Abstract
In the current work, two new zinc-porphyrinic complexes bearing pyrazine as axial ligand, i.e. (pyrazine)(meso-tetrakis-(4-phenoxyphenyl)porphyrinato)zinc(II) [Zn(TBOPP)(pyz)] (1) and (aqua)(pyrazine)(meso-tetrakis(3,4,5-trimethoxyphenyl)porphyrinato)zinc(II) monohydrate [Zn(TTMP)(pyz)(H2O)](center dot)H2O (2) were successfully synthesized. New complexes were extensively characterized using elemental analysis, H-1 NMR, UV-visible, single-crystal X-ray, and mass spectrometry (ESI) techniques. Single crystal X-ray studies revealed penta-coordinated environment around each Zn(II) metal in complexes with pyrazine as an axial ligand. The complexes were stabilized by weak C-H (...) Cg pi intermolecular interactions involving pyridyl, phenyl and pyrrole centroid rings. Optical absorption studies confirmed the medium band gap and semiconducting nature of the compounds. Emission studies indicated that the axial ligand has no significant effect on the fluorescence quantum yields (?(f)) and the lifetime (tau(f)) values. The ability of calmagite dye (an anionic dye) to remove the free bases and the Zn(II) complexes from aqueous solution has also been presented. Frontier molecular orbital (HOMO-LUMO) energies for H2TBOPP, H2TTMP, [Zn(TBOPP)] and [Zn(TTMP)] with calmagite were determined using density functional theory (DFT) calculation showing the charge transfer within the molecule.