Compound 2

4'-Bromo-7'-{4'-bromo-1',3',3'-trimethyl-6-nitro-1',3'-dihydrospiro[chromene-2,2'-indole]-7'-yl}-1',3',3'-trimethyl-6-nitro-1',3'-dihydrospiro[chromene-2,2'-indole]

From: Nanoporous frameworks exhibiting multiple stimuli responsiveness