Pyridine-Fused Bis(Norcorrole) through Hantzsch-Type Cyclization: Enhancement of Antiaromaticity by an Aromatic Bridge.

A non-catalytic condensation of NiII ß-aminonorcorrole with aryl aldehydes is shown to produce a family of pyrromethane dimers that undergo deaminative cyclization to yield pyridine-fused bis(norcorrole)s comprising two antiaromatic macrocycles communicating by an aromatic moiety. The new compounds were characterized by spectroscopic, structural, and electrochemical methods supported by DFT calculations, all of which revealed unexpected antiaromaticity enhancement in the fused system.

1,3-Dipolar cycloaddition of 2,6-dichlorobenzonitrile oxide to 2-methyl-N-confused porphyrin. Regio- and stereoselective synthesis and structural characterization of 2-aza-21-carbabacteriochlorin and resolution of 2-aza-21-carbachlorin enantiomers.

The 1,3-dipolar cycloaddition reaction of 2-methyl-N-confused porphyrin with 2,6-dichlorobenzonitrile oxide yielded four isomeric monoadducts of carbachlorin type and one diadduct of carbabacteriochlorin type. Two major carbachlorin products, constituting 82% of the monoadducts, were shown to be structural precursors of the unique 2-aza-21-carbabacteriochlorin. Enantiomers of the most abundant isomer of 2-aza-21-carbachlorin (55% of all carbachlorin products) have been resolved. The crystal structures of 2-aza-21-carbabacteriochlorin and the most abundant isomer of 2-aza-21-carbachlorin were characterized by X-ray diffraction.

Synthesis of N-confused porphyrin derivatives with a substituted 3-C position.

Active methylene compounds such as 5,5-dimethylcyclohexane-1,3-dione, cyclohexane-1,3-dione, 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, 1,3-dimethyl-1H-pyrazol-5(4H)-one, and 3-methylisoxazol-5(4H)-one react with the 3-C position of N-confused porphyrin in THF for 5 min to afford a novel type of N-confused porphyrin derivatives in good yield without the need of any catalyst.

Structure, properties, and nature of the pyridine-XY (X, Y = F, Cl, Br) complexes: an ab initio study.

Structure and properties (energies, electronic, and thermodynamic properties) of complexes pyridine-XY (X, Y = F, Cl, Br) have been investigated at the MP2/aug-cc-pVDZ level. Two types of geometries (pi-halogen bonded and sigma-halogen bonded) are observed. In contrast with the previous results on similar furan and thiophene complexes, the sigma-halogen bonded structures are more stable and the reasons are discussed. Charge transfer is found to be important in the formation of title system and the possible existing complexes under experimental conditions have been forecasted too. A symmetry-adapted perturbation theory energy decomposition analysis reveals that the pyridine-XY complexes are dominantly inductive in nature.

Investigation on the complex of diperoxovanadate with picolinamide.

A novel diperoxovanadate complex NH(4)[OV(O(2))(2)(picolinamide)].H(2)O was synthesized from aqueous solution under physiological conditions. The solution structure of the complex was characterized by multinuclear ((1)H, (13)C, (14)N, and (51)V), variable temperature as well as two-dimensional (DOSY) NMR techniques in the interaction system of NH(4)VO(3)/H(2)O(2)/picolinamide at room temperature. The crystal structure of the complex was determined at 223K by single-crystal X-ray diffraction method. It belongs to the monoclinic space group P21/c with a=7.323(3)A, b=14.255(7)A, c=10.022(5)A, beta=99.524(9) degrees , V=1031.7(8)A(3), and Z=4. The crystal is composed of ammonium ions, picolinamide oxodiperoxovanadate(V) ions, and water molecules, which are held together by ionic and hydrogen bond forces. The species [OV(O(2))(2)(picolinamide)](-) is seven-coordinated with a distorted pentagonal bipyramidal geometry both in solution and in crystal.

Preparation and optical properties of worm-like gold nanorods.

A type of worm-like nanorods was successfully synthesized through conventional gold nanorods reacting with Na2S2O3 or Na2S. The generated worm-like gold nanorods comprise shrunk nanorod cores and enwrapped shells. Therefore, a gold-gold sulfide core-shell structure is formed in the process, distinguishing from their original counterparts. The formation of the gold chalcogenide layers was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. Experimental results showed that the thickness of the gold chalcogenide layers is controllable. Since the increase of shell thickness and decrease of gold nanorod core take place simultaneously, it allows one to tune the plasmon resonance of nanorods. Proper adjustment of reaction time, temperature, additives and other experimental conditions will produce worm-like gold nanorods demonstrating desired longitudinal plasmon wavelength (LPW) with narrow size distributions, only limited by properties of starting original gold nanorods. The approach presented herein is capable of selectively changing LPW of the gold nanorods. Additionally, the formed worm-like nanorods possess higher sensitive property in localized surface plasmon resonance than the original nanorods. Their special properties were characterized by spectroscopic methods such as Vis-NIR, fluorescence and resonance light scattering. These features imply that the gold nanorods have potential applications in biomolecular recognition study and biosensor fabrications.

