Luminescent rhenium(I)-dipyrrinato complexes.

The first Re(I)-dipyrrinato complexes are reported. Complexes with the general formulas fac-[ReL(CO)(3)Cl](-), fac-[ReL(CO)(3)PR(3)], and [ReL(CO)(2)(PR(3))(PR'(3))] have been prepared, where L is one of a series of meso-aryl dipyrrinato ligands. Access to these complexes proceeds via the reaction of [Re(CO)(5)Cl] with the dipyrrin (LH) to produce fac-[ReL(CO)(3)Cl](-). A subsequent reaction with PR(3) (R = phenyl, butyl) leads to displacement of the chloride ligand to generate fac-[ReL(CO)(3)PR(3)], and further reaction with PR'(3) leads to the displacement of the CO ligand trans to the first PR(3) ligand to give trans(P), cis(C)-[ReL(CO)(2)(PR(3))(PR'(3))]. The structures of the complexes were determined in the solid state by X-ray crystallography and in solution by (1)H NMR spectroscopy. Electronic absorption spectroscopy reveals a prominent band in the visible region at relatively low energy (472-491 nm) for all complexes, which is assigned as a π-π* transition of the dipyrrin chromophore. Weak emission (λ(ex) = 485 nm, quantum yields <0.01) was observed for [ReL(CO)(3)Cl](-) and [ReL(CO)(3)PR(3)] complexes, but no emission was generally evident from the [ReL(CO)(2)(PR(3))(PR'(3))] complexes. On the basis of the large Stokes shift (~6000 cm(-1)), the emission is ascribed to phosphorescence from a triplet excited state. The emission intensity is sensitive to dissolved oxygen and methyl viologen; a Stern-Volmer plot in the latter case gave a straight line. Photochemical ligand substitution reactions of [ReL(CO)(3)PR(3)] were induced by excitation with a 355 nm laser in acetonitrile. [ReL(CO)(2)(PR(3))(CH(3)CN)] is formed as a putative intermediate, which reacts thermally with added PR'(3) to produce [ReL(CO)(2)(PR(3))(PR'(3))] complexes.

Postpartum follow-up for women with gestational diabetes mellitus.

We sought to determine the frequency of postpartum follow-up for women diagnosed with gestational diabetes mellitus. A retrospective cohort study of women with gestational diabetes mellitus from 2002 to 2008 ( N = 745) at an academic center was conducted. The primary outcome was either fasting blood glucose or 2-hour oral glucose tolerance, both measured at ≤6 months postpartum. Chi-square test and multivariable logistic regression analysis were used for statistical comparisons, and statistical significance was indicated by P < 0.05 and 95% confidence intervals. The frequency of follow-up for the study cohort was 33.7%. Of these women, 28.3% had values consistent with impaired glucose tolerance and 2.0% were diagnosed with type 2 diabetes mellitus. Asian women were the most likely to follow up (43%), and Latinas had the lowest follow-up frequency (18%; P < 0.001). Compared with their counterparts, women ≥35 years old, nulliparas, and women with GDM subtype A2 were more likely to return for postpartum glucose testing (odds ratio [OR] = 1.7, 95% confidence interval [CI] 1.2 to 2.5; OR = 1.9, 95% CI 1.3 to 2.7; OR = 2.28, 95% CI 1.4 to 3.6, respectively). The frequency of postpartum follow-up for women diagnosed with gestational diabetes mellitus is exceedingly low. More effective strategies are needed to increase the postpartum and longitudinal follow-up for all women with gestational diabetes mellitus.

Exciton coupling in coordination compounds.

This Perspective reviews the impact of exciton coupling on the spectroscopic properties of coordination compounds. Exciton coupling features arise in electronic absorption and circular dichroism spectra when chromophores are brought into close spatial proximity, for example by coordination to a metal centre. The analysis of these features can reveal much information such as the geometry of a complex and its absolute configuration. The extension of the exciton coupling model to polynuclear metallosupramolecular arrays is discussed.

Strongly absorbing pi-pi* states in heteroleptic dipyrrin/2,2'-bipyridine ruthenium complexes: excited-state dynamics from resonance raman spectroscopy.

A recently reported new class of ruthenium complexes containing 2,2'-bipyridine and a dipyrrin ligand in the coordination sphere exhibit both strong metal-to-ligand charge-transfer (MLCT) and pi-pi* transitions. Quantitative analysis of the resonance Raman scattering intensities and absorption spectra reveals only weak electronic interactions between these states despite direct coordination of the bipyridyl and dipyrrin ligands to the central ruthenium atom. On the basis of DFT calculations and time-dependent DFT (TD-DFT), we propose that the electronic excited states closely resemble "pure" MLCT and pi-pi* states. Resonance Raman intensity analysis demonstrates that a large amplitude transannular torsional motion provides a mechanism for relaxation on the pi-pi* excited-state surface. We assert that this result is generally applicable to a range of dipyrrin complexes such as boron-dipyrrin and metallodipyrrin systems. Despite the large torsional distortion between the phenyl ring and the dipyrromethene plane, pi-pi* excitation extends out onto the phenyl ring which may have important consequences in solar-energy-conversion applications of ruthenium-dipyrrin complexes.

Chromophoric dipyrrin complexes capable of binding to TiO2: synthesis, structure and spectroscopy.

The synthesis, characterisation, and TiO2 binding studies of a series of chromophoric complexes of 5-(4-carboxyphenyl)-4,6-dipyrrin (L(b)) are presented. The synthesis of [Ru(bipy)(L(b))2] (bipy = 2,2-bipyridine), [Rh(L(b))3], and [Pd(L(b))2] was achieved by initial coordination of 5-(4-methoxycarbonylphenyl)-4,6-dipyrrin (L(a)) followed by hydrolysis of the ester group. The carboxyl groups that are located on the peripheries of these complexes are able to engage in intermolecular hydrogen bonding interactions in the solid state, as revealed by X-ray crystallography. These groups also allow the complexes to anchor to the surface of TiO2 nanoparticles, as evidenced by colouration of the TiO2 and FT-IR spectroscopy. The ability of these complexes to capture a significant fraction of sunlight and to adhere to TiO2 surfaces renders them viable dyes for photochemical devices such as dye sensitised solar cells.

Prevalence of celiac disease in a cohort of women with unexplained infertility.

Several European studies have suggested a higher prevalence of celiac disease (CD) among infertile women (4% to 8%) compared with the general population (<1%). We screened a cohort of women with unexplained infertility in Northern California for the serum markers of CD, tissue transglutaminase and endomysium antibodies (EMA). Given that only one woman out of 121 (0.8%) screened positive for CD, it appears that CD is about as prevalent in this cohort of infertile women as in the general U.S. population (<1%).