Furoxánok és átmenetifém komplexeik előállítása és szerkezetvizsgálata = Synthesis, spectroscopy, and structure of furoxanes and their transition metal complexes

Munkánk során a nitril-oxidok (XCNO, X=F, Cl, Br, I, CN, CH3) ciklodimerizációs reakcióit vizsgáltuk ab initio módszerekkel. A nitril-oxidok kinetikailag kedvezményezett reakciója egy többlépéses reakció, ami furoxánokhoz vezet. Számitottuk az ICNO nitrilekkel és etinekkel való cikloaddícióját. Ezek a reakciók egylépéses folyamatok, melyek során 1,2,4-oxadiazol, illetve 1,2-oxazol származékok keletkeznek. Vizsgáltuk ezeket a reakciókat, úgy, hogy a molekulát AgCNO és jód reakciójával állítottuk elő. Tanulmányoztuk a furoxán molekula szerkezetét IR, Raman és fotoelektron spektroszkópiai módszerekkel. Számítottuk a molekula szerkezetét és aromásságát. Vizsgáltuk a furoxán gázfázisú bomlását. Tanulmányoztuk a furoxán és benzofuroxán Cr(0)-komplexek szerkezetét B3PW91 DFT módszerrel. Ez alapján az n-donor furoxan komplexek képződése termodinamikailag nem kedvezményezett. Az pi-donor furoxan komplexek nem léteznek, mert a furoxán-gyűrű kinyílik a króm atomon és dinitrozoetilén, illetve dinitrozobenzol krómkomplexek keletkeznek. Előállítottuk a HCNS és FCNS molekulákat Ar és Kr mátrixban. A molekulákat IR spektroszkópiával azonosítottuk. A mátrixok 15 K főlé melegítésével a HCNS esetén egy hidrogénkötéses komplex keletkezik a HCNS és a HCN között. Számítottuk a molekulák szerkezetét. Tanulmányoztuk az 1,2,5-tiadiazolok szerkezetét kvantumkémiai, valamint IR, Raman és UV fotoelektron spektroszkópiai módszerekkel. | The cyclodimerization processes of small nitrile oxides, XCNO (X=F, Cl, Br, I, CN, CH3) have been investigated by ab initio methods. The favoured dimerization process is a multi-step reaction to furoxans. The ICNO cycloaddition with nitriles and ethynyl derivatives is investigated and found to be a synchronous process, favouring the formation of 1,2,4-oxadiazole and 1,2-oxazole derivatives, respectively. These reactions have been studied experimentally by generating ICNO from AgCNO and I2. The parent furoxan has been investigated by IR, Raman and photoelectron spectroscopies. The geometry and aromaticity has been obtained from quantum-chemical calculations. Thermal decomposition of furoxan have been investigated. The structure and formation of furoxan and benzofuroxan Cr(0)-complexes have been studied using the B3PW91 method. Calculations have predicted that the formation of n-donor furoxan complexes is not favoured. pi-donor furoxan complexes do not exist. The furoxan ring opens-up upon coordination to chromium atom, leading to the formation of dinitrosoethylene or dinitrosobenzene complexes. HCNS and FCNS have been produced in Ar and Kr matrices and characterized by IR spectroscopy and quantum-chemical methods. Annealing the matrices after photolysis resulted in the formation of a hydrogen-bonded complex between HCNS and HCN. The structures of 1,2,5-thiadiazoles were studied by quantum-chemical calculations and by IR, Raman, and UV photoelectron spectroscopy

Structure, spectroscopy, and thermal decomposition of 5-chloro-1,2,3,4-thiatriazole: a He I photoelectron, infrared, and quantum chemical study

International audience5-Chloro-1,2,3,4-thiatriazole has been investigated in the gas phase for the first time by mid-infrared and He I photoelectron spectroscopy. The ground-state geometry has been obtained from quantum chemical calculations at the CCSD(T) and B3LYP levels using aug-cc-pVTZ basis set. Ionization potentials have been determined and the electronic structure has been discussed within the frame of molecular orbital theory. IR and photoelectron spectroscopies, supported by quantum chemical calculations at the B3LYP and SAC-CI levels, provide a detailed investigation into the vibrational and electronic character of the molecule. Thermal stability of 5-chloro-1,2,3,4-thiatriazole has been studied both experimentally and theoretically. Flash vacuum thermolysis of the molecule produces fast quantitatively N2, ClCN, and sulfur. Theoretical calculations at the CCSD(T)//B3LYP level predict competitive decomposition routes, starting either with a retro-cycloaddition reaction leading to N2S and ClCN or with a ring opening to chlorothiocarbonyl azide intermediate, to produce finally N2, S, and ClCN. Calculations also predict that N2S is reactive and decomposes in bimolecular reactions to N2 and S

PHOTOELECTRON SPECTROSCOPIC INVESTIGATIONS AT THE TECHNICAL UNIVERSITY OF BUDAPEST. POSSIBLE APPLICATIONS IN PHYSICAL CHEMISTRY

Four different physical-chemical applications of UV photoelectron spectroscopy have been presented in this work. In the first example the interpretation of electronic transitions of some five membered heterocycles have been studied. The second part gives an example for clarifying the mechanism of the tertiary butylation reaction of furan. The geometry of silyl pseudo-halides is considered in the third example, while the last topic is concerned by proving the aromaticity of cyclic molecules containing heteroatoms

