Mechanistic insights into heavy metal ion sensing by NOS2-macrocyclic fluorosensors via the structure-function relationship: influences of fluorophores, solvents and anions.

To obtain a mechanistic understanding of the effects derived from fluorophores, solvents and anions on heavy metal sensing, two NOS2-macrocycle-based fluorosensors with different fluorophores (L1: 9-methylanthracene, L2: benzothiazolyl) were synthesised. In this regard, particular attention was given to monitoring the cation-ligand, cation-anion and cation-solvent interactions from the detailed complexation processes in both the solution and solid states while considering the structure-function relationship. L1 showed turn-on type silver(i) selectivity over other metal ions, including mercury(ii), in ethanol. According to the complexation results obtained by titration (UV-vis, fluorescence and NMR), cold-spray ionization mass spectrometry and X-ray crystallography, the observed silver(i) sensing by L1 is mainly due to its 1 : 1 complexation with silver(i) via the Ag-Ntert bond and the strong solvation of mercury(ii). Thus, the turn-on sensing for silver(i) can be explained by the CHEF effect, in which the coordination of silver(i) to the receptor unit effectively prevents PET quenching. As a dual-probe (UV-vis and fluorescence) chemosensor, L2 showed fluorescence turn-off type selectivity for both silver(i) and mercury(ii) in ethanol. In acetonitrile, L2 showed improved fluorescence turn-off type selectivity for mercury(ii) with ClO4- and NO3-; however, no such responses were observed with other anions, such as Cl-, Br-, I-, SCN-, OAc- and SO42-. Together with the complexation results by titration, the crystal structures of an endocyclic mercury(ii) perchlorate complex and an exocyclic mercury(ii) iodide complex revealed that the anion-controlled mercury(ii) sensing by L2 arises from the endo- and exo-coordination modes depending on the anion coordinating ability, which induces either metal-receptor/fluorophore binding (Hg-Ntert and Hg-Nfl) or no binding. Taken collectively, the photophysical, thermodynamic and structural results of the complexations herein suggest that the sensing properties of heavy metal ions by macrocycle-based fluorosensors are very sensitive not only to the cation-receptor and cation-fluorophore interactions but also to the cation-anion (endo/exo-coordination modes) and/or cation-solvent interactions.

Effect of transportation method on preoperative anxiety in children: a randomized controlled trial.

BACKGROUND: This study was performed to evaluate the effect of a wagon as a transport vehicle instead of the standard stretcher car to reduce children's anxiety of separation from parents. The secondary goal was to evaluate whether this anxiolytic effect was related to age. METHODS: We divided 80 children (age 2-7 years) into two groups. The stretcher group was transferred to the operating room on a conventional stretcher car, whereas the wagon group was transferred using a wagon. The level of anxiety was evaluated three times using the Modified Yale Preoperative Anxiety Scale (mYPAS): in the waiting area (T0), in the hallway to the operating room (T1), and before induction of anesthesia (T2). RESULTS: The mYPAS score was significantly lower in the wagon group (36.7 [31.7, 51.7]) than in the stretcher group (51.7 [36.7, 83.3]) at T1 (P = 0.007). However, there was no difference in the mYPAS score between the two groups at T2 (46.7 [32.5, 54.2] vs. 51.7 [36.7, 75.0], respectively, P = 0.057). The baseline anxiety tended to be lower with increasing age (r = -0.248, P = 0.031). During transportation to the operating room, the increase in the mYPAS score (T1-T0) was greater as the age of children decreased in the stretcher group (r = -0.340, P = 0.034). However, no correlation was observed in the wagon group (r = -0.053, P = 0.756). CONCLUSION: The wagon method decreased preoperative anxiety, suggesting that it may be a good alternative for reducing preoperative anxiety in children.

Geometric change of a thiacalix[4]arene supramolecular gel with volatile gases and its chromogenic detection for rapid analysis.

