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The synthesis and characterization of a series of digermynes and distannynes stabilized by terphenyl ligands are described. The ligands are based on the Ar 0 (Ar 0 ¼ C 6 H 3 -2,6(C 6 H 3 -2,6-i Pr 2 ) 2 ) or Ar* (Ar* ¼ C 6 H 3 -2,6(C 6 H 2 -2,4,6-i Pr 3 ) 2 ) platforms which were modified at the meta or para positions of their central aryl rings to yield 4-X-Ar 0 (4-X-Ar 0 ¼ 4-X-C 6 H 2 -2,6(C 6 H 3 -2,6-i Pr 2 ) 2 , X ¼ H, F, Cl, OMe, t Bu, SiMe 3 , GeMe 3 ) and 3,5-i Pr 2 -Ar 0 or Ar* and 3,5-i Pr 2 -Ar*. The compounds were synthesized by reduction of the terphenyl germanium(II) or tin(II) halide precursors with a variety of reducing agents. The precursors were obtained by the reaction of one equivalent of the lithium terphenyl with GeCl 2 dioxane or SnCl 2 . For germanium, their X-ray crystal structures showed them to be either Ge-Ge bonded dimers with trans-pyramidal geometries or V-shaped monomers. In contrast, the terphenyl tin halides had no tin-tin bonding but existed either as halide bridged dimers or V-shaped monomers. Reduction with a variety of reducing agents afforded the digermynes ArGeGeAr (Ar ¼ 4-Cl-Ar 0 , 4-SiMe 3 -Ar 0 or 3,5-i Pr 2 -Ar*) or the distannynes ArSnSnAr (Ar ¼ 4-F-Ar 0 , 4-Cl-Ar 0 , 4-MeO-Ar 0 , 4-t Bu-Ar 0 , 4-SiMe 3 -Ar 0 , 4-GeMe 3 -Ar 0 , 3,5-i Pr 2 -Ar 0 , 3,5-i Pr 2 -Ar*), which were characterized structurally and spectroscopically. The digermynes display planar trans-bent core geometries with Ge-Ge distances near 2.26A and bending angles near 128 consistent with Ge-Ge multiple bonding. In contrast, the distannynes had either multiple bonded geometries with Sn-Sn distances that averaged 2.65A and an average bending angle near 123.8 , or single bonded geometries with a Sn-Sn bond length near 3.06 A and a bending angle near 98 . The 3,5-i Pr 2 -Ar*SnSnAr*-3,5-i Pr 2 species had an intermediate structure with a longer multiple bond near 2.73A and a variable torsion angle (14-28 ) between the tin coordination planes. M€ ossbauer data for the multiple and single bonded species displayed similar isomer shifts but had different quadrupole splittings.Scheme 1 Single bonded or multiple bonded trans-bent geometry of RMMR (M ¼ Si, Ge, Sn, Pb; R ¼ terphenyl or silyl substituents)

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New Pt(II) and Pd(II) complexes with donor-acceptor Schiff bases are conveniently prepared in only two steps. The complexes efficiently absorb in the red part of the spectrum (ε > 10(5) M(-1) cm(-1)) and show moderate to strong room-temperature phosphorescence in the near-infrared (NIR) region. Particularly, Pt(II) complexes possess phosphorescence quantum yields (Φ) of ~10%, but the emission of the respective Pd(II) complexes is less efficient (Φ ≈ 1%-2%). The complexes exhibit solvatochromic behavior, in which the absorption and emission spectra shift bathochromically in polar solvents. The Pt(II) complexes are embedded in polystyrene to produce oxygen-sensing materials. The Pd(II) and Pt(II) complexes are demonstrated to be efficient sensitizers in triplet-triplet annihilation-based upconversion systems.

Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition-metal chemistry. However, the stabilization of main-group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6-[ArNH-CH2 ]2 (NC5 H3 ) (Ar=C6 H3 -2,6-iPr2 )) with Sn[N(SiMe3 )2 ]2 produces the DIMPYSn complex (DIMPY=(2,6-[ArNCH]2 (NC5 H3 )) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low-valent Sn(II) complexes, including a [DIMPYSn(II) Cl](+) [SnCl3 ](-) ion pair, a bisstannylene DAMPY{Sn(II) [N(SiMe3 )2 ]2 }2 , and the enamine complex MeDIMPYSn(II) , were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and (119) Sn Mössbauer spectroscopy.

