title: Synthesis, structural characterization, and theoretical studies of gold(I) and gold(I)-gold(III) thiolate complexes: quenching of gold(I) thiolate luminescence.
abstract: The gold(I) thiolate complexes [Au(2-SC6H4NH2)(PPh3)] (1), [PPN][Au(2-SC6H4NH2)2] (2) (PPN = PPh3=N=PPh3), and [{Au(2-SC6H4NH2)}2(mu-dppm)] (3) (dppm = PPh2CH2PPh2) have been prepared by reaction of acetylacetonato gold(I) precursors with 2-aminobenzenethiol in the appropriate molar ratio. All products are intensely photoluminescent at 77 K. The molecular structure of the dinuclear derivative 3 displays a gold-gold intramolecular contact of 3.1346(4) A. Further reaction with the organometallic gold(III) complex [Au(C6F5)3(tht)] affords dinuclear or tetranuclear mixed gold(I)-gold(III) derivatives with a thiolate bridge, namely, [(AuPPh3){Au(C6F5)3}(mu2-2-SC6H4NH2)] (4) and [(C6F5)3Au(mu2-2-SC6H4NH2)(AudppmAu)(mu2-2-SC(6)H4NH2)Au(C6F5)3] (5). X-ray diffraction studies of the latter show a shortening of the intramolecular gold(I)-gold(I) contact [2.9353(7) or 2.9332(7) A for a second independent molecule], and short gold(I)-gold(III) distances of 3.2812(7) and 3.3822(7) A [or 3.2923(7) and 3.4052(7) A] are also displayed. Despite the gold-gold interactions, the mixed derivatives are nonemissive compounds. Therefore, the complexes were studied by DFT methods. The HOMOs and LUMOs for gold(I) derivatives 1 and 3 are mainly centered on the thiolate and phosphine (or the second thiolate for complex 2), respectively, with some gold contributions, whereas the LUMO for derivative 4 is more centered on the gold(III) fragment. TD-DFT results show a good agreement with the experimental UV-vis absorption and excitation spectra. The excitations can be assigned as a S --> Au-P charge transfer with some mixture of LLCT for derivative 1, an LLCT mixed with ILCT for derivative 2, and a S --> Au...Au-P charge transfer with LLCT and MC for derivative 3. An LMCT (thiolate --> Au(III) mixed with thiolate --> Au-P) excitation was found for derivative 4. The differing nature of the excited states [participation of the gold(III) fragment and the small contribution of sulfur] is proposed to be responsible for quenching the luminescence.
authors.affiliation: Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid, Spain. bardaji@qi.uva.es
authors.forename: Manuel
authors.initials: M
authors.lastname: Bardají
authors.forename: Maria José
authors.initials: MJ
authors.lastname: Calhorda
authors.forename: Paulo J
authors.initials: PJ
authors.lastname: Costa
authors.forename: Peter G
authors.initials: PG
authors.lastname: Jones
authors.forename: Antonio
authors.initials: A
authors.lastname: Laguna
authors.forename: M
authors.initials: M
authors.lastname: Reyes Pérez
authors.forename: M D
authors.initials: MD
authors.lastname: Villacampa
mesh_terms: D018360:Crystallography, X-Ray; D006046:Gold / Q000737:chemistry*; D008163:Luminescent Measurements / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D050607:Organogold Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D050607:Organogold Compounds; D013438:Sulfhydryl Compounds; D006046:Gold