title: 4-Amino derivatives of 7-nitro-2,1,3-benzoxadiazole: the effect of the amino moiety on the structure of fluorophores.
abstract: The crystal structures of three 4-amino derivatives of 7-nitro-2,1,3-benzoxadiazole with increasing substituent ring size, viz. 7-nitro-4-(pyrrolidin-1-yl)-2,1,3-benzoxadiazole, C(10)H(10)N(4)O(3), 7-nitro-4-(piperidin-1-yl)-2,1,3-benzoxadiazole, C(11)H(12)N(4)O(3), and 4-(azepan-1-yl)-7-nitro-2,1,3-benzoxadiazole, C(12)H(14)N(4)O(3), have been determined in order to understand their photophysical behaviour. All three were found to crystallize in centrosymmetric space groups. There is considerable electron delocalization compared with the parent compound, although the five-membered oxadiazole ring apparently does not participate in this. The length of the C-N bond between the amino N atom and the 7-nitrobenzoxadiazole system is found to be shorter than in similar compounds, as is the C-N(nitro) bond. In each structure, the nitro group lies in the plane of the benzoxadiazole unit.
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad 500 046, India. asscrs@uohyd.ernet.in
authors.forename: Satyen
authors.initials: S
authors.lastname: Saha