We have designed and synthesised a new carborane derivative containing two nitronyl nitroxides. This molecule can be considered as a prototype of a three-dimensional analogue of o-benzoquinodimethane. The magnetic susceptibility of a crystalline sample revealed that this biradical possesses a weak antiferromagnetic interaction (theta = -1.05(4) K) and an ESR study in frozen matrix in the 5.4-104 K range gave an intramolecular antiferromagnetic interaction of -27(2) K. The synthesis, physical properties and DFT calculation result are also reported.