NMR and theoretical study on interactions between diperoxovanadate complex and 4-substituted pyridines.

To understand the substituting group effects of organic ligands on the reaction equilibrium, the interactions between diperoxovanadate complex [OV(O2)2(D2O)]-/[OV(O2)2(HOD)](-) and a series of 4-substituted pyridines in solution were explored using multinuclear (1H, 13C, and 51V) magnetic resonance, DOSY, and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological condition. Some direct NMR data are given for the first time. The reactivity among the 4-substituted pyridines is pyridine > isonicotinate > N-methyl isonicotinamide > methyl isonicotinate. The competitive coordination results in the formation of a series of new six-coordinated peroxovanadate species [OV(O2)2L](n-) (L = 4-substituted pyridines, n = 1 or 2). The results of density functional calculations provide a reasonable explanation on the relative reactivity of the 4-substituted pyridines. Solvation effects play an important role in these reactions.

[Effect of acidity on the interaction of Ofloxacin and bovine serum albumin].

Bovine serum albumin (BSA) exists as N(pH -7.0), B(pH -9.0), and E (pH < 3.5) = isomeric forms in the solution of different pH. Acid effect on the structure of bovine serum albumin and the interaction of different structure of BSA with Ofloxacin were studied by UV-Vis and fluorescence spectroscopy. Based on the fluorescence quenching of bovine serum albumin and Förster energy transfer mechanism, the quenching constants, energy transfer efficiencies and the binding distances were determined at four different pHs. The results showed that Ofloxacin has the ability to quench bovine serum albumin fluorescence with the optimal condition of fluorescence quenching constants of 1.928 1 x 10(5) L x mo l(-1), binding distance of r = 2.55 nm and quenching efficiency of 8.63 x 10(4) L x mo x l(-1) at pH 4.9. Non-radiative energy transfer and static quenching were the cause of fluorescence quenching. The influence on the binding of Ofloxacin and bovine serum albumin under neutral, subacidity and alkalescent conditions was not obviously observed, and the electrostatic interaction was not the main force. The effect of Oflx on the conformation of BSA was also investigated using synchronous fluorescence spectrometry.

Fabrication of Water-soluble Fluorescent Polymeric Micelles for Selective Detection of Hg2+ in Blood Serum.

In this study, amphiphilic diblock copolymers were designed and synthesized via the incorporation of reversible addition-fragmentation chain transfer radical polymerization (RAFT) and a subsequent grafting technique. Subsequently, Hg2+-sensitive water-soluble fluorescent polymeric micelles (FNs) were prepared by a reprecipitation strategy. The spectroscopic characteristics demonstrate that the fluorescein isothiocyanate (FITC) was successfully linked into the polymer. Due to the promoted reaction of desulfurization cyclization by Hg2+, the fluorescence of fluorescein in FNs was obviously quenched. The as-prepared FNs showed admirable Hg2+-sensitivity (detection limit: 54 nM), excellent water-solubility and high selectivity. In addition, FNs were successfully used to determine Hg2+ in blood serum. We expected that the as-prepared FNs could perform potential applications in imaging, sensing, and bioanalytic chemistry.

One-pot fabrication of FRET-based fluorescent probe for detecting copper ion and sulfide anion in 100% aqueous media.

The design of effective tools for detecting copper ion (Cu2+) and sulfide anion (S2-) is of great importance due to the abnormal level of Cu2+ and S2- has been associated with an increase in risk of many diseases. Herein, we report on the fabrication of fluorescence resonance energy transfer (FRET) based fluorescent probe PF (PEI-FITC) for detecting Cu2+ and S2- in 100% aqueous media via a facile one-pot method by covalent linking fluorescein isothiocyanate (FITC) with branched-polyethylenimine (b-PEI). PF could selectively coordinate with Cu2+ among 10 metal ions to form PF-Cu2+ complex, resulting in fluorescence quenching through FRET mechanism. Furthermore, the in situ generated PF-Cu2+ complex can be used to selectively detect S2- based on the displacement approach, resulting in an off-on type sensing. There is no obvious interference from other anions, such as Cl-, NO3-, ClO4-, SO42-, HCO3-, CO32-, Br-, HPO42-, F- and S2O32-. In addition, PF was successfully used to determine Cu2+ and S2- in human serum and tap water samples. Therefore, the FRET-based probe PF may provide a new method for selective detection of multifarious analysts in biological and environmental applications, and even hold promise for application in more complicated systems.

