Tetrazine-Bridged Phthalocyaninato Metal Complexes: A new Class Of Intrinsic Semiconductors

Abstract

Stacked transition metal macrocycles [MacM(L)]_n with M e.g. Fe, Ru, Os, Co, Rh and Mac = phthalocyanine (Pc) 1,2- or 2,3-naphthalocyanine (1,2-, 2,3-Nc) have been synthesized by us. The bridging ligands (L) are e.g. pyrazine (pyz) or s-tetrazine (tz). In general, these complexes [MacM(L)]_n are insoluble in organic solvents, however, soluble oligomers [R₄PcM(L)]_n can be prepared using metallomacrocycles R_nPcM, R = t-bu, et, OR, M = Fe, Ru, which are substituted in the peripheric positions.

A systematic investigation of the influence of the bridging ligands on the semiconducting properties in [MacM(L)]_n reveal, that changing L, e.g from dabco over pyz to tz leads to a steady increase of the semiconducting properties without external oxidative doping. Powder conductivities in the order of 0.1 S/cm can be reached by using s-tetrazine, 3, 6-dimethyl-s-tetrazine (me₂tz) and others, e.g. fumarodinitrile as the bridging ligands. The intrinsic conductivities are a result of the low oxidation potential of tz and me₂tz and due to the low lying LUMO in the corresponding bridged systems [MacM(tz)]_n.

The electrical and physical properties, especially the UV and the Möβbauer spectra for the tetrazine-bridged macrocyclic metal complexes are discussed in respect to intrinsic semiconducting properties of these compounds.