Triazole‐Bridged Dinuclear Ru(II) and Ir(III) Complexes: Photophysics, Electrochemistry, and DFT/TD‐DFT Analysis
Alessandro Sinopoli, Baljinder S. Uppal, Paul A. Scattergood, Paul I. P. ElliottABSTRACT
The heteroditopic 1,2,3‐triazole ligand 4‐[4‐(pyridin‐2‐yl)‐1,2,3‐triazol‐1‐yl]‐2,2′‐bipyridine ( L3 ), prepared here following a reported CuAAC procedure, was employed as a bridging scaffold for the synthesis and study of dinuclear Ru(II) and Ir(III) complexes. The bis‐ruthenium [{Ru(bpy) 2 } 2 (L3)](PF 6 ) 4 ( Ru3 ) and bis‐iridium [{Ir(ppy) 2 } 2 (L3)](PF 6 ) 2 ( Ir3 ) species were prepared and fully characterized, and their electrochemical and photophysical properties were compared with those of mononuclear model complexes of the bipyridyl ( L1 ) and pyridyl–triazole ( L2 ) domains ( Ru1–2 and Ir1–2 ). Cyclic voltammetry shows quasi‐reversible Ru(II)/Ru(III) and Ir(III)/Ir(IV) couples in the range 0.89–1.00 V versus Fc + /Fc, with Ru3 and Ir3 displaying single, slightly broadened oxidation waves consistent with two closely spaced one‐electron processes at electronically decoupled metal centers. In deaerated acetonitrile, Ru1 and Ir1 exhibit redshifted 3 MLCT/ 3 LLCT emission compared to [Ru(bpy) 3 ] 2 + and [Ir(ppy) 2 (bpy)] + , respectively, while Ru2 is weakly emissive and Ir2 displays structured 3 LC emission with high quantum yield. The dinuclear complexes Ru3 and Ir3 show further redshifted emission ( λ max = 664 and 666 nm, respectively) and modified lifetimes relative to the mononuclear analogues. DFT/TD‐DFT calculations indicate a triazole/bipyridyl‐centered acceptor (LUMO) and near‐isoenergetic, metal‐centered HOMO/HOMO–1 levels localiZed on different termini in the dinuclear species, rationalising the weak intermetallic coupling and spectral tuning enabled by L3 .