Photocatalytic degradation of actual textile industrial wastewater in aqueous suspensions of polycrystalline TiO2

Heterogeneous photocatalytic oxidation of contaminants present in wastewater produced by a textile industry was carried out. The samples were withdrawn from the plant before and after a traditional biological treatment. The effluents were named A and A' (before the biological treatment), B and B' (after the biological treatment). Polycrystalline TiO2 (Degussa P25) was used as the catalyst in a batch photoreactor with immersed lamp. An almost complete decolorization was observed after about 0.5 divided by 1 hours for both kinds of effluents, but the decrease of the total organic carbon (TOC) concentration occurred more slowly. The influence of some chemical oxidants, i.e. ozone, hydrogen peroxide and peroxydisulfate on the photo-oxidation rate was also investigated. After addition of H2O2 or S2O8(2-) TOC decreased more quickly only for B and B'. The runs performed by using O3 as bubbling gas showed a mineralization rate higher than that observed in the presence of O2.     

Novel reaction of carbon suboxide. Synthesis of 6-amino-4-hydroxy-2(1H)-pyridone derivatives

The reaction of 2-cyanoacetamidines 1 with carbon suboxide 2 afforded 6-amino-4-hydroxy-2(1H)-pyri-dones 4 . Compounds 4 were also obtained by reaction of amidines 1 and 2,4,6-trichlorophenylmalonates 3 .     

Reactivity of 1-phenylsulfinyl-2-phenylsulfanylethylene (SOSE) with O-nucleophiles generated by potassium tert-butoxide

E-1-Phenylsulfinyl-2-phenylsulfanylethylene (E-SOSE) reacts with O-nucleophiles generated by means of t-BuOK via an addition-elimination mechanism, thus affording the product of substitution of the phenylsulfanyl group in a stereo-conservative process. When used alone, the strongly basic and hindered tert-butoxide brings about elimination of either the phenylthiolate or phenylsulfinate groups. Z-SOSE is much more prone to elimination: either with t-BuOK alone or with other O-nucleophiles generated by t-BuOK, it always leads to products derived from elimination. Other alkaline tert-butoxides or other bases appear not as effective in generating species nucleophilic enough to react with E-SOSE.     

A molecular spring for vision

Light absorption by the visual pigment rhodopsin leads to vision via a complex signal transduction pathway that is initiated by the ultrafast and highly efficient photoreaction of its chromophore, the retinal protonated Schiff base (RPSB). Here, we investigate this reaction in real time by means of unrestrained molecular dynamics simulations of the protein in a membrane mimetic environment, treating the chromophore at the density functional theory level. We demonstrate that a highly strained all-trans RPSB is formed starting from the 11-cis configuration (dark state) within approximately 100 fs by a minor rearrangement of the nuclei under preservation of the saltbridge with Glu113 and virtually no deformation of the binding pocket. Hence, the initial step of vision can be understood as the compression of a molecular spring by a minor change of the nuclear coordinates. This spring can then release its strain by altering the protein environment.     

Structure and Bonding in Pentacyano(L)ferrate(II) and Pentacyano(L)ruthenate(II) Complexes (L = Pyridine, Pyrazine, and N-Methylpyrazinium): A Density Functional Study

Density Functional Theory (DFT) at the generalized gradient approximation (GGA) level has been applied to the complexes [Fe(CN)(5)L](n-) and [Ru(CN)(5)L](n-) (L = pyridine, pyrazine, N-methylpyrazinium), as well as to [Fe(CN)(5)](3)(-) and [Ru(CN)(5)](3)(-). Full geometry optimizations have been performed in all cases. The geometrical parameters are in good agreement with available information for related systems. The role of the M(II)-L back-bonding was investigated by means of a L and cyanide Mulliken population analysis. For both Fe(II) and Ru(II) complexes the metal-L dissociation energies follow the ordering pyridine < pyrazine < N-methyl pyrazinium, consistent with the predicted sigma-donating and pi-accepting abilities of the L ligands. Also, the computed metal-L bond dissociation energies are systematically smaller in the Ru(II) than in the Fe(II) complexes. This fact suggests that previous interpretations of kinetic data, showing that ruthenium complexes in aqueous solution are more inert than their iron analogues, are not related to a stronger Ru-L bond but are probably due to solvation effects.     

Stereospecific beta-lithiation of oxazolinyloxiranes: synthesis of alpha,beta-epoxy-gamma-butyrolactones

[reaction: see text]. Stereospecific beta-lithiation of beta-aryl-substituted oxazolinyloxiranes is described. The trapping reaction of such reactive intermediates with carbonyl compounds gave alpha,beta-epoxy-gamma-butyrolactones after deblocking of the oxazoline moiety. This methodology has been also extended to the synthesis of optically active alpha,beta-epoxy-gamma-butyrolactones.     

