A rationally designed simple organic molecule exhibits white-light emission in methanol/water and acetonitrile/water mixtures.

A rationally designed probe L, which consists of both cation and anion binding sites, is capable of displaying interesting aggregation induced emission (AIE) properties. L not only can sense Al(3+) and Zn(2+) through selective turn-on fluorescence responses in 9 : 1 methanol-HEPES buffer (5 mM, pH 7.3; 9 : 1, v/v) medium due to metal ion triggered AIE activity, but also can distinguish them through individual emission signals. L can also detect Cu(2+) in mixed buffer medium and F(-) in acetonitrile through sharp colorimetric responses. All the sensing processes are conspicuous through the naked eye. A theoretical study strongly backed the proposed sensing mechanisms.

A meta-phenylenediamine-based disubstituted bis-urea receptor L1 with electron-withdrawing 3-chloro and electron-donating 4-methylphenyl terminals has been established as a potential system to fix and efficiently capture atmospheric CO as air-stable entrapment of an unprecedented {CO-(HO)-CO} cluster (complex 1a) within its tetrameric long straight pillar-like assembly entirely sealed by n-TBA cations via formation of a barrel-type architecture. L1 and its isomeric 4-bromo-3-methyl disubstituted bis-urea receptor L2 have been found to entrap similar kinds of water-free naked sulfate-sulfate double anion (complexes 1b and 2a) by cooperative binding of urea moieties inside the two pairs of the inversion-symmetric linear tetrameric barrel of L1 and L2, respectively. On the other hand, in the presence of excess halides, L1 self-assembles to form hexa-coordinated fluoride complex 1c and tetra-coordinated bromide complex 1d, while L2 self-assembles to form penta-coordinated fluoride complex 2b in the solid state via semicircular receptor architectures and non-cooperative H-bonding interactions of urea moieties.

meta-Phenylenediamine based two linear bis-urea anion receptors, L 1 (meta-nitro) and L 2 (para-nitro), have been synthesized which showed strong binding affinities toward halides as well as planar and tetrahedral oxyanions. In the presence of excess fluoride anion, L 1 self-assembles to entrap a cyclic fluoride–water tetrameric cluster within its tetrameric pillar-like assembly of each urea arm (complex 1a). In the presence of sulfate anion, L 1 self-assembles in an identical fashion to entrap the bigger tetrahedral anion (complex 1b), whereas two urea moieties of two different receptor molecules of L 1 have been structurally authenticated to be sufficient to stabilize the simple Y-shaped acetate anion in complex 1c. On the other hand, receptor L 2 , with a bis­(para-nitro urea) functional group, especially in the presence of sulfate anion, self-assembles like long straight pillars entrapping sulfate–water–sulfate cluster {SO4 2–-(H2O)3-SO4 2–} (complex 2a). Additionally, L 2 forms a host–guest assembly with the cation and solvent (DMSO) coordinated bromide anion (complex 2b) when treated with excess bromide anion as n-tetrabutylammonium salt. All the complexes have been characterized by powder X-ray diffraction and 1H NMR and 13C NMR spectroscopy, which are in full support and consistent with solid-state single crystal X-ray diffraction results.

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A logically synthesized ortho-phenylenediamine based chloro-methyl disubstituted neutral organic bis-urea receptor L 1 with the aid of three symmetry-independent units encapsulates an unusual triangular [(chloride)3-DMSO] guest assembly (complex 1a) via formation of DMSO + host + salt cocrystals within its trimeric paddle-wheel shaped cavity sealed by three n-TBA cations and exhibits diverse anion binding properties with oxyanions along with the chloride complex of its isomeric bromo-methyl disubstituted bis-urea receptor L 2 . Receptor L 2 and L 1 both form a similar kind of noncapsular 2:2 host–guest assembly in the presence of excess chloride (complex 2a) and acetate (complex 1b) respectively by noncooperative H-bonding interactions of urea groups which are attributed to the effect of meta-functionalization with respect to the adjacent N–H part of the urea moiety, whereas another planar oxyanion carbonate is doubly encapsulated within the tetrameric capsular cavity of L 1 in the solid state (complex 1c). Moreover, receptor L 2 conforms to a similar kind of cation sealed 2:1 host–guest pseudocapsular complex in the presence of larger coordinating anions such as tetrahedral sulfate (complex 2b) and octahedral hexafluorosilicate (complex 2c). 1H NMR titration experiments are also performed using n-TBA/TEA salts of anions to investigate the solution state anion binding behavior of isomeric L 1 and L 2 and corroborate the results obtained in the solid-state studies.

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