New bimetallic [(Cl)3Pt(dpop′)M(dpop′)](PF 6) (M = Ru(II) and Os(II); Dpop′ = dipyrido (2,3-a:3′,2′-j)phenazine) complexes using dpop′ as a novel mixed denticity bridging ligand

摘要

The dpop′ (dipyrido (2,3-a:3′,2′-j)phenazine) ligand structurally displays the possibility of a mixed denticity bridging ligand (BL) with low lying π~(a-) orbitals. Previously prepared complexes with Fe(II); Ru(II); Os(II) and Re(I) have only demonstrated tridentate coordination to dpop′ and it's use as a terminal ligand (TL). In this study two new bimetallic complexes [(Cl)_3Pt(dpop′) M(dpop′)](PF_6) (M = Ru(II) and Os(II)) were synthesized and are the first to use dpop′ as a bridging ligand (BL), with monodentate coordination to Pt(II) and tridentate coordination to Ru(II) and Os(II). The electronic absorption spectra display Ru(II) and Os(II) (dπ) → dpop′ (π~(a-)) (BL) MLCT transitions shifted to lower energy due to stabilization of the bridging dpop′ (π ~(a-)) acceptor orbitals. Cyclic voltammetry shows the reversible Ru~(+2/+3) and Os~(+2/+3) redox couples are at the same potentials as the respective [M(dpop′)_2](PF_6) _2 complexes while the bridging dpop~(′0/-1) reversible reductions are shifted to less negative potential by 0.2 V. NMR data show downfield shifts for protons bound to the dpop′ (BL) versus dpop′ (TL) ligands.