Dimolybdenum Paddlewheel as Scaffold for Heteromultimetallic Complexes: Synthesis and Photophysical Properties.

A diphenylphosphine functionalized benzoic acid was applied for the synthesis of a homoleptic dimolybdenum-based metalloligand, exhibiting four symmetrically placed phosphine donor sites. This allowed subsequent treatment with gold(I), rhodium(I), and iridium(I) precursors to obtain early-late heterometallic complexes as well as Lewis acid-base adducts with BH3. The compounds were in-depth investigated by spectroscopic techniques, single-crystal X-ray diffraction, and femtosecond laser spectroscopy. The coordination of different metal fragments to the dimolybdenum metalloligand leads to a fine-tuning of the system's optical properties, which correlates well with fluorescence quantum yield measurements. Nevertheless, triplet dynamics still remain the dominating channel in these systems with an intersystem crossing time constant below 1 ps.

Bis(mesitoyl)phosphinic acid: photo-triggered release of metaphosphorous acid in solution.

Bis(mesitoyl)phosphinic acid and its sodium salt display a unique photo-induced reactivity: both derivatives stepwise release two mesitoyl radicals and, remarkably, metaphosphorous acid (previously postulated as transient species in the gas phase), providing a new phosphorus-based reagent.

Acceleration of Long-Range Photoinduced Electron Transfer through DNA by Hydroxyquinolines as Artificial Base Pairs.

The C-nucleoside based on the hydroxyquinoline ligand (Hq) is complementary to itself and forms stable Hq-Hq pairs in double-stranded DNA. These artificial Hq-Hq pairs may serve as artificial electron carriers for long-range photoinduced electron transfer in DNA, as elucidated by a combination of gel electrophoretic analysis of irradiated samples and time-resolved transient absorption spectroscopy. For this study, the Hq-Hq pair was combined with a DNA-based donor-acceptor system consisting of 6-N,N-dimethylaminopyrene conjugated to 2'-deoxyuridine as photoinducible electron donor, and methyl viologen attached to the 2'-position of uridine as electron acceptor. The Hq radical anion was identified in the time-resolved measurements and strand cleavage products support its role as an intermediate charge carrier. Hence, the Hq-Hq pair significantly enhances the electron hopping capability of DNA compared to natural DNA bases over long distances while keeping the self-assembly properties as the most attractive feature of DNA as a supramolecular architecture.