ABSTRACT
A new series of bipyridine-capped oligothiophene ligands and their binuclear Ru(II) complexes of the general formula [(bpy)(2)Ru-bpy(th)(x)bpy-Ru(bpy)(2)](4+) (where bpy = 2,2'-bipyridyl, th = 2,5-thienyl, and x = 1, 3, or 6) has been synthesized. Comparison of the bipyridine-capped oligothiophenes to the corresponding uncapped oligomers shows that there is coupling of the bipyridine to the oligothiophene-conjugated pi-system. Each of the bipyridine-capped ligands reduces at a bipyridine cap at potentials less negative than those of free bipyridine. The lambda(max) values of the lowest pi-pi* transition increase and the E(pa) values for the first oxidation decrease with an increase in the number of thiophene rings in the bridge. The increase in the number of thiophene rings also leads to more accessible oxidation states, up to four for the x = 6 compound. Upon complexation of the ligands with the (bpy)(2)Ru(2+) moiety, the electronic spectra of the complexes show a significant redshift in comparison to the spectra of Ru(bpy)(3)(2+), the oligothiophene-based oxidation(s) shifts to more positive potentials, and new oxidation and reduction processes are also observed. A single concurrent Ru(II/III) oxidation process is observed in all cases at about the same potential (E(ave)(0) = 1.32 V (acetonitrile solution)) as is observed in the parent complex Ru(bpy)(3)(2+), suggesting that the couples are not strongly coupled. The series of complexes shows a unique range of ligand-based oxidation processes with respect to the position of the Ru(II/III) redox process. In the case of x= 1, no ligand-based oxidation process is observed; for x = 3, the first oligothiophene oxidation occurs at potentials less positive than those of the Ru(II/III) redox process, and for x = 6, two oligothiophene oxidations are less positive than the Ru(II/III) redox process. A series of bpy reduction processes that are similar to those observed for Ru(bpy)(3)(2+) also occurs. The x = 1 compound shows two, one-electron reductions and then two, two-electron reductions; the x = 3 and x = 6 compounds show three, two-electron reduction processes. The first reductions occur at the capping bipyridines of the bridging ligand in all three complexes, and subsequent reductions occur at the ancillary bipyridine ligands in a stepwise fashion.
ABSTRACT
We report a convenient synthesis of K(2)[Ru(bpy)(NO(2))(4)] via the thermal displacement of benzene from [(Bz)Ru(bpy)Cl]Cl (Bz = eta(6)-C(6)H(6); bpy = 2,2'-bipyridine) by nitrite ion in methanol solution. K(2)[Ru(bpy)(NO(2))(4)] has been fully characterized by elemental analysis, X-ray crystallography, and (1)H NMR, IR, UV-vis, and emission spectroscopy. Reaction of K(2)[Ru(bpy)(NO(2))(4)] with pyridine under mild or forcing conditions produces fac-K[Ru(bpy)(NO(2))(3)(py)] and cis-[Ru(NO(2))(2)(bpy)(py)(2)] (py = pyridine), respectively. We report full characterization data for these compounds, including crystal structures. The d pi(Ru) --> pi*(bpy) charge-transfer band in the electronic spectra of K(2)[Ru(bpy)(NO(2))(4)] and fac-[Ru(bpy)(NO(2))(3)(py)] displays a significant solvent dependence. The energy of the absorption band correlates linearly with the Gutmann solvent acceptor number. The solvatochromic response of these nitro complexes is essentially identical to that of the analogous cyanide complexes, indicating that the mechanism previously proposed to explain the solvatochromism of the cyanide complexes may need to be reexamined.
ABSTRACT
The near retinoscopy technique of refractive error determination was compared to the standard method of cycloplegic refraction using 10 "infants" (3-12 months of age) and 10 "children" (32-109 months of age). There was a significant difference between the techniques for both sphere and cylinder power. Although there was no interaction of refractive technique and age group, the difference between near retinoscopy and cycloplegic refractive error tended to be larger for infants than for children. No significant difference was found when the average refractive values were compared for monocular or binocular conditions and no significant effect was found for either gender or laterality (right versus left eye). Based on these findings, it is suggested that caution be used in substituting the near retinoscopy technique for cycloplegic refraction even utilizing a "correction" factor for the dioptric difference between techniques.
Subject(s)
Cyclopentolate/pharmacology , Pupil/drug effects , Refractive Errors/diagnosis , Analysis of Variance , Child , Child, Preschool , Female , Humans , Infant , Male , Methods , Random Allocation , Vision, Binocular , Vision, MonocularABSTRACT
Kingella species are rarely reported as a cause of endocarditis. We report two cases of K. denitrificans endocarditis occurring in patients with prosthetic valves. K. denitrificans has not been previously reported to cause prosthetic valve endocarditis. Both patients may have developed bacteremia from altered upper respiratory or oral mucosa with subsequent prosthetic valve infection. Treatment with penicillin G and streptomycin was successful in the first patient, whereas ampicillin alone resulted in clinical cure in the second case. Neither patient required further surgery. In vitro antibiotic susceptibility testing indicated that both organisms were highly sensitive to cefotaxime and ampicillin.
