Stable Inner 2H Tautomer of N-Confused-like Porphyrin Embedded with a Carbazole Subunit: Synthesis, Metal Coordination, and Magnetic and Anion Sensing Studies

A new class of N-confused porphyrin 1 embedded with a carbazole subunit was prepared via [3 + 1] acid-catalyzed condensation of appropriate precursors. 1 underwent smooth metal complexation with Pd(II) and Cu(II) salts to provide the corresponding diamagnetic 1-Pd and paramagnetic 1-Cu, respectively. The single-crystal X-ray structure of 1-Pd is evident with a square-planar Pd-center through C-H activation of inverted pyrrole. Superconducting quantum interference device analysis combined with electron paramagnetic resonance (EPR) results provided insights into the paramagnetic nature of 1-Cu. Further, a ratiometric enhancement of near-IR fluorescence at 746 nm was found to be reversible upon adding CN- and F- ions. The solid-state structure of 1-Pd confirms that the anionic species is due to NH deprotonation.

From Sn(II) to Sn(IV): Enhancing Lewis Acidity Via Oxidation

We demonstrate the increased Lewis acidity on going from Sn(II) to Sn(IV) by oxidizing TpMe2SnOTf (OTf = SO3CF3) to TpMe2SnF(OTf)2. Replacement of the fluoride ion in TpMe2SnF(OTf)2 by a triflate, resulting in TpMe2Sn(OTf)3 further enhances the Lewis acidity at tin. 119Sn NMR spectroscopy, modified Gutmann-Beckett test, computational analysis, and catalytic phosphine oxide deoxygenation support the claims.

Reactivity of a quasi-four-coordinate butylmagnesium cation

We present the reactivity of the Mg-C and the β-CH bonds in the trigonal pyramidal [(pmdta)Mg(nBu)]⁺ exhibiting a weak Mg⋯F interaction with counter anion, [B(C₆F₅)₄]^-. Instantaneous β-hydride reactivity with benzophenone, reductive alkylation of phenyl benzoate, and straightforward synthesis of [(pmdta)MgH]⁺via metathesis with pinacolborane/phenylsilane are discussed.

One-dimensional magnetism in a facile spin 1/2 Heisenberg antiferromagnet with a low saturation field

This work reports the synthesis, structure and magnetic properties of the single crystal of a facile spin 1/2 one dimensional Heisenberg antiferromagnet bis(4-aminopyridinium) bis(oxalato)cuprate(II) dihydrate, (C5H7N2)2[Cu(C2O4)2].2H2O. Single crystals of large...

Cationic Zinc Hydride Catalyzed Carbon Dioxide Reduction to Formate: Deciphering Elementary Reactions, Isolation of Intermediates, and Computational Investigations

Zinc has been an element of choice for carbon dioxide reduction in recent years. Zinc compounds have been showcased as catalysts for carbon dioxide hydrosilylation and hydroboration. The extent of carbon dioxide reduction can depend on various factors, including electrophilicity at the zinc center and the denticity of the ancillary ligands. In a few cases, the addition of Lewis acids to zinc hydride catalysts markedly influences carbon dioxide reduction. These factors have been investigated by exploring elementary reactions of carbon dioxide hydrosilylation and hydroboration by using cationic zinc hydrides bearing tetradentate tris[2-(dimethylamino)ethyl]amine and tridentate N,N,N',N'',N''-pentamethyldiethylenetriamine in the presence of triphenylborane and tris(pentafluorophenyl)borane.

Organoaluminum cations for carbonyl activation

In search of stable, yet reactive aluminum Lewis acids, we have isolated an organoaluminum cation, [(Me2NC6H4)2Al(C4H8O)2]+, coordinated with two labile tetrahydrofuran ligands. Its catalytic performance in aldehyde dimerization reveals turn-over frequencies reaching up to 6000 h-1, exceeding that of the reported main group catalysts. The cation is further demonstrated to catalyze hydroelementation of ketones. Mechanistic investigations reveal that aldehyde dimerization and ketone hydrosilylation occur through carbonyl activation.

