Modular fluorescent benzobis(imidazolium) salts: syntheses, photophysical analyses, and applications

A series of benzobis(imidazolium) (BBI) salts has been prepared and studied as a new class of versatile fluorescent materials. Using a high yielding, modular synthetic strategy, BBI salts with a range of functionality poised for investigating fundamental and applications-oriented characteristics, including emission wavelength tunability, solvatochromism, red-edge excitation, chemical stability, multiphoton excitation, and protein conjugation, were prepared in overall yields of 40-97%. Through structural variation, the BBIs exhibited lambda(em) ranging between 329 and 561 nm while displaying phi(f)s up to 0.91. In addition, the emission characteristics of these salts were found to exhibit strong solvent dependencies with Stokes shifts ranging from 4570 to 13 793 cm(-1), depending on the nature of the BBI core. Although red-edge effects for BBI salts with Br and BF4 counterions were found to be similar, unique characteristics were displayed by an analogue with MeSO4 anions. The stability of an amphiphilic BBI was quantified in aqueous solutions of varying pH, and >85% of the emission intensity was retained after 2 h at pH 3-9. Through multiphoton excitation experiments in aqueous solutions, a BBI salt was found to exhibit three-photon fluorescence action cross sections similar to serotonin. The application of BBI salts as fluorescent protein tags was demonstrated by conjugating bovine serum albumin to a maleimide-functionalized derivative.     

New cembranoid diterpenes from the Vietnamese soft coral Sarcophyton mililatensis stimulate osteoblastic differentiation in MC3T3-E1 cells

Chemical investigation of the Vietnamese soft coral Sarcophyton mililatensis resulted in the isolation of four new cembranoid diterpenes, namely (-)-7beta-hydroxy-8alpha-methoxydeepoxysarcophytoxide (1), (+)-7beta,8beta-dihydroxydeepoxysarcophytoxide (2), (-)-17-hydroxysarcophytonin A (3) and sarcophytol V (4), along with two known compounds, (+)-sarcophine (5) and sarcophytoxide (6). The NMR spectral data of the new compounds were completely assigned by using a combination of 2D NMR experiments including (1)H-(1)H COSY, HSQC, HMBC, and ROESY. To investigate the bioactivities of compounds, which act on bone metabolism, we studied the effects of compounds on the function of osteoblastic MC3T3-E1 cells. Compound 1 caused a significant elevation of alkaline phosphatase activity, collagen content, and nodules mineralization compared to those of the control (p<0.05). These results suggest that newly isolated compound 1 has a direct stimulatory effect on bone formation in vitro and may contribute to the prevention for osteoporosis.     

Synthesis of derivatives of pyrido-[1,2-<Emphasis Type="Italic">c</Emphasis>][1,3,2]oxazaborinine and pyrido-[2,1,6-<Emphasis Type="Italic">f,g</Emphasis>][1,3,7,2]dioxazaphosphacyclo-decane

The condensation of 2,6-di(o-hydroxyphenyl)-3,5-diphenyl-γ-piperidone with boric and boronic acids gave a series of 1,3,4,11b-tetrahydro-2H-benzo[e]pyrido[1,2-c][1,3,2]oxazaborinin-2-ones. The action of phosphorus oxytrichloride on this piperidone gave a derivative of 8,10-dioxa-21-aza-9-phospha-pentacyclohenicosahexaene. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1882–1886, December, 2008.     

Total annual effective dose and health risk due to intake of natural radionuclides of some vegetables cultivated in suburban Ho Chi Minh City,Vietnam

Journal of Radioanalytical and Nuclear Chemistry - In this work, activity concentration of 40K, 226Ra, 232Th, gross alpha and gross beta and annual effective dose due to ingestion of natural...     

Permselectivity and microstructure of anion exchange membranes

The water content, the ion exchange capacity, the transport number of counter-ion of the AMV and AMX anion exchange membranes were determined. The two-phase model (gel phase and interstitial phase) of structure microheterogeneity was validated by means of conductivity measurements. The chronopotentiometric results allowed us to affirm the overall surface homogeneity of the membranes. According to the two-phase model, the influence of the gel phase and the interstitial phase on the membrane permselectivity was discussed in detail. Majorities of co-ions exist in the interstitial phase, thus they have no influence on the transport of counter-ions in the gel phase. The determination of the KCl amount sorbed in the interstitial phase confirmed the existence of partition equilibrium between the interstitial phase and the external solution. Such partition equilibrium can be considered within the microheterogeneous model in order to represent the internal structure of the electromembranes.     

