Synthesis, Electronic Properties and OLED Devices of Chromophores Based on λ5 -Phosphinines.

A new series of 2,4,6-triaryl-λ5 -phosphinines have been synthesized that contain different substituents both on the carbon backbone and the phosphorus atom of the six-membered heterocycle. Their optical and redox properties were studied in detail, supported by in-depth theoretical calculations. The modularity of the synthetic strategy allowed the establishment of structure-property relationships for this class of compounds and an OLED based on a blue phosphinine emitter could be developed for the first time.

1,4-Diphosphinines from Imidazole-2-thiones.

1,4-Diphosphinines that are fused to two thiourea units were synthesized from the corresponding tricyclic 1,4-dichloro-1,4-dihydro-1,4-diphosphinines, and their structures and spectroscopic features are described. Electrochemical studies revealed very low oxidation potentials, which are due to the effective π-interaction between the 1,4-diphosphinine ring and the orbitals of the two ylidic C=S bonds. In accordance with the low-lying LUMO, which is largely localized at the two phosphorus centers, dianion formation is strongly preferred. Despite the small HOMO-LUMO gap, which is in accordance with the red color of the title compounds, theoretical calculations suggest considerable aromaticity for the 1,4-diphosphinine ring.

Clicking the Arsenic-Carbon Triple Bond: An Entry into a New Class of Arsenic Heterocycles.

Arsaalkynes can undergo regioselective and quantitative [3+2] cycloaddition reactions with organic azides to give hitherto unknown 3H-1,2,3,4-triazaarsole derivatives. The reaction product was obtained as a white, air- and moisture-stable solid, and the presence of a planar, five-membered arsenic heterocycle was unambiguously verified by means of X-ray crystallography. DFT calculations gave insight into the electronic structure of these novel compounds compared to tetrazoles and triazaphospholes. The coordination chemistry towards Re(I) was investigated and compared with the structurally related phosphorus-containing ligand. These preliminary investigations pave the way for a new class of arsenic heterocycles and fill the gap between the azaarsoles already known.

The morning after: Prescription-free access to emergency contraceptive pills.

We analyze the introduction of prescription-free access to morning-after pills-emergency contraceptives that aim to prevent unintended pregnancy and subsequent abortion after unprotected sexual intercourse. Exploiting a staggered difference-in-differences setting for Europe combined with randomization inference, we find sharp increases in sales and manufacturers' revenues of more than 90%. However, whilst not reducing abortions significantly, the policy triggers an unexpected increase in fertility of 4%, particularly among women aged 25-34. We elaborate on mechanisms by looking at within-country evidence from several EU countries, which suggests that fertility is driven by decreasing use of birth control pills in response to easier access to morning-after pills.

Comparative politics and the synthetic control method revisited: a note on Abadie et al. (2015).

Recently, Abadie et al. (Am J Polit Sci 59:495-510, 2015) have expanded synthetic control methods by the so-called cross-validation technique. We find that their results are not being reproduced when alternative software packages are used or when the variables' ordering within the dataset is changed. We show that this failure stems from the cross-validation technique relying on non-uniquely defined predictor weights. While the amount of the resulting ambiguity is negligible for the main application of Abadie et al. (Am J Polit Sci 59:495-510, 2015), we find it to be substantial for several of their robustness analyses. Applying well-defined, standard synthetic control methods reveals that the authors' results are particularly driven by a specific control country, the USA.