Homoleptic Copper(I) Arylthiolates as a New Class of p‐Type Charge Carriers: Structures and Charge Mobility Studies

Abstract

Polymeric homoleptic copper(I) arylthiolates [Cu(p-SC₆H₄-X)]_∞ (X=CH₃ (1), H (2), CH₃O (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(SCH₃)]_∞. 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(SCH₃)]_∞ have been found to exhibit p-type field-effect transistor behavior, with charge mobility (μ) values of 10⁻²–10⁻⁵ cm² V⁻¹ s⁻¹. Polycrystalline solid samples of 6 and 7 each showed a low charge mobility (−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.