engleski

Characterisation of Exchange of Solvent Ligands on Dicyclopalladated Azobenzenes in Solution

Organopalladium compounds, usually containing one palladium center per ligand, are one of the most popular transition-metal complexes investigated in organometallic chemistry.[1] Their rich chemistry enables easy preparation and wide scope of possible transformations in order to achieve desired physical properties that qualify them for potential application in organic synthesis and catalysis, supramolecular chemistry and as new materials.[1] As introducing the second palladium to investigated compounds broadens the scope of their applications and transformations, dicyclopalladated azobenzenes, which exhibit strong light absorption and emission in the visible region, recently became one of the main research focuses in our group.[2] In this work we have investigated exchange of solvent ligands (S = DMSO, DMF or pyridine) coordinated to palladium centers in seven dicyclopalladated azobenzenes (C1−7, Scheme 1) in DMF and DMSO by means of spectrophotometric and 1H NMR titrations. Special consideration was paid to varying substituents in 4, 4’-positions of azobenzene moiety as their electronic properties significantly influence spectral properties of the studied dicyclopalladated complexes. In the case of pyridine as a coordinated solvent, corresponding equilibrium constants have been determined. Results will be discussed in terms of solvent donor abilities as well as the electrondonating and electron-withdrawing properties of substituents in the 4, 4’-positions of the azobenzene.

Solvent Exchange ; Dicyclopalladated Azobenzenes ; NMR ; UV-Vis

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