M(II) effect on encapsulation of guests into a series of M3L2 chiral cages: enantio-recognition.

Self-assembly of M(ClO4)2 (M2+ = Ni2+, Cu2+, and Zn2+) with (1S,1'S,1''S,2R,2'R,2''R)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl) trinicotinate (s,r-L) and the corresponding enantiomer (r,s-L) as a pair of chiral tridentate donors gives rise to the chiral cage pairs [M3(s,r- and r,s-L)2](ClO4)6. For the two pairs of [(Me2CO)(H2O)@M3(r,-s and s,r-L)2](ClO4)6 (M2+ = Ni2+ and Zn2+), the inner cavity is occupied by both an acetone and a single water molecule, whereas for the copper(II) pair of [Me2CO@Cu3(r,s- and s,r-L)2](ClO4)6 under the same conditions, the cavity is filled by only one acetone molecule. Thus, the encapsulation of guest molecules into the cages during self-assembly shows significant metal(II) ion effects. These chiral cages are effective for the enantio-recognition of chiral (S)-2-butanol and (R)-2-butanol via the shifts of the electrochemical oxidation potentials obtained by the linear sweep voltammetry (LSV) technique, density functional theory (DFT) calculations, and the chiral 2-butanol adsorption in the single-crystal-to-single-crystal (SCSC) mode.

Self-assembly of Ni(II) with a chiral ligand pair vs. mixture of the chiral ligand pair: structural features and recognition ability of Ni2L4 cages.

The self-assembly of NiCl2 with a chiral bidentate ligand pair, (1R,2S)-(+)- and (1S,2R)-(-)-1-(nicotinamido)-2,3-dihydro-1H-inden-2-yl nicotinate (r,s-L and s,r-L) in a mixture of ethanol and dioxane, gives rise to stable crystals consisting of [2Cl@Ni2Cl2(s,r-L)4(H2O)2]·4C4H8O2·EtOH and [2Cl@Ni2Cl2(r,s-L)4(H2O)2]·4C4H8O2·EtOH chiral cages, respectively, with two encapsulated chloride anions in the cavities. The most interesting feature is that the self-assembly of NiCl2 with the mixture of r,s-L and s,r-L (1 : 1-1 : 4) produces crystals of thermodynamically stable achiral cages, [2Cl·2H2O@Ni2Cl2(s,r-L)2(r,s-L)2(H2O)2]·7C4H8O2, in the molar ratio range. Furthermore, the [2Cl@Ni2Cl2(s,r-L)4(H2O)2]·4C4H8O2·EtOH and [2Cl@Ni2Cl2(r,s-L)4(H2O)2]·4C4H8O2·EtOH chiral crystals can recognize the pairs of L-,D-tryptophan and L-,D-cysteine via cyclic voltammetry (CV) signals, in contrast to the [2Cl·2H2O@Ni2Cl2(s,r-L)2(r,s-L)2(H2O)2]·7C4H8O2 achiral crystal.

Coordinating nature of M6L12 double-stranded macrocycles: co-ligand competition of perchlorate, water, and acetonitrile depending on metal(II) ions.

Self-assembly of M(ClO4)2 (M(II) = Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) with dicyclopentyldi(pyridine-3-yl)silane (L) as a donor in a mixture of acetonitrile and toluene produces crystals consisting of M6L12 double-stranded macrocycles. The geometry around the M(II) cations is a typical octahedral arrangement, but the metallamacrocycles' outer axial coordination environment is sensitive to the M(II) cations. The conformation of the unique metallamacrocycles is informatively dependent on the nature of the coordination around the M(II) cations via subtle co-ligand competition among perchlorate anions, water, and acetonitrile. Both the coordinated acetonitriles and the solvate molecules of the crystals are removed at 170 °C, thereby transforming the crystals into new crystals that return to their original form in the mixture of toluene and acetonitrile. Catalytic oxidation of 3,5-di-tert-butylcatechol using [Cu6(ClO4)8(CH3CN)4L12]4ClO4·5C7H8 is much faster than those using the transformed product, [Cu(ClO4)2L2], and a simple mixture of Cu(ClO4)2 + L.

