Two AIE-active Schiff base fluorescent probes for highly selective recognition of Cu2+ ions.

Two helical Schiff base compounds (H4TPA and H4TPE) containing a triphenylamine (TPA) or tetraphenylethylene (TPE) scaffold were successfully synthesized and characterized. Both H4TPA and H4TPE exhibited typical aggregation-induced emission characteristics in the mixed solvent of THF/H2O. The two compounds also showed high selectivity and sensitivity for the recognition of Cu2+ over other ions in THF/HEPES (1:4, V/V, pH = 7.4, 2.0 × 10-5 M), and could be used as turn-off fluorescent probes for Cu2+. The stoichiometric ratios and association constants were estimated via Job's plots and UV-vis spectra titration, and the detection limits of H4TPA and H4TPE toward Cu2+ were calculated to be 2.41 × 10-7 M and 1.38 × 10-7 M, respectively. Besides, the crystal structure of the complex obtained from the interaction of H4TPA with Cu2+ well illustrated the binding modes, which helped us understand the Cu2+ recognition mechanism of H4TPA and H4TPE. Moreover, the detection of Cu2+ and spiked recovery experiments were carried out, which indicated that the two probes can be applied to Cu2+ detection in real samples with satisfactory recoveries.

Coordination-Driven Heterochiral Self-Assembly: Construction of Cd(II) Coordination Polymers with Sorption Behaviors for Iodine and Dyes.

A racemic bispyridyl ligand (L) was synthesized via a Schiff base condensation reaction. Four Cd(II) complexes, {[CdL2Cl2]·2DMF}n (1), [CdLI2]n (2), {[CdL2Br2]·4H2O}n (3), and {[CdL2(H2O)2](NO3)2·2CH3OH·8H2O}n (4), were synthesized and further characterized based on this ligand. Single-crystal structures show that the coordination-driven assembly of the bispyridyl ligand with Cd(II) salts bearing different counteranions can lead to multidimensional coordination polymers via a heterochiral self-discrimination process. Complex 1 exists as a one-dimensional (1D) looped chain polymer, and complex 2 exists as a 1D zigzag chain polymer. Complex 3 is a 2D grid coordination polymer, and complex 4 exists as a 3D framework polymer. Furthermore, the iodine sorption capacities of the four complexes were investigated in the solution of n-hexane and water as well as in the iodine steam. The dye sorption behaviors were investigated in water, which showed that complex 2 exhibited good adsorption for crystal violet (CV), while complex 4 had good adsorption capability toward direct yellow 4 (DY).

Five Porous Complexes Constructed from a Racemic Ligand: Synthesis, Chiral Self-Assembly, Iodine Adsorption, and Desorption Properties.

Herein, a chiral bispyridyl ligand (L) was designed and synthesized using a Schiff base condensation reaction, followed by a 1,3-H shift. Five complexes, [Zn2L2(OAc)4] (1), {[CdLCl2(DMF)]·4H2O}n (2), [Cd2L2I4]·4H2O (3), {[CdL2(H2O)2](NO3)2·2CH3OH}n (4), and [Hg2L2Cl4]·2DMF (5), were synthesized and characterized upon its reaction with Zn(II), Cd(II), or Hg(II) ions, respectively. X-ray crystallography shows that the organic compound exists as a racemic ligand with equal amounts of its R- and S-isomers, and all of the synthesized complexes exhibit heterochiral self-assembly via a chiral self-discrimination process. Complexes 1, 3, and 5 exist as centrosymmetric binuclear metallamacrocycles, while complexes 2 and 4 exist as 1D looped-chain coordination polymers. Inspired by the assembled structures of the five complexes, I2 adsorption/desorption measurements for the complexes were carried out. The results show that complexes 1 and 5 exhibit good adsorption capacities toward I2 in n-hexane and in water, respectively.

Coordination-Driven Self-Assembly of Complexes Constructed from Two Helical Ligands: Synthesis, Structures, and Selective Gas Adsorption Properties.

