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A calix[4]arene‐based gelator 1, with lower‐rim mono triazolylpyridine group, capable of spontaneous self‐assembly into microspheres in different ethanol/H2O mixtures, is synthesized. The concentration‐dependent 1H NMR spectra and X‐ray single‐crystal structure of 1 provided evidence for self‐assembly of gelator 1 via cooperative interactions of intermolecular noncovalent forces. Furthermore, metallogels by self‐assembly of 1 was found to exhibit remarkable selectivity toward Hg2+ ions. 1H NMR spectra support that Hg2+ ion was bound to the nitrogen atoms of two coordination sites of 1, which composed of triazole and pyridine. Moreover, the results of field emission scanning electron microscopy and rheology experiments indicated that Hg2+ ions not only enhanced the gelling ability of gelator 1 in ethanol but also led to morphological change of its self‐assembly through metal‐ligand interactions. Finally, the in situ gelation, triggered by mixing a gelator solution of 1 in ethanol with water samples such as deionized (DI), tap, and lake water, leads to the effective removal of Hg(II) from a water sample which reduced from 400 to 1.6 ppm. [ABSTRACT FROM AUTHOR]

Calix[4]arene 1, with two lower-rim isoxazolylchloroanthracene groups, is shown to be not only a chromogenic but also a fluorogenic chemodosimeter for the selective sensing of Cu2+. The binding properties of ligand 1 and control compounds 2 and 3 toward metal ions in CH3CN/CHCl3 (v/v, 1 : 1) were investigated by UV-vis and fluorescence spectroscopy. The results showed that only ligand 1 was highly selective for Cu2+ ions. When complexed with Cu2+, ligand 1 displayed a new absorption band around 435 nm and the color of the solution changed from colorless to yellow. Furthermore, the fluorescence of ligand 1 was severely quenched by Cu2+ and the limit of detection (LOD) was determined to be 1.674 μM. Therefore, compound 1 is not only a chromogenic but also a fluorogenic sensor for the detection of Cu2+ ions over other metal ions examined. When complexed with ligand 1, Cu2+ was reduced to Cu+ by the free phenolic-OH of ligand 1 and concurrently the phenol was oxidized by Cu2+ to quinones. The 1H NMR, EPR, and FTIR spectra provided evidence for the redox behavior of ligand 1 with Cu2+. The isolation of calix[4]diquinone 8 and Cu(CH3CN)4ClO4 from the reaction of ligand 1 with Cu(ClO4)2 confirmed their redox reaction. [ABSTRACT FROM AUTHOR]

Two structurally simple Pt(II)‐directed self‐assembly loop complexes were prepared by reactions of cis‐(PEt3)2Pt(OTf)2 and the corresponding pyridylamide‐functionalized pyridyl ligands. Both Pt(II)‐based complexes exhibit singlet fluorescence, indicating that the platinum metal serves only as a structural, rather than a direct photophysical role within the loop framework. The crystal structure of complex 1 shows a distorted loop conformation with a hydrophobic pocket defined by the bridging ligands. The anion binding affinities of these two complexes were investigated with a range of anions. Such studies using UV–vis absorption, fluorescence, and 1H NMR titrations showed that complex 1 exhibits excellent binding sensitivity and selectivity for benzoate over acetate in solution via a combination of electrostatic, hydrogen‐bonding, and π–π interactions, whereas complex 2 shows comparable binding affinities toward acetate and benzoate due to the lack of favorable aromatic π–π interaction. [ABSTRACT FROM AUTHOR]

The present article describes the design and synthesis of new biprivileged molecular scaffolds with diverse structural features. Commercially available, simple heterocyclic building blocks such as 4-fluoro-3-nitrobenzoic acid, 2-chloro-3-nitrobenzoic acid, and indoline were utilized for the synthesis of the novel heterocycles. Pictet-Spengler-type condensation was used as a key step to construct tetracyclic indolo-benzodiazepines and indolo-quinoxalines linked with substituted benzimidazoles. Analysis of single crystals of representative compounds showed that these molecular skeletons have the potential to present various substituents with distinct three-dimensional orientations. [ABSTRACT FROM AUTHOR]

Ligand 1, a rim-differentiated pillar[5]arene macrocycle modified with five naphthalimide groups through click chemistry, serves as an effective ratiometric fluorescent chemosensor for Cu 2+ . In contrast to the monomeric naphthalimide control compound 2, which shows only monomer emission, ligand 1 demonstrates dual emission characteristics encompassing both the monomer and excimer of the naphthalimide moieties. The binding properties of ligand 1 toward 15 different metal ions were systematically investigated in CH 2 Cl 2 /CH 3 CN (v/v, 1 : 1) by UV-vis and fluorescence spectroscopy. Remarkably, ligand 1 exhibits exceptional selectivity for Cu 2+ ions. Upon complexation with Cu 2+ , the excimer emission of ligand 1 diminishes, concomitant with an enhancement of its monomer emission. The binding ratio for 1·Cu 2+ was determined to be 1 : 1, with an association constant of (3.39 ± 0.40) × 10 5 M -1 calculated using a nonlinear least-squares curve-fitting method. Furthermore, the limit of detection (LOD) was found to be 185 ± 7 nM. Our results from 1 H NMR titration, high-resolution mass spectrometry analysis and density functional theory calculations of 1·Cu 2+ suggest synergistic coordination between Cu 2+ and the triazole groups on ligand 1.

