First-Row Transition Metal Complexes of Dipyrrinato Ligands: Synthesis and Characterization.

摘要

A library of variously-substituted dipyrrins and their first-row transition metal (Mn, Fe, Cu, Zn) complexes have been synthesized, and the effects of peripheral substituents on the spectroscopic, electrochemical, and structural properties of both the free-base dipyrrins and their metal complexes has been explored. The optical and electrochemical properties of the free dipyrrins follow systematic trends; with the introduction of electron-withdrawing substituents in the 2-, 3-, 5-, 7-, and 8-positions of the dipyrrin, bathochromic shifts in the absorption spectra are observed, oxidation becomes more difficult, and reduction becomes more facile. Similar effects are seen for iron(II) dipyrrinato complexes, where peripheral substitution of the dipyrrinato ligand induces red-shifts in the absorption spectra and increases the oxidation potential of the bound iron. Steric interactions between the peripheral halogens and the 5-substituent of the dipyrrinato ligand can induce distortion of the ligand from planarity, resulting in widely varying 57Fe Mossbauer quadrupole splitting (|DeltaEQ|) parameters.;The coordination number and geometry of metal atoms bound to widely-varied dipyrrinato ligands was analyzed by X-ray crystallography. Sterically encumbered substituents in the ligand 1- and 9-positions allowed the isolation of several three-coordinate species, including dipyrrinato complexes of Fe(II), Cu(I), and Cu(II). Less sterically demanding 1- and 9-substituents, such as mesityl, adamant-1-yl, and tert-butyl generally favored the formation of four-coordinate structures. Five-coordinate complexes could be crystallographically characterized with weakly coordinating anionic donor ligands (e.g. triflate). Each of these coordination numbers was analyzed by the angular overlap model to generate electronic configuration diagrams.;A series of free-base dipyrrin and metal dipyrrinato complexes bearing the 1- and 9-substituent Q (Q = 2&feet;,4&feet;,6&feet;-Ph3C 6H2) were synthesized, and their luminescence spectra were obtained. This series included highly luminescent Zn(II) and Li(I) dipyrrinato complexes (phiF = 0.67 and 0.51, respectively), the first appreciably luminescent dipyrrinato complexes of paramagnetic metals (phiF = 0.015 to 0.03), and the first molecular species containing Mn(II) to phosphoresce at room temperature (phiP = 0.015).