Structural characterisation and DFT calculations of three new complexes of zinc phthalocyanine with n-alkylamines

• Axially ligated by n-alkylamines zinc phthalocyanine derivatives are obtained.
• Solid state X-ray crystal structures of ZnPc(n-alkylamine) complexes are reported.
• UV–Vis spectra of ZnPcL dyes show that Pc π-system is not perturbed by the axial L.
• The ZnPcL dyes are about 5 times more soluble than that of the parent ZnPc pigment.
• 3D MESP maps are helpful for understand the interaction of ZnPc with n-alkylamines.

Three complexes of zinc phthalocyanine monoaxially ligated by n-alkylamines (n-butylamine, n-amylamine and n-heptylamine) in the crystalline form were obtained and studied. These zinc phthalocyanine ligated by n-alkylamine complexes crystallize with the n-alkylamine molecules as solvates in the centrosymmetric space group. Two of them (with n-butylamine and n-amylamine) crystallize in the P21/c space group of monoclinic system while the third (with n-heptylamine) in the triclinic system. The zinc centre of these molecules is 4 + 1 coordinated by four isoindole nitrogen atoms of phthalocyaninate(2-) macrocycle in the equatorial position, and by the nitrogen atom of n-alkylamine in an axial position. Owing to the interaction of electropositive zinc centre of zinc phthalocyanine with the amine nitrogen atom of n-alkylamines, the zinc atom is significantly displaced (∼0.5 Å) from the plane defined by the four isoindole nitrogen atoms of phthalocyaninate(2-) macrocycle. The monoaxially ligation of zinc centre of zinc phthalocyanine molecule by n-alkylamines leads to distortion of the planar zinc phthalocyanine molecule to the saucer-shape form. X-ray conformations of these molecules are compared with the conformation of that in the gas-phase as obtained by the density functional theory calculations. The calculated three-dimensional molecular electrostatic potential maps are helpful for understanding of the interaction between the zinc phthalocyanine and n-alkylamines molecules forming the monoaxially ligated zinc phthalocyanine complexes. Thermogravimetric analysis and the UV–Vis spectroscopy were used for characterisation of these complexes. The Q band of these complexes (at about 670 nm) does not change comparing to that of the parent colorant. The monoaxially ligated by n-alkylamines zinc phthalocyanine dyes are about 5 times more soluble than the parent zinc phthalocyanine pigment.

Saturated solution of ZnPc (light blue, left) and of ZnPc(n-alkylamine) dyes (dark blue, right).Figure optionsDownload as PowerPoint slide