Photoswitchable transition metal complexes with azobenzene-functionalized imine-based ligands: structural and kinetic analysis

Abstract

We report on the characterization of two imine type ligands containing photoresponsive azobenzene units as side groups and their transition metal ions complexes. The ligands, both free and in their complexes undergo trans- > cis photoisomerization after irradiation with UV light, but binding of metal ions reduces both the photoisomerisation reaction rates and cis isomer concentrations in the photostationary states. The greatest diminution in the photoisomerisation rate was observed for the complex containing Cd(ii), the heaviest among the various transition metal ions tested in this study.

Aluminium(iii) and zinc(ii) complexes of azobenzene-containing ligands for ring-opening polymerisation of ε-caprolactone and rac-lactide

“…1H has been reported previously by methods similar to those reported here. [31][32][33] The formation of the ligands was confirmed by NMR spectroscopy, with primarily (>97%) trans-azo species being present. The 1 H NMR spectra of 1-3H exhibit a sharp singlet resonance in the region δ = 8.50-8.70 ppm, corresponding to imine environments, with the concurrent 13 C{ 1 H} NMR signal at ca.…”

“…Zn(1) 2 has been reported previously by Markiewicz et al via a subcomponent self-assembly procedure, where the ligand was not isolated prior to complexation with the metal. 31 A single crystal suitable for X-ray diffraction of Zn(3) 2 was obtained. Following numerous attempts at forming a single crystal of Zn(1) 2 , the characterisation of Zn(1) 2 was based on NMR spectroscopy and elemental analysis, which both supported formation of the complex.…”

New copper(II) and zinc(II) complexes based on azo Schiff base ligand: Synthesis, crystal structure, photoisomerization study and antibacterial activity

“…The photoinduced trans to cis isomerization in azobenzene compounds consist of an S1 ← S0 (n → π*) excitation related to an inversion at one nitrogen atom of the N&dbond;N double bond. The isomerization can also procced through a rotation mechanism which involves an S2 ← S0 (π → π*) excitation and the cis to trans isomerization involves excitation into the S1 or S2 state …”

“…π*) excitation and the cis to trans isomerization involves excitation into the S1 or S2 state. [7,50,51] Figure 7 shows the absorption spectra of the copper complex before and after irradiation with 365 nm UV light. Little changes occurred: we noticed a small decrease in intensity and, at the same time, an enlargement for the π-π* absorption band at 398 nm.…”

Intrinsic Effect of Pyridine-N-Position on Structural Properties of Cu-Based Low-Dimensional Coordination Frameworks

“…Coordination-driven self-assembly processes harness the directionality and reversibility of metal–ligand interactions to allow formation of supramolecular architectures with strictly defined shape and topology [ 1 , 2 , 3 , 4 , 5 , 6 ]. The spontaneous but controlled generation of well-defined multimetallic architectures is seen in the formation of one-, two- and three-dimensional coordination polymers (CPs) with numerous applications in, e.g., magnetism, molecular separations, dye degradation and catalysis [ 7 , 8 , 9 ].…”