Types and properties of metal-free catalysts for living polymerizations of biomaterials

Syntéza biokompatibilních a biodegradabilních polyesterů, použitelných převážně v medicíně, využívá pro polymeraci za otevření kruhu katalyzátory na bázi kovu (např. Sn, Al atd.), které se mohou po implantaci deponovat v těle. Podstatou bakalářské práce je popis netoxických "metal-free" karbenových sloučenin a jejich vlastností použitelných jako katalyzátory pro polymeraci cyklických esterů. Příprava těchto stabilních karbenových katalyzátorů a jejich charakterizace je cílem experimentání práce.Synthesis of biocompatible and biodegradable polyesters applicable mainly in biomedicine uses metal catalysts (based on Sn, Al etc.) for ring opening polymerization, which could be deposited in a body after implantation. Objective of the bachelor thesis is description of non-toxic metal-free carbene compounds and their properties utilizable as catalysts for polymerization of cyclic esters. Preparation of these stable free carbene catalysts and their characterization is the main goal of the experimental work.

Zinc 2-((2-(benzoimidazol-2-yl)quinolin-8-ylimino)methyl)phenolates : synthesis, characterization and photoluminescence behavior

A series of 2-(2-(1H-benzoimidazol-2-yl)quinolin-8-yliminomethyl)phenol derivatives and their zinc complexes (C1 – C5) were synthesized and fully characterized. The molecular structure of the representative complex C2 was determined by single crystal X-ray diffraction, which revealed that the zinc was five-coordinated with the tetra-dentate ligand and a methanol bound to the metal afford a distorted square-pyramidal geometry. The UV-Vis absorption and fluorescence spectra of the organic compounds and their zinc complexes were measured and investigated in various solvents such as methanol, THF, dichloromethane, and toluene; significant influences by solvents were observed on their luminescent properties; red-shifts for the zinc complexes were clearly observed in comparisons to the free organic compounds

Improved synthesis of the hypoxia probe 5-deutero-5-fluoro-5-deoxy-azomycin arabinoside (FAZA) as a model process for tritium radiolabeling

Peer reviewedPublisher PD

Dialkylaluminium 2-imidazolylphenolates: Synthesis, characterization and ring-opening polymerization behavior towards lactides

The stoichiometric reaction of the 2-imidazolylphenols (L1–L9) with the trialkylaluminium reagents AlR₃ (R = Me, Et and iBu), afforded the corresponding dialkylaluminium 2-imidazolylphenolate complexes [R₂Al(L1–L9)] (C1–C11), which were characterized by ¹H/¹³C NMR spectroscopy and by elemental analysis. The molecular structures of the representative complexes C1, C2, C4, C6 and C11 were determined by single-crystal X-Ray diffraction, and revealed a distorted tetrahedral geometry at aluminum. These dialkylaluminium 2-imidazolylphenolates (C1–C11) could efficiently catalyze the ring-opening polymerization of lactides to afford high molecular weight polylactide, both in the presence and absence of BnOH, and as such represent rare examples of the use of bi-dentate ligation at aluminum in such lactide polymerization systems. On the basis of the polymerization results for l-lactide, d-lactide and rac-lactide, the nature of the ligands and the aluminum bound alkyls were found to significantly affect the catalytic activity as well as the properties of the resultant polylactides

Synthesis of nitroxyl radical by direct nucleophilic functionalization of a C-H bond in the azadiene systems

Cyclic dinitrones underwent nucleophilic substitution of the hydrogen atom in the reaction with a paramagnetic carbanion, the lithium derivative of 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide, to give polyfunctional nitronyl nitroxyls. © 2012 Springer Science+Business Media New York

Electrogenerated N-Heterocyclic Carbene in Ionic Liquid: An Insight into the Mechanism of the Oxidative Esterification of Aromatic Aldehydes

An N-heterocyclic carbene (NHC), generated by cathodic reduction of BMImBF4, mediates the oxidative esterification of aromatic aldehydes with organic bromides in the corresponding ionic liquid as solvent. The product recovery by simple extractive work-up with diethyl ether allowed the ionic liquid to be recycled up to 9 times for subsequent electrolyses, with no significant loss in the product yield. The isolation of an intermediate, whose structure was confirmed by synthesis and transformation into the ester, provided the key for a mechanistic insight into the reaction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

N-heterocyclic germylenes: structural characterisation of some heavy analogues of the ubiquitous N-heterocyclic carbenes

The X-ray crystal structures of three N-heterocyclic germylenes (NHGes) have been elucidated including the previously unknown 1,3-bis(2,6-dimethylphenyl)diazagermol-2-ylidene (1). In addition, the X-ray crystal structures of the previously synthesised 1,3-bis(2,4,6-trimethylphenyl)diazagermol-2-ylidene (2) and 1,3-bis(2,6-diisopropylphenyl)diazagermol-2-ylidene (3) are also reported. The discrete molecular structures of compounds 1 to 3 are comparable, with Ge-N bond lengths in the range 1.835-1.875 Å, while the N-Ge-N bond angles range between 83.6 and 85.2°. Compound 2 was compared to the analogous N-heterocyclic carbene species, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes). The major geometrical difference observed, as expected, was the bond angle around the divalent group 14 atom. The N-Ge-N bond angle was 83.6° for compound 2 versus the N-C-N bond angle of 101.4° for IMes. The Sn equivalent of (1), 1,3-bis(2,6-dimethylphenyl)diazastannol-2-ylidene (4), has also been synthesised and its crystal structure is reported here. In order to test their suitability as ligands, compounds 1 to 3 were reacted with a wide range of transition metal complexes. No NHGes containing metal complexes were observed. In all cases the NHGe either degraded or gave no reaction

Coupling of 1-alkyl-2-(bromomethyl)aziridines with heteroatom-centered nucleophiles towards 2-[(heteroatom)methyl]aziridines

The reactivity of 1-alkyl-2-(bromomethyl)aziridines with respect to different types of oxygen-, nitrogen- and sulphur-centered nucleophiles has been evaluated, pointing to the conclusion that these substrates can be applied successfully as synthetic equivalents for the aziridinylmethyl cation synthon towards the corresponding 2-[(heteroatom)methyl]aziridines in good yields

Mechanism of Reductive Elimination of Methyl Iodide from a Novel Gold(III)−Monomethyl Complex

Oxidation of (Idipp)AuMe (Idipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with I_2 gives a monomethyl Au(III) complex, (Idipp)AuI_2Me, which decomposes cleanly to MeI and (Idipp)AuI. Kinetics experiments show that this transformation occurs primarily via three-coordinate, cationic [(Idipp)AuIMe]^+, which undergoes intramolecular reductive elimination rather than nucleophilic attack by external I^−