Panchromatic Ru()-polypyridyl complexes as NIR emitters

Two novel mer -Ru( ii ) heteroleptic complexes containing stongly donating tridendate ligands (dgpy and dgpz) were synthesised and optoelectronically characterised. These complexes exhibited quasi-reversible ligand- and metal-based redox events and panchromatic absorption with the lowest energy absorption maxima trailing up to 750 nm. These panchromatic dyes were found to be NIR emissive at λ PL ∼ 835 nm with associated excited-state lifetimes ( τ PL ) of ∼10 ns. The enhanced photophysical properties of these complexes compared to those of [Ru(tpy) 2 ] 2+ (tpy = 2,2′:6′,2′′-terpyridine; λ abs < 575 nm, λ PL ∼ 629 nm and τ PL ∼ 0.25 ns) are due to the larger 3 MLCT- 3 MC energy-gap as a combined effect of larger bite angle and strong σ-donation offered by the dgpy and dgpz ligands. Novel heteroleptic Ru( ii )-polypyridyl complexes were synthesised that exhibit panchromatic absorption up to 750 nm and 3 MLCT NIR emission at λ em > 830 nm.