Control of the supramolecular structure of zinc(II) phthalocyanine by morpholine

The coordination preference of morpholine as an N- and O-donor ligand (NHC₄H₆O) for the coordination of zinc atom in ZnPc in solution was investigated. Under the conditions used, it has been shown that morpholine coordinates through the N atom to form a T-shaped ZnPc(Morph) complex, that crystallizes in the centrosymmetric space group of the triclinic system as morpholine disolvate, ZnPc(Morph)‧2(Morph) with two molecules in the asymmetric unit. Both independent ZnPc(Morph) molecules exhibit similar conformation with Zn atom out of the N₄-isoindole plane of the phthalocyanine macrocycle that adopts a saucer-shaped. Supramolecular arrangement of the ZnPc(Morph)‧2(Morph) in crystal is characterized by a reduction of π···π interactions and an improvement in inter-system crossing in relation to parent ZnPc and is controlled by the solvent morpholine molecules, which results in increase its solubility and improved photophysical and photochemical properties. The aggregation behaviour of ZnPc(Morph)‧2(Morph) building crystals in solutions was investigated by UV–Vis spectroscopy. Besides, the UV–Vis spectroscopic characterization of the ZnPc(Morph)‧2(Morph) crystals in solutions, the diffuse reflectance spectroscopic (DSR) characterization on the solid sample of ZnPc(Morph)‧2(Morph) was performed. The DSR spectra of ZnPc(Morph)‧2(Morph) exhibit broad bands with a slight blue-shift that might be attributed to a larger exciton coupling resulting from closer contacts between the molecules than in solution. In order to support and verify the experimental results, the DFT and time-dependent (TD) DFT calculations were performed.