A coordination polymer gel that is self-assembled to form a network structure between a thiacalix[4]arene derivative (L) and Co(2+) has been prepared. This gel is capable of selectively changing color in the presence of gases that yield hydrogen chloride upon hydrolysis. The UV-vis absorption spectrum of a coordination polymer gel derived from Co(NO3)2 exhibits an absorption band at 527 nm and is colored red, indicating the formation of an octahedral Co(2+) complex. Treatment with a small amount of volatile gases containing a chlorine atom (VGCl) causes a red shift of ∼150 nm, resulting in a new strong band with a maximum at 670 nm and a color change to blue. In addition, the red color of the filter paper coated with a Co(NO3)2 coordination polymer gel changed to blue upon exposure to VGCl, reflecting a change in the coordination geometry. Red and blue colors of single crystals of Co(2+) complexes were obtained from a basic solution. From X-ray crystallographic analysis, the red Co(2+) complex corresponds to an octahedral structure, while the blue Co(2+) complex reflects the presence of a tetrahedral structure. Thus, the induced color change of Co(2+) gel from red to blue upon exposure to VGCl is due to the coordination geometry. The quantitative concentration of VGCl was calculated by employing the RGB histogram available in a smartphone application.

A thin-layered chromatography plate prepared from naphthalimide-based receptor immobilized SiO2 nanoparticles as a portable chemosensor and adsorbent for Pb2+.

Fluorogenic naphthalimide-functionalized SiO2 nanoparticles have been easily prepared by intermolecular hydrogen-bonding interactions. Their ability to detect and remove metal ions was evaluated by fluorophotometry. The nanoparticles exhibited high affinity and selectivity for Pb(2+) over other competing metal ions. Furthermore, a thin-layered chromatography (TLC) plate modified with immobilized detected Pb(2+) in aqueous solution.

Fluorescent hydrogels formed by CH-π and π-π interactions as the main driving forces: an approach toward understanding the relationship between fluorescence and structure.

Amide-linked tripyridine derivatives 1, with a para-substituent, and 2, with a meta-substituent, were gelated in water or water-DMSO. The gelation capabilities of 1 and 2 were attributed to the cooperative effects of mainly CH-π and π-π stacking or strong intermolecular hydrogen bonding interactions between the amide groups. The fluorescence properties of gels 1 and 2 were dependent on the binding strength of the π-π stacking.

Remarkable reinforcement of a supramolecular gel constructed by heteroditopic [18]crown-6-based molecular recognition.

The heteroditopic crown ether-based ligand 1 containing the diazafluorenylimino group as a binding site for the Zn(2+) and Cs(+) was synthesized. The ligand 1 can be gelated in DMSO/water with and without Cs(+) in the presence of the Zn(2+) ion. Interestingly, the remarkable gelation reinforcement of gel 1 occurred with Cs(+) in the presence of Zn(2+), which is due to the formation of a sandwich complex. According to DFT calculations, one Zn(2+) is bound to two diazafluorenylimino moieties in a tetrahedral structure. In addition, one Cs(+) ion is bound to two crown-rings. The Zn(2+)-diazafluorenylimino ligand gel without Cs(+) shows a spherical structure with 250-800 nm diameter, whereas the Zn(2+)-diazafluorenylimino-based ligand gel with Cs(+) shows a fiber structure with 60-70 nm diameter and several micrometers of lengths. The rheological properties of the Zn(2+)-diazafluorenylimino-based ligand gel were strongly dependent on the presence of Cs(+).

A SAR study on a series of synthetic lipophilic chalcones as inhibitor of transcription factor NF-κB.

To define the structural features responsible for the activity of 2,4-dihydroxy-6-isopentyloxychalcone, a newly established inhibitor of LPS induced NF-κB activation (IC(50) = 10 µM), a series of its analogues was prepared and studied for their in vitro activities against LPS induced NF-κB inhibition in RAW 264.7 cells. Among the synthesized derivatives, (E)-1-(2-(decyloxy)-6-hydroxyphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (IC(50) = 2.7 µM) and (E)-1-(2-hydroxy-6-(tetradecyloxy)phenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (IC(50) = 4.2 µM) showed the most potent inhibition. The SAR studies confirmed that the length (C(8)-C(14)) and C-6 position of linear alkyl chain of ring A is an important factor for the inhibitory activity. Hydroxyl group and its location at 4-position on ring B is also important for the inhibition. The α,ß-unsaturated ketone moiety appears as a crucial motif of chalcones for the activity.

Supramolecular networking of macrocycles based on exo-coordination: from discrete to continuous frameworks.

