Darko Dolenc

The first oxalate-bridged one-dimensional polymer containing MoV2 dimers with single metal–metal bonds. Syntheses and structures of (MeNC5H5)2n[Mo2O4(C2O4)Cl2]n and (3-MePyH)2n[Mo2O4(C2O4)Cl2]n

Hydrothermal reactions of mononuclear oxochloromolybdate(V) with oxalic acid in alcohol (methanol or 2-propanol) and pyridines (pyridine or 3-methylpyridine) media have afforded two polymeric compounds of molybdenum(V): N-methylpyridinum catena-μ-oxalato-O1,O2:O1′,O2′-(dichloro-di-μ-oxo-dioxodimolybdate(V)), (MeNC5H5)2n[Mo2O4(C2O4)Cl2]n1 and 3-methylpyridinium catena-μ-oxalato-O1,O2:O1′,O2′-(dichloro-di-μ-oxo-dioxodimolybdate(V)), (3-MePyH)2n[Mo2O4(C2O4)Cl2]n2. The compounds were fully characterized by X-ray structural analysis, infrared and NMR spectroscopy. The essentially isostructural anionic chains in 1and 2 are built of alternating pairs of {Mo2O4}2+ containing edge-sharing octahedra and planar oxalates giving a Mo ∶ oxalate ratio of 2. The bisbidentate oxalate acts as a bridge between two dinuclear subunits. The formation of a N-methylpyridinium cation from methanol and pyridine in the presence of molybdenum(V) and oxalic acid has not been documented before.

Photolytic and photocatalytic degradation of 6-chloronicotinic acid

This work describes for the first time the photolytic and photocatalytic degradation of 6-chloronicotinic acid (6CNA) in double deionised water, which is a degradation product of neonicotinoid insecticides imidacloprid and acetamiprid, and it is known to appear in different environmental matrices. Photolytic experiments were performed with three UVA (ultraviolet A) polychromatic fluorescent lamps with broad maximum at 355 nm, while photocatalytic experiments were performed using immobilised titanium dioxide (TiO₂) on six glass slides in the spinning basket inside a photocatalytic quartz cell under similar irradiation conditions. Photolytic degradation revealed no change in concentration of 6CNA within 120 min of irradiation, while the photocatalytic degradation within 120 min, obeyed first-order kinetics. The observed disappearance rate constant was k=0.011 ± 0.001 min⁻¹ and t½ was 63.1 ± 5.5 min. Mineralisation rate was estimated through total organic carbon (TOC) and measurements revealed no carbon removal in case of photolysis after 120 min of exposure. However in photocatalytic experiments 46 ± 7% mineralisation was achieved within 120 min of irradiation. Nevertheless, the removal of total nitrogen (TN) was not observed across all experiments. Ion chromatographic analyses indicated transformation of chlorine atoms to chloride and increase of nitrate(V) ions only via photocatalytic experiments. Efficiency of selected advanced oxidation process (AOP) was investigated through toxicity assessment with Vibrio fischeri luminescent bacteria and revealed higher adverse effects of treated samples on bacteria following photocatalytic degradation in spite of the fact that higher mineralisation was achieved. New hydroxylated product generated in photocatalytic experiments with TiO₂, was confirmed with liquid chromatography-electro spray ionisation mass spectrometry (LC-ESI-MS/MS) analyses, gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (¹H NMR).

Complexation of Molybdenum(V) with Glycolic Acid : An Unusual Orientation of Glycolato Ligand in {Mo2O4}2+ Complexes

