Luminescence lifetimes of ruthenium(II) polypyridyls in water and water-d2 at high pressures

Abstract

The pressure dependence of the luminescence lifetimes of Ru(bpy)3Cl2 and Ru(phen)3Cl2 (bpy = bipyridine; phen = phenanthroline) in H20 and D20 is reported in the 0.1-300-MPa range at several temperatures (2-70 °C). The observed activation volumes for electronic relaxation are analyzed in terms of a small, negative AVf (-2 mL/mol) for the CT -> GS nonradiative process and a large, positive AVf (10 mL/mol) for the CT -*• LF decay channel. The observed magnitudes for the two intrinsic activation volumes are consistent with the changes expected from the calculated metal-nitrogen bonds of the complex in the ligand field (LF), charge transfer (CT), and ground (GS) electronic states. Superimposed on these principal trends is a small deuterium isotope effect in AV2 and a small ligand effect in AVf.

String-Attached Oligothiophene Substituents Determine the Fate of Excited States in Ruthenium Complexes for Photodynamic Therapy

“…Such features have been attributed to dissipation of excess vibrational energy from the initially hot 3 MLCT states in [Ru­(bpy) 3 ] 2+ -derived complexes . The resulting thermalized 3 MLCT state decays back to the ground state (Figure a,b) with characteristic time constants of 0.7 and 0.4 μs under deaerated and aerated conditions, respectively, for both Ru-ip-0T and Ru-ip-1T . , …”

“…44 The resulting thermalized 3 MLCT state decays back to the ground state (Figure 2a,b) with characteristic time constants of 0.7 and 0.4 μs under deaerated and aerated conditions, respectively, for both Ru-ip-0T and Ru-ip-1T. 29,46 The differential absorption spectrum of Ru-ip-2T recorded upon excitation of the 1 MLCT transitions at 480 nm resembles that of the photoexcited Ru-ip-0T and Ru-ip-1T at early times, with an initial bleach at the excitation wavelength concomitant with an ESA at 360 nm and at wavelengths > 510 nm (Figure 3). Unlike what was observed for Ru-ip-0T and Ru-ip-1T, where there was little change in the initially observed TA spectrum characteristic of the 3 MLCT state, the initially weak ESA band beyond 510 nm in the spectrum for Ru-ip-2T develops a pronounced maximum at 550 nm.…”

Metal centered ligand field excited states: Their roles in the design and performance of transition metal based photochemical molecular devices

“…in solution are also pressure dependent, growing longer as hydrostatic pressure is applied [146]. This observation was interpreted in terms of the 3 MC state distortions (lengthening of the Ru-N bonds) from the geometry of the 3 MLCT state; i.e., applied hydrostatic pressure raises the relative energy of the former and slows nonradiative deactivation via this pathway.…”

Control and utilization of ruthenium and rhodium metal complex excited states for photoactivated cancer therapy

“…3, absorbs strongly between 400 and 500 nm due to Ru(dπ) → bpy(π*) 1 MLCT transitions [42]. The 3 MLCT excited state of the complex is populated rapidly with unit efficiency ( Φ = 1), is relatively long-lived (0.61 μs in H 2 O and 1.00 μs in D 2 O) [47,48], and undergoes energy transfer to 3 O 2 to form the highly reactive 1 O 2 with Φ = 0.22 in air-saturated D 2 O [49], thus photocleaving pBR322 plasmid (λ irr > 450 nm) via the Type II PDT mechanism [46,50,51]. [Ru(bpy) 3 ] 2+ , a weak electrostatic DNA binder, is limited as a PDT agent by its inability to intercalate or covalently bind to DNA, resulting in less targeted 1 O 2 delivery.…”