Unusual Formation of a Stable 2D Copper Porphyrin Network

Copper­(II) 5,15-bis­(diethoxyphosphoryl)-10,20-diphenylporphyrin
was obtained and characterized by means of cyclic voltammetry, electron
paramagnetic resonance, Fourier transform infrared, and UV–visible
spectroscopy. Three crystalline forms were grown and studied by means
of X-ray diffraction methods (single crystal and powder). The highly
electron-withdrawing effect of phosphoryl groups attached directly
to the porphyrin macrocycle results in a self-assembling process,
with formation of a stable 2D coordination network, which is unusual
for copper­(II) porphyrins. The resulting 2D structure is a rare example
of an assembly based on copper­(II) porphyrins where the copper­(II)
central metal ion is six-coordinated because of a weak interaction
with two phosphoryl groups of adjacent porphyrins. The other polymorph
of copper­(II) 5,15-bis­(diethoxyphosphoryl)-10,20-diphenylporphyrin
contains individual (isolated) porphyrin molecules with four-coordinated
copper­(II) in a distorted porphyrin core. This polymorph can be obtained
only by slow diffusion of a copper acetate/methanol solution into
solutions of free base 5,15-bis­(diethoxyphosphoryl)-10,20-diphenylporphyrin
in chloroform. It converts to the 2D structure after dissolution in
chloroform followed by consecutive crystallizations, using slow diffusion
of hexane. A six-coordinated copper­(II) porphyrin containing two axially
coordinated dioxane molecules was also obtained and characterized
by X-ray diffraction crystallography. The association of copper­(II)
5,15-bis­(diethoxyphosphoryl)-10,20-diphenylporphyrin in solution was
also studied.