Synthesis and characterization of axially ligated zinc(II)-para-nitro-mesotetraphenylporphyrin

Department of Chemistry, University of Jammu, New Campus, Baba Sahib Ambedkar Road, Jammu-180 006,
Jammu & Kashmir, India
E-mail : gauribajju@gmail.com
Manuscript received 10 December 2010, accepted 09 March 2011

Reaction of p-nitro-meso-tetraphenylporphyrin (p-NO₂-H₂ TPP) with zinc(n) acetate (Zn(OAc)₂) and phenol result in the formation of corresponding axially ligated zinc(II)-p-nitro-meso-tetraphenylporphyrin (X-Zn^II-p-NO₂ TPP) (where X = axial phenolic ligands and TPP = tetraphenylporphyrin). The four-coordinated zinc porphyrin will accept one and only one axial ligand in 1 : 1 molar ratio to form five-coordinated complexes (Fig. 1), which are purified by column chromatographic method and characterized by UV/Vis, IR, NMR, Mass and elemental analysis. The visible spectra of the compounds in different solvents show a red shift (bathochromic shift) which increases in the magnitude depending upon the charge and polarizability of the axial ligation to Zn-p-NO₂TPP but not on the strength of the zinc ligand bond. The IR spectra show the appearance of metal-nitrogen (Zn-N) and metal-ligand (Zn-X) vibrations. The ¹H NMR results in CDCJ₃ indicate the merging of protons of the phenolic ring axially attached to the central metal ion with that
of the tetraphenyl ring of the Zn-p-NO₂TPP. The Mass spectra show that the molecular weight of the porphyrin agree well with the calculated m/z values. The elemental analysis shows the percentage of various elements In the compounds formed.