New bimetallic [(Cl)3Pt(dpop′)M(dpop′)](PF6) (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

•New complexes [(Cl)3Pt(dpop′)M(dpop′)](PF6) (M = Ru(II) and Os(II)) are reported.•These are the first complexes using dpop′ as a bridging ligand (BL).•Intense MLCT transitions are at longer wavelength versus the monometallic complexes.•Reversible dpop′ (BL) reductions shift +0.20 V due to platination.•NMR resonances for dpop′ (BL) are shifted downfield from dpop′(TL).

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∗ 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′)](PF6) (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∗) (BL) MLCT transitions shifted to lower energy due to stabilization of the bridging dpop′ (π∗) 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](PF6)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.

Graphical abstractDpop′ is used for the first time as a bridging ligand. Two new complexes, [(Cl)3Pt(dpop′)Os(dpop′)](PF6) and [(Cl)3Pt(dpop′)Ru(dpop′)](PF6) with tridentate coordination to Os(II) or Ru(II) and monodentate coordination to Pt(II) have been synthesized and their electronic absorption, electrochemical and NMR properties studied.Figure optionsDownload full-size imageDownload as PowerPoint slide