1 H NMR ( 400 MHz , DMSO - d 6 ) δ [ ppm ] = 7 . 10 ( t , 1 H ) , 7 . 59 ( br s , 1 H ) , 7 . 66 ( d , 2 H ) , 7 . 76 ( s , 1 H ) , 8 . 06 ( d , 2 H ) , 8 . 13 ( br d , 1 H ) , 8 . 63 ( br s , 1 H ) , 8 . 91 ( br s , 1 H ) .