Acylgermanes have been subject of great interest recently because of their low toxicity and the applicability as sources for germanium-centered radicals for visible-light induced free radical polymerization processes. We report on a novel and versatile method for the synthesis of tetraacylgermanes allowing the preparation of various tetra-substituted acylgermanes 1a−m. The formation of these derivatives was confirmed by NMR spectroscopy, mass spectrometry, and X-ray crystallography. UV−vis absorption spectra of the prepared compounds reveal absorption in the visible region. This transition was assigned by TD-DFT calculations. It enabled a general screening of the influence of different substitution patterns on the absorption properties. The radical formation upon irradiation was confirmed by TR-EPR spectroscopy.

A series of dinuclear metal(ii)-acetato complexes: [Ni2(μ-L(Cl)O)(μ2-OAc)2](PF6)·3H2O (1), [Ni2(μ-L(Cl)O)(μ2-OAc)2](ClO4)·CH3COCH3 (2), [Cu2(μ-L(Cl)O)(μ2-OAc)(ClO4)](ClO4) (3), [Cu2(μ-L(Cl)O)(OAc)2](PF6)·H2O (4), [Zn2(μ-L(Cl)O)(μ2-OAc)2](PF6) (5) and [Mn2(L(Cl)-O)(μ2-OAc)2](ClO4)·H2O (6), where L(Cl)O(-) = 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenolate, were synthesized. The complexes were structurally characterized by spectroscopic techniques and single crystal X-ray crystallography. Six-coordinate geometries with doubly bridged acetato ligands were found in Ni(ii), Zn(ii) and Mn(ii) complexes 1, 2, 5 and 6, whereas with Cu(ii) complexes a five-coordinate species was obtained with 4, and mixed five- and six-coordinate geometries with a doubly bridged dimetal core were observed in 3. The magnetic properties of complexes 1-4 and 6 were studied at variable temperatures and revealed weak to very weak antiferromagnetic interactions in 1, 2, 4 and 6 (J = -0.55 to -9.4 cm(-1)) and ferromagnetic coupling in 3 (J = 15.4 cm(-1)). These results are consistent with DFT calculations performed at the B3LYP/def2-TZVP(-f) level of theory. Under physiological conditions, the interaction of the dinculear complexes 1-5 with supercoiled plasmid ds-DNA did not show any pronounced nuclease activity, but Ni(ii) complexes 1 and 2 revealed a strong ability to unwind the supercoiled conformation of ds-DNA. The mechanistic studies performed on the interaction of the Ni(ii) complexes with DNA demonstrated the important impact of the nickel(ii) ion in the unwinding process. In combination with the DNA study, the phosphatase activity of complexes 1, 3, and 5 was examined by the phosphodiester hydrolysis of bis(2,4-dinitrophenol)phosphate (BDNPP) in the pH range of 5.5-10.5 at 25 °C. The Michaelis-Menten kinetics performed at pH 7 and 10.7 showed that catalytic efficiencies kcat/KM (kcat = catalytic rate constant, KM = substrate binding constant) decrease in the order: Ni(ii), 1 > Zn(ii), 5 > Cu(ii), 3. A similar trend was also observed with the turnover numbers at pH = 7. The results are discussed in relation to the coordination geometry and nature of the metal center as well as the steric environment imposed by the compartmental phenoxido ligand.

Ten microcosms of 0.088 m3 water volume (0.3 m i.d. and 1.20 m height) were designed for neutralization studies representing hypolimnic ecosystem models for acid mine pit lakes. Sediment and water were collected from an acid lignite mine pit lake (Brandenburg, Germany) and filled into the microcosms. To determine the efficacy of controlled in situ organic carbon amendments as a possible neutralization method, sediment and water were treated with ethanol and Carbokalk with and without wheat straw. The water chemistry was monitored for 1 yr. At start-up and end of the experiments, the sedimentwas characterized. Iron and sulfate were removed with varying intensity from the water phase as a result of microbial iron and sulfate reduction together with a subsequent precipitation of unsoluble sulfide minerals to the sediment. The pH rose, and alkalinity generation and bacterial growth were observed. Neutralization rates were calculated using equivalents of accumulated total reduced inorganic sulfur together with the nonsulfidic reactive ferrous iron in the sediment. In the treated microcosms, the neutralization rates were between 6 and 15 equiv m(-2) a(-1). Carbokalk was most effective in stimulating growth of sulfate-reducing bacteria and probably also served as inoculum. With Carbokalk together with wheat straw, the pH increased from 2.6 to around 6.5 within the whole microcosm. The critical revision of the results indicates that the application of Carbokalk (approximately 3.9 kg m(-2)) together with the application of wheat straw (approximately 9.3 kg m(-2)) is most suitable for further experiments in outdoor enclosures (mesocosms). For that case, the prediction of the water quality for a lake water column after multiple lake turnover events is presented based on batch reaction simulation using the geochemical model PHREEQC.