Two helical ligands (L1 and L2) were designed and synthesized by a Schiff base condensation reaction. Eight complexes, {[Zn(L1)I2]·H2O}n (1), [Cd2(L1)2I4(CH3OH)2] (2), [Hg2(L1)2I4] (3), [Ag(L1)NO3]n (4), [Ag2(L1)2(NO3)2DMSO]·H2O (5), {[Zn2(L2)2Cl4]·2CHCl3}n (6), {[Ag(L2)]·NO3}n (7), and {[Ag(L2)NO3]·CH3OH}n (8), were synthesized and characterized based on these two ligands. The crystal structures show that both Schiff base compounds exist as racemic ligands with equal amounts of P- and M-helicity, and the assembly of these racemic ligands with metal ions can lead to homochiral or heterochiral complexes via a chiral self-recognition or self-discrimination process. Complexes 2, 3, and 5 exist as heterochiral metallomacrocycles with a figure-eight conformation. Complexes 1, 6, and 8 exist as one-dimensional (1D) homochiral helical chain coordination polymers, while complexes 4 and 7 exist as 1D heterochiral helical chain coordination polymers. Furthermore, gas and vapor adsorption measurements show that all of the synthesized complexes exhibit good selective adsorption capacities toward methanol and ethanol vapor over N2, H2, and O2.

Twisted Schiff-base macrocycle showing excited-state intramolecular proton-transfer (ESIPT): assembly and sensing properties.

A Schiff-base macrocyclic host (MH) showing ESIPT and AIEE is reported for the first time; the fluorescent macrocycle exhibited good pH tolerance and could serve as a probe for Cu2+ and Fe3+ ion sensing and removal. In addition, a series of size-tunable nanoparticles was fabricated by the self-assembly of free MH and its coordination complex with Fe3+ in THF/water solution.

Self-Assembly by Tridentate or Bidentate Ligand: Synthesis and Vapor Adsorption Properties of Cu(II), Zn(II), Hg(II) and Cd(II) Complexes Derived from a Bis(pyridylhydrazone) Compound.

Four complexes, [Cu4L2(OCH3)2(CH3OH)2]·2H2O (1), [Zn2L2Cl4]·2H2O·2CH3OH (2), [Hg2L2Br4]·4CH3OH (3), and {[CdL2Cl2]·4H2O·4CH3OH}n (4), have been synthesized and characterized from a bis(pyridylhydrazone) ligand (L) with copper(II), zinc(II), mercury(II) or cadmium(II), respectively. Complex 1 exists as a centrosymmetric tetranuclear dimer with L as deprotonated tridentate ligand. Complexes 2 and 3 exist as centrosymmetric metallamacrocycles with L as bidentate ligand. Complex 4 exists as a 1D looped-chain coordination polymer. The thermal stabilities and vapor adsorption properties of the four complexes were investigated as well.

Outer surface interactions to drive cucurbit[8]uril-based supramolecular frameworks: possible application in gold recovery.

Q[8]-based honeycomb-like frameworks can be obtained in [AuCl4]--free aqueous HNO3 solution and aqueous HCl and HNO3 solutions that contain [AuCl4]-. The outer surface interaction of Q[8] with planar inorganic anions [AuCl4]- and NO3- is the main driving force. These frameworks exhibit a high selectivity for imprisoning [AuCl4]- that could establish a process for gold recovery.

Organic core-shell-shaped micro/nanoparticles from twisted macrocycles in Schiff base reaction.

Functional self-assemblies derived from noncovalent interactions such as lipid vesicles and DNA chiral double helices are a typical feature of natural life activity. Because of this phenomenon, a self-assembly approach for various functional organic particles is a desirable objective in supramolecular chemistry. Here, we report the discovery of enantiomeric conformers from a twisted macrocyclic host (MH), which was obtained from an achiral precursor by Schiff base reaction. Further studies suggest that a series of unexpected and stable core-shell-based organic micro/nanospheres can be directly precipitated from a simple reaction solution with high yield. A single-crystal X-ray diffraction analysis of MH revealed that the unusual C-H···π interaction triggered self-assembly of the enantiomeric forms in the solid state plays an important role in the formation of the core-shell-shaped organic particles.

Solvent-Switched Schiff-Base Macrocycles: Self-Sorting and Self-Assembly-Dependent Unconventional Organic Particles.

Organic reaction is a powerful and versatile tool for the creation of various new substrates and materials. However, there have been few reports of the direct fabrication of organic particles by organic reactions. Herein, we report that water as a co-solvent can efficiently switch a [2 + 2] macrocycle (3) to a [1 + 1] macrocycle (4) in a Schiff-base reaction from the same precursors at room temperature. Unexpectedly, a series of tunable organic micro/nanoparticles, including solid microspheres, core-shell spheres, and vesicles, could be directly precipitated in one-step from the reaction medium with high yield. X-ray structure analysis and other characterizations indicated that social self-sorting and narcissistic self-sorting of the macrocyclic frameworks of 3 and 4 through noncovalent interactions play crucial roles in the formation of such organic particles. Most interestingly, the facile and mild fabrication conditions of the particles allowed us to accurately and in situ monitor their intermediate formation by controlling the reaction time. This work thus provides an advancement of the fabrication of tunable organic particles.

