Homoleptic platinum(II) and palladium(II) organothiolates and phenylselenolates: solvothermal synthesis, structural determination, optical properties, and single-source precursors for PdSe and PdS nanocrystals.

Homoleptic d(8)-metal organothiolates and phenylselenolates M(EC(6)H(5))(2) (E=S, M=Pt 1, M=Pd 2, M=Ni 5; E=Se, M=Pt 3, M=Pd 4) were prepared as crystalline solids under solvothermal conditions. Their structures were solved using powder X-ray diffraction data. In each case, the EC(6)H(5) (E=S, Se) ligand binds to two metal ions (M=Pt, Pd, and Ni) to form chain-like structures with planar (in 1) or zig-zag (in 2-5) conformations. The M(SR)(2) complexes (M=Pt, R=4-tert-butylphenyl 6; R=2-naphthyl 8; R=4-nitrophenyl 10 and M=Pd, R=4-tert-butylphenyl 7; R=2-naphthyl 9; R=4-nitrophenyl 11) were prepared under similar solvothermal conditions. Based on the XPS binding energies and elemental analyses, complexes 6-11 have the same M(SR)(2) formulation as 1 and 2. The cyclic complex [Pd(6)(SCH(3))(12)] 12 was prepared as a crystalline solid by solvothermal annealing treatment of the amorphous precipitate. A chain-like polymer structure is proposed for both Pd(SC(12)H(25))(2) 13 and Pd(SC(16)H(33))(2) 14; these polymeric chains self-assemble to give layer-like structures. Solid-state diffuse reflectance spectra reveal that the optical band gap E(g) (eV) of complexes 1, 6, 8, 10 and of 2, 7, 9, 11 are in the range of 2.10-3.00 eV and 2.10-2.63 eV, respectively, and 5 has the lowest E(g) value (1.72 eV). Heating solid samples of 4 and 13 under solvothermal conditions afforded phase-pure Pd(17)Se(15) and PdS nanocrystals, respectively. Field-effect transistors fabricated with a drop-cast thin film made from Pd(17)Se(15) nanocrystals prior treated with an ethanolic solution of 1-hexadecanethiol displayed ambipolar charge transporting properties with hole and electron mobility being 7x10(-2) cm(2) V(-1) s(-1) and 6x10(-2) cm(2) V(-1) s(-1), respectively.