Low-coordinate erbium(III) single-molecule magnets with photochromic behavior

[Image: see text] The structures and magnetic properties of photoresponsive magnets can be controlled or fine-tuned by visible light irradiation, which makes them appealing as candidates for ternary memory devices: photochromic and photomagnetic at the same time. One of the strategies for photoresponsive magnetic systems is the use of photochromic/photoswitchable molecules coordinated to paramagnetic metal centers to indirectly influence their magnetic properties. Herein, we present two erbium(III)-based coordination systems: a trinuclear molecule {[Er(III)(BHT)(3)](3)(dtepy)(2)}(.)4C(5)H(12) (1) and a 1D coordination chain {[Er(III)(BHT)(3)(azopy)}(n)·2C(5)H(12) (2), where the bridging photochromic ligands belong to the class of diarylethenes: 1,2-bis((2-methyl-5-pyridyl)thie-3-yl)perfluorocyclopentene (dtepy) and 4,4′-azopyridine (azopy), respectively (BHT = 2,6-di-tert-butyl-4-methylphenolate). Both compounds show slow dynamics of magnetization, typical for single-molecule magnets (SMMs) as revealed by alternating current (AC) magnetic susceptibility measurements. The trinuclear compound 1 also shows an immediate color change from yellow to dark blue in response to near-UV irradiation. Such behavior is typical for the photoisomerization of the open form of the ligand into its closed form. The color change can be reversed by exposing the closed form to visible light. The chain-like compound 2, on the other hand, does not show significant signs of the expected trans–cis photoisomerization of the azopyridine in response to UV irradiation and does not appear to show photoswitching behavior

Asymmetric synthesis of bicyclic alkaloids with a pyrrolizidine structure

Niniejsza praca miała na celu syntezę alkaloidów pirolizydynowych, w której chiralnym prekursorem była L-prolina. Obejmowała ona optymalizację przekształcenia L proliny w aldehyd – prolinal z odpowiednio zabezpieczoną grupą aminową (grupy zabezpieczające: Boc lub Cbz), w której kluczowym etapem była redukcja zabezpieczonego aminokwasu do alkoholu oraz następujące po niej utlenianie.W dalszej części z otrzymanych aldehydów oraz wybranych hydroksyketonów przeprowadzono diastereoselektywną reakcję aldolową. Największym wyzwaniem było dobranie odpowiednich warunków procesu (temperatura, katalizator, rozpuszczalnik) pozwalających otrzymać docelowy produkt z możliwie najwyższą wydajnością oraz diastereoselektywnością. W końcowym etapie za pomocą aminowania reduktywnego dla wybranych produktów aldolowych przeprowadzono cyklizację drugiego pierścienia pięcioczłonowego tworząc tym samym układ pirolizydynowy ze zwornikowym atomem azotu.This work was aimed at the synthesis of pyrrolizidine alkaloids in which L-proline was the chiral precursor. It involved the optimization of the conversion of L proline to an appropriately protected amino group aldehyde (Boc or Cbz protecting groups), where the key step was the reduction of the protected amino acid to an alcohol and subsequent oxidation.Further, a diastereoselective aldol reaction was performed from the obtained aldehydes and chosen hydroxyketones. The biggest challenge was to select the appropriate process conditions (temperature, catalyst, solvent) to obtain the target product with the highest possible efficiency and diastereoselectivity.In the last stage, the second five-membered ring was closed using the previously obtained aldol products by means of reductive amination. Thus, a pyrolizidine system with a keystone nitrogen atom was obtained

Regioselectivity aldol reaction of hydroxyacetone - finding new catalysts

Celem pracy było znalezienie nowych katalizatorów dla bezpośredniej asymetrycznej reakcji aldolowej hydroksyacetonu w szczególności dla reakcji z acetonidem aldehydu (R)-glicerynowego. Podczas badań wykorzystano dostępne dane literaturowe w celu wybrania katalizatorów, które prowadziłyby do otrzymania głównie 1,4-dioli. Na podstawie uzyskanych wyników sprawdzono wpływ związków o podobnej budowie. Badania prowadzono w różnych warunkach, badając wpływ temperatury oraz czas trwanie reakcji na uzyskaną wydajność. W ramach pracy przeprowadzono kilkuetapową syntezę substratów (acetonid aldehydu (R)-glicerynowego i 1-(tert-butylodimetylosiloksy)-propan-2-onu oraz katalizatora ((S)-2-(((1S,2S)-2-hydroksy-1,2-difenylo)-1-pirolidyno)karboksyamid). Dla każdego z otrzymanych związków zostało zrobione widmo rezonansu magnetycznego.The purpose of the study was to find new catalysts for direct asymmetric aldol reaction of hydroxyacetone, in particular for reaction with acetonide of (R)-glyceraldehyd acetonide. During the tests all available data from literature was used with the aim of choosing the catalysts which would result to obtain mainly 1,4-diols. Based on the research obtained the influence of structurally related compounds was tested. The research was conducted under different conditions, examining the influence of temperature and the duration of reaction on efficiency achieved. As part of the study the multi-stage synthesis of substrates ( (R)-glyceraldehyd acetonide and 1-(tert-butylodimetylosiloxy)-propan-2-one with the catalyst ((S)-2-(((1S,2S)-2-hydroksy-1,2-diphenylo)-1-pyrrolidyne)karboxamide was conducted. For each of the compounds obtained the magnetic resonance spectra was performed

Low-Coordinate Erbium(III) Single-Molecule Magnets with Photochromic Behavior

The structure and magnetic properties of photo-responsive magnets can be controlled or fine-tuned by visible light irradiation which makes them appealing as candidates for ternary memory devices: photochromic and photomagnetic at the same time. One of the strategies for photo-responsive magnetic systems is the use of photochromic/photoswitchable molecules coordinated to paramagnetic metal centers to in-directly influence their magnetic properties. Herein, we present two erbium(III) based coordination systems: a trinuclear molecule {[ErIII(BHT)3]3(dtepy)2}.3C5H12 (1) and a 1-D coordination chain {[ErIII(BHT)3(azopy)}nnC5H12 (2), where the bridging photochromic ligands belong to the class of diarylethenes: 1,2-bis(2-methyl-5-pyridyl)thie-3-yl)perfluorocyclopentene (dtepy) and 4,4\u27-azopyridine (azopy), respectively (BHT = 2,6-di-tert-butyl-4-methylphenolate). Both compounds show slow dynamics of the magnetization, typical for single-molecule magnets (SMMs) as revealed by alternating current (AC) magnetic susceptibility measurements. The trinuclear compound 1, shows also an immediate color change from yellow to dark blue in response to near-UV irradiation. Such a behavior is typical for the photo-isomerization of the open-form of the ligand o-dtepy ligand into its closed-form c-dtepy. The color change can be reversed by exposing the c-dtepy to visible light. The chain-like compound 2, on the other hand, does not show significant signs of the expected trans-cis photoisomerization in response to UV irradiation and does not appear to show photoswitching behavior