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Uncommon examples of coordination compounds of high valent transition metals with α-diimines were obtained and characterized by IR and NMR spectroscopy, X-ray diffraction and/or DFT analysis. The 1 : 1 molar reactions of NbF5 with a selection of α-diimines afforded the ionic compounds [NbF4(DADR)2][NbF6] (DADR = DADDip, 1a; DADXyl, 1b; DADMes, 1c) in 80–90% yields. The addition of DADDip to NbOCl3 gave NbOCl3(DADDip), 7 (62% yield). [MBr4(DADDip)][MBr6] (M = Nb, 7a; M = Ta, 7b) were afforded in moderate yields from MBr5 and DADDip. The reactions of NbCl5 with DADDip and DADXyl proceeded with non-selective activation of the organic substrate affording complex mixtures of products, including the quinoxalinium salt [{2,6-C6H3(CHMe2)2}N(CH)2NCC(CHMe2)(CH)3C][NbCl6], 2, the Nb(IV) coordination complex NbCl4(DADDip), 3, the N-(monoprotonated) α-diimine salts [DADDip(H)][MCl6], 4a–b, and the iminomethyl-imidazolium [(2,6-C6H3Me2)NCHCHN(2,6-C6H3Me2)CCHN(2,6-C6H3Me2)][NbCl6], 5.

The modification of polymer surfaces by UV-induced graft polymerization is a powerful method to change the surface characteristics of a polymer without altering its bulk features [1]. In this work an alternative approach to modify the surface properties of an ethylene-octene copolymer (EOC) and of a polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) block copolymer is described. X-TEMPO derivatives were used as functional species in place of unsaturated monomers. Indeed TEMPO radicals can react with macroradicals by coupling giving rise to the functionalization of polymers in a peroxide-initiated radical process [2, 3]. In an UV photo-grafting process, the excited photo-initiator gives rise to macroradicals by H-abstraction from the polymer chains, and the X-TEMPO derivatives react with the carbon-centered macroradicals by coupling leading to the surface functionalization of the polymer material (Fig. 1). The 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BzO-TEMPO), the 4-(1-naphthoate)-2,2,6,6-tetramethylpiperidine-1-oxyl (NfO-TEMPO) and the 4-(4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro-nonanoate)-2,2,6,6-tetramethyl-piperidine-1-oxyl (Fluo-TEMPO) were used as functional X-TEMPO radicals, whereas the 4-methoxybenzophenone (MeOBP) was used as a photo-initiator. The resulting functionalized polymers were characterized by ATR-FTIR spectroscopy, Electron Paramagnetic Resonance (EPR) and thermogravimetric analysis (TGA). Data confirmed the grafting of X-TEMPO derivatives and allowed the evaluation of the amount of grafted species. The fluorescence emission spectroscopy was used to investigate the optical properties of the NfO-TEMPO functionalized samples, while the contact angle measurements highlighted the wettability of the polymer surface modified with Fluo-TEMPO. Results show that the properties of the free X-TEMPO derivatives were transferred to the polymer surface thus giving "functional" polymer films.

Recently, detection of antioxidant activity of plant extracts has caught the attention of researchers. Determination of antioxidant activity is usually performed using stable free radicals. A number of assays is available for screening the antioxidant activity of food constituents, but few of these methods are applicable to lipophilic substances. EPR is the analytical technique that directly measures free radicals making possible the analysis of turbid or highly colored samples. The aim of this study was to determine how the detection technique, plant species and the different growing conditions influenced the antioxidative activity of aqueous and lipid extracts from leaves. Sage (Salvia officinalis L.) and coneflower (Echinacea angustifolia DC.) grown in hydroponics and in soil, were analyzed. Radical decay kinetics, due to plant extracts, were monitored by an EPR spectrometer, equipped with a data acquisition system and a software package designed for analysis and simulation of spectra. Parameters obtained by the fitting of the curves allowed the calculation of the antioxidant potential. The radicals Fremy’s salt (hydrophilic) and 1,1-diphenyl-2-picrylhydrazyl (DPPH, lipophilic) were employed. Comparisons with data obtained by a spectrophotometric detection with the radical cation ABTS+ [2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] were also made. Fremy’s salt and DPPH gave 1st and 2nd order kinetics, respectively. EPR can give more reliable measurements of the antioxidant potential than spectrophotometric assay. The reduced sensitivity of spectrophotometric detection was showed both for sage and coneflower extracts. Antioxidant potential of sage resulted extraordinary high compared to coneflower and a different ratio of aqueous to lipid antioxidant potential in the two species could be monitored. Antioxidant potentials were also higher for coneflower grown in hydroponics than in soil. In addition to the technique adopted, the detection of antioxidant potential was influenced by the growing conditions of plants and hydroponics showed to be able to increase antioxidant potential of both coneflower lipophilic and hydrophilic extracts. By registration of EPR kinetics we can get reliable measurements of the antioxidant potential of plant extracts, avoiding the artifacts due to the appearance of other radicals resulting from oxidative processes.

Owing to the traditional phytotherapeutic use of basil and its importance as a basic component of the Mediterranean diet, this research aimed to study the nutraceutical properties of basil (Ocimum basilicum cv. Genova) grown in hydroponics in comparison with that grown in soil. The antioxidant activities of aqueous and lipid extracts of basil leaves were evaluated both by spectrophotometric detection with the 2,20-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS+) and by electron paramagnetic resonance (EPR) detection with the stable radicals peroxylamine disulphonate (Fremy's salt, hydrophilic) and 1,1-diphenyl-2-picrylhydrazyl (DPPH, lipophilic). From EPR decay kinetics analysis, it was possible to distinguish (in the lipid extract) a fast rate constant and a slow rate constant, likely attributable to two different kinds of lipophilic antioxidants. Hydroponic cultivation improved antioxidant activity of both aqueous and lipid extracts, increasing the contents of vitamin C, vitamin E, lipoic acid, total phenols and rosmarinic acid.