solitaire-Porphyrazines: Synthetic, structural, and spectroscopic investigation of complexes of the novel binucleating norphthalocyanine-2,3-dithiolato ligand

We have developed the synthesis of unsymmetrical metalloporphyrazines of the form M[pz(A:B₃)], where A and B refer to two different types of peripheral functionality, and have used it to prepare new bi- and trimetallic solitaire-porphyrazines in which A represents a mono- or bimetallic moiety. The macrocyclic complexes described are based on the binucleating ligand, [M(norphthalocyanine-2,3-dithiolate)]^2-, [M(norpc)]^2-. This can be thought of as a metalloporphyrazine where B is a fused benzo ring; A represents two thiolates fused at the β-pyrrole positions to form a dithiolene moiety that can bind a transition-metal ion in addition to one within the macrocyclic cavity. solitaire-Porphyrazines have been synthesized by chelation of [(L-L)M']²⁺ to the [M(norpc)]^2- ligand where M = '2H', Ni, Cu, or Mn-Cl, L-L is a bis(diphosphino) or bis(diamino) group and M' = Ni, Pd, or Pt. Crystal structures have been obtained for 11b, where the [H₂(norpc)]^2- ligand coordinates the diphosphinopalladium moiety, [Pd(dppf)]²⁺, by the two thiolate sulfur atoms at its periphery, and for 11h, with the diaminoplatinum moiety, [Pt(teeda)]²⁺, bound to the periphery of the [Ni(norpc)]^2- ligand. In crystals 11b and 11h, the molecules appear as face-to-face dimers. However, the dimer of 11b and the two crystallographically independent dimers of 11h each shows a distinctly different degree of overlap. The electronic absorption spectra of a series of porphyrazines in which the two peripheral sulfur atoms form thioether moieties with a modified benzyl-protecting group (6-10) show that the peripheral asymmetry of the macrocyclic framework causes a strong splitting of the (π-π*) Q-band. In contrast, when the peripheral sulfurs bind a metal ion to form solitaire-porphyrazines 11a-h. the optical spectra closely resemble that of the symmetrical pc, with unsplit Q band. The EPR spectrum of solitaire 11d, where M = Cu, L-L = a bis(diphosphino) cap, M' = Pd, has features consistent with other square-planar copper(II) porphyrins and phthalocyanines. Cyclic voltammograms of compound 11b shows two reversible ring reductions at potentials similar to those of H₂(pc) as well as a reversible oxidation associated with the ferrocene portion of the Pd(dppf) moiety.