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Abstract

A combined X-ray and density functional theory (DFT) study on the structure of 5,10,15,20-tetra(3-pyridyl)porphyrin (1) has been undertaken. Single-crystal X-ray diffraction revealed molecules of 1 in the ααββ conformation with molecular and crystallographic C_i point group symmetry. The porphyrin macrocycle shows no marked deviation from planarity. Positional disorder of the pyrrole NH atoms is discussed. The crystal packing of 1 is achieved through common off-set stacking of the porphyrin entities. Bulk material of 1 was further investigated by scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD). The crystal and molecular structure of 1 is compared to the known structures of the unsolvated free-base 2- and 4-pyridyl isomers. The molecular structure of 1 in solution has been investigated by variable temperature ¹H NMR spectroscopy in CDCl₃.