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The crystal structures of two thiolato complexes of the type [Au(SR)(PPh3)] with SR=2-mercaptobenzoxazol-2-yl (MBOx) and SR=2-mercaptoanthraceneoxazol-2-yl (MAOx) were determined from X-ray powder diffraction data. Both complexes include η1-S-monodentate ligands with the nitrogen atom preferably oriented towards the gold atom. [Au(MBOx)(PPh3)] ( 1a) represents a new triclinic polymorph of [Au(MBOx)(PPh3)], whereas [Au(MAOx)(PPh3)] ( 2) is hitherto unknown and yields information about the molecular structure of the ligand MAOx as well as the coordination geometry in 2. The structure determinations were validated by low temperature XRPD measurements. DTA-TG and in-situ XRPD measurements revealed a monotropic phase transition of 1a at 443 K to a monoclinic phase. Additionally, solid-state DFT-D calculations using CASTEP were carried out to evaluate the experimental results. [ABSTRACT FROM AUTHOR]

A series of three homologous arene[2,3-d]-oxazole-2-thiols (benzoxazole-2-thiol (BOxSH), naphthaleneoxazole-2-thiol (NOxSH), and anthraceneoxazole-2-thiol (AOxSH)) were deposited onto Au(111) to obtain surfaces suitable as injection layers for organic electronics. The guiding idea was that the increasingly extended conjugated system would lower the band gap of the films while the introduction of the annulated heteroaromatic ring would provide the opportunity for pseudosymmetric attachment of the sulfur anchor, what should lower the conformational freedom of the system. In fact, the annulation of the oxazole ring lowers the optical band gaps of the parent compounds to 3.1-4.0 eV, depending on the number of benzene rings. To characterize the respective monolayers, a variety of spectroscopic techniques such as ellipsometry, infrared reflection-absorption spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy have been utilized. The monolayers of BOxS exhibit a lower film quality than those of NOxS and AOxS, with enhanced molecular density and more upright molecular orientation with increasing molecular length. Infrared spectroscopy suggests that the nitrogen atoms of the oxazole rings are located more closely to the Au(111) surface than the oxygen atoms, although no hints for an electronic interaction between the N atoms and the gold surface could be found. This preferred orientation could be tentatively traced to packing effects, solving a conundrum of the literature. [ABSTRACT FROM AUTHOR]