Formation Process of SiF6@Cu2L4 Chiral Cage Pairs in a Glass Vessel: Catechol Oxidation Catalysis and Chiral Recognition.

Self-assembly of CuX2 (X- = BF4-, PF6-, and SbF6-) with a pair of chiral bidentate ligands, (1R,2S)-(+)- and (1S,2R)-(-)-1-(nicotinamido)-2,3-dihydro-1H-inden-2-yl-nicotinate (r,s-L or s,r-L), in a mixture solvent including ethanol in a glass vessel gives rise to SiF62--encapsulated Cu2L4 chiral cage products. The SiF62- anion from the reaction of X- with SiO2 of the glass-vessel surface acts as a cage template or cage bridge. One of the products, [SiF6@Cu2(SiF6)(s,r-L)4]·3CHCl3·4EtOH, is one of the most effective heterogeneous catalysts for the oxidation of 3,5-di-tert-butylcatechol. Furthermore, an l-DOPA/d-DOPA pair is recognizable by the cyclic voltammetry (CV) signals of its combination with chiral cages [SiF6@Cu2(BF4)2(s,r- or r,s-L)4]·4CHCl3·2EtOH pair and [SiF6@Cu2(SiF6)(s,r- or r,s-L)4]·3CHCl3·4EtOH pair.

Crystals of Ni6L12 Ellipsoidal Tubes as Single-Crystal-to-Single-Crystal Adsorption Matrix: Penetrative Study of Self-Assembled Crystals vs Guest-Exchanged Crystals.

Informative similarities/differences between self-assembled and single-crystal-to-single-crystal (SCSC) guest-exchanged crystals based on both the molecular structure and adsorption nature are observed. The self-assembly of Ni(ClO4)2 with a dicyclopentyldi(pyridine-3-yl)silane bidentate ligand (L) in a mixture of toluene and acetonitrile gives rise to purple crystals consisting of double-stranded ellipsoidal tubes, [Ni6(ClO4)4(CH3CN)8L12]·8ClO4·4CH3CN·5C7H8. The coordinated acetonitriles as well as the solvates are removed at 170 °C to transform the purple crystals into blue crystals of [Ni(ClO4)2L2]n that return to the original crystals in the mixture of toluene and acetonitrile. Further, the toluene and acetonitrile solvates of the original crystals are replaced by o-, m-, and p-xylene isomers within 5 min in a SCSC manner. In the present study, SCSC xylene-exchanged crystals were compared with crystals obtained from direct self-assembly in a mixture of each xylene isomer and acetonitrile.

Pair of (Hg2II)3L2 Chiral Cages and Successive Transformation into (HgII)3L2 Chiral Cages: Chiral DOPA Recognition via Chiral Cages.

Self-assembly of Hg(ClO4)2 with a pair of C3-symmetric chiral ligands, (1S,1'S,1″S,2R,2'R,2″R)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (s,r-L) and (1R,1'R,1″R,2S,2'S,2″S)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (r,s-L), produces a pair of chiral cages C4H8O2@[(Hg2II)3(ClO4)6(s,r-L)2(H2O)7](C4H8O2)7 and C4H8O2@[(Hg2II)3(ClO4)6(r,s-L)2(H2O)7](C4H8O2)7, respectively, via straightforward formation of the reduced Hg2II species with an inner cavity in which a single dioxane molecule is nestled. The pair of chiral cages are transformed into their downsized pair of cages, [Hg3II(ClO4)6(s,r-L)2] and [Hg3II(ClO4)6(r,s-L)2], respectively, in the presence of hydrochloric acid. The original chiral cages are more effective than the corresponding downsized cages for enantiorecognition of chiral 3,4-dihydroxyphenylalanine (DOPA) via the shifts of electrochemical oxidation potentials observed by linear sweep voltammetry (LSV) technique. Furthermore, the photoluminescence (PL) spectral shifts show that the downsized chiral cages significantly recognize chiral DOPA.

Insight into systematic formation of hexafluorosilicate during crystallization via self-assembly in a glass vessel.

