Stability analysis of the two rotational isomers of meta-fluorobenzaldehyde in the S0, S1, and S2 electronic states

For a determination of the stabilization energy between the two rotational isomers of m-fluorobenzaldehyde, the S(1,2)<--S0 absorption spectra were observed in fluid n-hexane solutions at 293 and 198 K. After employing a simulation method for the spectra, we succeeded in determining the stabilization energies in the ground and the relevant excited state at the same time. The energy was estimated to be 1.7 +/- 0.5 kJ mol(-1) for S0 and also for S1 while it was 2.9 +/- 0.5 kJ mol(-1) for S2. Ab initio calculations at MP2/6-311G** computational level predicted that the O-cis form in the S0 state is more stable by 1.9 +/- 0.5 kJ mol(-1) than the counterpart rotamer, O-trans form. In summary, a schematic energy level diagram of the two rotational isomers will be illustrated for the S0, S1, and S2 states in the fluid system.     

Static and dynamical potential surface distortions in aromatic aldehyde 3A″ (nπ*) states

Two quanta of the aldehyde H-wag vibrational mode are observed with relatively constant activity in the vibrational structure of ³A″ (nπ*) → ¹A′ phosphorescence spectra of benzaldehyde, deuterated benzaldehydes, pyridine aldehydes, p-methylbenzaldehyde, p-fluorobenzaldehyde, and p-chlorobenzaldehyde at 4.2°K in a methylcyclohexane polycrystalline environment. The fundamental is either missing or very weak. Contrasted to the aldehyde H-wag mode, higher quanta of the CHO torsional mode are observed in the phosphorescence of the same molecules with variable intensity and progression length. These results are interpreted in terms of a static (i.e., valence) distortion of the ³nπ potential surface along the aldehyde H-wagging coordinate, and pseudo-Jahn-Teller distortion along the CHO torsional coordinate. The valence distortion is analogous to a distortion found for the ³nπ* state in propynal and its origin probably lies in excess electron density at the carbonyl carbon in the excited state. The dynamical Jahn-Teller distortion is ascribed to vibronic interaction between ³A″ (nπ) and the nearest ³A′(nπ*) states.     

A high-pressure iron K-edge x-ray absorption spectral study of the spin-state crossover in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) and (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2)

The room temperature iron K-edge X-ray absorption near edge structure spectra of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) and (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) have been measured between ambient and 88 and 94 kbar, respectively, in an opposed diamond anvil cell. The iron(II) in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2)undergoes the expected gradual spin-state crossover from the high-spin state to the low-spin state with increasing pressure. In contrast, the iron(II) in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) remains high-spin between ambient and 78 kbar and is only transformed to the low-spin state at an applied pressure of between 78 and 94 kbar. No visible change is observed in the preedge peak in the spectra of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) with increasing pressure, whereas the preedge peak in the spectra of ((e[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) changes as expected for a high-spin to low-spin crossover with increasing pressure. The difference in the spin-state crossover behavior of these two complexes is likely related to the unusual behavior of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) upon cooling.     

Synthesis and evaluation of novel pyrimido-acridone, -phenoxadine, and -carbazole as topoisomerase II inhibitors

As part of a series of studies to discover new topoisomerase II inhibitors, novel pyrimidoacridones, pyrimidophenoxadines, and pyrimidocarbazoles were synthesized, and in vitro and in vivo antitumor activities and DNA-protein and/or DNA-topoisomerase II cross-linking activity as an indicator of topoisomerase II-DNA cleavable complex formation were evaluated. The pyrimidocarbazoles possessed high in vitro and in vivo potencies. Compound 26 (ER-37326), 8-acetyl-2-[2-(dimethylamino)ethyl]-1H-pyrimido[5,6,1-jk]carbazole-1,3(2H)-dione, showed in vitro growth inhibitory activity with respective IC(50) values of 0.049 microM and 0.35 microM against mouse leukemia P388 and human oral cancer KB. In vivo, this compound inhibited the tumor growth of mouse sarcoma M5076 implanted into mice with T/C values of 42% and 13% at 3.13 and 6.25 mg/kg/d respectively without significantly affecting the body weight. In addition, compound 26 (ER-37326) increased the formation of DNA-topoisomerase II cross-linking in P388 cells.     

