Synthesis and characterisation of luminescent rhenium tricarbonyl complexes with axially coordinated 1,2,3-triazole ligands

A series of 1-alkyl-4-aryl-1,2,3-triazoles (1-methyl-4-phenyl-1,2,3-triazole (1a); 1-propyl-4-phenyl-1,2,3-triazole (1b); 1-benzyl-4-phenyl-1,2,3-triazole (1c); 1-propyl-4-p-tolyl-1,2,3-triazole (1d)) have been prepared through a one-pot procedure involving in situ generation of the alkyl azide from a halide precursor followed by copper catalysed alkyne/azide cycloaddition (CuAAC) with the appropriate aryl alkyne. Cationic Re(I) complexes [Re(bpy)(CO)(3)(1a-d)]PF(6) (2a-d) were then prepared by stirring [Re(bpy)(CO)(3)Cl] with AgPF(6) in dichloromethane in the presence of ligands 1a-d. X-ray crystal structures were obtained for 2a and 2b. In the solid state, 2a adopts a highly distorted geometry, which is not seen for 2b, in which the plane of the triazole ligand tilts by 13° with respect to the Re-N bond as a result of a π-stacking interaction between the Ph substituent and one of the rings of the bpy ligand. This π-stacking interaction also results in severe twisting of the bpy ligand. Infrared spectra of 2a-d exhibit ν(CO) bands at ～2035 and ～1926 cm(-1) suggesting that these ligands are marginally better donors than pyridine (ν(CO) = 2037, 1932 cm(-1)). The complexes are luminescent in aerated dichloromethane at room temperature with emission maxima at 542 to 552 nm comparable to that of the pyridine analogue (549 nm) and blue shifted relative to the parent chloride complex. Long luminescent lifetimes are observed for the triazole complexes (475 to 513 ns) in aerated dichloromethane solutions at room temperature.     

A study of electron affinities using the initiator approach to full configuration interaction quantum Monte Carlo

For the atoms with Z ≤ 11, energies obtained using the "initiator" extension to full configuration interaction quantum Monte Carlo (i-FCIQMC) come to within statistical errors of the FCIQMC results. As these FCIQMC values have been shown to converge onto FCI results, the i-FCIQMC method allows similar accuracy to be achieved while significantly reducing the scaling with the size of the Slater determinant space. The i-FCIQMC electron affinities of the Z ≤ 11 atoms in the aug-cc-pVXZ basis sets are presented here. In every case, values are obtained to well within chemical accuracy [the mean absolute deviation (MAD) from the relativistically corrected experimental values is 0.41 mE(h)], and significantly improve on coupled cluster with singles, doubles and perturbative triples [CCSD(T)] results. Since the only remaining source of error is basis set incompleteness, we have investigated using CCSD(T)-F12 contributions to correct the i-FCIQMC results. By doing so, much faster convergence with respect to basis set size may be achieved for both the electron affinities and the FCIQMC ionization potentials presented in a previous paper. With this F12 correction, the MAD can be further reduced to 0.13 mE(h) for the electron affinities and 0.31 mE(h) for the ionization potentials.     

A Differential Harnack Inequality for the Newell-Whitehead-Segel Equation

This paper will develop a Li-Yau-Hamilton type differential Harnack estimate for positive solutions to the Newell-Whitehead-Segel equation on R^n.We then use our LYH-differential Harnack inequality to prove several properties about positive solutions to the equation,including deriving a classical Harnack inequality and characterizing standing solutions and traveling wave solutions.     

Does the local structure play a role in high temperature superconductivity?

Many highT_csystems exhibit structural distortions or anomalies, some of which correlate withT_c. We present our results for three such systems and discuss them in the context of providing any evidence for coupling of the lattice to the superconducting pairs. We then propose a modulation type of experiment that should provide unambiguous results if a significant lattice-pair coupling does exist.     

Wavelength-Resolved 3-Dimensional Fluorescence Lifetime Imaging

We have developed a compact system for wide-field fluorescence imaging, resolved in three spatial dimensions, lifetime and wavelength, that is based on a gated optical intensifier and an all-solid-state diode pumped Cr:LiSAF oscillator-amplifier system. Exploiting spectral separation, the system has been applied to human teeth, obtaining good lifetime contrast between enamel, dentin and caries. Exploiting spectral separation combined with depth resolution, the study of fluorescent microspheres led to an enhancement in both lifetime contrast and lateral resolution.     

A study of the 138Ba(d,p)139Ba reaction at 19 MeV

The ¹³⁸Ba(d,p) reaction has been studied at an incident deuteron energy of 19 MeV, using the injector-tandem accelerator and the multichannel magnetic spectrograph of the University of Oxford. Deuteron and proton optical model parameters have been obtained from the analysis of elastic scattering experiments on a ¹³⁸Ba target. The parameters have been used to calculate theoretical (d, p) angular distributions on the basis of the DWBA. From the comparison of experimental and theoretical distributions, orbital angular momentum transfers have been deduced and spectroscopic factors determined for all the levels observed up to an excitation energy of 2.5 MeV in ¹³⁹Ba. The spectroscopic information thus obtained is more complete than that from previous studies, and is in satisfactory agreement with expected sum rule limits. A notable item of new information is the assignment of an l_n = 6 transition to the level at 1.54 MeV in ¹³⁹Ba.     

Synthèse dc la pyrido[2,3-f] phtalazine et des diformyl-6,7; -4,6; -4,7; -2,4 quinoleines

This article describes the synthesis of a new heterocycle, pyrido[2,3,f]phtalazine and three new diformylquinolincs.     

A study of the 144Sm(d,p) reaction at 19 MeV

The ¹⁴⁴Sm(d, p) reaction has been studied at an incident deuteron energy of 19 MeV using the injector-tandem accelerator and the multichannel magnetic speetrograph of the University of Oxford. Angular distributions have been measured for transitions to levels of ¹⁴⁵Sm up to an excitation energy of 3.2 MeV. Theoretical (d, p) distributions have been calculated using the program DWUCK. and orbital angular momentum transfers and spectroscopic factors have been deduced by comparing these calculations with the experimental data. The spectroscopic information derived from this study is more complete than that previously reported and many new assignments have been made. The level scheme of ¹⁴⁵Sm has been found to resemble closely the level schemes of the other N = 83 nuclei.