Reaction between N-acyl-2,3-dihydrobenzo-1,4-thiazine and N-acylphenothiazine with organometallic reagents

the title $\text{N}$-acyl-derivatives react with $\text{n}$-BuLi and Grignard reagents leading to products, which, formally, can be considered as derived from a Claisen-type condensation reaction.     

New reactions of carbon suboxide with alkynes

Synthesis of 3,4,7,8‐tetraalkyl‐2‐oxa‐bicyclo[4.2.0]octa‐1(6),3,7‐trien‐5‐ones( 4a‐d ),4,5,7,8‐tetraalkyl‐2‐oxa‐bicyclo[4.2.0]octa‐1(6),4,7‐trien‐3‐ones ( 6a‐d ) and 3,4,7,8‐tetraalkyl‐2H,5H‐cyclobuta[b]pyrano‐[2,3‐d]pyran‐2,5‐diones ( 7a‐d ) from the reaction of alkynes ( la‐d ) with carbon suboxide ( 2 ) in various molar ratios is described.     

Mixed-valent [FeIV(mu-O)(mu-carboxylato)2FeIII]3+ core

The symmetrically ligated complexes 1, 2, and 3 with a (mu-oxo)bis(mu-acetato)diferric core can be one-electron oxidized electrochemically or chemically with aminyl radical cations [*NR3][SbCl6] in acetonitrile yielding complexes which contain the mixed-valent [(mu-oxo)bis(mu-acetato)iron(IV)iron(III)]3+ core: [([9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)2](ClO4)2 (1(ClO4)2), [(Me3[9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)2](PF6)2 (2(PF6)(2)), and [(tpb)(2FeIII2)(mu-O)(mu-CH3CO2)2] (3) where ([9]aneN3) is the neutral triamine 1,4,7-triazacyclononane and (Me3[9]aneN3) is its tris-N-methylated derivative, and (tpb)(-) is the monoanion trispyrazolylborate. The asymmetrically ligated complex [(Me3[9]aneN3)FeIII(mu-O)(mu-CH3CO2)2FeIII(tpb)](PF6) (4(PF6)) and its one-electron oxidized form [4ox]2+ have also been prepared. Finally, the known heterodinuclear species [(Me3[9]aneN3)CrIII(mu-O)(mu-CH3CO2)2Fe([9]aneN3)](PF6)2 (5(PF6)(2)) can also be one-electron oxidized yielding [5ox]3+ containing an iron(IV) ion. The structure of 4(PF6).0.5CH3CN.0.25(C2H5)2O has been determined by X-ray crystallography and that of [5ox]2+ by Fe K-edge EXAFS-spectroscopy (Fe(IV)-O(oxo): 1.69(1) A; Fe(IV)-O(carboxylato) 1.93(3) A, Fe(IV)-N 2.00(2) A) contrasting the data for 5 (Fe(III)-O(oxo) 1.80 A; Fe(III)-O(carboxylato) 2.05 A, Fe-N 2.20 A). [5ox]2+ has an St = 1/2 ground state whereas all complexes containing the mixed-valent [FeIV(mu-O)(mu-CH3CO2)2FeIII]3+ core have an St = 3/2 ground state. M?ssbauer spectra of the oxidized forms of complexes clearly show the presence of low spin FeIV ions (isomer shift approximately 0.02 mm s(-1), quadrupole splitting approximately 1.4 mm s(-1) at 80 K), whereas the high spin FeIII ion exhibits delta approximately 0.46 mm s(-1) and DeltaE(Q) approximately 0.5 mm s(-1). M?ssbauer, EPR spectral and structural parameters have been calculated by density functional theoretical methods at the BP86 and B3LYP levels. The exchange coupling constant, J, for diiron complexes with the mixed-valent FeIV-FeIII core (H = -2J S1.S2; S(1) = 5/2; S2 = 1) has been calculated to be -88 cm(-1) (intramolecular antiferromagnetic coupling) and for the reduced diferric form of -75 cm(-1) in reasonable agreement with experiment (J = -120 cm(-1)).     

Reactivity of 4-nitro- and 4-nitro-7-halogeno-2,1,3-benzothiadiazoles toward methoxide ion

4-Nitro-2,1,3-benzothiadiazole reacted with sodium methoxide (0.1-1 M) in methanol yielding 2,1,3-benzothiadiazole-4, 7-dione monoxime (syn+anti). Methoxy-dehalogenation of 4-nitro-7-halogeno-derivatives yielded 4-nitro-7-methoxy-2,1,3-benzothadiazole under similar conditions. In both eases transitions attributable to the formation of Meisenheimer complexes were detected.