Reaction of aldimine anions with vinamidinium chloride: three-component access to 3-alkylpyridines and 3-alkylpyridinium salts and access to 2-alkyl glutaconaldehyde derivatives

N-tert-Butylimino derivatives of aldehydes were deprotonated with LDA and reacted with vinamidinium chloride to give 2-alkylaminopentadienimine derivatives, which were isolated as their corresponding hydrochloride in 68-81% yield. Reaction of these derivatives with ammonium acetate or salts of primary amines, in n-butanol at 80 degrees C, afforded the corresponding 3-alkylpyridines or 3-alkylpyridinium salts in high yield. Alkaline hydrolysis of 2-alkylaminopentadieneimine derivatives allowed a practical accesss to potassium salts of 2-alkylglutaconaldehyde.     

Transformations of dibenzo(γ-oxopiperidino)aza-14-crowns-4 upon acylation. Molecular structure of dibenzo-16-crown-3

The result of acylation of dibenzoaza-14-crowns-4 containing a 4-oxopiperidine fragment with acetic anhydride depends on the substituent on the nitrogen atom. The NH-substrates initially undergo acylation at the piperidine nitrogen atom, followed by enolization and O-acylation. The acylation of N-methyl derivatives is accompanied by cleavage of the piperidine ring at the C-N bond with formation of acetylamino-substituted dibenzo-16-crowns-3. The structure of the latter was determined by X-ray analysis.     

Electronic structure of germanium monohydrides Ge(n)H, n = 1-3

Quantum chemical calculations were applied to investigate the electronic structure of germanium hydrides, Ge(n)H (n = 1, 2, 3), their cations, and anions. Computations using a multiconfigurational quasi-degenerate perturbation approach (MCQDPT2) based on complete active space wave functions (CASSCF), multireference perturbation theory (MRMP2), and density functional theory reveal that Ge(2)H has a (2)B(1) ground state with a doublet-quartet gap of approximately 39 kcal/mol. A quasidegenerate (2)A(1) state has been derived to be 2 kcal/mol above the ground state (MCQDPT2/aug-cc-pVTZ). In the case of the cation Ge(3)H(+) and anion Ge(3)H(-), singlet low-lying electronic states are derived, that is, (1)A' and (1)A(1), respectively. The singlet-triplet energy gap is estimated to 6 kcal/mol for the cation. An "Atoms in Molecules" (AIM) analysis shows a certain positive charge on the Ge(n) (n = 1, 2, 3) unit in its hydrides, in accordance with the NBO analysis. The topologies of the electron density of the germanium hydrides are different from that of the lithium-doped counterparts. On the basis of our electron localization function (ELF) analysis, the Ge-H bond in Ge(2)H is characterized as a three-center-two-electron bond. Some key thermochemical parameters of Ge(n)H have also been derived.     

A new simulation design of three-mode division (de)multiplexer based on a trident coupler and two cascaded 3 × 3 MMI silicon waveguides

We propose a design of a silicon three-mode (de)multiplexing device based on a trident and two cascaded 3 × 3 multimode interferometers. Input lights at fundamental, first-order, and second-order modes of transverse electric (TE) polarization are simultaneously converted to fundamental TE mode and demultiplexed at different ports at the outputs. The design is carried out through both theoretical analysis and numerical simulation using three dimensional-beam propagation method and effective index method. The results show a successful three-mode multiplexing in 100 nm wavelength range around 1550 nm with low insertion loss (< 0.71 dB) and crosstalk (? 18 dB). The proposed device also exhibit a small footprint (5 µm × 400 µm) that makes it potential for not only wavelength-division multiplexing and multimode-division multiplexing transmission systems, but also high bitrate and compact on-chip silicon photonics integrated circuits.