Creation of superior carboxyfluorescein dyes by blocking donor-excited photoinduced electron transfer

[Structure: see text] Carboxyfluoresceins are widely utilized as fluorescence labeling reagents, but we recently found that their emission intensity is markedly decreased after esterification. On the basis of our hypothesis that the fluorescence decrease is due to a donor-excited photoinduced electron transfer (d-PeT) process, we have developed novel carboxyfluorescein derivatives in which the d-PeT process is hampered, and the emission intensity is not decreased upon esterification. These novel dye derivatives display high quantum yields and are expected to be useful as labeling agents.     

MassBank: a public repository for sharing mass spectral data for life sciences

MassBank is the first public repository of mass spectra of small chemical compounds for life sciences (<3000 Da). The database contains 605 electron‐ionization mass spectrometry(EI‐MS), 137 fast atom bombardment MS and 9276 electrospray ionization (ESI)‐MSⁿ data of 2337 authentic compounds of metabolites, 11 545 EI‐MS and 834 other‐MS data of 10 286 volatile natural and synthetic compounds, and 3045 ESI‐MS² data of 679 synthetic drugs contributed by 16 research groups (January 2010). ESI‐MS² data were analyzed under nonstandardized, independent experimental conditions. MassBank is a distributed database. Each research group provides data from its own MassBank data servers distributed on the Internet. MassBank users can access either all of the MassBank data or a subset of the data by specifying one or more experimental conditions. In a spectral search to retrieve mass spectra similar to a query mass spectrum, the similarity score is calculated by a weighted cosine correlation in which weighting exponents on peak intensity and the mass‐to‐charge ratio are optimized to the ESI‐MS² data. MassBank also provides a merged spectrum for each compound prepared by merging the analyzed ESI‐MS² data on an identical compound under different collision‐induced dissociation conditions. Data merging has significantly improved the precision of the identification of a chemical compound by 21–23% at a similarity score of 0.6. Thus, MassBank is useful for the identification of chemical compounds and the publication of experimental data. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal decomposition behavior of mono-aminimides and their application to polymerization of epoxide

Mono-aminimide compounds [N,N-dimethyl-N-(2-hydroxypropyl)-amine-N′-propionimide ( 1 ), trimethylamine valerimide ( 2 ), and trimethylamine benzimide ( 3 )] were found to exhibit different thermal decomposition behaviors and polymerization efficiencies for an epoxide (phenyl glycidyl ether, PGE). The thermal decomposition rate of aminimides at 150°C decreased in the order 1 > 2 > 3 . It seemed that hydrogen bonding enchanced the decomposition rate, and the resonance effect induced by the phenyl group suppressed the decomposition. 1 was thermolyzed to give isocyanate and tertiary aminoalcohol, which subsequently reacted with each other to give isocyanate and tertiary aminoalcohol, which subsequently reacted with each other to give urethane. When 2 was heatted, the isocyanurate generated from 2 remained intact. On heating of 3 , we observed the formation of triphenyl isocyanurate. PGE reacted with those aminimides and gave different products depending on their thermolyzed products. Equimolar mixtures of isocyanate, tertiary amine, PGE were used in the model reactions, and the thermal reaction between the expected decompostion products of aminimides was investigated in the presence and absence of PGE. The rate of PGE consumption was in the order PGE + 2 > PGE + 1 > PGE + 3 . It is clear that the formation of urethanes and oxazolidone derivatives affects the polymerization process.     

Polymerization of mono-substituted acetylenes with a liquid crystalline moiety by Ziegler–Natta and metathesis catalysts

Polymerization of five monomers, 1-[p-(trans-4′-alkylcyclohexyl)phenoxy]alkyne (i.e., PCH001A, where PCH, 0, 01 and A represent phenylcyclohexyl mesogenic moiety, number of carbon in an alkyl group attached to cyclohexyl group, ether linkage + number of methylenic units in the spacer between phenoxy and acetylenic groups, and terminal acetylene, respectively) were carried out using Ziegler-Natta and metathesis catalysts. All polymers were soluble in organic solvents such as benzene, chloroform, and THF. A liquid crystalline phase was observed in the polymers of PCH303A and PCH503A through the polarized optical microscope and DSC measurements. Polymerization of PCH003A by the Fe(acac)₃-AlEt₃ catalyst yielded a high-molecular-weight polymer with M_w = ca. 3 × 10⁶. © 1993 John Wiley & Sons, Inc.     

Spectroelectrochemical studies on mixed-valence states in a cyanide-bridged molecular square, [Ru(II)(2)Fe(II)(2)(mu-CN)(4)(bpy)(8)](PF6)(4).CHCl(3).H(2)O

