The co-ordination chemistry of tellurium and related selenium ligands

2-(2-pyridyl)phenyl(p-ethoxyphenyl)tellurium(II), (RR1Te) reacts with HgC12 at room temperature to give white HgCl2.RR1Te. On setting aside, or on warming the reaction mixture a yellow material, [R1HgCl.(RTeCl)2] is formed. Multinuclear NMR(125Te, 199Hg, 1H) and mass spectroscopy confirm the formulation, and confirm the ease of transfer of the p-ethoxyphenyl group (R1) between the metal centres. The crystal structure of the yellow material consists of two discrete RTeCl molecules together with a R1HgCl molecule. There is no dative bond formation between these species, hence the preferred description of the formation of an inclusion complex. The reaction of RR1Te with Copper(I) chloride in the cold gives an air sensitive yellow product Cu3Cl3(RR1Te)2(0.5CH3CN); under reflux in air changes to the green Cu2Cl(RR1Te)(0.5 EtOH). By contrast, the reaction of RR1Te with acetonitrile solution of Copper(II) salts under mild conditions affords the white materials CuCl(RR1Te) and CuBr(RR1Te)H2O. RR1Te reacts with PdCl2 and PtCl2 to give materials albeit not well defined, can be seen as intermediates to the synthesis of inorganic phase of the type M3XTe2XCl2X. Paramagnetism is associated with some of the palladium and platinum products. The 195Pt NMR measurement in DMSO establishes the presence of six platinum species, which are assigned to Pt(IV), Pt(III) or Pt(II). The reactions show that in the presence of PdCl2 or PtCl2 both R and R1 are very labile. The reaction of RHgCl(R= 2-(2-pyridyl)phenyl) with SeX4(X= Cl, Br) gives compounds which suggest that both Trans-metallation and redox processes are involved. By varying reaction conditions materials which appear to be intermediates in the trans-metallation process are isolated. Potentially bidentate tellurium ligands having molecular formula RTe(CH2)nTeR,Ln, (R= Ph,(t-Bu). C6H4, n = 5,10) are prepared. Palladium and Platinum complexes containing these ligands are prepared. Also complex Ph3SnC1L(L = p-EtO.C6H4) is prepared.

Non-invasive phakometric measurement of corneal and crystalline lens alignment in human eyes

We describe a non-invasive phakometric method for determining corneal axis rotation relative to the visual axis (β) together with crystalline lens axis tilt (α) and decentration (d) relative to the corneal axis. This does not require corneal contact A-scan ultrasonography for the measurement of intraocular surface separations. Theoretical inherent errors of the method, evaluated by ray tracing through schematic eyes incorporating the full range of human ocular component variations, were found to be larger than the measurement errors (β < 0.67°, α < 0.72° and d < 0.08 mm) observed in nine human eyes with known ocular component dimensions. Intersubject variations (mean ± S.D.: β = 6.2 ± 3.4° temporal, α = 0.2 ± 1.8° temporal and d = 0.1 ± 0.1 mm temporal) and repeatability (1.96 × S.D. of difference between repeat readings: β ± 2.0°, α ± 1.8° and d ± 0.2 mm) were studied by measuring the left eyes of 45 subjects (aged 18-42 years, 29 females and 16 males, 15 Caucasians, 29 Indian Asians, one African, refractive error range -7.25 to +1.25 D mean spherical equivalent) on two occasions. © 2005 The College of Optometrists.

Three-dimensional magnetic resonance imaging of the phakic crystalline lens during accommodation

To quantify changes in crystalline lens curvature, thickness, equatorial diameter, surface area, and volume during accommodation using a novel two-dimensional magnetic resonance imaging (MRI) paradigm to generate a complete three-dimensional crystalline lens surface model.

Reactions of directly related tellurium and selenium heterocycic compunds with triiron dodecacarbonyl

