Provided herein are compositions and related methods useful for free radical scavenging, with particular selectivity for mitochondria. The compounds comprise a nitroxide-containing group attached to a mitochondria-targeting group. The compounds can be cross-linked into dimers without loss of activity. Also provided herein are methods, for preventing, mitigating and treating damage caused by radiation. The method comprises delivering a compound, as described herein, to a patient in an amount and dosage regimen effective to prevent, mitigate or treat damage caused by radiation.