Homoleptic copper(I) arylthiolates as a new class of p-type charge carriers: Structures and charge mobility studies

Polymeric homoleptic copper(I) arylthiolates [Cu(p-SC₆H ₄-X)]_∞ (X = CH₃ (1), H (2), CH ₃O (3), tBu (4), CF₃ (5), NO₂ (6), and COOH (7)) have been prepared as insoluble crystalline solids in good yields (75-95%). Structure determinations by powder X-ray diffraction analysis have revealed that 1-3 and 6 form polymers of infinite chain length, with the copper atoms bridged by arylthiolate ligands. Weak intra-chain π⋯π stacking interactions are present in 1-3, as evidenced by the distances (3.210 Å in 1, 3.016 Å in 2, 3.401 Å in 3) between the mean planes of neighboring phenyl rings. In the structure of 6, the intra-chain π⋯π interactions (d = 3.711 Å) are insignificant and the chain polymers are associated through weak, non-covalent C-H⋯O hydrogen-bonding interactions (d=2.586 Å). Samples of 1-7 in their polycrystalline forms proved to be thermally stable at 200-300°C; their respective decomposition temperatures are around 100°C higher than that of the aliphatic analogue [Cu(SCH₃)_∞. Data from in situ variable-temperature X-ray diffractometry measurements indicated that the structures of both 1 and 7 are thermally more robust than that of [Cu(SCH ₃)]_∞. TEM analysis revealed that the solid samples of 1-5 and [Cu(SCH₃)]_∞. contained homogeneously dispersed crystalline nanorods with widths of 20-250 nm, whereas smaller plate-like nanocrystals were found for 6 and 7. SAED data showed that the chain polymers of 1-3 and [Cu(SCH₃)]_∞ similarly extend along the long axes of their nanorods. The nanorods of 1-5 and [Cu(SCH ₃)_∞ have been found to exhibit p-type field-effect transistor behavior, with charge mobility (μ) values of 10 ^-2-10^-5Cm²V^-1S^-1. Polycrystalline solid samples of 6 and 7 each showed a low charge mobility (<10^-6 Cm² V^-1 S^-1). The charge mobility values of field-effect transistors made from crystalline nanorods of 1-3 and [Cu(SCH₃)]_∞ could be correlated with their unique chain-like copper-sulfur networks, with the para-substituent of the arylthiolate ligand influencing the charge-transport properties. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.