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
Authors: Gao Yingning , Chen Yanli , Li Renjie , Bian Yongzhong , Li Xiyou , Jiang Jianzhuang 
Published: October 2009

AbstractTo investigate the effects of metal–ligand coordination on 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(α‐OC4H9)8 (1) and its lead complex Pb[Pc(α‐OC4H9)8] (2), were synthesized. Single‐crystal X‐ray 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 an 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 π–π interactions between metal‐free phthalocyanine molecules led to the formation of nanoribbons several micrometers in length and with an 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 π–π interactions between neighboring Pb‐connected pseudo‐double‐decker building blocks. This revealed the effect of the molecular structure (conformation) associated with metal–ligand (PbNisoindole, PbNaza, and PbObutyloxy) coordination on the dimensions of the nanostructures. In the presence of Na+, additional metal–ligand (NaNaza and NaObutyloxy) coordination bonds formed between sodium atoms and aza‐nitrogen atoms and the neighboring butyloxy oxygen atoms of two metal‐free phthalocyanine molecules cooperate with the intrinsic intermolecular π–π interactions, thereby resulting in an Na‐connected pseudo‐double‐decker building block with a twisted structure for the phthalocyanine ligand, which self‐assembles into twisted nanoribbons with an average width of approximately 50 nm depending on the intertetrapyrrole π–π 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Naza and NaObutyloxy) coordination bonds between additionally introduced sodium ions and two phthalocyanine ligands of neighboring pseudo‐double‐decker building blocks.