Formation of the unexpected hexafluorosilicate (SiF6 2-) anion during crystallization via self-assembly in glassware is scrutinized. Self-assembly of M(BF4)2 (M2+ = Cu2+ and Zn2+) with tridentate N-donors (L) in a mixture solvent including methanol in a glass vessel gives rise to an SiF6 2--encapsulated Cu3L4 double-decker cage and a Zn2L4 cage, respectively. Induced reaction of CuX2 (X- = PF6 - and SbF6 -) instead of Cu(BF4)2, with the tridentate ligands, produces the same species. The formation time of SiF6 2- is in the order of anions BF4 - < PF6 - < SbF6 - under the given reaction conditions. The SiF6 2- anion, acting as a cage template or cage-to-cage bridge, seems to be formed from the reaction of polyatomic anions containing fluoride with the SiO2 of the surface of the glass vessel.

Dual Molecular Design toward a Lysosome-Tagged AIEgen and Heavy-Atom-Free Photosensitizers for Hypoxic Cancer Photodynamic Therapy.

To date, a large number of photosensitizers (PS) have introduced heavy atoms to improve the ISC process and 1O2 generation. However, they often show low efficiency in hypoxic conditions, aggregate states, and turn-off PDT in the dark. Besides that, the toxicity of heavy metals is also concerned. Therefore, we developed lysosome-targeted heavy-metal-free PS (3S and 4S) based on thionated naphthalimide for hypoxic cancer photodynamic therapy (PDT), not only under white light but also in the dark via thermal-induced 1O2 generation. AIEgen (3O and 4O) were prepared for studying the PDT action of PSs (3S and 4S) in lysosome and aggregate state. We also examined the photophysical properties of AIEgen (3O and 4O) and PS (3S and 4S) by UV-vis absorption, fluorescent emission spectra, and theoretical calculations.

Pair of chiral 2D silver(I) enantiomers: chiral recognition of L- and D-histidine via differential pulse voltammetry.

Self-assembly of AgPF6 with a pair of chiral tridentate ligands (1S,1'S,1''S,2R,2'R,2''R) and (1R,1'R,1''R,2S,2'S,2''S)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)triisonicotinate (s,r-L) and (r,s-L) in a mixture of methanol and dioxane yields 2D sheets consisting of [Ag(s,r-L)](PF6)·3C4H8O2·0.5H2O and [Ag(r,s-L)](PF6)·3C4H8O2·0.5H2O, respectively. The differential pulse voltammetric (DPV) technique using the pair of chiral 2D-sheet enantiomers was employed for chiral discrimination of amino acid enantiomers, and was found to be an effective tool for enantio-recognition of L- and D-histidines. Both the size and the binding site of amino acids were strongly dependent on electrochemical enantio-recognition via the chiral 2D sheets.

Structural properties of [Cu(II)3L6] cages: bridged polyatomic anion effects on unprecedented efficiency of heterogeneous catechol oxidation.

Self-assembly of CuX2 (X- = BF4-, ClO4-, PF6-, and SbF6-) with a bidentate ethylmethylbis(3-pyridine)silane ligand (L) in the presence of additional polyatomic anions (X' = SiF62- and PF6-) gives rise to single crystals consisting of the X'@[Cu(II)3L6] cage motif. These cages exist as discrete or anion-bridged 3D networks depending on outside anions. The anion-bridged 3D networks interpenetrate in a four-fold fashion, and show, to our best knowledge, the most effective heterogeneous catalysis in 3,5-di-tert-butylcatechol oxidation reaction within 20 min at room temperature. Surprisingly, the heterogeneous catalysis is more effective than its corresponding homogeneous catalysis. Such notable catalytic effects can be explained by the maintenance of 3D inter-cage Cu⋯Cu distance as a catalytic center.

Interconversion between a Pd3L2 trigonal prism and a Pd6L8 cube via anion exchange: binding affinity of monoatomic vs. polyatomic anions.

