Photofunctional supramolecular solution systems of chiral Schiff base nickel(II), copper(II), and zinc(II) complexes and photochromic azobenzenes

Preparations, crystal structures, electronic and CD spectra are reported for new chiral Schiff base complexes, bis(N-R-1-naphthylethyl-3,5-dichlorosalicydenaminato)nickel(II), copper(II), and zinc(II). Nickel(II) and copper(II) complexes adopt a square planar trans-[MN2O2] coordination geometry with Δ(R,R) configuration. While zinc(II) complex adopts a compressed tetrahedral trans-[MN2O2] one with Δ(R,R) configuration and exhibits an emission band around 21 000 cm−1 (λex = 27 000 cm−1). Absorption and CD spectra were recorded in N,N′-dimethylformamide, acetone, methanol, chloroform, and toluene solutions to discuss relationships between spectral shifts of d–d and π–π∗ bands by structural changes of the complexes and physical properties of the solvents. Moreover, we have attempted to investigate conformational changes of the complexes induced by photoisomerization of azobenzene, 4-hydroxyazobenzene, or 4-aminoazobenzene, in various solutions under different conditions. Weak intermolecular interactions between complexes and azobenzenes are important for the phenomenon by conformational changes of bulky π-conjugated moieties of the ligands.

We present preparations, crystal structures, electronic and CD spectra of chiral Schiff base complexes, bis(N-R-1-naphthylethyl-3,5-dichlorosalicydenaminato)nickel(II), copper(II), and zinc(II), and investigate their conformational changes induced by photoisomerization of azobenzenes via intermolecular interactions in solutions.Figure optionsDownload as PowerPoint slide