The cyclic trinuclear system, [(en)3Pd3(4,7-phen)3]6+, undergoes a ligand exchange reaction with 5-R-2-hydroxypyrimidine derivatives (HRpymo; R = ethynylferrocene, 5-(dimethylamino)-N-(2-propynyl)-1-naphthalene sulfonamide) to give [(en)3Pd3(4,7-phen)2 (Rpymo)]5+, functional supramolecular receptors of mononucleotides.