Systematic interconversion between trigonal prisms [Pd3X6L2] (X- = Cl-, Br-, and I-) and cubic cages [Pd6L8]12+(X-)12 (X- = BF4- and CF3SO3-) via anion exchange was established. Self-assembly of K2PdX4 (X- = Cl- and Br-) with a C3-symmetric tridentate 1,3,5-tris(2-isonicotinamidephenoxy)benzene (L) produces a trigonal prism, [Pd3X6L2]. Further photoreaction of the [Pd3X6L2] (X- = Cl- and Br-) with CH2I2 gives rise to a halide-exchanged species, [Pd3I6L2]. In contrast, anion exchange of [Pd3X6L2] (X- = Cl-, Br-, and I-) with BF4- yields cubic-shaped cages, [Pd6L8]12+(BF4-)12, with an inner cavity of 15.9 × 15.9 × 15.9 Å3. Successive anion exchange of [Pd6L8]12+(BF4-)12 with CF3SO3- gives rises to anion-exchanged [Pd6L8]12+(CF3SO3-)12 and vice versa without cage destruction. Thus, the cage system is specifically sensitive to anions, enabling cage formation to recognize the binding affinity and size of various anions.

Straightforward formation of dianionic acetonylate: self-assembly of mercury(II) with pyridyl donor ligands in acetone.

Self-assembly of Hg(ClO4)2 with a new bidentate ligand (L) in acetone at room temperature produces single crystals consisting of unusual discrete tetranuclear complexes [Hg4(ClO4)4(CH2COCH2)2L2]·CH3COCH3via straightforward formation of dianionic acetonylate -CH2COCH2- in a quantitative yield.

Trimetallic coordination cage formation for nitrate encapsulation: transformation of kinetic products into thermodynamic products.

A procedure for the formation of a nitrate-encapsulating tripalladium(II) cage via self-assembly of Pd(NO3)2 with 1,3-bis(dimethyl(pyridin-4-yl)silyl)propane (L) was developed. The self-assembly reaction initially produces spiro-type macrocycles, PdL2, and finally results in transformation into a nitrate-encapsulated cage, [(NO3)@Pd3L6], in the mother liquor. The reaction of PdX2 (X- = BF4-, ClO4-, PF6-, and CF3SO3- instead of NO3-) with L gives rise to a spiro species, PdL2, as the final product, and anion exchange of the spiro products, [PdL2](X)2, with NO3- produces the tripalladium cage [(NO3)@Pd3L6].

Hypochlorite-Activated Fluorescence Emission and Antibacterial Activities of Imidazole Derivatives for Biological Applications.

The ability to detect hypochlorite (HOCl/ClO-) in vivo is of great importance to identify and visualize infection. Here, we report the use of imidazoline-2-thione (R 1 SR 2 ) probes, which act to both sense ClO- and kill bacteria. The N2C=S moieties can recognize ClO- among various typical reactive oxygen species (ROS) and turn into imidazolium moieties (R 1 IR 2 ) via desulfurization. This was observed through UV-vis absorption and fluorescence emission spectroscopy, with a high fluorescence emission quantum yield (ՓF = 43-99%) and large Stokes shift (∆v∼115 nm). Furthermore, the DIM probe, which was prepared by treating the DSM probe with ClO-, also displayed antibacterial efficacy toward not only Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) but also methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum ß-lactamase-producing Escherichia coli (ESBL-EC), that is, antibiotic-resistant bacteria. These results suggest that the DSM probe has great potential to carry out the dual roles of a fluorogenic probe and killer of bacteria.

A cyclic manipulation of cage isomers via anion exchange and thermal isomerism.

A cyclic manipulation of peanut cage isomers has been achieved via anion exchange and unusual cage isomerism.

A molecular design towards sulfonyl aza-BODIPY based NIR fluorescent and colorimetric probe for selective cysteine detection.

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) are essential biothiols for cellular growth, metabolism, and maintenance of a biological system. Thus, the detection of biothiols is highly important for early diagnosis and evaluation of disease progression. In this article, a series of sulfonyl aza-BODIPYs was synthesized, characterized, and examined by 1H-NMR, 13C-NMR, crystallization, photophysical properties and DFT calculation. Among these structures, a fluorescent probe, BDP-1, exhibited selective detection of Cys among various biothiols via nucleophilic aromatic substitution and typical size of Cys molecules. BDP-1 showed color change and near-infrared (NIR) fluorescence enhancement after reaction with Cys to generate BDP-OH, confirmed by HRMS. The red shift of absorption wavelength showed a similar tendency resulting in time-dependent density functional theory (TD-DFT). Furthermore, the calculated detection limit of BDP-1 toward Cys was 5.23 µM. This probe facilitates the colorimetric and fluorescent detection of Cys over other biothiols.

