Abstract
The synthesis and X‐ray structure (as the tetrahydrate) of the platinum(IV) complex trans,trans,trans‐[Pt(N~3~)~2~(OH)~2~(NH~3~)~2~] 3 are described and its photochemistry and photobiology are compared with those of the cis isomer cis,trans,cis‐[Pt(N~3~)~2~(OH)~2~(NH~3~)~2~] 4. Complexes 4 and 3 are potential precursors of the anticancer drug cisplatin and its inactive trans isomer transplatin, respectively. The trans complex 3 is octahedral, contains almost linear azide ligands, and adopts a layer structure with extensive intermolecular hydrogen bonding. The intense azide‐to‐platinum(IV) charge‐transfer band of complex 3 (285 nm; ε=19 500 M^−1^ cm^−1^) is more intense and bathochromically shifted relative to that of the cis isomer 4. In contrast to transplatin, complex 3 rapidly formed a platinum(II) bis(5′‐guanosine monophosphate) (5′‐GMP) adduct when irradiated with UVA light, and did not react in the dark. Complexes 3 and 4 were non‐toxic to human skin cells (keratinocytes) in the dark, but were as cytotoxic as cisplatin on irradiation for a short time (50 min). Damage to the DNA of these cells was detected by using the “comet” assay. Both trans‐ and cis‐diammine platinum(IV) diazide complexes therefore have potential as photochemotherapeutic agents.