No abstract

Bimetallic nitrogen (N2) splitting to form metal nitrides is an attractive method for N2 fixation. Although a growing number of pincer-supported systems can bind and split N2, the precise relationship between the ligand properties and N2 binding/splitting remains elusive. Here we report the first example of an N2-bridged rhenium­(III) complex, [(trans-P2 tBuPyrr)­ReCl2]2(μ-η1:η1-N2) (P2 tBuPyrr = [2,5-(CH2PtBu2)2C4H2N]−). In this case, N2 binding occurs at a higher oxidation level than that in other reported pincer analogues. Analysis of the electronic structure through computational studies shows that the weakly π-donor pincer ligand stabilizes an open-shell electronic configuration that leads to enhanced binding of N2 in the bridged complex. Utilizing SQUID magnetometry, we demonstrate a singlet ground state for this Re–N–N–Re complex, and we offer tentative explanations for antiferromagnetic coupling of the two local S = 1 sites. Reduction and subsequent heating of the rhenium­(III)–dinitrogen complex leads to chloride loss and cleavage of the N–N bond with isolation of the terminal rhenium­(V) nitride complex (P2 tBuPyrr)­ReNCl.

Rhenium–PNP complexes split N2 to nitrides, but the nitrides do not give ammonia. Here, the thermodynamics of the hypothetical N–H bond forming steps are evaluated through the reverse reaction, showing that the first H addition is the bottleneck.

Four groups of rare-earth complexes, comprising 11 new compounds, with fluorinated O-donor ligands ([K­(THF)6]­[Ln­(OC4F9)4(THF)2] (1-Ln; Ln = Ce, Nd), [K]­(THF) x [Ln­(OC4F9)4(THF) y ] (2-Ln; Ln = Eu, Gd, Dy), [K­(THF)2]­[Ln­(pinF)2(THF)3] (3-Ln; Ln = Ce, Nd), and [K­(THF)2]­[Ln­(pinF)2(THF)2] (4-Ln; Ln = Eu, Gd, Dy, Y) have been synthesized and characterized. Single-crystal X-ray diffraction data were collected for all compounds except 2-Ln. Species 1-Ln, 3-Ln, and 4-Ln are uncommon examples of six-coordinate (Eu, Gd, Dy, and Y) and seven-coordinate (Ce and Nd) LnIII centers in all-O-donor environments. Species 1-Ln, 2-Ln, 3-Ln, and 4-Ln are all luminescent (except where Ln = Gd and Y), with the solid-state emission of 1-Ce being exceptionally blue-shifted for a Ce complex. The emission spectra of the six Nd, Eu, and Dy complexes do not show large differences based on the ligand and are generally consistent with the well-known free-ion spectra. Time-dependent density functional theory results show that 1-Ce and 3-Ce undergo allowed 5f → 4d excitations, consistent with luminescence lifetime measurements in the nanosecond range. Eu-containing 2-Eu and 4-Eu, however, were found to have luminescence lifetimes in the millisecond range, indicating phosphorescence rather than fluorescence. The performance of a pair of multireference models for prediction of the Ln = Nd, Eu, and Dy absorption spectra was assessed. It was found that spectroscopy-oriented configuration interaction as applied to a simplified model in which the free-ion lanthanide was embedded in ligand-centered Löwdin point charges performed as well (Nd) or better (Eu and Dy) than canonical NEVPT2 calculations, when the ligand orbitals were included in the treatment.

In der Industrie werden hochflexible und kostengünstige Produktionstechnologien benötigt, die den Funktionalitätsgrad von Komponenten erhöhen. Digitale Druckverfahren erlauben das hierfür notwendige direkte Applizieren von Sensoren, Aktoren und Leiterbahnen auf eine Vielzahl von Komponenten. Daraus resultiert eine stückzahlunabhängige Produktivität, die zu einer vereinfachten Logistik, Gewichtsreduzierung und Einsparung von Montageschritten führt.   Industry requires highly flexible and cost-effective production technologies to simultaneously increase the degree of functionality of components. Digital printing processes enable the necessary direct application of sensors, actuators and conductors to a large number of components. This results in productivity independent of the number of units, which leads to simplified logistics, weight reduction and savings in assembly steps.