Laser-Induced Fluorescence of Molybdenocene and Tungstenocene in Low-Temperature Matrices

The reactive metallocenes, tungstenocene and molybdenocene (M(t75-C5H5)2; M = Mo, W), have been generated by photolysis of the corresponding dihydride complexes, M(í;5-C5H5)2H2, in argon and nitrogen matrices at 12 K. The metallocenes have been probed by laser-induced fluorescence with a pulsed tunable laser and by UV/vis absorption spectroscopy. Structured emission is observed from the LMCT excited states (lifetimes < 10 ns). The spectra are complicated by multiple sites/conformers, but emission spectra of a single site/ conformer may be obtained with appropriate selection of matrix and excitation wavelength. Corresponding excitation spectra are measured from the area of selected emission peaks as a function of excitation wavelength. Vibrational progressions are dominated by the ring—metal-ring symmetric stretching mode (v4 ~ 300 cm-1). Nevertheless, this mode changes in frequency by <4 cm-1 (< 1.3%) in the LMCT excited state. The bestresolved peaks have a full width at half-maximum of ca. 10 cm-1. Most of the emission is vibrationally fully relaxed, but weak emission peaks arising from ' = 1 states are found for MoCp2 in N2 matrices

Photophysical and Electrochemical Properties of meso-Substituted Thien-2-yl Zn(II) Porphyrins

The influence of the thiophene ring on the ground and excited state properties of the porphyrin ring is investigated, when substituted at the meso-position. A series of mono-, di-, tri-, and tetra-meso-thien-2-yl porphyrins are studied and discussed with respect to the reference compounds zinc(II)-5,10,15,20-tetra(thien-2′-yl)porphyrin (1a) and zinc(II)-5,10,15,20-tetraphenylporphyrin (ZnTPP). The extended conjugated system zinc(II)-5-(5′-(5′′-ethynyl-2′′-thiophenecarboxaldehyde)thien-2′-yl)-10,15,20-triphenylporphyrin (4d) is also studied and shows enhanced charge transfer character due to the presence of the terminal aldehyde accepting group. A detailed analysis of ground and excited state UV−vis absorption, steady-state and time-resolved fluorescence, laser flash photolysis, and electrochemical data all point toward substantial electronic communication between the central Zn(II) porphyrin ring and the meso-thien-2-yl substituents, which is evident from excited state charge transfer character

Electrochemical formation of N–substituted polypyrrole nanowires, microwires and open microtubes and their decoration with copper structures

The substituted pyrrole monomer, N–(2–cyanoethyl)pyrrole, was electropolymerised in a 70% water and 30% ethanol solution with ClO4– and H2PO4– as the dopant species to give nanowires at short electropolymerisation times and microwires at longer deposition periods. On adding toluene to the electropolymerisation solution, hollow microtubes were formed. This was attributed to the adsorption of toluene droplets at the electrode surface which served to separate the dopants from the monomer, with the monomer being highly soluble in the toluene droplet and the inorganic dopants soluble in the water/ethanol mixture. As a result electropolymerisation was confined to the toluene-water/ethanol interface. These polymer systems exhibit redox activity with the oxidation wave centred at about 0.40 V vs SCE, and the broader reduction wave positioned between 0.75 V and 0.25 V vs SCE. Although N-substitution reduces the conductivity of the polymer, various copper deposits, including cubes, leaves and hierarchical structures were deposited at the microwires and microtubes using high overpotentials. The hierarchical structures were wrapped around the microtubes at considerable distances, typically 3–4 µm, from the substrate

Laser Photochemistry and Transient Raman Spectroscopy of Silyl-Substituted Fischer-Type Carbene Complexes

