VISIBLE-LIGHT-DRIVEN “ON”/“OFF” PHOTOCHROMISM OF A POLYOXOMETALATE DIARYLETHENE COORDINATION COMPLEX
Herein we report the first photochromic polyoxometalate (POM)-based diarylethene (DAE) coordination complex, prepared by ligation of two cobalt(III)-incorporated borotungstates [BIIIWVI11O39CoIII]6– with the ditopic pyridyl-containing diarylethene (C25H16N2F6S2). The solution-state composition, structure, and stability of the assembly were probed using 1H and 19F nuclear magnetic resonance spectroscopy (NMR), electrospray ionization quadrupolar time-of-flight mass spectrometry (ESI-QTOF-MS), ultraviolet–visible spectroscopy (UV–vis), and small-angle X-ray scattering (SAXS), revealing that the complex self-organizes to adopt a molecular dumbbell structure due to electrostatic and steric considerations. This conformation is a prerequisite for the photocyclization reaction. The assembly was found to be switchable between two states using visible light due to the perturbation of the DAE electronic structure on coordination to the POM. We present photophysical data, including the reaction quantum efficiency of the molecular switch in both directions measured using a custom-built quantum yield determination setup in addition to fatigue resistance on prolonged irradiation.
MICROWAVE-ASSISTED SYNTHESIS OF ORGANICALLY FUNCTIONALIZED HEXA-MOLYBDOVANADATES
The microwave-assisted reaction of (TBA)4[β-Mo8O24] and (TBA)3[H3V10O28] with pentaerythritol or tris(hydroxymethyl)aminomethane yields polyanions with the general formula (TBA)2[V3Mo3O16(O3-R)] (R: C5H8OH-1; R: C4H6NH2-3). Post-synthetic esterification of 1 yields the acylated derivative 2, with all compounds being characterized in the solid and solution state. DOI: 10.1039/C7NJ02820B
HIGHLY FLUORESCENT PYRIDINIUM BETAINES FOR LIGHT HARVESTING
We report the findings of our experimental and theoretical investigations into the properties of pyridinium enolates and their potential utility in light-harvesting applications, such as in luminescent solar concentrators (LSCs). We present the synthesis, structures, photophysical characterization, and wavefunction-based quantum-chemical studies of five cyclobetaines. The performance of an LSC device incorporating one of these cyclobetaines is shown to be comparable to state-of-the-art devices. DOI: 10.1002/anie.201704832
NON-AQUEOUS MICROWAVE-ASSISTED SYNTHESES OF DECA- AND HEXA-MOLYBDOVANADATES
We report a new approach for the synthesis of heterohexa- and heterodecametalates via the use of non-aqueous, microwave-assisted reaction conditions. The two novel molybdovanadates have been isolated and characterized in the solid and solution states using single-crystal X-ray diffraction, FT-IR, UV/Vis, multinuclear NMR spectroscopy, and ESI-MS. The relative stabilities of the possible structural isomers were probed using dispersion-corrected DFT calculations for both polyoxometalate systems. DOI: 10.1002/anie.201608589