Compositionally Dependent Nonlinear Optical Bandgap Behavior of Mixed Anodic Oxides in Niobium-Titanium System.

Optical bandgap mapping of Nb-Ti mixed oxides anodically grown on a thin film parent metallic combinatorial library was performed via variable angle spectroscopic ellipsometry (VASE). A wide Nb-Ti compositional spread ranging from Nb-90 at.% Ti to Nb-15 at.% Ti deposited by cosputtering was used for this purpose. The Nb-Ti library was stepwise anodized at potentials up to 10 V SHE, and the anodic oxides optical properties were mapped along the Nb-Ti library with 2 at.% resolution. The surface dissimilarities along the Nb-Ti compositional gradient were minimized by tuning the deposition parameters, thus allowing a description of the mixed Nb-Ti oxides based on a single Tauc-Lorentz oscillator for data fitting. Mapping of the Nb-Ti oxides optical bandgap along the entire compositional spread showed a clear deviation from the linear model based on mixing individual Nb and Ti electronegativities proportional to their atomic fractions. This is attributed to the strong amorphization and an in-depth compositional gradient of the mixed oxides. A systematic optical bandgap decrease toward values as low as 2.0 eV was identified at approximately 50 at.% Nb. Mixing of Nb2O5 and TiO2 with both amorphous and crystalline phases is concluded, whereas the possibility of complex NbaTibOy oxide formation during anodization is unlikely.

Boron-centered soft ligands based on tetrazole units and their complexes with sodium, potassium and bismuth ions.

The syntheses of Na(Ttt(Me)) (), K(Ttt(Me)) (), K(Btt(Me)) (), and Na(Btt(Ph)) () are reported, where (Ttt(Me))(-) and (Btt(R))(-) (R = Me, Ph) are tri- and di-substituted boron-centered soft ligands; they were produced by the reaction of NaBH4 and KBH4 with the corresponding tetrazole heterocycles: 1-methyl-5-thiotetrazole (L(1)H) and 1-phenyl-5-thiotetrazole (L(2)H). The syntheses of Na(Ttt(Me)) () and K(Ttt(Me)) () were carried out following Trofimenko's protocol. The anion (Ttt(Me))(-) is a typical Janus scorpionate ligand. Na(Ttt(Me)) () and Na(Btt(Ph)) () were reacted with Bi(CH3COO)3 to observe the coordination pattern of these ligands towards bismuth ions. These reactions afforded the complexes [Bi(Ttt(Me))2(CH3COO)] (), [Bi(L(2))2]2 (, ) and [Bi(L(2))3] (). The products were characterized by NMR spectroscopy, elemental analyses and mass spectrometry. Solid state structures were determined by X-ray diffraction of single crystals of , , , , , , and . M(Ttt(Me)) (M = Na (), K ()) and K(Btt(Me)) () exhibit sheet-like structures. The alkali metal complexes dissociate in solution as observed in (1)H, (13)C NMR and (1)H diffusion NMR experiments. Negative mode ESI-MS data also indicate the presence of monomers. Both the sodium salts of (Ttt(Me))(-) and (Btt(Ph))(-) as well as the Bi complexes and were investigated by absorption and emission spectroscopy.

Synthesis, structural and photo-physical studies of bismuth(III) complexes with Janus scorpionate and co-ligands.

Some novel complexes of bismuth(III) with the Janus scorpionate ligand [HB(mtda(Me))3](-) (mtda(Me) = 2-mercapto-5-methyl-1,3,4-thiadiazolyl) were synthesised. Na[HB(mtda(Me))3] (1) was reacted with BiX3 (X = Cl, I, NO3) in the molar ratio 2 : 1 to afford the bismuth complexes {HB(mtda(Me))3}2BiCl (3), Na[{HB(mtda(Me))3}2BiI2] (4) and [{HB(mtda(Me))3}2Bi(NO3)]n (5). Two mixed complexes {HB(mtda(Me))3}Bi(phen)Cl2 (6) and {HB(mtda(Me))3}Bi(bipy)Cl2 (7) were obtained using Janus scorpionate as the primary ligand in the presence of 1,10-phenanthroline and 2,2'-bipyridyl, respectively, as co-ligands in the 1 : 1 ratio. The obtained complexes were characterised by (1)H, (13)C and diffusion NMR (DOSY), elemental analyses and mass spectrometry. Structures of the compounds NBu4[HB(mtda(Me))3] (2), 3, 4, 5, 6 and 7 were determined by single crystal X-ray diffraction. The molecular dynamic process in complex 3 was also studied by variable temperature NMR measurements. All bismuth complexes, except for the polymeric 5, are monomeric. Complexes 6 and 7 exhibit (B)H···Bi distances of 2.76(3) and 2.71(2) Å length, respectively. Compounds 2, 6 and 7 were screened for their luminescence activity. At 77 K in ethanol solution, complexes 6 and 7 exhibit phosphorescence from ligand-to-ligand charge transfer (LLCT) and the ligand-centred (LC) excited state, respectively.