In this studyw eh ave analysed the comparative photophysical and electrochemical properties of two isomeric heterotrinuclear Pt II-Ir III-Pt II complexes 3 and 6 and the four corresponding intermediate isomeric homonuclear cyclometalated iridium(III) complexes 1, 2, 4 and 5.T he isomerisation originates from positional differences in the formyl,d i-2-picolylamine and Pt-di-2-picolylaminem oieties appended to cyclometalated or ancillary ligands.The interaction of 5'-GMP with the trinuclearc omplexes 3 and 6 shows that platinumc entres appended to the cyclometalated ligandi n3 facilitatet he binding of two 5'-GMPu nits per Pt II centrei npreference to as ingle 5'-GMP unit per Pt II centre as observed in 6.T he 1:2a nd 1:1P t II-5'-GMP binding patterns probablya rise from the convenient arrangements of the Ptdi-2-picolylamine units in different planes in complex 3, whichi sa bsentinc omplex 6.