Search

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. [ABSTRACT FROM AUTHOR]

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 (π-halogen bonded and σ-halogen bonded) are observed. In contrast with the previous results on similar furan and thiophene complexes, the σ-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. [ABSTRACT FROM AUTHOR]

A series of C-2 cholestan-3-one spiro-oxindole derivatives were prepared by the 1:3 dipolar cycloaddition reaction between the cholestan-3-one substituted by a C-2 arylidene and the azomethine ylid derived from isatin and sarcosine. The dipolarophiles were efficiently obtained by a Claisen-Schmidt reaction of cholestan-3-one and aromatic aldehydes. The structures of the products were established by a combination of NMR, high-resolution mass spectrometry (HRMS) and X-ray data analysis. [ABSTRACT FROM AUTHOR]

Photoswitchable fluorescent polymericnanoparticles (PFPNs) withcontrollable molecular weight, high contrast, biocompatibility, andprominent photostability are highly desirable but still scarce forrewritable printing, super-resolution bioimaging, and rewritable datastorage. In this study, novel amphiphilic BODIPY-based PFPNs withconsiderable merits are first synthesized by a facile one-pot RAFT-mediatedminiemulsion polymerization method. The polymerization is performedby adopting polymerizable BODIPY and spiropyran derivatives, togetherwith MMA as monomer, and mediated by utilizing biocompatible PEO macro-RAFTagent as both control agent and reactive stabilizer. The amphiphilicBODIPY-based PFPNs not only exhibit reversibly photoswitchable fluorescenceproperties under the alternative UV and visible light illuminationthrough induced intraparticle fluorescence resonance energy transfer(FRET) but also display controllable molecular weight with narrowpolydispersity index (PDI), high contrast of fluorescence, tunableenergy transfer efficiency, good biocompatibility, excellent photostability,favorable photoreversibility, etc. The as-prepared PFPNs are successfullydemonstrated for rewritable fluorescence patterning and high-contrastdual-color fluorescence imaging of living cells, implying its potentialfor rewritable data storage and broad biological applications in cellbiology and diagnostics. [ABSTRACT FROM AUTHOR]

A microporous acylamide-functionalized MOF with a 2-fold interpenetrated and methyl decorated framework (HNUST-4) has been designed and synthesized from [Cu2(COO)4] motifs and a C2-symmetric acylamide-linking tetracarboxylate, which exhibits good water stability, permanent porosity as well as high and selective CO2 uptake at ambient temperature. [ABSTRACT FROM AUTHOR]

The structure characteristics, interaction energies, cooperative energies of the complexes between chalcogen hydrides (H2Y) and halogen hydrides (HX) have been studied theoretically at the MP2 level with aug-cc-pVTZ basis set in this paper. The conclusions show that there are strong interactions between H2Y and HX. The stability of the complex is decided by the electronegativity of the negatively charged atom. The cooperativity is observed in the two or three hydrogen bonds of each trimer structures in title system. The values of the cooperative energies and the cooperative contributions all illustrate that the cooperativity is of great importance in these complexes. The "atoms in molecules" (AIM) analyses show that the complexes in title system are mainly electrostatic interactions (closed-shell interactions) in character. For H⋯O bonds in H2O⋯HF⋯H2O, H2O⋯HBr⋯H2O and HF⋯H2O⋯HF, the 1 < |Vc|/Gc < 2 and -Gc < Hc < 0 indicate the interactions in these compounds are between closed-shell interaction and opened-shell interaction. [ABSTRACT FROM AUTHOR]

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 (1H, 13C, and 51V) 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 heptacoordinated 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-Esterpzpy ≈ 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. [ABSTRACT FROM AUTHOR]

