¹H NMR (700 MHz, CDCl₃) δ 10.04 (s, 1H), 8.61 (d, J = 4.1 Hz, 2H), 8.31 (d, J = 7.8 Hz, 2H), 7.91 (t, J = 7.6 Hz, 2H), 7.79 (d, J = 7.9 Hz, 5H), 7.48 (q, J = 3.9 Hz, 2H), 7.39 (t, J = 7.7 Hz, 5H), 7.15 (t, J = 7.4 Hz, 2H).