Zinc(II)-methimazole complexes: synthesis and reactivity

The tetrahedral S-coordinated complex [Zn(MeImHS)(4)](ClO4)(2), synthesised from the reaction of [Zn(ClO4)(2)] with methimazole (1-methyl-3H-imidazole-2-thione, MeImHS), reacts with triethylamine to yield the homoleptic complex [Zn(MeImS)(2)] (MeImS = anion methimazole). ESI-MS and MAS C-13-NMR experiments supported MeImS acting as a (N, S)-chelating ligand. The DFT-optimised structure of [Zn(MeImS)(2)] is also reported and the main bond lengths compared to those of related Zn-methimazole complexes. The complex [Zn(MeImS)(2)] reacts under mild conditions with methyl iodide and separates the novel complex [Zn(MeImSMe)(2)I-2] (MeImSMe = S-methylmethimazole). X-ray diffraction analysis of the complex shows a ZnI2N2 core, with the methyl thioethers uncoordinated to zinc. Conversely, the reaction of [Zn( MeImS)(2)] with hydroiodic acid led to the formation of the complex [Zn(MeImHS)(2)I-2] having a ZnI2S2 core with the neutral methimazole units S-coordinating the metal centre. The Zn-coordinated methimazole can markedly modify the coordination environment when changing from its thione to thionate form and vice versa. The study of the interaction of the drug methimazole with the complex [Zn(MeIm)(4)](2+) (MeIm = 1-methylimidazole) - as a model for Zn-enzymes containing a N-4 donor set from histidine residues shows that methimazole displaces only one of the coordinated MeIm molecules; the formation constant of the mixed complex [Zn(MeIm)(3)(MeImHS)](2+) was determined

Silica-based nanoparticles: a versatile tool for the development of efficient imaging agents

This review describes the recent advances in the development of imaging agents based on silica nanoparticles. Different techniques (magnetic resonance imaging, optical imaging, positron emission tomography, X-ray computed tomography, and ultrasound imaging) are described as well as the possibility of combining together different imaging techniques in the same nanoplatform and simultaneously performing imaging and therapy

Arsenic speciation in marine sediments: A comparison between two sequential extraction procedures

Arsenic distribution and mobility in marine sediments was investigated by means of total extraction and two sequential extraction procedures i.e. a modified sequential extraction procedure proposed by the European Standard, Measurementand Testing (SM&T) program, formerly the Community Bureau of Reference (BCR) procedure and a five steps sequential extraction based on the Wenzel extraction procedure, called modified Wenzel extraction. Sediments were collected from Cagliari’s harbour and Cagliari’s gulf, in Western Mediterranean Sea, Italy. The modified Wenzel extraction provided a more detailed As binding pattern and turned out to be much more appropriate than the modified SM&T procedure for gaining information regarding the mobilization of As within marine sediments. In the harbour, the largest part of As is contained in the residual fraction. At the contrary, As concentration, which is higher in the Cagliari’s gulf, is primarily associated with amorphous and crystalline hydrous Fe(Mn, Al) oxide. Moreover, this study suggests the possibility to segregate different types of marine sediments depending of human or industrial activities and to trace As contaminated marine sediments to determine the origin of contamination following the percentile of As contained in each extraction steps

Operational DGT threshold values for metals in seawater from protected coastal areas in Sardinia (Western Mediterranean)

Diffusive gradients in thin films (DGTs) were used for monitoring metal (Cd, Cu, Ni, and Pb) concentrations in protected and non-protected coastal areas in Sardinia (Western Mediterranean). The deployment of DGTs in relatively undisturbed areas enabled calculation of operational DGT threshold values, which can be used for assessments of the environmental quality of coastal areas. The DGT thresholds were defined as the median metal concentrations that were found in protected areas, which ensured consideration of the natural variability of the different study sites. The calculated DGT thresholds were 11.6 ng L−1 for Pb, 5.1 ng L−1 for Cd, 63 ng L−1 for Cu and 152 ng L−1 for Ni. A comparison of the calculated DGT thresholds with previous DGT studies in the area demonstrated their suitability for identifying sites of environmental concern in the Western Mediterranean