2-[Hy-droxy(4-meth-oxy-phen-yl)methyl-idene]indane-1,3-dione.

In the title compound, C(17)H(12)O(4), there is an intra-molecular O-H⋯O hydrogen bond. The dihedral angle between the indane ring system [maximun deviation = 0.023 (2) Å] and the benzene ring is 37.42 (9)°.

Polymeric di- and discrete trinuclear silver(I) assemblies incorporating gamma-carbon bonded, neutral acetylacetone-imine motifs assembled from racemic and diastereopure N,N'-bis(acetylacetone)cyclohexanediimine units.

Diastereopure (1R,2R)-N,N'-bis(acetylacetone)cyclohexanedi-imine L(1) and its corresponding (1R,2R)L(1)/(1S,2S)L(2) enantiomeric mixture react with AgNO(3) to yield the unusual coordination polymer [Ag(2)(L(1))(L(2))(NO(3))(2)](n) (1) and the unique trimetallic discrete species {[Ag(3)(L(1))(3)(micro(3)-O,O,O-NO(3))(H(2)O)(3)](2)(NO(3))}(NO(3))(3) x 8.5H(2)O (2) which incorporates a symmetrical micro(3)-bridging nitrato group that gives rise to a C(3)-symmetric triskelion motif; both species also feature gamma-carbon eta(1) aryl-like coordination of neutral bridging acetylacetone-imine units to the respective Ag(I) centres.

4-(4-Oxopent-2-en-2-yl-amino)-1,2,4-triazol-1-ium-5-thiol-ate.

In the title compound, C(8)H(12)N(4)OS, an intra-molecular N-H⋯O hydrogen bond links the imine N atom to the oxo O atom. In the crystal, mol-ecules are linked by inter-molecular N-H⋯O and N-H⋯S hydrogen bonds, forming a two-dimensional framework.

Four zinc(II) helical coordination polymers and 78-membered six-node zinc metallacycle assembled from diastereopure N,N'-bis(acetylacetone)cyclohexanediimine.

The interaction of the diastereopure N,N'-bis(acetylacetone)cyclohexanediimine ligands, L(1)(1R,2R), L(2)(1S,2S), and their 1:1 mixture, with Zn(II) chloride has been investigated. Four new coordination polymers, [ZnL(1)Cl2 x H2O]n (1), [ZnL(2)Cl2 x H2O]n (2), [ZnL(2)Cl2]n (3), and [Zn6(L(2))6Cl12 x 2 H2O]n (4), each consisting of an infinite single helical chain displaying different pitches and/or handedness have been isolated. The complexed Schiff base ligands are present in their deprotonated enol forms, and the nitrogen atoms, which do not coordinate, are protonated because of proton transfer from the adjacent enol oxygen (coupled with concomitant N-H...O bond formation); each bound ligand is thus pseudo-zwitterionic. The respective zinc centers are bound to two chloro ligands and two oxygen donors from acacH-imine units belonging to different N,N'-bis(acetylacetone)cyclohexanediimine ligands such that the coordination at each zinc is distorted tetrahedral. Compounds 1 and 2, prepared from enantiopure L(1) and L(2), respectively, are enantiomers with similar structures, with the helical pitch in each being 17.0 A. Overall, the structure of 3 may be described as a one-dimensional helical chain with a pitch of 17.3 A, with each period corresponding to two L(2) ligands and two metal centers. The structure of [(Zn6L(2)6Cl12) x 2 H2O]n (4) contains six Zn(II) centers connected via six L(2) ligands to form a "bowed" helical repeat unit, with the pitch of the helix corresponding to 43.5 A. Supramolecular (intra- and intermolecular) aspects of all these unusual polymeric structures are discussed. Finally, the synthesis and characterization of an unprecedented six zinc-node discrete supramolecular assembly, [Zn6(L(1))3(L(2))3Cl12] (5), incorporating a 78-membered metallacycle, is also reported.

3,3'-Dibromo-4,4'-[(1R,2R)-cyclohexane-1,2-diyldiimino]dipent-3-en-2-one.

The asymmetric unit of the title compound, C(16)H(24)Br(2)N(2)O(2), contains two independent mol-ecules, each which has two intra-molecular N-H⋯O hydrogen bonds linking the amine N atoms to the enolic O atoms of the same acacH-imine unit. In the crystal, the mol-ecules are lined up by inter-molecular weak C-H⋯O hydrogen bonds, forming two vertical each other two-dimensional chains along the a axis and b axis of the unit cell, respectively.