A calix[4]arene-based gelator 1, with lower-rim mono triazolylpyridine group, capable of spontaneous self-assembly into microspheres in different ethanol/H 2 O mixtures, is synthesized. The concentration-dependent 1 H NMR spectra and X-ray single-crystal structure of 1 provided evidence for self-assembly of gelator 1 via cooperative interactions of intermolecular noncovalent forces. Furthermore, metallogels by self-assembly of 1 was found to exhibit remarkable selectivity toward Hg 2+ ions. 1 H NMR spectra support that Hg 2+ ion was bound to the nitrogen atoms of two coordination sites of 1, which composed of triazole and pyridine. Moreover, the results of field emission scanning electron microscopy and rheology experiments indicated that Hg 2+ ions not only enhanced the gelling ability of gelator 1 in ethanol but also led to morphological change of its self-assembly through metal-ligand interactions. Finally, the in situ gelation, triggered by mixing a gelator solution of 1 in ethanol with water samples such as deionized (DI), tap, and lake water, leads to the effective removal of Hg(II) from a water sample which reduced from 400 to 1.6 ppm., (© 2023 Wiley-VCH GmbH.)

Calix[4]arene 1, with two lower-rim isoxazolylchloroanthracene groups, is shown to be not only a chromogenic but also a fluorogenic chemodosimeter for the selective sensing of Cu 2+ . The binding properties of ligand 1 and control compounds 2 and 3 toward metal ions in CH 3 CN/CHCl 3 (v/v, 1 : 1) were investigated by UV-vis and fluorescence spectroscopy. The results showed that only ligand 1 was highly selective for Cu 2+ ions. When complexed with Cu 2+ , ligand 1 displayed a new absorption band around 435 nm and the color of the solution changed from colorless to yellow. Furthermore, the fluorescence of ligand 1 was severely quenched by Cu 2+ and the limit of detection (LOD) was determined to be 1.674 μM. Therefore, compound 1 is not only a chromogenic but also a fluorogenic sensor for the detection of Cu 2+ ions over other metal ions examined. When complexed with ligand 1, Cu 2+ was reduced to Cu + by the free phenolic-OH of ligand 1 and concurrently the phenol was oxidized by Cu 2+ to quinones. The 1 H NMR, EPR, and FTIR spectra provided evidence for the redox behavior of ligand 1 with Cu 2+ . The isolation of calix[4]diquinone 8 and Cu(CH 3 CN) 4 ClO 4 from the reaction of ligand 1 with Cu(ClO 4 ) 2 confirmed their redox reaction.

A series of platinum(II) acetylide complexes with elaborate long-chain pyridine-2,6-dicarboxamides was synthesized. These metal complexes are capable of immobilizing organic solvents to form luminescent metallogels through a combination of intermolecular hydrogen bonding, aromatic π-π, and van der Waals interactions. Fibrillar morphologies were identified by TEM for these metallogels. Unique photophysical properties associated with the sol-to-gel transition have been disclosed with luminescence enhancement at elevated temperatures, which is in sharp contrast to typical thermotropic organogels or metallogels reported in the literature. Such unusual luminescence enhancement is attributed to the increased degree of freedom at higher temperatures that results in the formation of favorable molecular aggregates in the excited state through enhanced aromatic π-π and metallophilic Pt(II)···Pt(II) interactions. Structurally similar Pt-bp3 is not able to gel any common organic solvents. The inability of Pt-bp3 to form gels illustrates the importance of gelation to the macroscopic photophysical properties; Pt-bp3 does not show emission enhancement at elevated temperatures due to its low tendency to form strong aggregates in the ground state., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of platinum(II) terpyridine complexes featuring an aminostilbene donor-acceptor framework was synthesized. The complex with a dithiaazacrown moiety exhibits a highly sensitive and selective colorimetric response to a Hg(2+) cation through modulation of the relative strength of ICT and MLCT transitions. The results from (1)H NMR titration suggest the existence of a weak Pt(II)···Hg(II) metallophilic interaction at low Hg(2+) concentration.