High-performance fluorescent particles prepared via miniemulsion polymerization

Highly fluorescent polymer particles were prepared with Eu beta-diketonates complex as a fluorophore by miniemulsion polymerization technique. Eu beta-diketonates complex has a long decay time, a large Stokes shift, and very narrow emission bands in comparison with other organic fluorescent compounds. Aqueous miniemulsion was prepared by mixing monomer, crosslinker, hydrophobe, and Eu beta-diketonates complex and then putting the mixture into an aqueous solution of surfactant, followed by ultrasonication. An aqueous solution of initiator was added to the miniemulsion to obtain fluorescent polymer particles, which were monodispersed without aggregation. Particle size was decreased to deca-nano scale by increasing the amount of surfactant. Fluorescent intensity was increased by using Eu beta-complex coordinated with additional ligand. Further fluorescence quantum yields and fluorescent properties in the presence of DNA were investigated to the confirm superiority of Eu beta-diketonates complexes in polymer particles.     

Synthesis of 12-deoxyroyleanone, cryptoquinone, 11,14-dihydroxy-8,11,13-abietatrien-7-one, and related derivatives from dehydroabietic acid

Naturally occurring abietane quinones and hydroquinone, namely, 12-deoxyroyleanone (1a), cryptoquinone (4a), and 11,14-dihydroxyabieta-8,11,13-trien-7-one (5a), together with the epimers of tryptoquinones D (2) and F (3), were first synthesized from dehydroabietic acid (6).     

Photoinduced Molecular Transformations. Part 142. One-step syntheses of 1H-benz[f]indole-4,9-diones and 1H-indole-4,7-diones by a new regioselective photoaddition of 2-amino-1,4-naphthoquinones and 2-amino-1,4-benzoquinones with alkenes

The 2,3-dihydro-1H-benz[f]indole-4,9-diones 3a–d , h were formed in a one-step reaction in 13–82% yield by an unprecedented [3 + 2] regioselective photoaddition of 2-amino-1,4-naphthoquinone ( 1 ) with various electronrich alkenes 2 (Scheme 1, Table). The [3 + 2] photoadducts derived from 1 with vinyl ethers and vinyl acetate gave 1H-benz[f]indole-4,9-diones 4e , f , i , in 33–72% yield, by spontaneous loss of the corresponding alcohol or AcOH from the resulting adducts; 4i has a kinamycin skeleton. The [3 + 2] photoaddition also took place on irradiation of the differently substituted amino-1,4-benzoquinones 6 , 7 , and 12 and excess alkenes 2 in benzene, giving 1H-indole-4,7-dione derivatives 13 and 14 (Scheme 3), 15a and 16 (Scheme 4), and 18 (Scheme 4), respectively. The initial products in these photoadditions were proved to be hydroquinones, the air oxidation of which yielded the heterocyclic quinones; 2,3-dihydro-2-methoxy-2-methyl-5-phenyl-1H-indole-1,4,7-triyl triacetate ( 19 ) was isolated after treatment of the crude photoaddition mixture obtained from 2-amino-5-phenyl-1,4-benzoquinone ( 7 ) and 2-methoxyprop-1-ene ( 2f ) with Ac₂O and pyridine under N₂. A pathway leading to the annelated hydroquinones involving ionic intermediates arising from an electron transfer in these photoadditions is proposed (Scheme 5).     

Xenophilic complexes bearing a Tp(R) Ligand, [Tp(R)M--M'Ln] [Tp(R) = Tp(iPr2), Tp(#) (Tp(Me2,4-Br)); M=Ni, Co, Fe, Mn; M'Ln = Co(CO)4, Co(CO)3(PPh3), RuCp(CO)2]: the two metal centers are held together not by covalent interaction but by electrostatic attraction

A series of dinuclear complexes, [Tp(R)M--M'L(n)] [Tp(iPr(2) )M--Co(CO)(4) (1; M=Ni, Co, Fe, Mn); Tp(#)M--Co(CO)(4) (1'; M=Ni, Co); Tp(#)Ni--RuCp(CO)(2) (3')] (Tp(iPr(2) )=hydrotris(3,5-diisopropylpyrazolyl)borato; Tp(#) (Tp(Me(2),4-Br))=hydrotris(3,5-dimethyl-4-bromopyrazolyl)borato), has been prepared by treatment of the cationic complexes [Tp(iPr(2) )M(NCMe)(3)]PF(6) or the halo complexes [Tp(#)M--X] with the appropriate metalates. Spectroscopic and crystallographic characterization of 1-3' reveals that the tetrahedral, high-spin Tp(R)M fragment and the coordinatively saturated carbonyl-metal fragment (M'L(n)) are connected only by a metal-metal interaction and, thus, the dinuclear complexes belong to a unique class of xenophilic complexes. The metal-metal interaction in the xenophilic complexes is polarized, as revealed by their nu(CO) vibrations and structural features, which fall between those of reference complexes: covalently bonded species [R--M'L(n)] and ionic species [M'L(n)](-). Unrestricted DFT calculations for the model complexes [Tp(H(2) )Ni--Co(CO)(4)], [Tp(H(2) )Ni--Co(CO)(3)(PH(3))], and [Tp(H(2) )Ni--RuCp(CO)(2)] prove that the two metal centers are held together not by covalent interactions, but by electrostatic attractions. In other words, the obtained xenophilic complexes can be regarded as carbonylmetalates, in which the cationic counterpart interacts with the metal center rather than the oxygen atom of the carbonyl ligand. The xenophilic complexes show divergent reactivity dependent on the properties of donor molecules. Hard (N and O donors) and soft donors (P and C donors) attack the Tp(R)M part and the ML(n) moiety, respectively. The selectivity has been interpreted in terms of the hard-soft theory, and the reactions of the high-spin species 1-3' with singlet donor molecules should involve a spin-crossover process.     