The reactions of directly related tellurium and selenium heterocyclic compounds with triiron dodecacarbonyl are described. The reaction of 2-telluraphthalide, C8H8OTe with [Fe3(CO)12 gave [Fe{C6H4(CH2)Te}(CO)3]2, (1). An iron atom has inserted into the telluracyclic ring, and it is probable that one co-ordinated CO ligand arises from the initially organic carbonyl group. X-ray analysis of compound (1) showed that the compound has a Fe2Te2 core, which is achieved by dimerisation. The reaction of telluraphthalic anhydride, C8H402Te with [Fe3(CO)12] gave a known, but unexpected, organic phthalide product, C8H602, which was confirmed by X-ray crystallography. Selenaphthalic anhydride,  C8H4O2Se gave intractable products on reaction with [Fe3(CO)12], 2-selenaphthalide, C8H6OSe, on reaction with [Fe3(CO)12] gave a major product [Fe2{C6H4(CH2)Se}(CO)6], (2) and a minor product [Fe3{C6H4(CH2)Se}(CO)8], (3) which is an intermediate in the formation of (2). X-ray analysis of (2) shows that compound (2) is very similar to (1) except that the 18 electron rule is satisfied by co-ordination of a Fe(CO)3 moiety, rather than dimerisation. Compound (3), also studied by X-ray crystallography, differs from (2) mainly in the addition of an Fe(CO)2 moiety. Telluraphtbalic anhydride, C8H402Te, and selenaphthalic anhydride, C8H402Se, are both monoclinic and crystallise in space group P21/n. 2-Selenaphthalide, C8H402Se, is also monoclinic, space group P21/C. The reactions of the following compounds (l,3-dihydrobenzo[c]selenophene, 1,3,7,9-tetrahydrobenzo[1,2c; 4,5c'] ditellurophene, dibenzoselenophene, phenoxselenine, 3, 5-naphtho-1-telluracyclohexane and 3,5-naphtho-1-selenacyclohexane) with [Fe3lCO)12] are reported. It is unfortunate that the above compounds do not react under the conditions employed; this may be due to differing degrees of ring strain. 1,8-bis(bromomethyl)naphthalene, C12H10Br2 is monoclinic and crystallises in space group C2/c. 1,1-diiodo-3,5-naphthotelluracyclohexane, C12H10TeI2 and 3,5-naphtho-l-telluracyclohexane, C12H10Te are monoclinic and crystallise in space group P21/c. 3,5-naphtho-l-selenacyclohexane, C12H10Se and 2,2,8,8-tetraiodo-1,3,7,9-tetrahydrobenzo[1,2c;4,5c']ditellurophene are also monoclinic, space group P21/a. The syntheses of intramolecular stabilised organo-tellurium and selenium compounds are reported, having a general formula of REX (where R = phenylazophenyl; E = Se, Te; X = electronegative group, for example C1, Br or I). The crystal structures of R'TeBr, RTeI, RSeCI, RSeCI/I and RSeI (where R = phenylazophenyl) are reported. The tellurium containing X-ray structures are triclinic and have a space group P-1. The selenium containing X-ray structures are monoclinic with space group P21/n. The inclusion of nitrogen in selenium heterocycles provides access to an entirely new area of organometallic chemistry. The reaction of 2-methylbenzoselenazole with [Fe3(CO)12] gave [Fe2{C6H4(NCH2CH3)Se}(CO)6]. The reactions of 2-(methyltelluro)benzanilide or 2-(methylseleno)benzanilide with [Fe3(CO)12] gave reaction products [Fe2(μTeMe)2(CO)6] and [Fe2 (μ-SeMe)2(CO)6] respectively, which were confmned by X-ray crystallography. The use of Mossbauer spectroscopy on the products obtained from the reactions of heterocyclic compounds with [Fe3(CO)12] can give useful information, for example the number of iron sites and the environments of these iron sites within the products.

A sensitivity study of the human crystalline lens using finite element analysis

Finite element analysis is a useful tool in understanding how the accommodation system of the eye works. Further to simpler FEA models that have been used hitherto, this paper describes a sensitivity study which aims to understand which parameters of the crystalline lens are key to developing an accurate model of the accommodation system. A number of lens models were created, allowing the mechanical properties, internal structure and outer geometry to be varied. These models were then spun about their axes, and the deformations determined. The results showed the mechanical properties are the critical parameters, with the internal structure secondary. Further research is needed to fully understand how the internal structure and properties interact to affect lens deformation.

Experimental and theoretical studies on six-membered ring hydrogen bond systems in crystalline drug substances

DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

Experimental and theoretical studies on molecular geometry and polymorphism in crystalline drug substances

DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

Analysis of femtosecond laser surface patterning on bulk single-crystalline diamond

Preliminary work is reported on 2-D and 3-D microstructures written directly with a Yb:YAG 1026 nm femtosecond (fs) laser on bulk chemical vapour deposition (CVD) single-crystalline diamond. Smooth graphitic lines and other structures were written on the surface of a CVD diamond sample with a thickness of 0.7mm under low laser fluences. This capability opens up the opportunity for making electronic devices and micro-electromechanical structures on diamond substrates. The fabrication process was optimised through testing a range of laser energies at a 100 kHz repetition rate with sub-500fs pulses. These graphitic lines and structures have been characterised using optical microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Using these analysis techniques, the formation of sp2 and sp3 bonds is explored and the ratio between sp2 and sp3 bonds after fs laser patterning is quantified. We present the early findings from this study and characterise the relationship between the graphitic line formation and the different fs laser exposure conditions. © 2012 Taylor & Francis.

A holistic multi evidence approach to study the fragmentation behaviour of crystalline mannitol

Mannitol is an essential excipient employed in orally disintegrating tablets due to its high palatability. However its fundamental disadvantage is its fragmentation during direct compression, producing mechanically weak tablets. The primary aim of this study was to assess the fracture behaviour of crystalline mannitol in relation to the energy input during direct compression, utilising ball milling as the method of energy input, whilst assessing tablet characteristics of post-milled powders. Results indicated that crystalline mannitol fractured at the hydrophilic (011) plane, as observed through SEM, alongside a reduction in dispersive surface energy. Disintegration times of post-milled tablets were reduced due to the exposure of the hydrophilic plane, whilst more robust tablets were produced. This was shown through higher tablet hardness and increased plastic deformation profiles of the post-milled powders, as observed with a lower yield pressure through an out-of-die Heckel analysis. Evaluation of crystal state using x-ray diffraction/differential scanning calorimetry showed that mannitol predominantly retained the β-polymorph; however x-ray diffraction provided a novel method to calculate energy input into the powders during ball milling. It can be concluded that particle size reduction is a pragmatic strategy to overcome the current limitation of mannitol fragmentation and provide improvements in tablet properties.