Structural, Magnetic, and Charge-Transport Properties of a New One-Dimensional Molecular Conductor, Ni(tprpc)I_1.67 (tprpc = 2,7,12,17-Tetrapropylporphycenato)

Chemical oxidation of (2,7,12,17-tetrapropylporphycenato)nickel(II), Ni(tprpc), with iodine affords the new onedimensional molecular conductor Ni(tprpc)I_1.67· The compound is composed of partially oxidized (+1/3) Ni(tprpc) cations packed in a slip-stack manner along the b axis. The stacks are surrounded by disordered chains of iodine, identified as I₅^- by Raman spectroscopy. The interplanar distance between Ni(tprpc) macrocycles is 3.306(10) Å, but the Ni-Ni distance is the b axis repeat distance, 4.982(1) Å. The conductivity measured along the needle (crystallographic b) axis of a single crystal is 2.5 × 10^-2Ω^-1 cm^-1 at room temperature and may be fit to the expression σ= σ₀ exp(-ΔE/k_BT) (σ₀ ≈ 1, ΔE= 0.15(2) eV). EPR measurements confirm that the tprpc ligand is oxidized. The compound crystallizes in space group C⁶_2h-C2/c of the monoclinic system with four formula units (C₃₂H₃₆- I_1.67N₄Ni) in a cell of a = 22.548(5) Å, b = 4.982(1) Å, c = 27.156(5) Å, β = 109.51(3)° (K= 2875.4(10) ų) at 108 K. The structure has been refined on F²(2923 unique reflections) to R_w(F₀²) = 0.209. The conventional agreement index R(F) is 0.099 for the 1240 reflections having F₀² > 2σ(F₀²). The relatively high R index results from our inability to model adequately the disordered iodine chains.