A DFT,X- and W-band EPR and ENDOR Study of Nitrogen-Centered Species in (Nano)Hydroxyapatite

Incorporation of the nitrogen-containing impurities in hydroxyapatite (HAp) powders with the sizes of the crystallites of (20–50) nm was studied using first-principles modeling combined with the multi-frequency (9 and 94 GHz) electron paramagnetic resonance (EPR) methods. It is shown that the observed EPR spectra are undoubtedly due to the presence of the bulk radiation-induced NO₃ ^2? radicals. This conclusion is based on spin-polarized density functional theory calculations of spectroscopic parameters within gauge-including projector augmented wave framework followed by the exact comparison of the simulated EPR and electron–nuclear double resonance spectra with the experimental findings. In addition, a comprehensive analysis of the simulated properties allows us to suggest that the paramagnetic centers preferably occupy PO₄ ^3? sites in the HAp structure.     

Narrow operators on lattice-normed spaces

The aim of this article is to extend results of Maslyuchenko, Mykhaylyuk and Popov about narrow operators on vector lattices. We give a new definition of a narrow operator, where a vector lattice as the domain space of a narrow operator is replaced with a lattice-normed space. We prove that every GAM-compact (bo)-norm continuous linear operator from a Banach-Kantorovich space V to a Banach lattice Y is narrow. Then we show that, under some mild conditions, a continuous dominated operator is narrow if and only if its exact dominant is so.     

Tuning the Electronic Properties in Ruthenium–Quinone Complexes through Metal Coordination and Substitution at the Bridge

A rare example of a mononuclear complex [(bpy)₂Ru(L¹_?H)](ClO₄), 1 (ClO₄) and dinuclear complexes [(bpy)₂Ru(μ‐L¹_?2H)Ru(bpy)₂](ClO₄)₂, 2 (ClO₄)₂, [(bpy)₂Ru(μ‐L²_?2H)Ru(bpy)₂](ClO₄)₂, 3 (ClO₄)₂, and [(bpy)₂Ru(μ‐L³_?2H)Ru(bpy)₂](ClO₄)₂, 4 (ClO₄)₂ (bpy=2,2′‐bipyridine, L¹=2,5‐di‐(isopropyl‐amino)‐1,4‐benzoquinone, L²=2,5‐di‐(benzyl‐amino)‐1,4‐benzoquinone, and L³=2,5‐di‐[2,4,6‐(trimethyl)‐anilino]‐1,4‐benzoquinone) with the symmetrically substituted p‐quinone ligands, L, are reported. Bond‐length analysis within the potentially bridging ligands in both the mono‐ and dinuclear complexes shows a localization of bonds, and binding to the metal centers through a phenolate‐type “O^?” and an immine/imminium‐type neutral “N” donor. For the mononuclear complex 1 (ClO₄), this facilitates strong intermolecular hydrogen bonding and leads to the imminium‐type character of the noncoordinated nitrogen atom. The dinuclear complexes display two oxidation and several reduction steps in acetonitrile solutions. In contrast, the mononuclear complex 1 ⁺ exhibits just one oxidation and several reduction steps. The redox processes of 1 ¹⁺ are strongly dependent on the solvent. The one‐electron oxidized forms 2 ³⁺, 3 ³⁺, and 4 ³⁺ of the dinuclear complexes exhibit strong absorptions in the NIR region. Weak NIR absorption bands are observed for the one‐electron reduced forms of all complexes. A combination of structural data, electrochemistry, UV/Vis/NIR/EPR spectroelectrochemistry, and DFT calculations is used to elucidate the electronic structures of the complexes. Our DFT results indicate that the electronic natures of the various redox states of the complexes in vacuum differ greatly from those in a solvent continuum. We show here the tuning possibilities that arise upon substituting [O] for the isoelectronic [NR] groups in such quinone ligands.     

Determination of fluoroquinolone antibiotics through the fluorescent response of Eu(III) based nanoparticles fabricated by layer-by-layer technique

The present work introduces the determination of fluoroquinolone antibiotics (FQs) in aqueous solutions through the fluorescent response of Eu(TTA)₃ and [Eu(TTA)₃1] (TTA⁻ and 1 are thenoyltrifluoroacetonate and phosphine oxide derivative) complexes encapsulated into the polyelectrolyte capsules fabricated through layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI). The variation of luminescent core, polyelectrolyte deposition and concentration conditions reveals two modes of fluorescent response on FQs of diverse structure namely the sensitization and quenching of Eu(III) centered luminescence. The obtained regularities reveal the ternary complex formation and the ligand exchange occurring at the interface of polyelectrolyte coated [Eu(TTA)₃1] based colloids as the reasons of the diverse fluorescent response of Eu(III) centered luminescence on FQs. The factors affecting the fluorescent response have been revealed, which are: the content of luminescent core, the mode of polyelectrolyte deposition, concentration and structure of FQs. The discrimination of moxifloxacin and lomefloxacin from levofloxacin, ofloxacin, difloxacin, perfloxacin through the quenching of Eu(III) luminescence in PSS-[Eu(TTA)₃1] colloids has been revealed.     

Heteroanthracyclines-III: 6,7,11-tri-O-methyl-4-demethoxy-12-sulfonodaunomycinone [6,10,11-trimethoxy-8-hydroxy-8-acetyl 7,8,9,10-tetrahydrobenzo(B)-thioxanthen-12-one-5-dioxide

The sulfone analogue of 6,7,11-tri-O-methyl-4-demethoxydaunomyacinone, namely 6,7,11-tri-O-methyl-4-demethoxy-12-sulfonodaunomycinone (12) was synthesized using 5,8-dimethoxy-2-acetyltetralin (13) as starting material which can be prepared in large scale by hydrogen chloride catalysed cyclization of 3- (2,5-dimethoxybenzyl)-l,4-dioxopent shortening and simplifying our earlier procedures and eliminating the handling of large quantity of liquid hydrogen fluoride. The intermediate 15 can be easily prepared in large scale according to the procedure which we reported earlier.^13c Reaction of 13 with 2,2'-dithiosalicylic acid gave an isomeric mixture of 17 and 18 which were separated and their structure differentiated by dipole moment studies¹⁴ Isomer 17 was reduced by Zn dust to 22 and 23 which reacted with anhydrous methanol to form 24 and 25. Both 24 and 25 as an isomeric mixture were oxidized to 28 and29 by oxygen in basic N,N-dimethylformamide solution and finally to the stable sulfones 30 and 31 by m-chloroperoxybenzoic acid. These two isomeric sulfones were separated and fully characterized and then oxidized further to form 34 which was converted to the title compound 12 by free radical bromination and reaction with anhydrous methanol in the presence of silver trifluoromethanesulfonate. The structure of 12 was positively established by detailed analysis of its high field PMR spectrum (Fig. 1)     

Diastereoselective synthesis of α,α′-disubstituted β-ketophosphonates derivatives as building blocks for automated syntheses

A convenient and efficient synthesis of α,α′-disubstituted β-ketophosphonic derivatives in good to excellent de’s and yields has been achieved by α-acylation followed by diastereoselective α-alkylation of chiral 5-membered cyclic phosphonamidates.