Structural, Magnetic, and Charge Transport Properties of Bis[(5,10,15,20-tetramethylporphyrinato)palladium(II)] Perrhenate, [Pd(tmp)]₂[ReO₄]

Electrochemical oxidation of (5,10,15,20-tetramethylporphyrinato)palladium(II), Pd(tmp), in the presence of the perrhenate ion affords the new molecular conductor [Pd(tmp)]₂[ReO₄]. The compound is composed of partially oxidized (+1/2) Pd(tmp) cations stacked metal-over-metal (Pd-Pd_av = 3.373 (4) Å) and surrounded by chains of ReO₄ anions. Single-crystal room-temperature conductivity along the needle (crystallographic c) axis averages 30 Ω^-1 cm^-1 and may be fit to an expression that describes a semiconductor with temperature-dependent carrier mobility, σ = σ₀T^-a exp(-ΔE/k_aT) (ΔE = 0.10 (2) eV; α = 2.2 (5)). ESR measurements confirm the tmp ligand as the site of oxidation. The compound crystallizes in space group [formula omited] of the tetragonal system with two formula units in a cell of dimensions a = 16.778 (6) Å and c = 6.723 (3) Å (V = 1892 ų) at 110 K. Full-matrix least-squares refinement of 67 variables gives a final value of 0.187 for the R index on F² for 2404 unique observations and a value of 0.090 for the R index on F for the 1179 observations having F_o² > 3σ(F_o²).