“…215 °C (ref. 16: 220–224 °C); IR (KBr): $\tilde \nu$ =1667 (C=O), 1640 (C=O), 1590 , 1544, 1514, 1491, 1461, 1449, 1407 (N=N), 1353, 1306, 1278, 1185, 1167, 1132, 1069, 1011, 926, 825, 810, 734, 709 cm −1 ; MS (CI, isobutane): m / z : 342 [ M +H] + .…”