Patent ID: 8754230

Claim:
A compound having the structure: or a salt thereof, wherein: X is NO 2 or NH 2 ; and PAm is —NH—R b , —NHC(O)OR a , —NHC(═O)R a , —NH(CH 2 R c ), —NHSi(R d ) 3 , —NH(PO(OR d ) 2 , —NHSO 2 R e , —N(R b ) 2 , —N(C(O)OR a ) 2 , —N(C(O)R a ) 2 , —N(CH 2 R c ) 2 , —N(Si(R d ) 3 ), —N═C(R a ) 2 , or each R a is independently H, alkyl, haloalkyl, benzyl, or aryl; each R b is independently alkyl, haloalkyl, benzyl, methoxybenzyl, or aryl; each R c is independently allyl or alkoxy; each R d is independently alkyl; R e is alkyl, alkyl substituted with —Si(alkyl) 3 , phenyl, or nitrophenyl; and each R f is independently alkyl or benzyl.