Codruta C. Paraschivescu

1,3,4-Oxadiazoles as luminescent materials for organic light emitting diodes via cross-coupling reactions

Highly efficient materials for the fabrication of OLEDs have been extensively investigated in terms of properties and convenient synthetic procedures. 2,5-Diaryl-1,3,4-oxadiazoles were found to display suitable structural features in order to act as good electron-transporters, and numerous research groups have focused on the synthesis of various small-molecules and polymers bearing this heterocyclic moiety. Characterisation of their optical and electronic properties indicated the oxadiazole derivatives as good candidates for the fabrication of electroluminescent devices. Chemical synthesis of compounds containing a variety of heterocyclic cores and functional organic groups has witnessed a tremendous evolution concomitant with the development of metal-catalysed cross-coupling reactions. This new approach to create molecular diversity was also observed in the field of oxadiazoles, in an attempt to prepare complex molecules whose structural particularities were able to furnish the properties required for the fabrication of functional materials. Herein, we describe a collection of literature studies that refer to 1,3,4-oxadiazole-based small-molecules and polymers that have found applications as materials for OLEDs, combined with their synthetic accesibility involving, as key step(s), cross-coupling reactions.

Identification of (CuCl(acac)(tmed)), a copper(II) complex with mixed ligands, as a modulator of Cu,Zn superoxide dismutase (Sod1p) activity in yeast

Superoxide dismutases (SODs) stand in the prime line of enzymatic antioxidant defense in nearly all eukaryotic cells exposed to oxygen, catalyzing the breakdown of the superoxide anionic radical to O2 and H2O2. Overproduction of superoxide correlates with numerous pathophysiological conditions, and although the native enzyme can be used as a therapeutic agent in superoxide-associated conditions, synthetic low molecular weight mimetics are preferred in terms of cost, administration mode, and bioavailability. In this study we make use of the model eukaryote Saccharomyces cerevisiae to investigate the SOD-mimetic action of a mononuclear mixed-ligand copper(II) complex, [CuCl(acac)(tmed)] (where acac is acetylacetonate anion and tmed is N,N,N′,N′-tetramethylethylenediamine). Taking advantage of an easily reproducible phenotype of yeast cells which lack Cu–Zn SOD (Sod1p), we found that the compound could act either as a superoxide scavenger in the absence of native Sod1p or as a Sod1p modulator which behaved differently under various genetic backgrounds.

CCDC 1547795: Experimental Crystal Structure Determination

Related Article: Anca G. Coman, Codruta C. Paraschivescu, Anca Paun, Andreea Diac, Niculina D. Hădade, Laurent Jouffret, Arnaud Gautier, Mihaela Matache, Petre Ionita|2017|New J.Chem.|41|7472|doi:10.1039/C7NJ01698K

Synthesis of novel profluorescent nitroxides as dual luminescent-paramagnetic active probes

We describe herein the synthesis of new profluorescent nitroxides based on 2,5-disubstituted-1,3,4-oxadiazoles as fluorescent moieties and the 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO) as paramagnetic probes. The synthesis and optical and electronic properties of the oxadiazole-based precursors of the profluorescent nitroxides, as well as the nitroxides and their reduced forms are also described. Physical investigations (i.e. absorption and emission spectroscopy, cyclic voltammetry) indicate a different luminescence behaviour function to the oxadiazole substituent. A linear response to reducing agents, i.e. sodium ascorbate, monitored by fluorescence spectroscopy, suggests the possibility of using the synthesized compounds as potent active probes in detection of various analytes of interest.

Long-lived states detect interactions between small molecules and diamagnetic metal ions

Long-lived states of nuclear spin order were used for the first time to probe interactions between molecules and diamagnetic metal ions. Proton spin states with lifetimes twice as long as the spin-lattice relaxation time constants of the same nuclei were promoted on the methoxyphenyl and tolyl substituents of a 1,3,4-oxadiazole derivative. The transient interaction of this oxadiazole derivative with silver(I) ions significantly speeds up the relaxation rate constants of proton long-lived states. The interactions between silver and organic compounds lead to the formation of coordination polymers that can be used for the preparation of bio-compatible materials.