Oxidation reactions of stable chalcogenamides with iodine are intriguing due to their broad application in various organic syntheses. In the present study we report on the utilization of N-heterocyclic carbene and cyclic-alkyl-amino carbenes L(1-3): (L(1): = :C[N(2,6-iPr2-C6H3)CH]2, L(2): = :C(CH2)(CMe2)(C6H10)N-2,6-iPr2-C6H3, L(3): = :C(CH2)(CMe2)2N-2,6-iPr2-C6H3) for the syntheses of chalcogenamides L(1-3)=E (E = S, Se, Te) 1-4 and zwitterionic adducts L(1-3)=E-I-I 5-8. The synthesis of compounds 1-4 involved the addition reaction of ligand L(1-3): and elemental chalcogen. Treatment of 1-4 with iodine resulted in the formation of adducts 5-8. Compounds 5-8 are well characterized with various spectroscopic methods and single-crystal X-ray structural analysis.

Fluorescence spectroscopy investigations of the new acridine derivative bis(N,N-dimethylaminemethylene)acridine (3) show remarkable selectivity and sensitivity towards Zn(2+) and Cd(2+) ions in methanol and for the latter even in water. Through the chelation of the metal ions the present PET effect is quenched, significantly enhancing the emission intensity of the fluorophore. In solution, the bonding situation is studied by fluorescence and NMR spectroscopy, as well as ESI-TOF mass-spectrometry measurements. The solid state environment is investigated by X-ray diffraction and computational calculations. Here, we can show the complexation of the zinc and cadmium ions by the methylene bridged amine receptors as well as by the nitrogen atom of the acridine system.

A domino approach consisting of up to five consecutive steps to access either highly substituted dispiranes or π-helicenes from oligoyne chains is reported. The domino sequence consists of several carbopalladation reactions, a Stille cross-coupling to obtain the helicenes, and, depending on the steric demands of the helicene, a final 6π-electrocyclization to afford the dispiranes. Formally, the latter transformation contravenes the Woodward-Hoffmann rules, as revealed by X-ray crystallography of the dispirane. Additionally, the racemization barrier of the (Z,Z,Z)-triene-based helicene has been determined by a kinetic analysis and compared with results from density functional theory calculations. Characteristic points on the reaction coordinate were further analyzed according to their relaxed force constants (compliance constants).

The chromophore building-block 9-methylanthracene is selectively deprotonated at the methyl group and activated for reactions with electrophiles.

Scheme 1.1: Illustration of the Lewis diagrams of 2-azaanthracene (left) and 10-azaanthracene (right) including the correct IUPAC numbering of the atoms.