Abstract
Diazide diamino complexes of Pt(iv) are considered as prospective prodrugs in oxygen-free photodynamic therapy (PDT). Primary photophysical and photochemical processes for cis,trans,cis-[Pt(N3)2(OH)2(NH3)2] and trans,trans,trans-[Pt(N3)2(OH)2(NH3)2] complexes were studied by means of stationary photolysis, nanosecond laser flash photolysis and ultrafast kinetic spectroscopy. The process of photolysis is multistage. The first stage is the photosubstitution of an azide ligand to a water molecule. This process was shown to be a chain reaction involving redox stages. Pt(iv) and Pt(iii) intermediates responsible for the chain propagation were recorded using ultrafast kinetic spectroscopy and nanosecond laser flash photolysis. The mechanism of photosubstitution is proposed.
Highlights
Photodynamic therapy (PDT) involves the selective damage of target tissue by using a photosensitizing drug and light
The scheme of PDT used in clinical practice is based on the formation of singlet oxygen resulted by quenching of triplet states of sensitizers by dissolved oxygen.[1,2]
In this paper we describe the case study of the first stage in photochemistry of diazide diamino complexes 1 and 2 by means of stationary photolysis, nanosecond laser flash photolysis and ultrafast kinetic spectroscopy
Summary
Photodynamic therapy (PDT) involves the selective damage of target tissue by using a photosensitizing drug and light. In the case of 1 in PBS Phillips et al.[14] found that the primary photochemical reaction caused by UVA irradiation is the exchange of the N3− anion to a water molecule or a hydroxide anion ( product [1] in Scheme 2A). In this case the irradiation time was probably small enough to examine the primary stage of photolysis. Photolysis of 2 was reported to demonstrate the similar solvent effect as in the case of 1.18 Primary processes caused by UVA irradiation of 2 in PBS (Scheme 2C) were identified as the exchange of azide anions to water molecules (or hydroxide anions). We present evidence that photolysis of both complexes is started with the chain photoaquation
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