摘要
Strategically designed salen ligand 2,3-bis[4-(di-p-tolylamino)-2- hydroxybenzylideneamino]maleonitrile (1), which has pronounced excitedstate 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 (IZ) to the ground-state (IE) potential-energy surface in the singlet manifold; IZ and 1E are neither thermally inconvertible at ambient temperature (25-30°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 . © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.