Photostability of Phenoxazine Derivatives.

Phenoxazine is a commonly used molecular building block, for example in optoelectronic applications and pharmaceuticals. However, it is highly susceptible to rapid photodegradation, especially in halogenated solvents. In the present study, we identify the degradation products in both halogenated and non-halogenated solvents by UV/Vis absorption, NMR spectroscopy and mass spectrometry.

Dihedral Angles and Photoluminescence Quantum Yields: An NMR Analysis.

The synthesis of two different series of donor-acceptor (D-A) molecules is reported, consisting of a series of four structurally related donors and two different acceptors. The subtle differences in the electron density of these D-A-D and D-A compounds are clearly reflected in the different chemical shifts of certain donor protons in the H NMR spectra. These shifts show a cosine squared correlation of the dihedral angle between the donor units and the neighbouring phenyl unit of the acceptor.

Revealing the Origin of Fast Delayed Fluorescence in a Donor Functionalized Bisterpyridine.

A new carbazole-substituted bisterpyridine with pronounced delayed fluorescence is presented. While the molecular donor-acceptor-donor design suggests the origin of this to be thermally activated delayed fluorescence (TADF), results from various photophysical characterizations, OLED characteristics, temperature-dependent NMR spectroscopy, and DFT calculations all point against the involvement of triplet states. The molecule exhibits blue emission at about 440 nm with two or more fast decay channels in the lower nanosecond range in both solution and thin films.

Static Scanning Tunneling Microscopy Images Reveal the Mechanism of Supramolecular Polymerization of an Oligopyridine on Graphite.

Supramolecular polymerization of a donor-acceptor bisterpyridine (BTP) equipped with an electron-rich carbazole unit is observed by scanning tunneling microscopy (STM) at the highly oriented pyrolytic graphite (HOPG)|solution interface. It is shown that two-dimensional crystals of supramolecular (co)polymers are formed by chain growth polymerization, which in turn can be described by copolymerization statistics. From concentration-dependent measurements, derived copolymerization parameters and DFT calculations, a mechanism for self-assembly is developed that suggests a kinetically driven polymerization process in combination with thermodynamically controlled crystallization.