Pulsed laser irradiation of the silyl-substituted carbene complexes (CO)5W=C(XR)SiPh3 (XR = NC4H8 (1); = OEt (2)) in various solvents has been investigated using transient absorbance and time-resolved resonance Raman scattering as monitoring techniques. Irradiation of (1) in noncoordinating or weakly-coordinating solvents at 355 nm within the ligand field absorption band results in the rapid formation, within the laser pulse duration, of a permanent photoproduct. Saturation of the irradiated solution with CO results in regeneration of the starting complex 1. IR and Raman spectral data suggest that the photoproduct is the internally stabilized 16- electron species (CO)4W=C(NC,iH8)SiPh3. The observations are discussed in relation to the previously reported formation of the same 16-electron species by thermolysis of 1. When the irradiation is carried out in CH3CN as solvent, UV-visible evidence suggests formation of the photosubstituted species (CO)4(CH3CN) W=C(NC4Hg)SiPh3. No photoactivity, either transient or permanent, is seen in any solvent when the irradiation is carried out at 416 nm, a wavelength which falls within the MLCT absorption region of 1. When the ethoxy-substituted carbene complex 2 is irradiated in either the LF or MLCT absorption regions a transient species forms rapidly, within the laser pulse duration, and decays on a time scale of several μß, with a lifetime dependent on solvent polarity but independent of CO concentration in solution. Time-resolved resonance Raman studies in which the sample is photolyzed at 355 nm and probed by means of a delayed pulse at 406 nm show the formation and decay of a transient consistent with the flash photolysis results. The data are interpreted in terms of photoinduced anti-syn isomerization of 2 about the Ccarbene~0 bond

Preparation and Antimicrobial Properties of Alginate and Serum Albumin/Glutaraldehyde Hydrogels Impregnated with Silver(I) Ions

peer-reviewedCalcium alginate (CaALG) hydrogel beads and two sets of composite beads, formed from a combination of calcium alginate/propylene glycol alginate/human serum albumin (CaALG/PGA/ HSA) and from calcium alginate with the quaternary ammonium salt, (3-(trimethoxysilyl)propyl)- octadecyldimethylammonium chloride (QA), (CaALG/QA), were prepared. Bovine serum albumin (BSA) was condensed with glutaraldehyde (GLA) to form a BSA/GLA hydrogel. The corresponding Ag+-containing gels of all of the above hydrogels were also formed, and slow leaching of the biocidal transition metal ion from the gels bestowed broad spectrum antimicrobial activity. In the absence of added Ag+, CaALG/QA was the only material to deliver marginal to moderate antibacterial and antifungal effects. The Ag+ impregnated hydrogel systems have the potential to maintain the antimicrobial properties of silver, minimising the risk of toxicity, and act as reservoirs to afford ongoing sterility.Irish Department of Agriculture Food and Marin

Charge-transfer Interactions between Sulfur Dioxide and Group 8 Half-sandwich Complexes

M ulliken-type charge-transfer complexes have been formed between basic half-sandwich compounds and SO, when [M(q5-C,R,)(CO),] (M = Rh or Ir; R, = Me,, H, or H,CF,), [Ir(q5-C,H,)(CO)(C,H,)]. and [M(q5-C,H,)(C,H,),] (M = Co, Rh or Ir) are isolated in SO,-doped argon matrices at 20 K; the v(C0) bands of the complexes are shifted to high frequency of those of the precursor molecules and prominent charge-transfer bands are observed; the same species have been detected when the compounds [M(q5-C,Me,)(CO),] (M = Rh or Ir) are embedded in polyethylene discs and treated with SO, at 213-298 K; the enthalpy of complexation of [Ir(q5-C,Me,)(CO),] with SO, is -13 f 3 kJ mo1V

Sequence of a complete chicken BG haplotype shows dynamic expansion and contraction of two gene lineages with particular expression patterns.

Many genes important in immunity are found as multigene families. The butyrophilin genes are members of the B7 family, playing diverse roles in co-regulation and perhaps in antigen presentation. In humans, a fixed number of butyrophilin genes are found in and around the major histocompatibility complex (MHC), and show striking association with particular autoimmune diseases. In chickens, BG genes encode homologues with somewhat different domain organisation. Only a few BG genes have been characterised, one involved in actin-myosin interaction in the intestinal brush border, and another implicated in resistance to viral diseases. We characterise all BG genes in B12 chickens, finding a multigene family organised as tandem repeats in the BG region outside the MHC, a single gene in the MHC (the BF-BL region), and another single gene on a different chromosome. There is a precise cell and tissue expression for each gene, but overall there are two kinds, those expressed by haemopoietic cells and those expressed in tissues (presumably non-haemopoietic cells), correlating with two different kinds of promoters and 5' untranslated regions (5'UTR). However, the multigene family in the BG region contains many hybrid genes, suggesting recombination and/or deletion as major evolutionary forces. We identify BG genes in the chicken whole genome shotgun sequence, as well as by comparison to other haplotypes by fibre fluorescence in situ hybridisation, confirming dynamic expansion and contraction within the BG region. Thus, the BG genes in chickens are undergoing much more rapid evolution compared to their homologues in mammals, for reasons yet to be understood.This is the final published version. It was originally published by PLOS in PLOS Genetics here: http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1004417