Heterobimetallic Eu(iii)/Pt(ii) single-chain nanoparticles: a path to enlighten catalytic reactions

We introduce the formation and characterization of heterometallic single-chain nanoparticles entailing both catalytic and luminescent properties. A terpolymer containing two divergent ligand moieties, phosphines and phosphine oxides, is synthesized and intramolecularly folded into nanoparticles via a selective metal complexation of Pt(ii) and Eu(iii). The formation of heterometallic Eu(iii)/Pt(ii) nanoparticles is evidenced by size exclusion chromatography, multinuclear NMR (¹H, ³¹P{¹H}, ¹⁹F, ¹⁹⁵Pt) as well as diffusion-ordered NMR and IR spectroscopy. Critically, we demonstrate the activity of the SCNPs as a homogeneous and luminescent catalytic system in the amination reaction of allyl alcohol.

A bifunctional terpolymer containing two orthogonal ligand moieties was synthesized, giving way to the facile formation of heterometallic Eu(iii)/Pt(ii) single-chain nanoparticles, which display both catalytic and luminescent properties.     

Pencils of quadrics and Gromov–Witten–Welschinger invariants of $$\mathbb {C}P^3$$

We establish a formula for the Gromov–Witten–Welschinger invariants of \(\mathbb {C}P^3\) with mixed real and conjugate point constraints. The method is based on a suggestion by J. Kollár that, considering pencils of quadrics, some real and complex enumerative invariants of \(\mathbb {C}P^3\) could be computed in terms of enumerative invariants of \(\mathbb {C}P^1\times \mathbb {C}P^1\) and of elliptic curves.     

Adlayer geometry and structural effects in the CO/Ni(110) system

The formation of ordered adlayers of CO on Ni(110) and the correlation between structure and adsorption energy, sticking coefficient and adsorbate induced change of work function was investigated. LEED, TDS and work function measurements served to monitor adsorption and desorption. Models are presented for the structures formed at intermediate coverages (0.5 < θ < 0.85) - identified as a c(8×2) and a c(4×2) structure - and the (2×1) formed close to saturation: The CO molecules are adsorbed on the Ni rows in the [110] direction, their separation is dominated by short range COCO repulsions rather than by the NiCO interaction. The repulsions in the [001] direction lead only to the formation of structures with staggered configurations. In the first two structures formed only below room temperature the CO stands upright and the repulsion is weak, leading to considerable disorder (antiphase domains) and a streaky LEED pattern. In the (2×1) structure which does not thermally disorder in the experimental temperature range, the high density of the adlayer results in a lateral tilt of the CO, and subsequently also to good correlation in the [001] direction. The repulsions become evident in TDS as a low temperature shoulder at the main peak (c(8×2) and c(4×2) structure) or as a distinct extra peak at 330 K ((2×1) structure). The adsorption kinetics can be modelled by a first order precursor model (K = 0.95). The work function almost linearly increases with coverage to 1500 mV at saturation. Both quantities are not noticeably affected by the degree of order in the adlayer.     

Theoretical investigation of the bonding properties of N-heterocyclic carbenes coordinated to electron-rich d metal centers

Density functional theory (DFT) at the generalized gradient approximation (GGA) level has been applied for the analysis of the bond between group 10 metals and N-heterocyclic carbene (NHC) in complexes [MX₃(NHC)]⁻ (M = Ni, Pd, Pt, X = H, Cl, I). For comparative purposes, similar calculations have been performed for analogous pyridine complexes [MX₃(py)]⁻ (py = pyridine). Full geometry optimizations have been performed for all complexes. The role of the M-L π interaction was investigated by the aid of respectively, energy decomposition analysis, Hirshfeld atomic charge variation, molecular orbital considerations and bond order decomposition analysis. The π-bonding contribution increases in the order I < Cl < H, and Pt < Pd < Ni. Most significantly, the absolute π-acceptor ability of the NHC in these complexes is larger than that of pyridine. However, due to the dominant σ donor interactions, the relative contribution, that is the π/σ ratio, is predicted to be smaller.     

