Platinum(ii) complexes bearing 1,1′-bis(diphenylphosphino)ferrocene as building blocks for functionalized redox active porphyrins

Abstract

Reactions of the cationic complex ions [PtMe(Me₂SO)(PP)]⁺ (PP = dppf (1,1′-bis(diphenylphosphino)ferrocene) and dppe (1,2-bis(diphenylphosphino)ethane)) with 5,10,15,20-tetrakis(4-pyridyl)-21H,23H-porphyrin (TpyP) led to the formation of the symmetrical tetraplatinated porphyrin complexes, [PtMe(PP)]₄TpyP·X₄ (PP = dppf, X = CF₃SO₃⁻, 3, and PP = dppe, X = BF₄⁻, 5) containing the organometallic fragment {PtMe(PP)}. The precursor sulfoxide platinum complexes [PtMe(Me₂SO)(dppf)]CF₃SO₃, 2 and [PtMe(Me₂SO)(dppe)]BF₄, 4, were prepared by halide abstraction from [PtMeCl(dppf)], 1, and by controlled protonolysis of [PtMe₂(dppe)] respectively, in the presence of a small amount of dimethyl sulfoxide. All these starting platinum(II) compounds, as well as the porphyrin derivatives 3 and 5, were fully characterized through elemental analysis, ¹H NMR mono- and bidimensional, ³¹P{¹H}, ³¹P–¹H HMBC, UV/Vis absorption and photophysical measurements. The X-ray crystal structure of complex 1 has been determined. In order to ascertain the electronic influence of ferrocene, the spectroscopic and redox properties of 3 were compared with those of TPyP and of the analogous 5. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), ¹H and ³¹P NMR data, and UV/Vis data, all suggest a certain degree of communication between the central porphyrin and the peripheral hetero-bimetallic fragments. In contrast, no detectable interaction among these peripheral groups seem to come into play. Unlikely from the porphyrin derivative 5, formation of well defined fluorescent mesoscopic ring structures was easily achieved by simple evaporation from diluted dichloromethane solutions of 3.