The observed coupling distribution is likely further narrowed by the pulses used only exciting certain orientations of the nitroxide spin centre, and so not all orientations of the inter-spin vector will contribute to the oscillations (Figure ). While the distribution of inter-spin interactions could be reduced further by orienting the sample, we find that the coupling frequency is well enough defined in frozen solution to demonstrate a proof-of-principle entangling gate. The coherence times were measured by 2P-Electron Spin Echo Envelope Modulation (2P-ESEEM) (Figure ) and the fitted value of 6.89 μs is significantly longer than the two-qubit gate time, which is itself significantly longer than the one-qubit gate time. This relationship between operation times make compound 1 a suitable candidate for the generation and detection of entanglement via free evolution under the inter-qubit coupling.