1 H NMR ( 400 MHz , DMSO - d 6 ) : δ [ ppm ] = - 0 . 04 ( s , 9 H ) , 0 . 83 - 0 . 89 ( m , 2 H ) , 3 . 56 - 3 . 61 ( m , 2 H ) , 5 . 50 ( s , 2 H ) , 7 . 57 - 7 . 61 ( m , 2 H ) , 8 . 10 - 8 . 15 ( m , 2 H ) , 8 . 23 ( s , 1 H ) , 8 . 46 ( s , 1 H ) , 8 . 70 ( s , 1 H ) , 13 . 86 ( br s , 1 H ) .