(PyH)5[Mo(V)OCl4(H2O)]3Cl2 and (PyH)n[Mo(V)OBr4]n reacted with glycolic acid (H2glyc) or its half-neutralized ion (Hglyc(-)) to afford a series of novel glycolato complexes based on the {Mo(V)2O4}2+ structural core: (PyH)3[Mo2O4Cl4(Hglyc)]. (1)/ 2CH 3CN (1), (PyH) 3[Mo 2O 4Br 4(Hglyc)].Pr(i)OH(2), (PyH)2[Mo2O4(glyc) 2Py 2] (3), (PyH) 4[Mo 4O 8Cl 4(glyc) 2].2EtOH (4), and [Mo 4O 8(glyc) 2Py 4] (5) (Py = pyridine, C 5H 5N; PyH(+) = pyridinium cation, C 5H 5NH (+) and glyc (2-) = a doubly ionized glycolate, (-)OCH 2COO (-)). The compounds were fully characterized by X-ray crystallography and infrared spectroscopy. The Hglyc (-) ion binds to the {Mo 2O 4} (2+) core through a carboxylate end in a bidentate bridging manner, whereas the glyc (2-) ion adopts a chelating bidentate coordination through a deprotonated hydroxyl group and a monodentate carboxylate. The orientations of glyc (2-) ions in 3- 5 are such that the alkoxyl oxygen atoms occupy the sites opposite the multiply bonded oxides. {(C6H5) 4P}[Mo(VI)O 2(glyc)(Hglyc)] ( 6), an oxidized complex, features a reversed orientation of the glyc(2-) ion. The theoretical DFT calculations on the [Mo(V)2O4(glyc) 2Py 2](2-) and [Mo(VI)O2(glyc)2](2-) ions confirm that binding of glycolate with the alkoxyl oxygen to the site opposite the MoO bond is energetically more favorable in {Mo(V)2O4}(2+) species, whereas a reversed orientation of the ligand is preferred in Mo(VI) complexes. An explanation based on the orbital analysis is put forward.

LC/MS study of the UV filter hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]-benzoate (DHHB) aquatic chlorination with sodium hypochlorite.

The fate of modern personal care products in the environment is becoming a matter of increasing concern because of the growing production and assortment of these compounds. More and more chemicals of this class are treated as emerging contaminants. Transformation of commercially available products in the environment may result in the formation of a wide array of their metabolites. Personal care products in swimming pools and in drinking water reservoirs may undergo oxidation or chlorination. There is much data on the formation of more toxic metabolites from original low toxicity commercial products. Therefore, reliable identification of all possible transformation products and a thorough study of their physicochemical and biological properties are of high priority. The present study deals with the identification of the products of the aquatic chlorination of the hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]-benzoate ultraviolet filter. High-performance liquid chromatography/mass spectrometry (HPLC/MS) and HPLC/MS/MS with accurate mass measurements were used for this purpose. As a result, three chlorinated transformation products were identified.

EDA Complexes of N-halosaccharins with N- and O-donor ligands

A series of EDA complexes of N-iodosaccharin (NISac) and N-bromosaccharin (NBSac) with nitrogen and oxygen electron-pair donors, NISac·H2O, NISac·THF, NISac·Py, NISac2·Pyz and NBSac2·Pyz, was prepared and examined by X-ray diffraction and NMR. The complexes are relatively stable, crystalline compounds with the ligand bound to the halogen atom in a nearly linear arrangement N–halogen–ligand. The halogen–ligand distances are inversely proportional to the donor ability of the ligand. The interactions between ligand and halogen are stronger for iodine than bromine. The X-ray structure analysis has shown that for some compounds the N–X bond in the halosaccharin moiety is not coplanar with the isothiazole ring, and the quantum-chemical calculations demonstrate a high flexibility of the corresponding angle. Complexes were modelled also by DFT calculations using B3LYP and MPW1K functionals. A better fit of the computed geometry was obtained by the geometry optimization in a polar solvent continuum than in vacuum.

Iodination of Enol Acetates and 1,3-Diones Using N-Iodosaccharin

Abstract Iodination of enol acetates and 1,3-diones with N-iodosaccharin yielding the corresponding α-iodoketones and 2-iodo-1,3-diones is presented. Reactions are carried out at room temperature under neutral conditions and in short reaction times.

