Abstract
New Ru(II) arene complexes of formula [(η6-p-cym)Ru(N-N)(X)]2+ (where p-cym = para-cymene, N-N = 2,2'-bipyrimidine (bpm) or 2,2'-bipyridine (bpy) and X = m/p-COOMe-Py, 1–4) were synthesised and characterized, including the molecular structure of complexes [(η6-p-cym)Ru(bpy)(m-COOMe-Py)]2+ (3) and [(η6-p-cym)Ru(bpy)(p-COOMe-Py)]2+ (4) by single-crystal X-ray diffraction. Complexes 1–4 are stable in the dark in aqueous solution over 48 h and photolysis studies indicate that they can photodissociate the monodentate m/p-COOMe-Py ligands selectively with yields lower than 1%. DFT and TD-DFT calculations (B3LYP/LanL2DZ/6-31G**) performed on singlet and triplet states pinpoint a low-energy triplet state as the reactive state responsible for the selective dissociation of the monodentate pyridyl ligands.
Highlights
Fuelled by the success of photodynamic therapy (PDT) [1], photoactivation of transition metal complexes for application in biology and medicine has gained momentum and several promising families of complexes have been developed in the last few years as alternative PDT agents for the treatment of precancerous and cancerous diseases [2,3]
It was shown that when the monodentate X ligand is a pyridine or a substituted pyridine these complexes are extremely stable in aqueous solution in the dark, but they can be selectively photoreleased upon light excitation
UV-Vis absorption spectra were recorded on a Cary 5000 spectrophotometer (Agilent Technologies, Santa Clara, CA, USA) using 1-cm path length quartz cuvettes (1 mL) and a PTP1 Peltier temperature controller
Summary
Fuelled by the success of photodynamic therapy (PDT) [1], photoactivation of transition metal complexes for application in biology and medicine has gained momentum and several promising families of complexes have been developed in the last few years as alternative PDT agents for the treatment of precancerous and cancerous diseases [2,3]. It was shown that when the monodentate X ligand is a pyridine or a substituted pyridine these complexes are extremely stable in aqueous solution in the dark, but they can be selectively photoreleased upon light excitation. Controlling this process with light holds promise since reactive aqua species as [(η6-arene)Ru(N-N)(OH2)]2+ can be generated in situ, potentially triggering the biological activity of the complexes. In this contribution, we report on new complexes of the family [(η6-p-cym)Ru(N-N)(X)]2+ (Figure 1). DFT-based computational methods were successfully used to obtain insights on the singlet and triplet excited states, allowing individuation of the dissociative state responsible for the photochemical behaviour of 1–4
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