Trace metal levels in the edible tissues of sea cucumbers (Holothuria tubulosa and Holothuria polii) from Sardinia (Western Mediterranean)

Sea cucumbers represent an important part of the diet in Asian and Pacific regions and are also used in traditional medicine. These habits have led to the overexploitation of local sea cucumber populations in these areas, driving the pursuit of new stock regions, such as Mediterranean areas. In Italy, contrarily to that observed for other Mediterranean countries, the exploitation of sea cucumber stocks is not extensive, which opens a new market opportunity. Thus, from a food safety perspective, this work aims at reporting the first assessment of trace metal concentrations (As, Cd, Cr, Cu, Hg, Ni, Pb) in the edible tissues of Holothuria polii and Holoturia tubulosa collected in Sardinia, the second-largest island in the Mediterranean Sea. Metal concentrations found in H. polii were generally higher than in H. tubulosa. However, in both species, they were lower than those reported for other areas of the Western Mediterranean. Cd, Hg, and Pb were below the limits established for seafood in Europe. As concentrations were in the range of those measured in other commercial seafood species in the Mediterranean. Thus, these species may be harvested and traded to fulfil the demands of local and international markets

Geochemical fractionation and risk assessment of trace elements in sediments from tide-dominated Hooghly (Ganges) River Estuary, India

The geochemical fractionation and potential mobilization of cadmium, chromium, copper, nickel and lead were studied in surficial sediments (top 0–10 cm; <63 μm grain-size) of the Hooghly (Ganges) River Estuary, eastern part of India, using a sequential extraction procedure. The risk assessment was evaluated at three specific levels; i.e., enrichment level (enrichment factor, geo-accumulation index), the availability level (elements bound to different fractions, risk assessment code, Individual and Global contamination factors) and biological toxicity level (Potential ecological risk index; sediment quality guidelines). Different geochemical phases indicated heterogeneities in TE distribution patterns as follows: (i) Cd was dominant in the exchangeable phase and significant proportion of Pb was bounded to the reducible fractions; (ii) the potential mobile fraction (ΣF1 − F3) in the sediments was higher for Cd and Pb (>46%), reflecting their adverse impact on benthic organisms as they are weakly bound to the sediment and can migrate to water; (iii) a minor fraction of Cu (<10%) was found in the oxidizable fraction suggesting less environmental risk to the aquatic biota and (iv) the dominance of the Ni, Cr and Cu in the residual fraction supports the assumption of their geogenic origin. Both Cd and Cu posed medium to high ecological risk values based on risk assessment code (RAC). Global Contamination Factor (GCF) values allowed to identify the “pollution hotspots” in the study area

Zinc(II)-methimazole complexes : synthesis and reactivity

The tetrahedral S-coordinated complex [Zn(MeImHS)4](ClO4)2, synthesised from the reaction of [Zn(ClO4)2] with methimazole (1-methyl-3H-imidazole-2-thione, MeImHS), reacts with triethylamine to yield the homoleptic complex [Zn(MeImS)2] (MeImS = anion methimazole). ESI-MS and MAS 13C-NMR experiments supported MeImS acting as a (N,S)-chelating ligand. The DFT-optimised structure of [Zn(MeImS)2] is also reported and the main bond lengths compared to those of related Zn-methimazole complexes. The complex [Zn(MeImS)2] reacts under mild conditions with methyl iodide and separates the novel complex [Zn(MeImSMe)2I2] (MeImSMe = S-methylmethimazole). X-ray diffraction analysis of the complex shows a ZnI2N2 core, with the methyl thioethers uncoordinated to zinc. Conversely, the reaction of [Zn(MeImS)2] with hydroiodic acid led to the formation of the complex [Zn(MeImHS)2I2] having a ZnI2S2 core with the neutral methimazole units S-coordinating the metal centre. The Zn-coordinated methimazole can markedly modify the coordination environment when changing from its thione to thionate form and vice versa. The study of the interaction of the drug methimazole with the complex [Zn(MeIm)4]2+ (MeIm = 1-methylimidazole) as a model for Zn-enzymes containing a N4 donor set from histidine residues shows that methimazole displaces only one of the coordinated MeIm molecules; the formation constant of the mixed complex [Zn(MeIm)3(MeImHS)]2+ was determined