The optimized structures of the neutral molecules, the radical anions, the C5′O5′ bond-breaking transition states, and the corresponding bond-broken products of 5′-dCMPH and 5′-dTMPH. Bond distances are in Å. Orange arrows in the transition states represent the single imaginary frequency-related vibration mode. Red represents oxygen, gray is carbon, blue is nitrogen, orange is phosphorous, and white is hydrogen.