Visual Simultaneous Detection and Real-Time Monitoring of Cadmium Ions Based on Conjugated Polydiacetylenes.

We prepared the monomer PCDA-HP composed of 5-hydroxy-N 1,N 3-bis(pyridin-2-ylmethyl)isophthalamide (HP) as a cadmium ion tweezer and then polymerized them to form a polydiacetylene (PDA)-based sensor (PDA-HP), which displayed selective and sensitive colorimetric and fluorometric change upon addition of a cadmium ion (Cd2+) at both pH 7.4 and 6.8. The PDA-HP polymer was highly selective for Cd2+ over other metal ions with colorimetric change. In addition, the PDA-HP chemosensor also showed a red fluorescence change in the presence of Cd2+ at both pH 7.4 and 6.8. Naked-eye detection of Cd2+ was accomplished in an aqueous solution through a PDA-based sensor system. Finally, the lowest energy structure of an HP chelator was obtained by the crystal structure and density functional theory (DFT) calculations.

Flexibility and anion exchange of [(X)@Pd2L4] cages for recognition of size and charge of polyatomic anions.

The self-assembly of Pd(NO3)2 with L (L = 1,2-bis(dimethyl(pyridin-3-yl)silyl)ethane) gives rise to [PdL2](NO3)2 in high yields. Anion exchange of [PdL2](NO3)2 with X- (X- = BF4-, ClO4-, and PF6-) changes the skeleton into a cage of [(X)@Pd2L4](X)3. Successive anion exchange of [(X)@Pd2L4](X)3 (X- = BF4-, ClO4-, and PF6-) with X- (X- = ReO4- and SiF62-) produces [(ReO4)@Pd2L4](ReO4)3 and [(SiF6)@Pd2L4](SiF6), respectively, irrespective of anion charge. The flexible nature and conformation of cages are significantly dependent on the nestled polyatomic anions. Thus, this system can be used as a molecular recognizer of the size and charge of ubiquitous polyatomic anions.

Diverse anion exchange of pliable [X2@Pd3L4]4+ double cages: a molecular ruler for recognition of polyatomic anions.

Reaction of Pd(BF4)2 with L (L = bis(pyridin-3-yl-propyl)pyridine-3,5-dicarboxylate) in the 1 : 2 mole ratio gives rise to a spiro-type [PdL2]·(BF4)2·2C6H6·2CH3CN, and further self-assembly of [PdL2]·(BF4)2·2C6H6·2CH3CN with Pd(NO3)2 in the 2 : 1 mole ratio in Me2SO at 90 °C produces a uniquely pliable double cage of [(NO3)2(H2O)2@Pd3L4](BF4)4·6C3H7NO. Both the encapsulated NO3- and the outside BF4- anions are exchanged by X- to form [(X)2@Pd3L4](X')4 (X- = PF6-, ClO4-, and/or NO3-; X'- = BF4-, PF6-, ClO4-, and NO3-) with all-inclusive pure or mixed anions. The pliable and characteristic properties of the double cages were confirmed by anion exchange of the nestled or outside anions in the present study. This system can be used as a ruler for recognition of ubiquitous polyatomic anions.

Chiral Pd6L8 Nanocube Pairs: Recognition of Chiral Amino Acids via Electrochemistry.

The self-assembly of PdX2 (X- = ClO4- and PF6-) with C3-symmetric l- and d-L [L = (2S,2'S,2″S)- and (2R,2'R,2″R)-[benzenetricarbonyltris(azanediyl)]tris(3-phenylpropane-2,1-diyl)triisonicotinate] produces the chiral nanocube pair [Pd6(l-L)8](X)12 and [Pd6(d-L)8](X)12 (X- = ClO4- and PF6-, respectively) with an inner cavity of 12.3 × 12.3 × 12.3 Å3. These chiral nanocubes are effective for the enantiorecognition of various chiral amino acids via the square-wave-voltammetry technique. In the present study, the site of enantiorecognition was confirmed by density functional theory calculated interactions between each nanocube and the chiral amino acids, and the calculated interactions were coincident with the shifts of the electrochemical oxidation potentials.