Macrocyclic ligands typically show high selectivity for specific metal ions and small molecules, and these features make such molecules attractive candidates for nanoscale chemical sensing applications. Crown ethers are macrocyclic structures with polyether linkages where the oxygen donors are often separated by an ethylene unit (-O-CH(2)-CH(2)-O-). Because the oxygen lone pairs in crown-type macrocycles are directed inward, the preorganized macrocyclic cavity tends to form complexes where metals coordinate inside the cavity (endo-coordination). However, sulfur-containing macrocycles often demonstrate metal coordination outside of the cavity (exo-coordination). This coordination behavior results from the different torsion arrangements adopted by the X-CH(2)-CH(2)-X atom sequence (X = O, gauche; X = S, anti) in these molecules. Exo-coordination is synthetically attractive because it would provide a means of connecting macrocyclic building blocks in diverse arrangements. In fact, exo-coordination could allow the construction of more elaborate network assemblies than are possible using conventional endocyclic coordination (which gives metal-in-cavity products). Exo-coordination can also serve as a tool for crystal engineering through the use of diverse controlling factors. Although challenges remain in the development of exo-coordination-based synthetic approaches and, in particular, for the architectural control of supramolecular coordination platforms, we have established several strategies for the rational synthesis of new metallosupramolecules. In this Account, we describe our recent studies of the assembly of metallosupramolecules and coordination polymers based on sulfur-containing macrocycles that employ simple and versatile exo-coordination procedures. Initially, we focus on the unusual topological products such as sandwich (1:2, metal-to-ligand), club sandwich (2:3), and cyclic oligomeric complexes as discrete network systems. The primary structures we achieve in these networked macrocycles are one to three dimensional coordination polymers based on homo- and heteronuclear metal systems. Using crystal engineering methods, we have also investigated variation in the donors, interdonor distances, ligand isomer structures, and the effect of counter anions on the chemical and physical properties of the products. Understanding the relationship between structure and function in these exo-coordination products is an important step in the design of these new supramolecules for practical applications. We investigated the photophysical properties of the exocyclic complexes and a chromogenic macrocycle, which exhibited cation-selective and anion-controlled color change depending on an exo- or endo- ligand binding mode. Overall, we suggest that the exocyclic coordination behavior provides a versatile strategy for the preparation of new molecular networks and materials.

3,3'-Dimethyl-1,1'-[2,2'-bipyridine-5,5'-diylbis(methyl-ene)]diimidazol-3-ium bis-(hexa-fluoro-phosphate).

The title compound, C(20)H(22)N(6) (2+)·2PF(6) (-), was prepared by the reaction of 5,5'-bis-(bromo-meth-yl)-2,2'-bipyridine with 1-methyl-imidazole. The main mol-ecule lies on an inversion center located at the mid-point of the C-C bond joining the two pyridine rings. The asymmetric unit therefore contains one half-mol-ecule and one hexa-fluoro-phosphate anion. The dihedral angle between the pyridine and imidazole rings is 76.93 (7)°. In the crystal, weak inter-molecular C-H⋯F hydrogen bonds contribute to the stabilization of the packing.

Microstructural properties at the interfaces of ZnO nanorods and ZnO homo-buffer layers.

Uniformly and vertically well-aligned ZnO nanorods were fabricated in-situ and ex-situ on ZnO films using a catalyst-free metal-organic chemical vapor process. Microstructural properties of the initial growth of ZnO nanorods on ZnO films with different surface roughnesses were investigated. We observed that the ZnO nanorods grown on ZnO films with surface roughness of less than 1.0 nm were well-aligned along the c-axis and in the ab-plane. When the nanorods grew on ZnO films with a large surface roughness, they had three different growth directions of 28 degrees, 62 degrees, and 90 degrees to the film surface. The slant angle of 62 degrees corresponds to the angle between the ZnO(001) and (101) planes. The initial growth direction difference caused structural disorder at the interface of the ZnO nanorod and film, and prevented epitaxial growth and the alignment of the nanorods.

Discrete mercury(II) complexes, one-dimensional and palladium(II)-mediated two-dimensional silver(I) coordination polymers of NS2-macrocycle: synthesis and structural characterization.