Study on the interaction between Besifloxacin and bovine serum albumin by spectroscopic techniques.

The interaction between Besifloxacin (BFLX) and bovine serum albumin (BSA) was investigated by spectroscopic (fluorescence, UV-Vis absorption and circular dichroism) techniques under imitated physiological conditions. The experiments were conducted at different temperatures (298, 304 and 310 K) and the results showed that the BFLX caused the fluorescence quenching of BSA through a static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process was spontaneous and the acting force between BFLX and BSA were mainly electrostatic forces. According to Förster non-radiation energy transfer theory, the binding distance between BFLX and BSA was calculated to be 4.96 nm. What is more, both synchronous fluorescence and circular dichroism spectra confirmed conformational changes of BSA.

Binding interaction of gatifloxacin with bovine serum albumin.

The binding of gatifloxacin to bovine serum albumin (BSA) in aqueous solution was studied using fluorescence spectroscopy and absorbance spectra, Further, the interactions influenced by Fe3+ and Cu2+ were also explored in this work. Based on Scatchard's site-binding model and florescence quenching, practical formulas for small molecule ligands to bio-macromolecules have been proposed. The binding parameters were measured according to suggested models, and the binding distance and the transfer efficiency of energy between gatifloxacin and BSA were also obtained in view of the Förster theory of non-radiation energy transfer. The effect of gatifloxacin on the conformation of BSA has also been analyzed using synchronous fluorescence spectroscopy.

Interaction between pirenoxine and bovine serum albumin in aqueous solution.

This work concerns the interaction of prenoxine sodium (PRX) and bovine serum albumin (BSA), which was conducted by spectroscopic means: fluorescence spectra, ultraviolet-visible spectra (UV-vis) and circular dichroism spectra (CD spectra) in physiological conditions. The results revealed the PRX can quench the fluorescence of BSA remarkably in aqueous solution. The quench mechanism has been obtained after corrected the fluorescence intensities for inner filter effects. The binding constants (Ka) were calculated according to the relevant fluorescence data at different temperatures. Moreover, from a series of analyses, we have obtained the binding sites, the binding distance and binding force. The effect of PRX on the conformation of BSA has been analyzed using synchronous fluorescence under experimental conditions. In addition, the CD spectra proved that the secondary structure of BSA changed in the presence of PRX in aqueous solution.

The investigation of the interaction between Tropicamide and bovine serum albumin by spectroscopic methods.

The fluorescence and ultraviolet-visible (UV-Vis) spectroscopy were explored to study the interaction between Tropicamide (TA) and bovine serum albumin (BSA) at three different temperatures (292, 301 and 310K) under imitated physiological conditions. The experimental results showed that the fluorescence quenching mechanism between TA and BSA was static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process is spontaneous, hydrogen binds and vander Waals were the main force to stabilize the complex. According to Förster non-radiation energy transfer theory, the binding distance between TA and BSA was calculated to be 4.90 nm. Synchronous fluorescence spectroscopy indicated the conformation of BSA changed in the presence of TA. Furthermore, the effect of some common metal ions (Mg(2+), Ca(2+), Cu(2+), and Ni(2+)) on the binding constants between TA and BSA were examined.

A spectroscopic study on the coordination and solution structures of the interaction systems between biperoxidovanadate complexes and the pyrazolylpyridine-like ligands.

In order to understand the substitution effects of pyrazolylpyridine (pzpy) on the coordination reaction equilibria, the interactions between a series of pzpy-like ligands and biperoxidovanadate ([OV(O2)2(D2O)](-)/[OV(O2)2(HOD)](-), abbrv. bpV) have been explored using a combination of multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, heteronuclear single quantum coherence (HSQC), and variable temperature NMR in a 0.15 mol L(-1) NaCl D2O solution that mimics the physiological conditions. Both the direct NMR data and the equilibrium constants are reported for the first time. A series of new hepta-coordinated peroxidovanadate species [OV(O2)2L](-) (L = pzpy-like chelating ligands) are formed due to several competitive coordination interactions. According to the equilibrium constants for products between bpV and the pzpy-like ligands, the relative affinity of the ligands is found to be pzpy > 2-Ester-pzpy ≈ 2-Me-pzpy ≈ 2-Amide-pzpy > 2-Et-pzpy. In the interaction system between bpV and pzpy, a pair of isomers (Isomers A and B) are observed in aqueous solution, which are attributed to different types of coordination modes between the metal center and the ligands, while the crystal structure of NH4[OV(O2)2(pzpy)]·6H2O (CCDC 898554) has the same coordination structure as Isomer A (the main product for pzpy). For the N-substituted ligands, however, Isomer A or B type complexes can also be observed in solution but the molar ratios of the isomer are reversed (i.e., Isomer B type is the main product). These results demonstrate that when the N atom in the pyrazole ring has a substitution group, hydrogen bonding (from the H atom in the pyrazole ring), the steric effect (from alkyl) and the solvation effect (from the ester or amide group) can jointly affect the coordination reaction equilibrium.

