Add time:09/27/2019         Source:sciencedirect.com

In this work, the synthesis and characterization of fac-[Re(CO)3(Nqphen)(L)]PF6 complexes is reported. Nqphen is the quinone substituted acceptor ligand [3,2-a:2′,3′-c]-benzo[3,4]-phenazine-11,16-quinone, and L represents the donor monodentate pyridine substituted ligands 4-tert-butylpyridine (t-Bupy), 4-methoxypyridine (MeO-py) or 10-(4-picolyl)phenothiazine (py-PTZ). The complexes were synthesized by refluxing in methanol the metal precursor fac-Re(CO)3(Nqphen)TfO (TfO = trifluoromethanesulphonate anion) with the corresponding L ligand. The UV–Vis spectra of the complexes are dominated by intense intraligand (IL) bands, and less intense metal ligand charge transfer (MLCT) bands with maxima in the 380–400 nm region. The IR shows the typical pattern for tricarbonyl Re complexes with facial (fac) geometry. An additional v(CO) stretching band, attributed to the quinone fragment of Nqphen, is observed.Electrochemical data indicate that the acceptor capacity of Nqphen is increased in the complexes with regard to the free ligand. This effect is sensitive to the nature of the L ligand, following the order: MeO-py < t-Bupy < py-PTZ, indicating therefore that the donor capacity of L affects the rest of the molecule. The results obtained for the fac-[Re (CO)3(Nqphen)(pyPTZ)]PF6 complex here reported were compared with those observed for the homologous complex fac-[Re(CO)3(Aqphen)(L)]0/+, with Aqphen = 12,17-dihydronaphtho[2,3-h]dipyrido[3,2-a:2′,3′-c]-phenazine-12,17-dione, and L = Cl−, TfO−, py-PTZ.

► New rhenium complexes with a quinone functionalized ligand were synthesized. ► The changes in redox properties of the complexes, which correlate with donor properties of the monodentate ligands. ► The effect of structural linearity of quinone functionalized ligand Nqphen, that favors electron delocalization, could in turn favor an excited state charge separation.

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