A cyanide-bridged molecular square of [Ru(II) (2)Fe(II) (2)(mu-CN)(4)(bpy)(8)](PF(6))(4).CHCl(3).H(2)O, abbreviated as [Ru(II) (2)Fe(II) (2)](PF(6))(4), has been synthesised and electrochemically generated mixed-valence states have been studied by spectroelectrochemical methods. The complex cation of [Ru(II) (2)Fe(II) (2)](4+) is nearly a square and is composed of alternate Ru(II) and Fe(II) ions bridged by four cyanide ions. The cyclic voltammogram (CV) of [Ru(II) (2)Fe(II) (2)](PF(6))(4) in acetonitrile showed four quasireversible waves at 0.69, 0.94, 1.42 and 1.70 V (vs. SSCE), which correspond to the four one-electron redox processes of [Ru(II) (2)Fe(II) (2)](4+) right arrow over left arrow [Ru(II) (2)Fe(II)Fe(III)] (5+) right arrow over left arrow [Ru(II) (2)Fe(III) (2)](6+) right arrow over left arrow [Ru(II)Ru(III)Fe(III) (2)](7+) right arrow over left arrow [Ru(III) (2)Fe(III) (2)](8+). Electrochemically generated [Ru(II) (2)Fe(II)Fe(III)](5+) and [Ru(II) (2)Fe(III) (2)](6+) showed new absorption bands at 2350 nm (epsilon =5500 M(-1) cm(-1)) and 1560 nm (epsilon =10 500 M(-1) cm(-1)), respectively, which were assigned to the intramolecular IT (intervalence transfer) bands from Fe(II) to Fe(III) and from Ru(II) to Fe(III) ions, respectively. The electronic interaction matrix elements (H(AB)) and the degrees of electronic delocalisation (alpha(2)) were estimated to be 1090 cm(-1) and 0.065 for the [Ru(II) (2)Fe(II)Fe(III) (2)](5+) state and 1990 cm(-1) and 0.065 for the [Ru(II) (2)Fe(III) (2)](6+) states.     

A cyclic tetramer of [Ag(1,4,7‐trithiacyclononane)]+, cyclo‐tetrakis(μ‐1,4,7‐trithiacyclononane‐κ3S1,S4,S7:κS1)tetrasilver(I) tetrakis(trifluoromethanesulfonate) nitromethane disolvate

(1,4,7‐Tri­thia­cyclo­nonane)silver tri­fluoro­methane­sulfonate crystallizes in a tetrameric form from nitro­methane, to give the title compound, [Ag₄(C₆H₁₂S₃)₄](CF₃SO₃)₄·2CH₃NO₂. The complex cation consists of four [AgL]⁺ units (L is 1,4,7‐tri­thia­cyclo­nonane), with four Ag—S—Ag bridges forming a cyclic tetramer. The almost planar Ag₄S₄ ring takes an octagonal form.     

Evolution of fluorescein as a platform for finely tunable fluorescence probes

Fluorescence imaging is the most powerful technique currently available for continuous observation of dynamic intracellular processes in living cells. Suitable fluorescence probes are naturally of critical importance for fluorescence imaging, but only a very limited range of biomolecules can currently be visualized because of the lack of flexible design strategies for fluorescence probes. At present, design is largely empirical. Here we show that the carboxylic group of traditional fluorescein dyes, formerly considered indispensable, has been replaced with other substituents, affording various kinds of new fluoresceins. Further, by breaking out of the traditional structure of fluorescein, we developed the first and totally rational design strategy for novel fluorescence probes based on a strict photochemical basis. The value of this approach is exemplified by its application to develop a novel, highly sensitive, and membrane-permeable fluorescence probe for beta-galactosidase, which is the most widely used reporter enzyme.     

Thermodynamic properties of binary mixtures: Hexamethylphosphoric triamide (HMPA) with a non-polar liquid at 25°C

Excess isobaric heat capacities C _p ^E , densities and speeds of sound u of HMPA+heptane and+benzene were measured at 25°C. C _p ^E of both mixtures were positive in the range of small x and negative in the other region. The mixture containing benzene showed higher C _p ^E than the heptane mixture. They both exhibited considerably smaller C _V ^E than C _p ^E . V^E was positive for HMPA+heptane and negative for HMPA+benzene. The compressibilities K _s ^E and K _p ^E of both mixtures were negative. In both mixtures, non-random mixing is expected and [(CH₃)₂N]₃PO molecules are inhomogeneously distributed.     

Simple fluorophotometric determination of cobalt(II) with p-hydroxy-2-anilinopyridine and hydrogen peroxide

Summary A simple and sensitive determination of cobalt(II) is based on its fluorescence reaction with p-hydroxy-2-anilinopyridine and hydrogen peroxide. The relative standard deviation is 2.5% (n=5). An application to pharmaceutical preparations is recommended.The application of diarylamine compounds in analytical chemistry. IV.-Part III see ref. [1]     

The first triple thiol-thiolate hydrogen bond versus triple diselenide bond that bridges two metal centers

Treatment of fac(S)-[Rh(aet)3] (aet = 2-aminoethanethiolate) with aqueous HBF4 in air led to the protonation at coordinated thiolato groups to give a rhodium(III) dimer, [{Rh(aet)2(Haet)}{Rh(aet)(Haet)2}](BF4)3 ([1](BF4)3). On the other hand, similar treatment of fac(Se)-[Rh(aes)3] (aes = 2-aminoethaneselenolate) produced a dinuclear rhodium(III) complex, [Rh2(selenocystamine)3](BF4)6 ([2](BF4)6), because of the autoxidation of coordinated selenolato groups by air. The crystal structures of [1](BF4)3, DeltaDelta-[1](BF4)3, and [2](BF4)6 were determined by X-ray crystallography. In [1]3+ two RhIII octahedrons are connected through a strong triple thiol-thiolate S-H...S hydrogen bond, while two RhIII octahedrons are directly joined by a triple diselenide bond in [2]6+. The cyclic voltammetry indicated that in acidic media the RhIII center in fac(Se)-[Rh(aes)3] is more easily oxidized to RhIV than that in fac(S)-[Rh(aet)3], which is responsible for the formation of coordinated diselenide bonds.