Oligoarenes are regarded as subunits of p-extended carbon nanoforms,s uch as graphene and nanotubes,w ith exceptional technological importance.F used arenes can thus providef undamental insight into the nature of the electronic properties of fused polyaromatic rings and pave the way for the design of extended graphene-like materials.However,large pextended arenes often show lowstability.Herein we report the straightforwardp reparation of linearly fused diphosphahexaarenes containing two six-membered phosphorus heterocycles. They are highly stable towards air,water,and light over months in both solution and the solid state.S ingle-crystal X-ray crystallography confirmed the molecular structure of all derivatives.I nvestigations of their optoelectronic properties revealed that the diphosphahexaarenes exhibit ambipolar redox behavior and high fluorescence quantum yields.Embedding six-membered phosphorus rings into large acenes thus opens up new opportunities for the investigation of polyaromatic systems. Angewandte ChemieCommunications
Oligoarenes are regarded as subunits of π‐extended carbon nanoforms, such as graphene and nanotubes, with exceptional technological importance. Fused arenes can thus provide fundamental insight into the nature of the electronic properties of fused polyaromatic rings and pave the way for the design of extended graphene‐like materials. However, large π‐extended arenes often show low stability. Herein we report the straightforward preparation of linearly fused diphosphahexaarenes containing two six‐membered phosphorus heterocycles. They are highly stable towards air, water, and light over months in both solution and the solid state. Single‐crystal X‐ray crystallography confirmed the molecular structure of all derivatives. Investigations of their optoelectronic properties revealed that the diphosphahexaarenes exhibit ambipolar redox behavior and high fluorescence quantum yields. Embedding six‐membered phosphorus rings into large acenes thus opens up new opportunities for the investigation of polyaromatic systems.
Metal-assisted salphen organic frameworks (MaSOFs) are known to possess high affinities to CO2 due to Lewis acidic metal sites and are therefore able to selectively adsorb CO2 over CH4 or N2. By aligning two metal centers in a carefully designed geometry, a “single molecular trap” (SMT) effect is generated, resulting in an interaction of two metal centers with one molecule CO2 by synergic effects. A condensation of a rigid triptycene based trissalicylaldehyde with tetrammino benzene is used to realize these metal alignments into MaSOFs. Characterization of the discrete trinuclear complexes proves that the chosen geometry is nearly optimal for synergic CO2 adsorption. The corresponding MaSOFs show high selectivities of CO2 against CH4 with a selectivity S IAST (according to the Ideal Adsorbed Solution Theory) of up to 13 and a selectivity of S IAST up to 70 against N2, which are also reflected by isosteric heat of adsorptions (Q st) of up to 35 kJ/mol. Density functional theory (DFT) calculations support the hypothesis by geometry optimized models and furthermore show a positive cooperative effect by an energy gain of ∼14 kJ/mol during the adsorption of CO2 in the second binding pocket of the trinuclear metal–salphen compared to a monomolecular adsorption.
Application of steric control principles allows for simplification of the magnetic behavior of an iconic single-ion magnet architecture as well as the preparation of its previously inaccessible representative.
Molecularly defined and classical heterogeneous Mo-based metathesis catalysts are shown to display distinct and unexpected reactivity patterns for the metathesis of long-chain α-olefins at low temperatures (<100 °C). Catalysts based on supported Mo oxo species, whether prepared via wet impregnation or surface organometallic chemistry (SOMC), exhibit strong activity dependencies on the α-olefin chain length, with slower reaction rates for longer substrate chain lengths. In contrast, molecular and supported Mo alkylidenes are highly active and do not display such dramatic dependence on the chain length. State-of-the-art two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) spectroscopy analyses of postmetathesis catalysts, complemented by Fourier transform infrared (FT-IR) spectroscopy and molecular dynamics calculations, evidence that the activity decrease observed for supported Mo oxo catalysts relates to the strong adsorption of internal olefin metathesis products because of interactions with surface Si–OH groups. Overall, this study shows that in addition to the nature and the number of active sites, the metathesis rates and the overall catalytic performance depend on product desorption, even in the liquid phase with nonpolar substrates. This study further highlights the role of the support and active site composition and dynamics on activity as well as the need for considering adsorption in catalyst design.
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