Ethylenediamine control of the solid-state supramolecular chemistry of zinc phthalocyanine

Abstract

The two axially ligated H-shaped and T-shaped zinc phthalocyanine derivatives, ZnPc(EDA)ZnPc and ZnPc(EDA), were obtained directly by thermal reaction of ZnPc in ethylenediamine (EDA) solution. Both complexes, ZnPc(EDA)ZnPc and ZnPc(EDA), co-crystallize with the EDA and water molecules yielding good-quality single crystals [ZnPc(EDA)ZnPc][ZnPc(EDA)]2∙2EDA·6H2O − 1. The interaction of Zn center of ZnPc with the axial substituent containing lone electron pair on NH2 groups with zinc phthalocyanine in both zinc phthalocyanine derivatives, ZnPc(EDA)ZnPc and ZnPc(EDA), leads to a deviation of Zn from the centre of cavity by 0.442(3) and 0.514(3) Å in the T- and H-shaped molecules as well as causes, as expected, the deformation of the planar molecule ZnPc into a saucer-shape conformation. Thus, in both types of molecules the central Zn atom of ZnPc complexes with EDA molecule exhibits 4 + 1 coordination formed by the four isoindole nitrogen atoms of the Pc macrocycle at the equatorial position and the nitrogen atom of the amino group of the EDA molecule at the axial position. Supramolecular arrangement of the T-shaped and H-shaped ZnPc-derivatives 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 NH∙∙∙O, NH∙∙∙N and OH∙∙∙O hydrogen bonds formed between the T- and H-shaped molecules and lattice EDA and water molecules, which results in increase its solubility and improved photophysical and photochemical properties. The aggregation behaviour of T- and H-shaped ZnPc derivatives building crystals 1 in solutions was investigated by UV–Vis spectroscopy. In order to support and verify the experimental results, the DFT and time-dependent (TD) DFT calculations were performed.