1 H NMR ( 499 . 8 MHz , DMSO - d 6 ) δ 2 . 60 ( 4 H , t ) , 3 . 22 ( 4 H , t ) , 3 . 73 ( 2 H , s ) , 7 . 54 ( 1 H , s ) , 7 . 72 - 7 . 75 ( 1 H , m ) , 7 . 90 - 7 . 94 ( 2 H , m ) , 8 . 05 - 8 . 07 ( 1 H , m ) , 8 . 75 ( 1 H , s ) ; m / z = 431 [ M + H ] +.