Nonperipherally Octa(butyloxy)-Substituted Phthalocyanine Derivatives with Good Crystallinity: Effects of Metal-Ligand Coordination on the Molecular Structure, Internal Structure, and Dimensions of Self-Assembled Nanostructures

To investigate the effects of metal-ligand coordination oil the molecular structure, internal structure, dimensions, and morphology of self-assembled nanostructures, two nonperipherally octa(alkoxyl)-substituted phthalocyanine compounds with good crystallinity, namely, metal-free 1,4,8,11,15,18,22,25-octa(butyloxy)-phthalocyanine H2Pc(alpha-OC4H9)(8) (1) and its lead complex Pb[Pc(alpha-OC4H9)(8)] (2), were synthesized. Single-crystal Xray diffraction analysis revealed the distorted molecular structure of metal-free phthalocyanine with a saddle conformation. In the crystal of 2, two monomeric molecules are linked by coordination of the Pb atom of one molecule with ail aza-nitrogen atom and its two neighboring oxygen atoms from the butyloxy substituents of another molecule, thereby forming a Pb-connected pseudo-double-decker supramolecular structure with a domed conformation for the phthalocyanine ligand. The self-assembling properties of 1 and 2 in the absence and presence of sodium ions were comparatively investigated by scanning electronic microscopy (SEM), spectroscopy, and X-ray diffraction techniques. Intermolecular pi-pi interactions between metal-free phthalocyanine molecules led to the formation of nanoribbons several micrometers in length and with ail average width of approximately 100 nm, whereas the phthalocyaninato lead complex self-assembles into nanostructures also with the ribbon morphology and micrometer length but with a different average width of approximately 150 nm depending on the pi-pi interactions between neighboring Pb-connected pseudo-double-decker building blocks. This revealed the effect of the molecular structure (conformation) associated with metal-ligand (Pb-N-isoindole, Pb-N-aza, and Pb-O-butyloxy) coordination on the dimensions of the nanostructures. In the presence of Na+, additional lmetal-ligand (Na-N-aza and Na-O-butyloxy) coordination bonds formed between sodium atoms and aza-nitro-gen atoms and the neighboring butyloxy oxygen atoms of two metal-free phthalocyanine molecules cooperate with the intrinsic intermolecular pi-pi interactions, thereby resulting in ail Na-connected pseudo-double-decker building block with a twisted structure for the phthalocyanine ligand, which self-assembles into twisted nanoribbons with ail average width of approximately 50 nm depending on the intertetra-pyrrole pi-pi interaction. This is evidenced by the X-ray diffraction analysis results for the resulting aggregates. Twisted nanoribbons with an average width of approximately 100 nm were also formed from the lead coordination compound 2 in the presence of Na+ with a Pb-connected pseudo-double-decker as the building block due to the formation of metal-ligand (Na-N-aza and Na-O-butyloxy) coordination bonds between additionally introduced sodium ions and two phthalocyanine ligands of neighboring pseudo-double-decker building blocks.