Exploiting Orthogonal C–C Cross-Coupling Reactions for Chemistry-on-the-Complex: Modular Assembly of 2,6-Di(quinolin-8-yl)pyridine Ruthenium(II) Photosensitizer Triads

GND
1333863659
Affiliation
Laboratory of Organic and Macromolecular Chemistry (IOMC) ,Friedrich Schiller University Jena ,Humboldstr. 10 ,07743 Jena ,Germany
Kleine, Alexander;
GND
113792077
ORCID
0000-0003-4978-4670
Affiliation
Laboratory of Organic and Macromolecular Chemistry (IOMC) ,Friedrich Schiller University Jena ,Humboldstr. 10 ,07743 Jena ,Germany
Schubert, Ulrich S.;
GND
1214845037
ORCID
0000-0003-0400-1812
Affiliation
Laboratory of Organic and Macromolecular Chemistry (IOMC) ,Friedrich Schiller University Jena ,Humboldstr. 10 ,07743 Jena ,Germany
Jäger, Michael

In this work, we present a concise modular assembly strategy using one universal heteroleptic 2,6-di­(quinolin-8-yl)­pyridine-based ruthenium­(II) complex as a starting building block. Extending the concept from established ligand modifications and subsequent complexation ( classical route ), the later appearing chemistry-on-the-complex methodology was used for late-stage syntheses, i.e. , assembling discrete building blocks to molecular architectures (here: dyad and triads). We focused on Suzuki–Miyaura and Sonogashira cross-couplings as two of the best-known C–C bond forming reactions. Both were performed on one building block complex bearing a bromine and TIPS-protected alkyne for functional group interconversion (bromine to TMS-protected alkyne, a benzyl azide, or a boronic acid pinacol ester moiety with ≥95% isolated yield and simple purification) as well as building block assemblies using both a triarylamine-based donor and a naphthalene diimide-based acceptor in up to 86% isolated yield. Additionally, the developed purification via automated flash chromatography is simple compared to tedious manual chromatography for ruthenium­(II)-based substrates in the classical route . Based on the preliminary characterization by steady-state spectroscopy, the observed emission quenching in the triad (55%) serves as an entry to rationally optimize the modular units via chemistry-on-the-complex to elucidate energy and electron transfer. The present work shows the investigation of photosensitizer triad syntheses via chemistry-on-the-complex. The heteroleptic bis­(di­(quinoline-8-yl)­pyridine) ruthenium­(II)-based parental photosensitizer was transformed in terms of functional group interconversion from bromide (to azide, protected alkyne, boronic acid ester), and coupling chemistry to introduce both electron-rich and -deficient moieties with simple workup procedures after chemistry-on-the-complex throughout.

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