Chemical forms of radioactive iodine in seawater and its effects upon marine organisms

Chemical forms of radioactive iodine and its effects upon marine organisms were studied by the tracer experiments. Seaweeds or fish were held in the aquarium in which the 125I tracer in either iodide or iodate form was inoculated. Iodide form of 125I was taken by Dorome (Chasmichthys gulosus) with the concentration factor of about 10 and excreted with the biological half-life of 15 days, while iodate form of 125I was not taken up appreciably and the concentration factor did not greatly exceed unity. Uptake and loss of 125I were studied as well for 3 species of seaweeds, Hijiki(Hizikia fusiforme), Nejimoku (Sargassum sagamianum) and Tsunomata (Chondrus ocellatus). Iodate form of 125I was accumulated less than iodide form by these seaweeds but the concentration factor of iodate by these seaweeds was very high compared to those by fish.     

Palladium complex-catalyzed carbonylation of organic halides in the presence of cyclic ethers: Halohydrin ester synthesis

Cyclic ethers were cleaved by palladium complex-catalyzed carbonylation of organic halides to give halohydrin esters.     

Heat-pulse induced delayed phosphorescence (HIDP) of xanthone

A heat-pulse modulation technique has been applied to the phosphorescence study of xanthone in n-pentane at 1.5 and 4.2 K. The heat-pulse induced delayed phosphorescence (HIDP) was observed via the internal and back-internal conversion processes among the phosphorescent levels. Decay properties were examined as a function of pulse-delay time.     

Shape Coexistence and the N=28 Shell Closure Far from Stability

A mass measurement experiment by a time of flight method with the SPEG spectrometer at GANIL has been performed to investigate the N=20 and N=28 shell closures far from stability. The masses of 31 neutron-rich nuclei in the range A=29–47 have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S and P isotopes are seen to exhibit a change in shell structure around N=28. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. The evidence of an isomeric state in the ⁴³S and its interpretation by a shell model calculation confirm the analysis of the masses and constitutes the first evidence of the predicted shape coexistence around N=28. This revised version was published online in July 2006 with corrections to the Cover Date.     

FICA,a new chiral derivatizing agent for determining the absolute configuration of secondary alcohols by 19F and 1H NMR spectroscopies

Optically active 1-fluoroindan-1-carboxylic acid (FICA) was designed and prepared as its methyl ester for determining the absolute configuration of chiral molecules by both ¹H and ¹⁹F NMR spectroscopies. Enantiomerically pure isomers of FICA methyl esters (FICA Me esters) were obtained by chromatographic separation using HPLC with a Daicel Chiralcel OJ-H column. The absolute configuration of the (+)-FICA Me ester was deduced to be (S) by X-ray crystallographic analysis of the (+)-FICA amide of (R)-α-phenethylamine. Both enantiomers were derived to the diastereomeric esters of chiral secondary alcohols by an ester exchange reaction. In the ¹H NMR spectra, the signs of Δδ_H (δ_R ? δ_S) were consistent on each side of the FICA molecular plane. Therefore, the concept of the modified Mosher’s method could be successfully applied to the FICA-based procedure. Moreover, the consistency in the signs of Δδ_F (δ_R ? δ_S) values suggests that the FICA method would be reliable in assigning the absolute configurations of secondary alcohols based on ¹⁹F NMR spectroscopy.     

Novel des-fatty acyl-polymyxin B derivatives with Pseudomonas aeruginosa-specific antimicrobial activity

Polymyxin B (PMB) is a cationic cyclic decapeptide antibiotic with a fatty acyl (FA) modification at the α-amino group of Dab1 (Dab: L-α,γ-diaminobutyric acid). In this study, which is part of a series of PMB structure-activity relationship investigations focused on identifying clinically useful peptide antibiotics, we synthesized ten des-FA PMB derivatives whose N-terminal moieties were changed to basic or hydrophilic amino acids. The antimicrobial and lipopolysaccharide (LPS) binding activities of these synthetic analogs were tested. The analogs showed more potent antimicrobial activity against Pseudomonas aeruginosa (P. aeruginosa) compared with the PMB nonapeptide. In particular, [Ser2-Dap3]-PMB(2-10), Guanyl-[Thr2-Dab3]-PMB(2-10), Guanyl-[Dab1-Thr2-Dab3]-PMB(1-10), and N(α,γ)-diguanyl-[Dap3]-PMB(3-10) had antimicrobial activity equivalent to PMB. In LPS binding assays, the displacement curves shifted in a manner proportional to the number of positive charges available to bind to Escherichia coli (E. coli) and P. aeruginosa. Furthermore, peptides with basic side chains were comparable to PMB in binding activity assays against E. coli and P. aeruginosa. The acute toxicities of the peptides were evaluated by intravenously administering the peptides to mice through the tail vein. The toxicities of [Ser2-Dap3]-PMB(2-10), [Dap3]-PMB(3-10), and [Ser3]-PMB(3-10) were lower that of PMB (LD??, 4.8 μmol/kg).