1 H - NMR ( DMSO - d 6 , δ , ppm ) : 5 . 65 ( 2 H , s ) , 6 . 96 ( 1 H , t ) , 7 . 23 ( 1 H , m ) , 7 . 57 ( 1 H , d ) , 7 . 80 ( 1 H , m ) , 7 . 91 ( 1 H , m ) , 8 . 28 ( 1 H , m ) , 8 . 49 ( 1 H , d ) , 9 . 13 ( 2 H , brs )