The 1,3-dipolar cycloaddition of azomethine ylide generated in situ from isatin and sarcosine to 5-arylmethylidene thiazolo[3,2- b][1,2,4]triazol-6(5 H)-ones afforded novel 1′-methyl-4′-aryldispiro[indole-3,2′-pyrrolidine-3′,5″-[1,3]thiazolo[3,2- b][1,2,4]triazole]-2,6″ (1 H)-diones in moderate yields. The structures of all the products were characterized thoroughly by NMR, infrared spectroscopy (IR), mass spectroscopy (MS) elemental analysis together with X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The interaction between imidazo[2,1-b]thiazole (IMTZ) and bovine serum albumin (BSA) was analyzed by fluorescence and ultraviolet spectroscopy at 302 and 310K under simulative physiological conditions. The results show that IMTZ can effectively quench the intrinsic fluorescence of BSA via static and dynamic quenching. The binding constant, binding sites of IMTZ with BSA were calculated. According to the Förster non-radiation energy transfer theory, the average binding distance between IMTZ and BSA was obtained. What''s more, the synchronous fluorescence spectra indicated that the conformation of BSA has been changed. The results provided the information for the binding of IMTZ to BSA, and the influences of substituent group on the interaction were also discussed. [Copyright &y& Elsevier]

A new class of spiro thiazolo[3,2- a]pyrimidine compounds were synthesized by the one-pot sequential 1,3-dipolar cycloaddition of azomethine ylide (generated from isatin and sarcosine)-nitrile oxide to 2-arylmethylidene-6,7-dihydro-5 H-thiazolo[3,2- a]pyrimidin-3-ones in moderate yields. The structures of all the products were characterized thoroughly by NMR, MS, IR, elemental analysis, and NMR together with X-ray crystallographic analysis. J. Heterocyclic Chem., (2011). [ABSTRACT FROM AUTHOR]

The 1,3-dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and isatin to 7-arylmethylidene-3-aryl-3,4-dihydro-2 H-thiazolo[3,2- a][1,3,5]triazin-6(7H)-ones afforded novel dispiro[oxindole-pyrrolidine]-thiazolo[3,2- a][1,3,5]triazines in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, and elemental analysis. The results of experiment indicated that this 1,3-dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity. J. Heterocyclic Chem., (2011). [ABSTRACT FROM AUTHOR]

In the present study, novel polymeric nanoparticles of ca. 55 nm in diameter with reversibly photoswitchable fluorescence properties were synthesized using a facile one-step miniemulsion polymerization, in which the donor of fluorescence resonance energy transfer (FRET), 4-methamino-9-allyl-1,8-naphthalimide (MANI), and the acceptor, spiropyran-linked methacrylate (SPMA), were covalently incorporated into a polymeric matrix during the polymerization process. The fluorescence emission of MANI dye in nanoparticles can be reversibly switched using the alternating irradiation of UV and visible light, which can induce the structural interconversion between the SP form and MC form of spiropyran moieties inside nanoparticles and thus reversibly switch on and switch off the FRET process. The prepared photoswitchable fluorescent polymer nanoparticles not only show a high load capacity of dyes, controllable amount and ratio of the two dyes, and tunable FRET efficiency but also exhibit higher spectral stability because of covalent linkage between dye molecules and the particle, relatively fast photoresponsibility, and better photoreversibility compared to some previously reported systems. [ABSTRACT FROM AUTHOR]

Both lomefloxacin (LOM) and ofloxacin (OFL) have a powerful ability to quench the fluorescence of bovine serum albumin (BSA). The fluorescence quenching action is much stronger when the two drugs coexist. The synergism between LOM and OFL was studied using fluorescence and ultraviolet spectroscopy under imitated physiological conditions. The results show that static quenching and non-radiation energy transfer are the main reasons for the fluorescence quenching. The synergism results in both the reduction of the binding stability between drugs and BSA and an increase of the free drug concentration, which will increase the efficacy of drugs. The thermodynamic parameters at different temperatures were calculated and the binding distances r between the drugs and BSA were obtained based on Försters theory of non-radiation energy transfer. The synchronous fluorescence spectra indicated that the effect of synergism affected the conformation of BSA. [ABSTRACT FROM AUTHOR]