Complexes of zinc phthalocyanine with monoaxially coordinated imidazole-derivative ligands

• Zinc phthalocyanine axially ligated complexes are obtained.
• Solid state X-ray crystal structures of ZnPcL complexes are reported.
• UV–Vis spectra of ZnPcL dyes show that Pc π-system is not perturbed by the axial L.
• MESP maps are helpful for understand the interaction between ZnPc and the axial L.

Three complexes of zinc phthalocyanine (ZnPc) monoaxially ligated by imidazole, N-methylimidazole and N-(2-pyrimidinyl)imidazole were obtained in crystalline forms. Complexes containing imidazole and N-methylimidazole crystallise in the centrosymmetric space group of the triclinic system, while with the N-(2-pyrimidinyl)imidazole complex crystallises in P21/n space group of monoclinic system. Interaction of the electropositive polarised Zn centre of a planar ZnPc with nucleophilic ring nitrogen atom of imidazole derivatives leads to deviation of Zn form the N4-plane of phthalocyaninato(2-) macrocycle by ∼0.45 Å. Steric hindrance of the axial ligands of ZnPc-L complexes modify the π∙∙∙π interactions between the Pc(2-) macrocycles when compared to that of the parent ZnPc pigment. The calculated three-dimensional MESP maps are helpful for understanding of the interaction between the ZnPc and imidazole derivatives forming the monoaxially ligated complexes. Theoretical calculations of axial bonds energies and UV–Vis spectroscopic measurements in solutions also were performed.

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