An Air-Stable, Neutral Phenothiazinyl Radical with Substantial Radical Stabilization Energy.

The vital effect of radical states on the pharmacological activity of phenothiazine-based drugs has long been speculated. Whereas cationic radicals of N-substituted phenothiazines show high stability, the respective neutral radicals of N-unsubstituted phenothiazines have never been isolated. Herein, the 1,9-diamino-3,7-di-tert-butyl-N1 ,N9 -bis(2,6-diisopropylphenyl)-10H-phenothiazin-10-yl radical (SQH2 . ) is described as the first air-stable, neutral phenothiazinyl free radical. The crystalline dark-blue species is characterized by means of EPR and UV/Vis/near-IR spectroscopy, as well as cyclic voltammetry, spectro-electrochemical analysis, single-crystal XRD, and computational studies. The SQH2 . radical stands out from other aminyl radicals by an impressive radical stabilization energy and its parent amine has one of the weakest N-H bond dissociation energies ever determined. In addition to serving as open-shell reference in medicinal chemistry, its tridentate binding pocket or hydrogen-bond-donor ability might enable manifold uses as a redox-active ligand or proton-coupled electron-transfer reagent.

Synthesis of Electron-Rich, Planarized Silicon(IV) Species and a Theoretical Analysis of Dimerizing Aminosilanes.

Equipping silicon(IV) with electron-rich, geometrically constrained NNN- and ONO-tridentate substituents leads to aminosilanes with increased Lewis acidity-expressed through the formation of Si2 N2 rings by head-to-tail dimerization. Depending on the substituents, the dimerization can be controlled for the first time, yielding monomeric, structurally reversible and dimeric states. The monomeric species display substantial distortions from tetrahedral towards planar geometry at silicon. The dimerization and the Lewis acidity of aminosilanes are rationalized by (conceptual) DFT, NBO, ETS-NOCV and QTAIM methods. The preorganization at silicon, London dispersion between the substituents and resonance phenomena inside the formed Si2 N2 tetracycles are identified as driving forces for the dimerization. Comparison with selected aminosilanes permits general conclusions to be reached on the Lewis acidity of silicon species and on the aggregation of amphiphilic compounds.

Smoking cessation in long-term survivors of germ cell tumour.

PURPOSE: Long-term survivors of germ cell tumours (GCT) are at increased risk of cardiovascular morbidity. We investigated the use of tobacco in patients after therapy for GCT. METHODS: Four hundred and seventy-four patients treated between 1979 and 2000 at the University of Munich were asked to complete a self-report questionnaire on psychosocial dimensions which included items on tobacco smoking before and after treatment of GCT. RESULTS: Three hundred and forty-one patients (72%) returned a completed questionnaire. The median follow-up period was 9.6 years. 160 of 341 patients (47%) reported to smoke at the time of GCT diagnosis. Of those, 134 (84%) had changed their smoking behavior with 32 patients (20%) having reduced, 56 (35%) having intermittently quitted and 46 (29%) having definitively quitted smoking. Patients reduced or stopped smoking irrespective of tumour histology, tumour stage, whether they had received chemotherapy or not, and irrespective of the number of chemotherapy courses applied. CONCLUSION: Most patients changed their habit of tobacco smoking after diagnosis and treatment of GCT but only a minority of patients are sustained quitters. Patients with GCT should be strongly encouraged to stop smoking or to participate in smoking cessation programs.