title: Photoisomerization of a maleonitrile-type salen Schiff base and its application in fine-tuning infinite coordination polymers.
abstract: Strategically designed salen ligand 2,3-bis[4-(di-p-tolylamino)-2-hydroxybenzylideneamino]maleonitrile (1), which has pronounced excited-state charge-transfer properties, shows a previously unrecognized form of photoisomerization. On electronic excitation (denoted by an asterisk), 1Z*-->1E isomerization takes place by rotation about the C2--C3 bond, which takes on single-bond character due to the charge-transfer reaction. The isomerization takes place nonadiabatically from the excited-state (1Z) to the ground-state (1E) potential-energy surface in the singlet manifold; 1Z and 1E are neither thermally inconvertible at ambient temperature (25-30 degrees C), nor does photoinduced reverse 1E*-->1Z (or 1Z*) isomerization occur. Isomers 1Z and 1E show very different coordination chemistry towards a Zn(II) precursor. More prominent coordination chemistry is evidenced by a derivative of 1 bearing a carboxyl group, namely, N,N'-dicyanoethenebis(salicylideneimine)dicarboxylic acid (2). Applying 2Z and its photoinduced isomer 2E as building blocks, we then demonstrate remarkable differences in morphology (sphere- and needlelike nanostructure, respectively) of their infinite coordination polymers with Zn(II).
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei, Taiwan.
authors.forename: Chun-Wei
authors.initials: CW
authors.lastname: Lin
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
authors.forename: Yong-Hong
authors.initials: YH
authors.lastname: Liao
authors.forename: Ying-Chih
authors.initials: YC
authors.lastname: Lin
authors.forename: Ching-Ting
authors.initials: CT
authors.lastname: Chen
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Chin-Hung
authors.initials: CH
authors.lastname: Lai
authors.forename: Bo-So
authors.initials: BS
authors.lastname: Chen
authors.forename: Yi-Hung
authors.initials: YH
authors.lastname: Liu
authors.forename: Chih-Chieh
authors.initials: CC
authors.lastname: Wang
authors.forename: Mei-Lin
authors.initials: ML
authors.lastname: Ho