Modification of aluminium alkoxides with dialkylmalonates

Abstract  

Depending on the reaction conditions, different aluminium dialkylmalonate derivatives were obtained by reaction of aluminium alkoxides Al(OR)₃ (R = Et, iPr, tBu) with dialkylmalonates, viz. Al(malonate)₃ (malonate = dimethyl, diethyl, di-iso-propyl and di-tert-butyl malonate), Al₂(OiPr)₄(malonate)₂ (malonate = di-iso-propyl and di-tert-butyl malonate), Al₂(OiPr)₂(di-iso-propylmalonate)₄ and Al₃(OH)(OEt)₃(diethylmalonate)₅. All compounds were characterized by NMR spectroscopy, and single crystal structure analyses are reported for each type of compound. An Al₂(OiPr)₂(dialkylmalonate)₄ derivative was only obtained by disproportionation of Al₂(OiPr)₄(di-iso-propylmalonate)₂, but not by reaction of Al(OiPr)₃ with dialkylmalonates in the corresponding molar ratio. Reactions of Al(OtBu)₃ only resulted in Al(malonate)₃ derivatives, but no transesterification was observed, contrary to the reaction of Al(OiPr)₃ with dimethyl or diethyl malonate.     

Journal of Radioanalytical and Nuclear Chemistry, 2005–2009: a citation-based bibliography and impact analysis using Hirsch-type statistics

All papers published in the Journal of Radioanalytical and Nuclear Chemistry (JRNC) in the period 2005–2009 (source dataset) and all papers citing these papers and published in other journals (target dataset) have been compiled. A scientometric analysis of the datasets has been performed using Hirsch-type statistics. A comprehensive bibliography of the citing papers is presented.     

Coordination-driven self assembly of a brilliantly fluorescent rhomboid cavitand composed of bodipy-dye subunits

The two sp(3) hybridized fluorine atoms of a Bodipy dye have been synthetically replaced with the linear donor ligand 4-ethynylpyridine (-C≡C-Py) to form a rigid and highly symmetrical 109.5° building block in which the fluorophore subunit is vertically aligned to the plane formed by the -C≡C-Py donors. Upon reaction of the above tecton with a 90° organoplatinum acceptor unit, an intensely fluorescent rhomboid cavitand was manifested in solution. In contrast to the vast majority of coordination-driven self-assembled chromophoric systems, the present one fully conserves the excellent photophysical properties of the parent Bodipy dye. These unique features of the present metallosupramolecular entity constitute a fascinating metal-to-ligand self-assembled prototype for building compact and intensely luminescent materials with host-guest capabilities.     

Intermittent Lower Bound on Quantum Diffusion

An intermittent lower bound on quantum diffusion is proven in presence of a multifractal spectral measure.     

Über die neue Grundlagenkrise der Mathematik

Ohne Zusammenfassung     

Protagon im Blute

Ohne Zusammenfassung     

Medium Entropy Reduction and Instability in Stochastic Systems with Distributed Delay

Many natural and artificial systems are subject to some sort of delay, which can be in the form of a single discrete delay or distributed over a range of times. Here, we discuss the impact of this distribution on (thermo-)dynamical properties of time-delayed stochastic systems. To this end, we study a simple classical model with white and colored noise, and focus on the class of Gamma-distributed delays which includes a variety of distinct delay distributions typical for feedback experiments and biological systems. A physical application is a colloid subject to time-delayed feedback control, which is, in principle, experimentally realizable by co-moving optical traps. We uncover several unexpected phenomena in regard to the system’s linear stability and its thermodynamic properties. First, increasing the mean delay time can destabilize or stabilize the process, depending on the distribution of the delay. Second, for all considered distributions, the heat dissipated by the controlled system (e.g., the colloidal particle) can become negative, which implies that the delay force extracts energy and entropy of the bath. As we show here, this refrigerating effect is particularly pronounced for exponential delay. For a specific non-reciprocal realization of a control device, we find that the entropic costs, measured by the total entropy production of the system plus controller, are the lowest for exponential delay. The exponential delay further yields the largest stable parameter regions. In this sense, exponential delay represents the most effective and robust type of delayed feedback.