¹H NMR (700 MHz, CDCl₃) δ 10.55 (s, 1H), 8.64 (ddd, J = 0.9, 1.6, 4.7 Hz, 2H), 8.42 (td, J = 0.8, 8.3 Hz, 2H), 8.37 (ddd, J = 0.8, 1.9, 4.9 Hz, 2H), 8.30 (td, J = 1.0, 7.8 Hz, 2H), 7.91 (dt, J = 1.7, 11.5 Hz, 2H), 7.76 (m, J = 2.2 Hz, 2H), 7.49 (ddd, J = 1.2, 4.7, 7.5 Hz, 2H), 7.08 (ddd, J = 1.0, 7.3, 4.9 Hz, 2H).