Solvation-induced switching of the conformational state of alkoxy- and crown-substituted trisphthalocyaninates studied by UV-Vis and H-1-NMR spectroscopy

Solvation-induced switching between staggered and gauche conformers of europium(III) triple-decker complexes with n-butoxy- and crown-substituted phthalocyanine ligands [(BuO)(8)Pc]2-and [(15C5)(4)Pc]2-was studied by UV-Vis and H-1-NMR in toluene and chloroform media. The crown-substituted complex Eu-2[(15C5)(4)Pc](3) was conformationally invariant, adopting the staggered arrangement of adjacent ligands in both solvents. In contrast, in the case of butoxy-substituted complex Eu-2[(BuO)(8)Pc](3), the staggered and gauche forms were stabilized in toluene and chloroform, respectively. These conclusions could easily be drawn from the UV-Vis data. In contrast, a comparison of the H-1-NMR spectra of the complexes in both solvents showed that the spectral manifestation of conformational switching was obscured by media effects, although some characteristic spectral patterns of each conformation could still be identified on the example of the complex with hexa-n-butoxy-15-crown-5-phthalocyanine ligands Eu-2[(BuO)(6)(15C5)Pc](3).