Figure 1.

a) Molecular structure of fully deuterated ¹³C₂‐TPE derivatives with J coupling values. b) The J couplings of trans‐¹⁵N, ¹⁵N’‐azobenzene‐d₁₀. c) Experimental decay curves of long‐lived singlet state for ¹³C₂‐TPE‐d₂₀, ¹³C₂‐DPP‐d_18, ¹³C₂‐DBC‐d₁₆ and trans‐¹⁵ N,¹⁵ N‐Azobenzene‐d₁₀. All the samples were degassed by three times freeze‐pump‐thaw cycling. Experimental data points of fully deuterated ¹³C₂‐TPE derivatives and trans‐¹⁵N, ¹⁵N’‐azobenzene‐d₁₀ were observed at the magnetic fields of 7.05 T and 16.5 T, respectively. The pulse sequence SLIC ^[46] was employed and the data points have been normalized to the value of the first point. Solid lines are fitted to the exponential decays.