Fém-ligandum kölcsönhatás vizsgálata gázfázisú molekulaspektroszkópiai módszerekkel = Investigation of transition metal complexes by gas phase molecular spectroscopic methods

- Új kvantumkémiai eljárást dolgoztunk ki az átmenetifém-származékok fotoelektron (pe) színképének értelmezéséhez. - UPS vizsgálatok alapján meghatároztuk a CS és CSe ligandumok CO-hoz viszonyított donor-akceptor sajátságát. - Előállítottuk a Co(CO)2(N | Novel quantumchemical method has been worked out for the interpretation of the photoelectron (pe) spectra of transition metal derivatives.-Donor-acceptor properties of CS and CSe related to CO have been determined on the basis of UPS investigations.-New compound of Co(CO)2(NO)(t-BuNC) has been prepared and investigated by HeI UPS and threshold PEPICO methods. From the PEPICO measurements energetic and thermochemical data were derived.-Trimethyl phosphane, -arsane, and –stibane derivatives of CpMnCO3 and CoCO3NO have been investigated by HeI and HeII UPS methods and conclusions were drawn concerning the ?-acceptor and ?-donor ability of the ligands.-A new series of isonitrile-substituted cobalt tricarbonyl nitrosyl (Co(CO)2(NO)CNR, R= Me, Et, nPr, iPr, nBu, nPe, CH2SiMe3) has been synthesized and studied by HeI UPS. The relative importance of electronic and steric effects of the isonitrile ligands, as a function of the size of group –R were determined. Metallocene ions (Cp2M+, M=Cr,Co,Ni) were studied by TPEPICO spectroscopy to investigate the mechanism, energetics and kinetics of the ionic dissociation processes.-Me3Si and Me3Ge radicals were generated by the gas phase thermolysis of (Me3Si/Ge)2Hg. The HeI pe spectra were recorded and assigned.-Electronic structure determination of precursors (diiodofuroxan and thiadiazoles) of some exotic molecules has been performed. Pyrolizer/ reactor directly attached to the pe spectrometer has been constructed

Evidence of quasi-intramolecular redox reactions during thermal decomposition of ammonium hydroxodisulfitoferriate(III), (NH4)(2)[Fe(OH)(SO3)(2)]center dot H2O

Synthesis of ammonium hydroxodisulfitoferriate(III), (diammonium catena-{bis(mu (2)-sulfito-kappa O,kappa O)-mu (2)-hydroxo-kappa O-2}ferrate(III) monohydrate) (NH4)(2)[Fe(OH)(SO3)(2)]center dot H2O (compound 1) and its thermal behavior is reported. The compound is stable in air. Its thermal decomposition proceeds without the expected quasi-intramolecular oxidation of sulfite ion with ferric ions. The disproportionation reaction of the ammonium sulfite, formed from the evolved NH3, SO2 and H2O in the main decomposition stage of 1, results in the formation of ammonium sulfate and ammonium sulfide. The ammonium sulfide is unstable at the decomposition temperature of 1 (150 A degrees C) and transforms into NH3 and H2S which immediately forms elementary sulfur by reaction with SO2. The formation and decomposition of other intermediate compounds like (NH4)(2)SnOx (n = 2, x = 3 and n = 3, x = 6) results in the same decomposition products (S, SO2 and NH3). Two basic iron sulfates, formed in different ratios during synthesizing experiments performed under N-2 or in the presence of air, have been detected as solid intermediates which contain ammonium ions. The final decomposition product was proved to be alpha-Fe2O3 (mineral name hematite)

Advances in Detecting Ciguatoxins in Fish

Ciguatera fish poisoning (CFP) is currently the most common marine biotoxin food poisoning worldwide, associated with human consumption of circumtropical fish and marine invertebrates that are contaminated with ciguatoxins. Ciguatoxins are very potent sodium-channel activator neurotoxins, that pose risks to human health at very low concentrations (>0.01 ng per g of fish flesh in the case of the most potent Pacific ciguatoxin). Symptoms of CFP are nonspecific and intoxication in humans is often misdiagnosed. Presently, there is no medically approved treatment of ciguatera. Therefore, to mitigate the risks of CFP, reliable detection of ciguatoxins prior to consumption of fish tissue is acutely needed, which requires application of highly sensitive and quantitative analytical tests. During the last century a number of methods have been developed to identify and quantify the concentration of ciguatoxins, including in vivo animal assays, cell-based assays, receptor binding assays, antibody-based immunoassays, electrochemical methods, and analytical techniques based on coupling of liquid chromatography with mass spectrometry. Development of these methods, their various advantages and limitations, as well as future challenges are discussed in this review

Biosensors for Non-Invasive Detection of Celiac Disease Biomarkers in Body Fluids

Celiac disease is a chronic gluten-initiated autoimmune disorder that predominantly damages the mucosa of the small intestine in genetically-susceptible individuals. It affects a large and increasing number of the world’s population. The diagnosis of this disease and monitoring the response of patients to the therapy, which is currently a life-long gluten-free diet, require the application of reliable, rapid, sensitive, selective, simple, and cost-effective analytical tools. Celiac disease biomarker detection in full blood, serum, or plasma offers a non-invasive way to do this and is well-suited to being the first step of diagnosis. Biosensors provide a novel and alternative way to perform conventional techniques in biomarker sensing, in which electrode material and architecture play important roles in achieving sensitive, selective, and stable detection. There are many opportunities to build and modify biosensor platforms using various materials and detection methods, and the aim of the present review is to summarize developments in this field