Anion-assisted trans-cis isomerization of palladium(II) phosphine complexes containing acetanilide functionalities through hydrogen bonding interactions

The anion-assisted shift of trans-cis isomerization equilibrium of a palladium(II) complex containing acetanilide functionalities brought about by allosteric hydrogen bonding interactions has been established by UV/Vis, 1H NMR, 31P NMR and ESI-MS studies.     

A highly selective bifunctional luminescence probe for potassium and fluoride ions

A novel bifunctional molecule 1 by a combination of 1,3-alternate calix[4]-crown-5 and triarylborane moieties through alkynyl linkers has been designed and synthesized. Compound 1 shows intense fluorescence with a photoluminescence quantum yield of 0.70 in CH(2)Cl(2) solution and can serve as a bifunctional luminescent probe for potassium and fluoride ions with high sensitivity and selectivity.     

Positronium: Precision determination of the ground-state fine-structure interval Δv,and measurement of density shifts in the noble gases

The positronium n = 1 fine-structure interval, Δv, has been measured in nitrogen yielding Δv = 203.3849(12) GHz. Comparison with theory shows the need to calculate higher-order theoretical terms. The positronium density shifts in the noble gases were also measured.     

Synthesis, characterization, spectroscopic, and electrochemiluminescence properties of a solvatochromic azacrown-containing cyanoruthenate(II): potential applications in separation and indirect photometric detection of cations and amino acids in HPLC

A new anionic ruthenium(II) complex, (Et4N)[Ru(tpyA18C6)(CN)3] (tpyA18C6=N-[4'-(2,2':6',2'-terpyridyl)]-1,4,7,10,13-pentaoxa-16-azacyclohexadodecane), has been synthesized and characterized. The complex was found to show pronounced solvatochromic behavior and, when dissolved in solution, changed its color from purple to yellow when the solvent system was varied from pure acetonitrile to pure water. Its absorption and emission energies in various solvents showed a linear dependence of the Gutman's acceptor number. The characteristic photoluminescence and electrochemiluminescence (ECL) of the complex were also found to be progressively quenched as the proportion of water in a water/acetonitrile mixture increased. Large changes in the chemical shifts of the 1H NMR and 13C NMR signals of [Ru(tpyA18C6)(CN)3]- in different solvents were observed. The complex has also been demonstrated to serve as a mobile-phase additive in high-performance liquid chromatography for separation of metal cations and amino acids. Comparison studies with the crown-free analogue, (Et4N)[Ru(tpy)(CN)3] (tpy = 2,2':6',2'-terpyridine), showed that other than the ion-pair effect, the allosteric host-guest interaction provided by the presence of the pendant crown was essential to the separation performance of the complex. Indirect detection of nonabsorbing analytes has been achieved by monitoring the absorbance changes of the eluent at the metal-to-ligand charge-transfer (MLCT) absorption band maximum of the complex at 445 nm. The effects of pH, ionic strength, and polarity of the mobile phase as well as the complex concentration on the selectivity and resolution have also been studied.     

Sensitive single-layered oxygen-sensing systems: polypyridyl ruthenium(II) complexes covalently attached or deposited as langmuir-blodgett monolayer on glass surfaces

Oxygen-sensing elements containing single-layered structures of luminescent indicators of ruthenium(II) bipyridyl complexes on glass surfaces prepared by covalent attachment and LB deposition are described. They are capable of detecting gaseous oxygen concentration by luminescence quenching of the indicator with reproducible and large quenching efficiencies that are comparable to the best quenching efficiencies obtained by other ruthenium(II) polypyridine based complexes immobilized in matrixes. The large quenching efficiencies for both films imply that the probe complexes are effectively quenched by oxygen, which is probably due to the thin single-layered structures with large surface-to-area ratio and short distance between the probe complexes and oxygen.     

Photochromic thienylpyridine-bis(alkynyl)borane complexes: toward readily tunable fluorescence dyes and photoswitchable materials

A series of diarylethene-containing N^C chelated thienylpyridine-bis(alkynyl)borane complexes has been designed and synthesized. Their photophysical and photochromic properties have been investigated and presented. The characteristic low-energy absorption band of their closed forms could be readily tuned from the visible range to the near-infrared region.