Efficient eosin y dye-sensitized solar cell containing Br-/Br3- electrolyte

We found that Br-/Br3- is more suitable than an I-/I3- couple in dye-sensitized solar cells in terms of higher open-circuit photovoltage (Voc) production and higher overall energy conversion efficiency (eta) if the dye sensitizer has a more positive potential than that of Br-/Br3-. Under simulated AM1.5 one sun, an eosin Y dye-sensitized solar cell containing 0.4 M LiBr + 0.04 M Br2 electrolyte in acetonitrile yielded a short-circuit photocurrent (Jsc) of 4.63 mA cm(-2), Voc of 0.813 V, and fill factor (FF) of 0.693, corresponding to 2.61% of eta. Under the same conditions except for the electrolyte 0.4 M LiI + 0.04 M I2 in acetonitrile instead, the device produced 1.67% of eta (Jsc = 5.15 mA cm(-2), Voc = 0.451 V, FF = 0.721). Replacement of I-/I3- with Br-/Br3- in eosin Y dye-sensitized solar cells yielded a significant increase in Voc offset by slight decreases in Jsc and FF, leading to an increase in eta by 56%. The significant gain in Voc was attributed to the enlarged energy level difference between the redox potential of the electrolyte and the Fermi level of TiO2 and the suppressed charge recombination as well. The rate for charge recombination between bromine and the injected electrons was determined to be first order in bromine.     

Syntheses and reactions of functional polymers. XLII. Preparation and use of polymers having N-hydroxy-succinimide unit in the chain

Styrene-maleic anhydride alternating copolymer was converted to N-hydroxymaleimide-styrene copolymer by reaction with hydroxylamine in pyridine at room temperature. The conversion was more than 90%. From this copolymer, N-acetoxy- or N-benzoyloxymaleimide-styrene copolymers were derived by action of acetic anhydride or benzoyl chloride in dimethylformamide at room temperature. Acylation of several primary amines was carried out effectively by use of these N-acyloxyimide-styrene copolymers. The reaction of the acetylated copolymer with diethylamine at room temperature afforded N-hydroxyimide copolymer.     

Efficient synthesis of N-acyl-α-amino acids via polymer incarcerated palladium-catalyzed amidocarbonylation

A novel polymer incarcerated Pd catalyst (PI Pd 7c) was synthesized from amide-containing polymer 6b, and this catalyst was shown to be effective in amidocarbonylation, which is a versatile one-pot method for the preparation of N-acyl-α-amino acids. The reactions proceeded smoothly with a wide variety of substrates, and no leaching of the Pd metal to the reaction mixture was detected.     

Influence of the Coordination of Donor Solvent Molecules to 1,4,7,10-Tetramethyl-1,4,7,10- tetraazacyclododecanenickel(II) and Analogous Nickel(II) Complexes on Their Steric Factors

Coordination equilibrium constants (K _NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me₄[12]aneN₄)]²⁺) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K _NiS1) and second stepwise coordination equilibrium constants (K _NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN₄)]²⁺), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN₄)]²⁺), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS₄)]²⁺) were also reinvestigated. The K _NiS values for [Ni(Me₄[12]aneN₄)]²⁺ were compared to those of [Ni([12]aneN₄)]²⁺, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺), R,R,S,S-[Ni(Me₄[14]aneN₄)]²⁺, [Ni([14]aneN₄)]²⁺, and [Ni([14]aneS₄)]²⁺. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me₄[12]aneN₄)]²⁺ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺. The K _NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm³⋅mol⁻¹, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺, but such waters did not coordinate to [Ni(Me₄[12] aneN₄)]²⁺. Also, the K _NiS2 values were larger than the corresponding K _NiS1 values for [Ni([14]aneS₄)]²⁺. Furthermore, the K _NiS1 values for [Ni([12]aneN₄)]²⁺ were the largest among these nickel(II) complex cations. The K _NiS, K _NiS1, and K _NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations.     

Fragmentation study of peptides using Fourier transform ion cyclotron resonance with infrared multiphoton dissociation: experiment and simulation

In this study, the fragmentation of gas-phase protonated Angiotensin II is investigated using electrospray ionization (ESI), Fourier-transform ion cyclotron resonance (FT-ICR), and mass spectrometry (MS) with a laser cleavage infrared multiphoton dissociation (IRMPD) technique. The experimental results show that the spectra peaks for the photoproducts are y2/b6- and y7-type ions, corresponding to the cleavage of His-Pro and Asp-Arg in the parent amino acid sequence. The fragmentation of the peptide under collision-free vacuum conditions is modeled using molecular dynamics simulations (MD). The binding energy for the peptide bonds (C'-N bond) of Angiotensin II is estimated from ab initio calculations. The calculations are directed at predicting experimental measurements of the product ions from the photodissociation of the peptide. The product distributions simulated by the MD dissociation trajectories include predominantly y7/b1 and y2/b6 pair ions.     

Aryl-aryl coupling reaction using a novel and highly active palladium reagent prepared from Pd(OAc)2, 1,3-bis[diphenylphosphino]propane (DPPP), and Bu3P

A palladium-assisted coupling reaction of aryl triflate with arene was investigated, and a novel Pd reagent prepared from equimolar Pd(OAc)2, 1,3-Bis[diphenylphosphino]propane (DPPP), and Bu3P was developed. This method is useful for intramolecular biaryl coupling reactions, not only between aryl triflate and arene (triflate-amide), but also between aryl halide and arene (halo-amide).