Highly unusual effects of pi-conjugation extension on the molecular linear and quadratic nonlinear optical properties of ruthenium(II) ammine complexes

We have used several techniques, including hyper-Rayleigh scattering and Stark spectroscopy, to investigate the effects of polyene chain length on the optical properties of complexes containing ruthenium(II) electron donor groups and pyridinium electron acceptors. In marked contrast with all other known donor-acceptor polyenes, conjugation extension beyond a single double bond in the dipolar complexes studied leads to blue-shifting of the intramolecular charge-transfer absorptions. Furthermore, the static first hyperpolarizabilities beta0 become maximized with trans-1,3-butadienyl linkages and then decrease in complexes with three CH=CH bonds. Our results clearly demonstrate that the molecular engineering criteria for metal-containing nonlinear optical chromophores can differ dramatically from those for purely organic compounds.     

Syntheses and spectroscopic and quadratic nonlinear optical properties of extended dipolar complexes with ruthenium(II) ammine electron donor and N-methylpyridinium acceptor groups

In this paper, we describe the extremely unusual optical properties of Ru(II)-based electron donor-acceptor (D-A) polyene and some closely related chromophores. For three different polyene series, the intense, visible d-->pi* metal-to-ligand charge-transfer bands unexpectedly blue-shift as the number of E-ethylene units (n) increases from 1 to 3, and the static first hyperpolarizabilities beta(0) determined via hyper-Rayleigh scattering and Stark spectroscopy maximize at n = 2, in marked contrast to other known D-A polyenes in which beta(0) increases steadily with n. Time-dependent density-functional theory and finite field calculations verify these empirical trends, which arise from the orbital structures of the complexes. This study illustrates that transition metal-based nonlinear optical chromophores can show very different behavior when compared with their more thoroughly studied purely organic counterparts.     

Chiral 2-Aryl-2-methyl-2H-1-benzopyrans: Synthesis,characterization of enantiomers,and barriers to thermal racemization

The ease of thermal breaking of the C(sp³)? O bond of the 2-aryl-2-methyl-2H-1-benzopyrans 1 – 9 was evaluated by measuring the free energy (ΔG) of the racemization reaction of optically active compounds. The variation of ΔG of the thermal ring opening in terms of structural modifications is discussed. The synthesis of the studied compounds, the preparative separation of enantiomers by liquid chromatography, the determination of enantiomeric purity, the circular dichroism of enriched enantiomers, and the measurement of rate constants of enantiomerization by monitoring the decrease of the polarimetric angle of rotation at suitable temperatures are described.     

The isoindolobenzazepine alkaloids

Three Chilean barberries, $\text{Berberis}$$\text{actinacantha}$ Mart. ex Schult., $\text{B}$. $\text{darwinii}$ Hook and [ulbar|B. $\text{valdiviana}$Phil. (Berberidaceae), have yielded several new isoindolobenzazepine and protoberberine alkaloids. Novel isoindolobenzazepines are (±)-13-deoxychilenine ($\text{a}$), pictonamine ($\text{10}$), chileninone ($\text{12}$), (±)-chileniimi ($\text{18}$) and (±)-palmanine ($\text{19}$). Highly oxidized protoberberines of particular interest include (±)-O-methylprechilenine ($\text{6}$) and (±)-prepseudopalmanine ($\text{21}$), together with 13-methoxy-8-oxyberberine ($\text{8}$). Isoindolobenzazepine alkaloids arise biogenetically from the rearrangement of highly oxidized protoberberines.     

Some group IVB derivatives of 1,6-methano[10]annulene. Synthesis, substituent effects and reactivity

Certain Group IVB derivatives of 1,6-methano[10]annulene have been synthesised, and their ¹³C nuclear magnetic resonance spectra recorded and assigned, to provide a measure of the substituent effects exerted by metalloid-containing groups in this non-benzenoid aromatic system. Comparisons are made with the corresponding naphthalene and some anthracene derivatives. Protiodemetallations of a number of arylsilanes and -stannanes have been examined, and in protiodestannylation by CH₃CO₂H/dioxane at 27°C (an electrophilic aromatic substitution) the - (or 2-) position of 1,6-methano[10]annulene is ca. 35 times as reactive as the (or 1-) position of naphthalene, whereas in protiodesilylation by CF₃CO₂H/CH₃CO₂H at 27°C it is ca. 700 times the more reactive.     

Polypyrrole/poly(methylmethacrylate) blend as selective sensor for acetone in lacquer

A film of α-naphthalene sulfonate-doped polypyrrole/poly(methylmethacrylate), PPy/α-NS⁻/PMMA, obtained from solution mixing was successfully used as sensing material for acetone vapor in lacquer with a high degree of selectivity based on electrical conductivity over acetic acid and a high degree of stability over the humidity change. Compared with pure PPy/α-NS⁻, the selectivity ratio of acetone/acetic acid response of PPy/α-NS⁻/PMMA blend with a PMMA/PPy weight ratio of 3.0 was ca. 3.9 times higher. The film was found to be insensitive to moisture unless the relative humidity (RH) was lower than 20% RH in which the selectivity ratio of acetone/acetic acid response was enhanced. The time required to reach the equilibrium for acetone exposure was found to increase slightly with increasing humidity.     

Squaraine dyes for photodynamic therapy: study of their cytotoxicity and genotoxicity in bacteria and mammalian cells

Halogenated squaraine dyes are characterized by long wavelength absorption (>600 nm) and high triplet yields and therefore represent new types of photosensitizers that could be useful for photodynamic therapy. We have analyzed the cytotoxicity and genotoxicity of the bromo derivative 1, the iodo derivative 2 and the corresponding nonhalogenated dye 3 in the absence and presence of visible light. At concentrations of 1-2 microM, 1 and 2 reduced the cloning efficiency of AS52 Chinese hamster ovary cells to less than 1% under conditions that were well tolerated in the dark. Similarly, the proliferation of L5178Y mouse lymphoma cells was inhibited by photoexcited 1 and 2 with high selectivity. The squaraine 3 was much less efficient. Both 1 and 2 induced only few mutations in the gpt locus of the AS52 cells in the presence of light and were not mutagenic in the dark. No mutagenicity with and without irradiation was observed in Salmonella typhimurium TA100 and TA2638. However, both 1 and 2 plus light increased the frequency of micronuclei in AS52 cells. The results indicate that halogenated squaraines exhibit photobiological properties in vitro that are favorable for photodynamic therapeutical applications.     

Bildung und Schwingungsspektrum des Pentachloro-oxo-niobat(V)-Ions. Die Kristallstruktur von [As(C6H5)4]2NbOCl5 · 2 CH2Cl2

Formation and Vibrational Spectrum of the Pentachloro-oxo-niobate(V) Ion. Crystal Structure of [As(C₆H₅)₄]₂NbOCl₅ · 2 CH₂Cl₂ [As(C₆H₅)₄]₂NbOCl₅ is formed by reaction of NbOCl₃ with [As(C₆H₅)₄]Cl in CH₂Cl₂; form the solution it crystallizes with two molecules of CH₂Cl₂. The i.r. and Raman spectrum is in accord with a NbOCl₅ ion of symmetry 4mm. The crystals are triclinic (space group P1 ) with the lattice constants a = 1043, b = 1187, c = 2269 pm, α = 97.4, β = 106.3 and γ = 101.4°. The crystal structure was determined with X-ray diffraction data and refined to a residual index of R = 0.042. In the structure there are two of each crystallographic independent As(C₆H₅)₄⁺ ions and CH₂Cl₂ molecules. The NbOCl₅ ion has an octahedral shape with a Nb? O distance of 197 pm.