In the current work, the nitroxide radical groups are utilized to functionalize the nucleobases, obtaining the nucleobase diradical building blocks for magnetic DNA with significant ferromagnetic or antiferromagnetic coupling characteristics. The nitroxide functionalization strategies include introduction of nitroxide radical group to the carbon site and oxidization of the amino group in nucleobases, and the diradical-functionalized nucleobases are denoted by 2NOX, where X = A, G, T, and C bases. The density functional theory calculations reveal that these nitroxide diradicalized nucleobases are stable and have large magnetic spin coupling magnitudes. Almost all of them possess antiferromagnetic-like spin coupling characteristics with considerably large spin coupling constants [J = −671.7 (2NOA1), −463.3 (2NOA3), −370.5 (2NOG), −494.9 (2NOC1), −3265.5 (2NOT), and −2445.5 cm–1 (2NOC3)] expect for 2NOC2 and 2NOA2 which have the ferromagnetic-like spin coupling characteristics (J = 149.1 and 440.7 cm–1), res...