Molecular structure reorganisation of Fe-, Co- and Ni-phthalocyanines upon milling

A method for preparation of carbon nanotubes with relatively low concentration of defects requires milling and subsequent pyrolysis of metal-phthalocyanines (MPc, MC32H16N8). The molecular structure rearrangements in Fe-, Ni- and Co-phthalocyanines precursors upon milling in argon for 100 h have been investigated using short–range spectroscopic methods. Carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectra, acquired in bulk sensitive fluorescence-yield mode, show that packing order of the metal phthalocyanines has changed during the milling. The new packing shows similar order for the pyrrole subunits of the phthalocyanine macromolecule but less for the phenyl subunits. The increased energy potential due to loose packing of the milled phthalocyanines can explain the observed substantial reduction in the vaporisation temperature of the milled phthalocyanines.