated that this binary carbazole exhibited higher binding abilities to both Ct-DNA and nucleotides than its monomeric form, owing to the structurally flexible nature of double carbazole moieties fine-tuned by this non rigid methylene-linkage.Graphical abstract