Synthesis and structural characterization of novel neutral hexacoordinate silicon(IV) complexes with SiO2N4 skeletons containing cyanato-N or thiocyanato-N ligands

A series of novel hexacoordinate silicon(IV) complexes with an SiO2N4 skeleton (compounds (OC-6-12)-3, (OC-6-12)-4, (OC-6-12)-5, (OC-6-12)-6, and (OC-6-2'2)-7) were synthesized, starting from Si(NCO)4 or Si(NCS)4. These compounds contain (i) two bidentate O,N-chelate ligands (or one tetradentate O,N,N,O-chelate ligand) derived from 4-aminopent-3-en-2-ones of the formula type Me-C(NRH)=CH-C(O)-Me (R = organyl) and (ii) two monodentate cyanato-N or thiocyanato-N ligands. Formally, the bidentate singly negatively charged O,N-chelate ligands (tetradentate 2-fold negatively charged O,N,N,O-chelate ligand) behave as ligands of the imino-enolato type. In addition, the adduct trans-8 was synthesized by reaction of Si(NCS)4 with 2 molar equiv of Me-C(Ni-PrH)=CH-C(O)-Me. This hexacoordinate silicon(IV) complex contains (i) four monodentate thiocyanato-N ligands and (ii) two neutral monodentate ligands of the iminio-enolato type. All compounds synthesized were structurally characterized by single-crystal X-ray diffraction and solid-state and solution NMR spectroscopy. To get more information about the stereochemistry of these compounds, the experimental investigations were complemented by computational studies.     

The hexacoordinate silicate dianions mer-tris[glycolato(2-)-O(1),O(2)]silicate and fac-tris[benzilato(2-)-O(1),O(2)]silicate: syntheses and structural characterization

Treatment of tetramethoxysilane with glycolic acid and morpholine (molar ratio 1:3:2) in methanol, followed by crystallization from methanol/tetrahydrofuran, yielded morpholinium mer-tris[glycolato(2-)-O(1),O(2)]silicate (mer-7). Treatment of benzilic acid with sodium hydride, followed by addition of tetrachlorosilane and triethylamine (molar ratio 3:4:1:2), afforded, after crystallization from 1,4-dioxane/acetonitrile/diethyl ether/n-pentane, triethylammonium fac-tris[benzilato(2-)-O(1),O(2)]silicate-hemi-1,4-dioxane (fac-8.(1)/(2)C(4)H(8)O(2)). Single-crystal X-ray diffraction studies showed that the Si-coordination polyhedra of the hexacoordinate silicon(IV) complexes mer-7 and fac-8.(1)/(2)C(4)H(8)O(2) are distorted octahedra. Both compounds were additionally characterized by solid-state VACP/MAS NMR studies ((13)C, (29)Si), and fac-8.(1)/(2)C(4)H(8)O(2) was studied in solution by (1)H, (13)C, and (29)Si NMR experiments. The structural investigations were complemented by computational studies (MP2 studies, TZP level) of the dianions of fac-7 and mer-7.     

Hydrothermal synthesis, structural characterisation and magnetic behaviour of hybrid complexes of N-(phosphonomethyl)iminodiacetate

Two new compounds containing multidentate chelating organic residues of N-(phophonomethyl)iminodiacetic acid (H₄pmida), [M(pyr)(H₂O)₄][M₂(Hpmida)₂(pyr)(H₂O)₂]·2(H₂O) (where pyr=pyrazine and M=Co²⁺ or Ni²⁺ for I and II, respectively) have been synthesised and structurally characterised by single-crystal and powder X-ray diffraction, elemental analysis, infrared spectroscopy, thermal analysis and solid-state ³¹P MAS NMR. The compounds contain discrete binuclear anionic [M₂(Hpmida)₂(pyr)(H₂O)₂]²⁻ units in which one pyrazine ligand bridges two M²⁺ cations which are completely trapped inside three five-membered chelate rings formed by the Hpmida³⁻ ligands. These moieties close pack in the ac plane via a series of strong and highly directional O–HO hydrogen bonds leading to the formation of anionic layers. One-dimensional cationic coordination polymers are placed in-between and strongly hydrogen-bonded to these layers. The magnetic properties of these two materials are also reported.     

The effect of formaldehyde on the growth ofCandida diddensii 74-10 andCandida tropicalis R-70

The effects of formaldehyde on the growth of two strains of fodder yeastsCandida diddensii 74-10 andCandida tropicalis R-70 were investigated using the method of continuous cultivation under conditions of carbon limitation and at dilution rates of 0.1/h and 0.25/h. The results indicate that formaldehyde induces a decrease in the yield of biomass, but stimulates the synthesis of protein and RNA. The authors studied the activities of the following enzymes: NADPH-linked glutamate dehydrogenase, NADH-linked glutamate dehydrogenase, alanine dehydrogenase, glutamine synthetase, and glutamate synthase, which are utilized in nitrogen metabolism. The data obtained showed an increase in the activity of the glutamate dehydrogenase pathway of ammonium assimilation. It was also established that formaldehyde caused considerable changes in the micro-organisms at the higher dilution rate.