Chemical and photochemical degradation of chlorantraniliprole and characterization of its transformation products

This study aimed at assessing the photodegradation of the insecticide chlorantraniliprole (CAP) in deionized water and in tap water amended with humic acids and nitrate. Photolysis was carried out under simulated solar or UV-A light. CAP (39 μM) photodegradation was slightly faster in tap water than in deionized water with half lives of 4.1 and 5.1 days, respectively. Photodegradation rate of CAP was hardly affected by humic acids (up to 100 mg L(-1)) and nitrate. Photodegradation pattern was different in slightly acidic (pH=6.1) deionized water compared to basic (pH=8.0) tap water. Four main degradation products have been isolated and characterized spectroscopically, and crystal structure was recorded for the first two photodegradation products. CAP also degraded in the dark controls, but only at basic pH (23% loss at pH 8.0 in tap water after 6 days), resulting in the formation of one single degradation product. Our study shows that the degradation of chlorantraniliprole in water is a combination of chemical and photochemical reactions, which are highly dependent on the pH of the solution.

Daphnid Life Cycle Responses to the Insecticide Chlorantraniliprole and Its Transformation Products

Chlorantraniliprole (CAP) is a newly developed, widely applied insecticide. In the aquatic environment, several transformation products are formed under natural conditions, one by dehydration and others by photoinduced degradation. Data on aquatic ecotoxicity of CAP can mainly be found in registration and regulatory evaluation reports. Moreover, the toxicity of its transformation products and especially effects upon chronic exposure remain completely unknown. Hence, our aim was to investigate the acute and chronic toxicity of CAP and its transformation products to the daphnid Daphnia magna. The results showed that CAP is extremely toxic to D. magna, with an acute and chronic LC50 of 9.4 and 3.7 μg/L, respectively. No effects on daphnid reproduction were observed, but the impact on daphnid survival also affected population growth rate, with an EC50 of 3.5 μg/L. In contrast, no negative effects of the two main degradation products were observed. The present study demonstrated a high sensitivity of nontarget microcrustaceans to CAP. However, the actual risk of CAP in water diminishes with its spontaneous or light-induced degradation into two transformation products, showing no toxicity to the daphnids in the present study.

Polymers as reagents and catalysts - part 29 the role of polymeric mediator structure in electrochemical oxidation'

Abstract Electrochemical oxidations of phenylsubstituted alkanes and alcohols in the presence of various polymeric mediators were studied. The effect of halide (X=: F, Cl, Br, l ) bonded to an insoluble resin, on the oxidation of diphenylmethane and triphenylmethane was investigated and poly(styrene-co-4-vinylpyridinium) chloride was found to be the most effective. In contrast, crosslinked poly(styrene-co-4-vinylpyridinium) bromide was the most effective mediator in the oxidation of alcohols to ketones, where also the influence of polymer matrix, i.e., functionalized polystyrene or poly(styrene-co-4-vinylpyridine) bearing bromide ion, is most evident. The structure of the substrate played an important role in electrochemical oxidations in the presence of polymer mediators.

Synthesis, characterisation and aquatic ecotoxicity of the UV filter hexyl 2-(4-diethylamino-2-hydroxybenzoyl)benzoate (DHHB) and its chlorinated by-products

Environmental context Various UV-filtering chemicals are added to sunscreens in order to protect humans from the harmful effects of the sun. As a consequence of disinfection processes in swimming pools, sunscreen components may be chlorinated and change their structure and properties, leading to derivatives with higher toxicity. The safety of sunscreen components as well as that of their transformation products during their use requires further study. Abstract In this work is presented a synthesis pathway for the UV filter hexyl 2-(4-diethylamino-2-hydroxybenzoyl)benzoate (DHHB) and its chlorinated by-products in order to investigate the transformation behaviour and toxicity changes of DHHB during chlorination disinfection treatment. Acute toxicity was measured using standardised tests with aquatic model organisms. The potency of DHHB was compared with other benzophenone-like UV filters tested in the same experimental set-up. The toxicity of chlorinated compounds tested with photobacteria was found to be in a similar range to that of the starting compound. Microalgae were more sensitive to DHHB than to its chlorinated by-products, whereas daphnids were affected more by DHHB’s chlorinated products. The comparative toxicity data showed DHHB and even more its chlorinated by-products as more highly biologically potent to daphnids than other tested UV filters. The toxic potential of benzophenone-like UV filters should be interpreted together with data on their chemical properties, chlorination effects and affected organisms.