We report the synthesis of 4-nitrophenyl (4-NP) functionalised Pt(IV) complexes as a colorimetric strategy for monitoring Pt(IV) reduction in aqueous solution. Treatment of each 4-NP functionalised Pt(IV) complex with the biological reductant sodium ascorbate led to a colour change from clear to yellow, which was attributed to the reduction of Pt(IV) to Pt(II) and simultaneous release of 4-nitroaniline. Trends in reduction profiles and a photocatalysed reduction for each Pt(IV) complex were observed. [ABSTRACT FROM AUTHOR]