Tuning the morphology of self-assembled nano-structures of phthalocyaninato zinc complex bearing two binaphthyl units

The self-assembly properties of phthalocyaninato zinc complex Zn{Pc(OBNP)2} bearing two aromatic binaphthyl units at the non-peripheral positions in mixed chloroform and methanol solution have been studied by Fourier transform infrared (FTIR) spectroscopy, transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), and X-ray diffraction (XRD) techniques. The compound self-assembles into ordered nano-structures with hollow sphere morphology depending on the intermolecular π–π interaction at ambient temperature. However, addition of equal amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) into the same solution system induces the formation of nano-rods, due to the dominant Zn–N metal–ligand coordination bonding interaction between the zinc center of Zn{Pc(OBNP)2} molecule and the nitrogen atom of DABCO molecule during the self-assembly process. This reveals the effect of synergistic noncovalent interaction of π–π interaction with metal–ligand coordination bonding on tuning the morphology of self-assembled nano-structures of Zn{Pc(OBNP)2}. The electronic absorption spectra of both the nano-scale hollow spheres and nano-rods have a blue-shift, compared with that of the compound in chloroform solution, which reveals the formation of H-aggregates in the two kinds of aggregates. Furthermore, XRD data confirm the molecular packing models in these aggregates. The present study will be helpful in designing and preparing self-assembled nano-structures of phthalocyanine derivatives with controlled molecular packing conformation and morphology through molecular modification.

Competition and/or cooperation between the inter-molecular metal–ligand coordination bonding and π–π interaction of phthalocyaninato zinc complex molecules lead to different molecular packing conformation and in turn different nano-structures during the self-assembly process.Figure optionsDownload as PowerPoint slideHighlights
► Zn{Pc(OBNP)2} self-assembles into ordered nano-scale hollow spheres.
► Zn{Pc(OBNP)2} self-assembles into ordered nano-rods in the presence of DABCO.
► This reveals the effect of synergistic noncovalent interaction on nano-structures.