Axial coordination in nickel(II) porphyrins has been thoroughly investigated and is well understood. However, isolated five-coordinate nickel(II) porphyrins are still elusive after 50 years of intense research, even though they play a crucial role as intermediates in enzymes and catalysts. Herein we present the first fully stable, thoroughly characterized five-coordinate nickel(II) porphyrin in solution and in the solid state (crystal structure). The spectroscopic properties indicate pure high-spin behavior (S = 1). There are distinct differences in the NMR, UV−vis, and redox behavior compared to those of high-spin six-coordinate [with two axial ligands, such as NiTPPF 10 •(py) 2 ] and low-spin fourcoordinate (NiTPPF 10 ) nickel(II) porphyrins. The title compound, a strapped nickel(II) porphyrin, allows a direct comparison of four-, five-, and six-coordinate nickel(II) porphyrins, depending on the environment. With this reference in hand, previous results were reevaluated, for example, the switching efficiencies and thermodynamic data of nickel(II) porphyrin-based spin switches in solution.

The synthesis and crystal structure of 5,10,15,20-tetra­kis α,α,α,α 2-iso­thio­cyanato­phenyl zinc(II) porphyrin are reported. The crystal structure consists of discrete porphyrin complexes that are located on a twofold rotation axis with the ZnII cation in a square-pyramidal coordination environment defined by the porphyrin N atoms at the basal sites and a diethyl ether mol­ecule at the apical site.