A range of thiaphilic mononuclear (Hg(2+) and Ag(+)) and heterobinuclear (Ag(+)/Pd(2+)) complexes (1-6) of an NS(2)-donor macrocycle L with discrete and networked forms were prepared and structurally characterized. Reaction of L with HgCl(2) afforded a unique 1:1 (cationic/anionic) complex [Hg(2)(L)Cl(5)][Hg(L)Cl] (1). Reaction of L with Hg(ClO(4))(2) yielded the sandwich-type 1:2 (metal-to-ligand) complex [Hg(L)(2)](ClO(4))(2) (2). Contrasting with the mercury(II) salts, the reactions of L with AgX (X = NO(3)(-) and CF(3)SO(3)(-)) yielded an isostructural one-dimensional (1D) zigzag networks [Ag(L)X](n) (3; X = NO(3)(-) and 4; X = CF(3)SO(3)(-)) in which each ring of L is exo-coordinated via two S atoms and one N atom to a silver ion which is also bound to one S atom in the neighboring L such that the overall coordination geometry about each silver is four-coordinate. Whereas, reaction of L with K(2)PdCl(4) gave a discrete exocyclic complex 5, [cis-Cl(2)Pd(L)]. Through a successive reaction of the complex 5 with AgNO(3), a heterobinuclear two-dimensional (2D) coordination polymer 6, [Pd(L)Ag(2.5)(NO(3))(4.5)(H(2)O)(0.5)](n), utilizing exocyclic Pd(II) and Ag(I) was isolated and characterized.

Copper(I), silver(I), and palladium(II) complexes of a thiaoxamacrocycle displaying unusual topologies.

Coordination behavior of the 14-membered dibenzo-O(2)S(2) macrocycle, L, with the soft metal ions such as Pd(II), Cu(I), and Ag(I) is reported. The X-ray structures of the complexes have been determined, and a range of less common structural types, including mono-, di-, and multinuclear species with discrete and continuous forms were obtained. A two-step approach via reaction of dichloro-palladium(II) complex of L as a metalloligand, with L through a treatment of silver(I) perchlorate, led to the formation of bis(ligand) monopalladium(II) complex, [Pd(L)(2)] x 2 ClO(4) x 2 CH(3)NO(2) (1). In this case, the square-planar stereochemical demand of Pd(II) coupled with the coordination of the S(2)-donors of L to a metal center results in the formation of the bis(ligand)-type mononuclear complex. In 1, the ether oxygens of the ring are unbound. L reacts with CuBr to yield related 2:2:2 (metal/ligand/anion) complex of type [Cu(2)Br(2)(L)(2)] (2), in which two ligand molecules are linked by a rhomboid-type Cu-Br(2)-Cu cluster unit. However, the parallel reaction with CuI afforded the mixture of the isostructural 2:2:2 type complex [Cu(2)I(2)(L)(2)] (3a) and double-stranded 1D coordination polymer {[Cu(2)I(2)(L)(2)] x 2 CH(3)CN}(n) (3b). The framework of 3b contains four bridging L coordinated to a rhomboidal Cu-I(2)-Cu motif through the exomonodentate Cu-S bonds. Again, the ether oxygens do not coordinate in copper(I) halide complexes. The observed different reactivity between copper(I) bromide and copper(I) iodide was also confirm by an XRPD measurement. Unlike the Pd(II) and Cu(I) cases, L afforded an unusual tris(L)-disilver(I) (club-sandwich-type) complex [Ag(2)(L)(3)](PF(6))(2) (4) on its reaction with AgPF(6). Each silver adopts a trigonal planar coordination environment with coordination sites occupied by two S atoms from one terminal ligand, and by one S atom from the bridging ligand; once again the ether oxygens are not coordinated. An NMR titration of the formation of complex 4 confirmed that the Ag/L stoichiometry of 2:3 found in the solid state is also maintained in solution.

Unsymmetrical calixcrowns incorporating hard and soft loops as a new scaffold for multinuclear endo/exocyclic complexation and networking.

Unsymmerical calix[4]crowns containing [(O(4)S)(O(5))] (L(1)) and [(O(4)S(2))(O(5))] (L(2)) as crown loops were employed as new scaffolds both for complexation studies and for network formation. Reactions of L(1) and L(2) with KI in the presence of CuI afforded a copper(I) iodide cluster linked 1D-type endocyclic dipotassium(I) complex [K(2)(L(1))(Cu(7)I(9))](n) (1) and a copper(I) iodide cluster linked 1D-type endocyclic monopotassium(I) complex [KL(2)(mu(2)-Cu(3)I(4))](n) (2), respectively. By comparison, the reaction of L(2) with KPF(6) in the presence of CuI and HgI(2) afforded the 1-D endocyclic potassium(I) complex [K(L(2))(CuHgI(4))](n) (3), linked with a CuHgI(4) cluster unit. The formation of homo- and heterodinuclear complexes in solution was also confirmed by comparative NMR studies.

