Synthesis, Electronic Spectroscopy, Cyclic Voltammetry, Photophysics, Electrical Properties and X‐ray Molecular Structures of meso‐{Tetrakis[4‐(benzoyloxy)phenyl]porphyrinato}zinc(II) Complexes with Aza Ligands

Abstract

The synthesis of the new meso‐porphyrin tetrakis[4‐(benzoyloxy)phenyl]porphyrin (H2TPBP), the meso‐{tetrakis[4‐(benzoyloxy)phenyl]porphyrinato}zinc(II) starting material [Zn(TPBP)] (1), and the 1,4‐diazabicyclo[2.2.2]octane (dabco), pyrazine (pyz), 4,4′‐bipyridine (4,4′‐bpy), 4,4′‐diaminodiphenylmethane (4,4′‐mda), and 4‐cyanopyridine (4‐CNpy) coordination compounds with [Zn(TPBP)] (2–7) are described. The preparation of the dabco derivative in chlorobenzene leads to a crystalline monomeric five‐coordinate zinc porphyrin species (2), whereas the synthesis in dichloromethane gives a five‐coordinate zinc metalloporphyrin dimer (3) in the solid state. The pyrazine derivative crystallizes as a bis‐pyrazine six‐coordinate zinc metalloporphyrin (4). Complex 5 in the solid state is a dimer with 4,4′‐bpy as a bridging ligand, whereas the 4,4′‐mda species (6) is a five‐coordinated monomeric zinc derivative in the solid state. All of structures of 2–6 possess cavities with different dimensions in which solvent molecules are located. The solution UV/Vis spectra of 2–7 exhibit redshifted Soret bands that indicate that these derivatives are five‐coordinate zinc(II) porphyrin complexes in solution. UV/Vis titrations show that the association constants of 2–7 are close to those of known five‐coordinate zinc(II) meso‐porphyrins. The 1H NMR spectra of these species confirm this deduction. The photophysical proprieties of 1–7 are similar to those of related zinc(II) meso‐porphyrins. The cyclic voltammograms of the H2TPBP free base and 1–7 present a third one‐electron reversible oxidation wave. Single‐layer diode devices of the [iridium tin oxide/zinc porphyrin/aluminum] configuration show relatively low turn‐on voltages.