Metalloporphines: Dimers and Trimers

Procedures for the purification and
subsequent crystallization of the slightly soluble four-coordinate
metallporphines, the simplest possible porphyrin derivatives, are
described. Crystals of the porphine derivatives of cobalt­(II), copper­(II),
platinum­(II), and two polymorphs of zinc­(II) were obtained. Analysis
of the crystal and molecular structures shows that all except the
platinum­(II) derivative form an unusual trimeric species in the solid
state. The isomorphous cobalt­(II), copper­(II), and one zinc­(II) polymorph
pack in the unit cell to form dimers as well as the trimers. Interplanar
spacings between porphine rings are similar in both the dimers and
trimers and range between 3.24 and 3.37 Å. Porphine rings are
strongly overlapped with lateral shifts between ring centers in both
the dimers and trimers with values between 1.52 and 1.70 Å or
in Category S as originally defined by Scheidt and Lee. Periodic trends
in the M–Np bond distances parallel those observed
previously for tetraphenyl- and octaethyl­porphyrin derivatives.