Amidomagnesium cations

We report the synthesis, structure and reactivity of molecular amidomagnesium cations bearing tris{2-(dimethylamino)-ethyl}amine (Me₆TREN). Me₆TREN binds to the cationic magnesium centre exhibiting κ⁴ and κ³ coordination modes in [Me₆TREN-Mg-N(SiHMe₂)₂]⁺ and [Me₆TREN-Mg-N(SiMe₃)₂]⁺ respectively. [Me₆TREN-Mg-N(SiHMe₂)₂]⁺ reacts with benzophenone resulting in the insertion of the carbonyl group across β-SiH bond. The reaction between [Me₆TREN-Mg-N(SiMe₃)₂]⁺ and CO₂ leads to [Me₆TREN-Mg-OSiMe₃]⁺, while the reaction with H₂O results in [Me₆TREN-Mg-OH]₂²⁺. Attempts to prepare hydridomagnesium cations from [Me₆TREN-Mg-N(SiMe₃)₂]⁺ using KH resulted in the precipitation of MgH₂ and the isolation of [(Me₆TREN)K(THF)₃]⁺.

Terminal hydridozinc cation

Thermally stable hydridozinc cation catalytically converts CO₂ to PhSi(OCHO)₃ using PhSiH₃ in the presence of a mild Lewis acid BPh₃.

Manifestation of helicity in one-dimensional iodobismuthate

The first example of an inorganic–organic hybrid material incorporating a helical iodobismuthate [BiI₄]_∞ is presented.

Association of retinal vessel caliber and visual field defects in glaucoma

PURPOSE

This study evaluates the asymmetry of peripapillary retinal vessel caliber between inferior and superior hemispheres in eyes with visual field defects predominantly in one hemifield.

DESIGN

Observational case series.

METHODS

In a retrospective study, 64 eyes of 64 patients with primary open-angle glaucoma who had a marked difference in visual field defects between hemifields and who had no history of diabetes, trauma, or vascular occlusive disease were studied. The diameters of the superior and inferotemporal vessels were measured at the optic disk border with calipers on an enlarged image.

RESULTS

In 64 eyes, the average ratio of the superior temporal artery diameter to inferotemporal artery diameter was significantly greater in the eyes with predominantly superior visual field defects as compared with those with inferior defects (1.10 +/- 0.22 vs. 0.92 +/- 0.19, respectively, P =.002, two-tailed t test). This indicates that the arteriole corresponding to the hemifield with the greater visual field defect was narrower than the arteriole in the other hemifield. This relationship was confirmed using chi(2) analysis (P =.002) comparing the proportions of eyes with ratios greater or less than normal vessel caliber ratios (normal ratio = 0.95 from data reported by Jonas and associates to the location of the dominant field defect. No statistically significant relationship was detected between retinal vein diameter and localized visual field defects, as determined by both the unpaired t test and chi(2) analysis.

CONCLUSION

In eyes with primary open-angle glaucoma, this study demonstrates a strong association between decreased peripapillary arteriole diameter and visual field defects in the corresponding hemifield. This reflects either an ischemic basis for glaucomatous damage or vascular constriction when there are fewer axons to nourish.

Ocular manifestations of child abuse

Certain ophthalmic signs have great significance in the diagnosis of child abuse. As Eisenbrey has stated, "unexplained retinal hemorrhages in children under three without external evidence of head injury should be considered diagnostic of child abuse until proven otherwise." While no one single ocular manifestation is pathognomic of child abuse, ocular examination can provide significant and compelling information which can aid in its diagnosis.

Corneal endothelial polymerization of histoacryl adhesive: a report of a new intraocular complication

Tissue adhesive are commonly used in ophthalmology to seal small corneal perforations. We report a case of inadvertent instillation of cyanoacrylate adhesive (Histoacryl) in the anterior chamber resulting in polymerization of the glue on the corneal endothelial surface, with iridocorneal and iridolenticular adhesion.

Small angle neutron scattering studies of structural characteristics of agarose gels

The 30 m small angle neutron scattering facility at the National Institutes of Standards and Technology has been used to examine neutron scattering from agarose gels formed in D2O. Differential scattering cross sections have been acquired over a continuous range of Q between 0.005 and 0.3 A-1. Subtle changes in gel structure are observed when pre-gelation agarose concentration is varied. Similarly, except when the gelling solution is rapidly cooled to a low temperature, the rate at which the gels are formed does not seem to have much effect. Clearer evidence of structural rearrangement is observed when the solvent quality is changed by the addition of dimethyl sulfoxide, or when the temperature of the gel is elevated above 70 degrees C. These data are consistent with a description of a randomly structured polymer network containing discrete self-similar, hydrogen-bonded, junctions normally of minimal thickness approximately 35-40 A.

Medical records: disclosing what law permits

Confidentiality and medical records is an issue which gives rise to real problems for staff who are called upon to reveal or disclose information. Here A.P. Andrews, principal law lecturer, SW Thames RHA, shows that while it is not possible to foresee every eventuality a clear understanding of the legal principles involved will help staff resolve some, if not all, their dilemmas.