Synthesis, EPR and DFT calculations of rare Ag(II)porphyrins and the crystal structure of [Zn(II)tetrakis(4-bromo-2-thiophene)porphyrin]

Meso-tetrakis (4-bromo-2-thiophene) and (5-bromo-2-thiophene) porphyrins were synthesized in 18% yield from freshly distilled pyrrole and the corresponding aldehydes in refluxing propionic acid. Reaction of both porphyrins with either Zn(OAc)2 · 2H2O or Ag(OAc) afforded the corresponding metal complexes in 20% yield. The free bases and metal complexes were characterized by IR, NMR, EPR, MS and XPS. The crystal structure of 5,10,15,20(4-bromo-2-thiophene)porphyrinato Zn(II) was determined by X-ray diffraction and shows a ‘zigzag-like’ packing pattern due to S···S intermolecular interaction. Structural features of these molecules are discussed by DFT quantum chemical calculations.