Structural trends in a series of bulky dialkylbiarylphosphane complexes of CuI.

CuI complexes containing the bulky dialkylbiarylphosphane 2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl (tBuXPhos, L) and an ancillary ligand (Cl-, Br-, I-, MeCN, ClO4- or SCN-) have been structurally characterized, namely, chlorido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuCl(C29H45P)], 1, bromido[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I), [CuBr(C29H45P)], 2, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]iodidocopper(I), [CuI(C29H45P)], 3, (acetonitrile-κN)[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I) hexafluoridophosphate, [Cu(CH3CN)(C29H45P)]PF6, 4, [2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP](perchlorato-κO)copper(I), [Cu(ClO4)(C29H45P)], 5, and di-µ-thiocyanato-κ2S:N;κ2N:S-bis{[2-(di-tert-butylphosphanyl)-2',4',6'-triisopropylbiphenyl-κP]copper(I)}, [Cu2(NCS)2(C29H45P)2], 6. Iodide complex 3 shows significant CuI-arene interactions, in contrast to its chloride 1 and bromide 2 counterparts, which is attributed to the weaker interaction between the iodide ion and the CuI centre. When replacing iodide with an acetonitrile (in 4) or perchlorate (in 5) ligand, the reduced interaction between the CuI atom and the ancillary ligand results in stronger CuI-arene interactions. No CuI-arene interactions are observed in dimer 6, due to the tricoordinated CuI centre having sufficient electron density from the coordinated ligands.

Modified Lundie loops improve apraxia of eyelid opening.

BACKGROUND: Current treatments are unsatisfactory for improving apraxia of eyelid opening, defined as a delay or inability to open closed eyelids voluntarily in the presence of intact motor pathways. METHODS: Improvement in functional health was assessed using the Blepharospasm Disability Scale (BDS) in five consecutive patients with apraxia of eyelid opening treated with wire loops affixed behind ordinary spectacles (Lundie loops) and modified to provide pressure on the brow as a stimulus to keep the eyelids elevated. RESULTS: All five patients showed improvement in BDS scores. The mean percentage of normal activity of the study population improved from 25% to 37.6%. Outdoor activities were not significantly altered with the use of the device. CONCLUSIONS: Modified Lundie loops appear to be helpful in improving the functional health of patients with eyelid apraxia. These results will need to be verified in larger trials.

The impact of cataract severity on measurement acquisition with the IOLMaster.

PURPOSE: The Zeiss IOLMaster optical biometry system provides superior prediction of refractive outcome of cataract surgery compared to applanation ultrasound. However, measurement is not always possible in the presence of dense cataract. The purpose of this study was to elucidate the rate of measurement acquisition failure due to cataract and how this varies with morphology and severity. METHODS: A total of 149 subjects were prospectively enrolled and visual acuity, Lens Opacities Classification System III (LOCS III) scores, ultrasonic A-scan and IOLMaster axial lengths were measured. Chi-squared analysis was used to test the null hypothesis that cataract severity has no effect on measurement failure rate. RESULTS: Measurements could not be obtained with the IOLMaster in nine cases for reasons other than cataract. Cataract caused measurement acquisition failure in 22 (15.9%) cases, including all mature cataracts (n=3) and posterior subcapsular cataracts (PSC) with LOCS III (p>3.5; n=18). The null hypothesis was accepted for cortical (chi(2)=2.94, d.f.=2, p>0.05) and nuclear (chi(2)=7.91, d.f.=4, p>0.05) ataract, but rejected for PSC (chi(2)=111, d.f.=3, p<0.001). All cases could be measured with ultrasound. CONCLUSIONS: The IOLMaster fails to acquire axial length measurement in approximately 20% of UK public hospital cataract patients. Failure is principally due to PSC, whereby the LOCS III score of p=3.5 defines the limit of PSC severity that the IOLMaster can measure.

Structural and spectroscopic studies on mercury(II) tribenzylphosphine complexes.

The tribenzylphosphine (PBz3) complexes of mercury(II), [Hg(PBz3)2](BF4)2, [Hg(PBz3)2(NO3)2] and [HgX(NO3)(PBz3)](X = Cl, Br, I and SCN), have been synthesised and their structures determined by single-crystal X-ray crystallography. [Hg(PBz3)2](BF4)2 contains [Hg(PBz3)2]2+ cations with linear P-Hg-P coordination, the first example of a truly two-coordinate [Hg(PR3)2]2+ complex. The mercury coordination in [Hg(PBz3)2(NO3)2] can be described as distorted tetrahedral, with a significant deviation of the P-Hg-P angle from linearity as a result of coordination of the nitrate groups. Nitrate coordination is also observed in [HgX(NO3)(PBz3)](X = Cl, Br, I), resulting in significantly non-linear P-Hg-X coordination. The thiocyanate complex is a centrosymmetric thiocyanate-bridged dimer with distorted trigonal-pyramidal mercury coordination to the P atom of PBz3, to the S and N atoms of two bridging thiocyanate groups, and to the O atom of one nitrate group. For all the nitrato complexes, secondary mercury-nitrate interactions (Hg-O 2.7-3.1 A) effectively raise the coordination number of the Hg(II) centres to six. High-resolution 31P solid-state NMR spectra of the six tribenzylphosphine mercury(II)-complexes, obtained by combining magic-angle spinning, proton dipolar decoupling and proton-phosphorus cross-polarization (CP-MAS), have been recorded. The spectra of [Hg(PBz3)2](BF4)2 and [HgX(NO3)(PBz3)](X = Cl, Br, I and SCN) exhibit a single line, due to species that contain non-magnetic isotopes of mercury, and satellite lines, due to 1J(31P-199Hg) coupling. The asymmetric unit of [Hg(PBz3)2(NO3)2] contains two molecules with four phosphorus environments, resulting in two AB spectra with 2J(31P-31P) coupling, due to species that contain non-magnetic isotopes of mercury, and satellite lines consisting of two ABX spectra, due to 1J(31P-199Hg) coupling. These spectra have been analysed to yield all of the chemical shifts and coupling constants involved. A remarkable increase in 1J(31P-199Hg) is observed from [Hg(PBz3)2](BF4)2 to [Hg(PBz3)2(NO3)2] as a consequence of the incorporation of the nitrate group into the Hg coordination sphere in the latter case. Several of the spectra also exhibit broader satellites due to the presence of scalar spin-spin coupling between 31P and the quadrupolar 201Hg nucleus. Slow-spinning methods have been used to analyze the spinning-sideband intensities of the NMR spectra, in order to obtain the 31P shielding anisotropy and asymmetry parameters Deltasigma and eta. The 199Hg and 31P NMR shielding tensors of PMe3 models of the above six compounds have been calculated using relativistic density functional theory. The 31P results are in good agreement with experiment and assist in the assignment of some of the signals.