The oxygen-sensing performance of [Ru(IP)(2)(HNAIP)(2+) (Ru1, IP = imidazo[4,5-f][1, 10] and HNAIP = 2-(2-hydroxy-1-naphthyl)imidazo [4,5-f] [1,10]phenanthroline) in the presence of DNA conformational transition has been investigated by means of absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopies, and circular dichroism spectroscopy. Ru1 shows a good linear response toward oxygen between pure nitrogen and pure oxygen with an on- off emission intensity ratio (I-0/I-100) of up to 9.3 via a dynamic quenching mechanism. Compared with [Ru(IP)(2)(DHPIP)](2+) (Ru2, DHPIP = 2-(2,4-dihydroxyphenyl)imidazo [4,51] [1,10]phenanthroline, I-0/I-100 = 5.8), the HNAIP ligand endows Ru1 with favorable oxygen binding sites to achieve larger energy and electron transfer rates. Simultaneously, Ru1 can induce the B-to-Z DNA conformational transition via a groove interaction with an intrinsic binding constant (K-b) of 7.9 X 10(4) M-1, whereas there is no same phenomenon for Ru2 intercalated into DNA (K-b = 3.3 x 10(5) M-1). Furthermore, the B-to-Z DNA conformational transition is interestingly found to decrease the Ru1-based oxygen-sensing rate by about 33%.