Copper(II) interaction with mono-, bis- and tris-ring N3O2 macrocycles: synthetic, X-ray, competitive membrane transport, and hypochromic shift studies.

New N-phenyl (L(1)), azo-coupled (L(2)), and tri-linked (L(3)) substituted derivatives of a parent dibenzo-N(3)O(2) macrocycle, 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacycloheptadecane (L(4)), have been synthesized. Competitive seven-metal transport studies across a bulk chloroform membrane employing an aqueous source phase containing equal molar concentrations of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Ag(I), and Pb(II) as their nitrate salts have been performed using both L(1) and L(3) as the ionophore, with the results discussed in terms of those obtained previously for related mono-ring (L(5)) and di-linked (L(6)) macrocyclic systems. Sole transport selectivity for Cu(II) was observed in each case. On a per macrocyclic cavity basis the tri-linked analogue L(3) gave less efficient Cu(II) transport than its monomeric or di-linked analogues. At least in part, this may reflect the tendency of tri-linked derivative L(3) to form a 2:1 complex (metal/ligand) with Cu(II) under the conditions employed; such a stoichiometry was demonstrated to occur in acetonitrile using both spectrophotometric titration and Job plot procedures. The azo-coupled derivative (L(2)) yields a red solution (lambda(max) = 495 nm, epsilon(max) = 23000 M(-1) cm(-1)) and undergoes significant hypochromic metal-induced shifts (Delta lambda(max) = 54-174 nm) on metal addition. Cu(II) induces the largest shift (Delta lambda(max) = 174 nm), corresponding to a color change from red to pale-yellow. The X-ray structures of red L(2) x HNO(3) together with its Cu(II) complexes, [Cu(L(2))NO(3)]NO(3) x CH(2)Cl(2) (6) (pale-yellow) and [{Cu(L(2))}(2)(mu-OH)(2)](ClO(4))(2) x 2 CH(2)Cl(2) x 2 H(2)O (7) (dark-red), are reported. The structural determinations have allowed insight into the structure-function relationships governing the observed color variation between these species.

Ligand- and anion-directed assembly of exo-coordinated mercury(II) halide complexes with O2S2-donor macrocycles.

Assembly reactions of mercury(II) halides (Cl, Br, and I) with two O2S2 macrocycles (L(1) and L(2)) having different interdonor (S...S) distances were investigated, and four types of supramolecular complexes (1-4b) were obtained depending on the S...S distances as well as the size of the halide anions. Photoluminescence of these compounds was also studied.

Charge influence and growth mechanism of ZnO nanorods.

We demonstrate the influence of charges near the substrate surface on vertically aligned ZnO nanorod growth. ZnO nanorods were fabricated on n-type GaN with and without H+ treatments by catalyst-free metal-organic chemical vapor deposition. The ZnO nanorods grown on n-GaN films were vertically well-aligned and had a well-ordered wurtzite structure. However, the ZnO did not form into nanorods and the crystal quality was very degraded as they were deposited on the H+ treated n-GaN films. The charge influence was also observed in the ZnO nanorod growth on sapphire substrates. These results implied that the charges near the substrate surface dominantly affected on the crystalization and formation of ZnO nanorods.

Charge influence and growth mechanism of ZnO nanorods.

We demonstrate the influence of charges near the substrate surface on vertically aligned ZnO nanorod growth. ZnO nanorods were fabricated on n-type GaN with and without H+ treatments by catalyst-free metal-organic chemical vapor deposition. The ZnO nanorods grown on n-GaN films were vertically well-aligned and had a well-ordered wurtzite structure. However, the ZnO did not form into nanorods and the crystal quality was very degraded as they were deposited on the H+ treated n-GaN films. The charge influence was also observed in the ZnO nanorod growth on sapphire substrates. These results implied that the charges near the substrate surface dominantly affected on the crystallization and formation of ZnO nanorods.