Gold halide

Abstract: Ab initio calculations were carried out on cis- and trans-(diphosphino)ethylene digold halide, Au2X2C2H2(PH2)2 (X = Cl, Br, I), the model compounds for dinuclear gold(I) bis(diphenylphosphino)ethylene complexes, Au2X2(dppee). The calculations reveal aurophilic interactions in the cis compound, thus stabilizing the cis complex with respect to the trans species. The aurophilic interaction, caused by an interplay between relativistic and electron correlation effects, increases with increasing softness of the ligand attached to gold. Excited-state calculations show ethylene π* contributions only for the cis compound, but not for the trans compound, thus explaining why the trans complex does not isomerize to the cis compound upon UV radiation at wavelengths greater than 220 nm. The singlet excitation can be best described as a charge-transfer transition from the halogen lone pair to the Au (5d6s6p) orbitals with strong intermixing from phosphorus (sp) orbitals. Because of symmetry reasons, these orbitals mix w...

Abstract: PURPOSE: Vinyl chloride is prepared in high selectivity and high yield by the reaction of acetylene with hydrogen chloride in the presence of a catalyt having high activity and long life comprising gold halide and platinium halide or palladium halide dissolved in a solvent. COPYRIGHT: (C)1977,JPO&Japio

Abstract: Perovskite solar cells have recently enabled power conversion efficiency comparable to established technologies such as silicon and cadmium telluride. Ongoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However, the presence of toxic heavy element lead (Pb) remains a major concern requiring further attention. Herein, we report three new Pb-free hybrid organic-inorganic perovskite-type halides based on gold (Au), (CH3 NH3 )AuBr4 ⋅H2 O (1), (CH3 NH3 )AuCl4 ⋅H2 O (2), and (CH3 NH3 )AuCl4 (3). Hydrated compounds 1 and 2 crystallize in a brand-new structure type featuring perovskite-derived 2D layers and 1D chains based on pseudo-octahedral AuX6 building blocks. In contrast, the novel crystal structure of the solvent-free compound 3 shows an exotic non-perovskite quasi-2D layered structure containing edge- and corner-shared AuCl6 octahedra. The use of Au metal instead of Pb results in unprecedented low band gaps below 2.5 eV for single-layered metal chlorides and bromides. Moreover, at room temperature the three compounds show a weak blue emission due to the electronic transition between Au-6s and Au-5d, in agreement with the density function theory (DFT) calculation results. These findings are discussed in the context of viability of Au-based halides as alternatives for Pb-based halides for optoelectronic applications.

Abstract: Crystal structures of a series of organic-inorganic hybrid gold iodide perovskites, formulated as A2 [AuI I2 ][AuIII I4 ] [A=methylammonium (MA) (1) and formamidinium (FA) (2)], A'2 [I3 ]1-x [AuI I2 ]x [AuIII I4 ] [A'=imidazolium (IMD) (3), guanidinium (GUA) (4), dimethylammonium (DMA) (5), pyridinium (PY) (6), and piperizinium (PIP) (7)], systematically changed depending on the cation size. In addition, triiodide (I3- ) ions were partly incorporated into the AuI2- sites of 3-7, whereas they were not incorporated into those of 1 and 2. Such a difference comes from the size of the organic cation. Optical absorption spectra showed characteristic intervalence charge-transfer bands from AuI to AuIII species, and the optical band gap increased as the size of the cation became larger.