A highly porous 4,4-paddlewheel-connected NbO-type metal-organic framework with a large gas-uptake capacity.

A highly porous 4,4-paddlewheel-connected NbO-type metal-organic framework (HNUST-2, HNUST represents Hunan University of Science and Technology) has been designed and synthesized by self-assembling [Cu2(COO)4] SBUs with a nanosized tetracarboxylate ligand prolonged by alkyne groups, 5,5'-(naphthalene-1,4-diylbis(ethyne-2,1-diyl))diisophthalic acid (H4NDED). HNUST-2 exhibits high structural stability, a porous non-interpenetration framework with open metal sites and excellent gas-uptake capacity. This MOF material possesses a high BET surface area of 2366 m² g⁻¹, a large unsaturated excess and total H2 uptake of 4.57 wt% and 5. 20 wt% at 20 bar and 77 K, respectively. Meanwhile, HNUST-2 also exhibits an excellent adsorption capacity for CO2 (18.07 mmol g⁻¹ at 20 bar and 298 K) and CH4 (85.6 cm³ cm⁻³ at 20 bar and 298 K) with a high selectivity for CO2 over N2 (22.9) and CH4 (4.9) at 298 K.

The investigation of the interaction between Oxymetazoline hydrochloride and mucin by spectroscopic approaches.

The fluorescence and ultraviolet spectroscopy were explored to study the interaction between Oxymetazoline hydrochloride (OMZH) and mucin under imitated physiological condition. The results demonstrated that the fluorescence quenching mechanism between OMZH and mucin is a combined quenching process. The binding constants (K(a)), binding sites (n) and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) of the interaction system were calculated at different temperatures. The hydrogen bonds and van der Waals forces play a major role in the interaction between OMZH and mucin. According to Förster non-radiation energy transfer theory, the binding distance between OMZH and mucin was calculated.

Spectroscopic studies on the interaction of carteolol hydrochloride and urea-induced bovine serum albumin.

The interaction of carteolol hydrochloride, to 0.2 mol L(-1) urea-induced bovine serum albumin in aqueous solution has been first investigated by fluorescence spectra and ultraviolet-visible (UV-vis) spectra at pH 7.40. The quenching mechanism, binding parameter and sites (n), the binding mode (ΔG, ΔH, and ΔS) as well as the binding distance (r) have been obtained according to the experimental results. We also use the synchronous fluorescence method to study the effect of CTL on the conformation change of urea-induced BSA.

Study on the interaction between NCP-(4-hydroxycoumarins) and bovine serum albumin by spectroscopic techniques.

The interaction between N-confused porphyrins-(4-hydroxycoumarins) diad (NCP-(4-hydroxycoumarins)) and bovine serum albumin (BSA) was studied using fluorescence and ultraviolet spectroscopy at different temperatures under imitated physiological conditions. The experimental results showed that the fluorescence of BSA was quenched by NCP-(4-hydroxycoumarins) through a combined quenching procedure. The binding constants, binding sites and corresponding thermodynamic parameters between NCP-(4-hydroxycoumarins) and BSA at different temperatures were obtained. According to Förster non-radiation energy transfer theory, the binding distance between BSA and NCP-(4-hydroxycoumarins) was calculated to be about 2.1 nm. The effect of NCP-(4-hydroxycoumarins) on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effect of some metal ions Cu(2+), Ca(2+), Mg(2+), and Ni(2+) on the binding constant between NCP-(4-hydroxycoumarins) and BSA was examined.

Design and synthesis of FRET-mediated multicolor and photoswitchable fluorescent polymer nanoparticles with tunable emission properties.

Novel multicolor and photoswitchcable fluorescent polymer nanoparticles were prepared by one-step miniemulsion via methyl methacrylate (MMA) copolymerization with 4-ethoxy-9-allyl-1,8-naphthalimide (EANI), allyl-(7-nitro-benzo[1,2,5]oxadiazol-4-yl)-amine (NBDAA) and spiropyran-linked methacrylate (SPMA). Under visible-light conditions, SPMA moieties in polymer nanoparticles are colorless and nonfluorescent, by varying the incorporating ratio of two dyes (EANI and NBDAA), fluorescence resonance energy transfer (FRET)-mediated emission signatures can be tuned so that the nanoparticles exhibit multiple colors under a single wavelength excitation. Moreover, the fluorescence emission of EANI and NBDAA dyes in nanoparticles can be reversibly switched "on" and "off" through the FRET process by the alternating irradiation of UV and visible light. This class of novel photoswitchable multicolor fluorescent polymer nanoparticles may find potential applications in multiplexed bioanalysis.