Pyrene modification enables enhanced two-photon excited ligand dissociation of a Ru(II) complex containing monodentate ligands

Abstract Ru(II) complexes which can undergo photo-induced ligand dissociation display potentials for biological applications in some aspects. However, their short excitation wavelengths limit tissue penetration and therefore applications. Two-photon technic is a general way to shift the excitation wavelength to the near-infrared region (NIR), but few Ru(II) complexes with photolabile ligands having large two-photon absorption cross sections (δ2) have been reported so far. In this work, by modification with a pyrene group on the tpy ligand, the resultant complex [Ru(tpy-py)(CH3CN)3]2+ (1) displayed enhanced two-photon induced ligand dissociation compared with the parent complex [Ru(tpy)(CH3CN)3]2+ (2), probably through an intramolecular energy transfer mechanism. The ligand dissociation process was investigated in detail by absorption, 1H NMR, ESI MS spectra and theoretical calculations.