Formation Of L2 Research Articles

Adsorption of linear and cyclic siloxanes on activated carbons for biogas purification: Sorbents regenerability

Two commercial activated carbons, namely STIX and AP4, were selected to investigate their ability for siloxane adsorption and further thermal regeneration in relation with their different physico-chemical properties. In the frame of biogas purification, the studied siloxanes were L2, L3, L4 (linear molecules) and D4, D5 (cyclic molecules). The maximum capacity of adsorption was estimated by gas chromatography and gravimetric methods. AP4 presents better adsorptive properties comparing with STIX irrespective of the type of siloxane. Thermal regeneration after siloxanes adsorption was followed up to 400 °C by both gas chromatography and in situ DRIFTS. Except L2, the siloxane polymerization proceeds on the AC containing alkali metals (K, Na) as revealed by the observed release of their decomposition products during the thermodesorption treatment. The same sites are responsible for the cleavage of SiO bonds in linear molecules and formation of L2 as primary product above 100 °C. The presence of such sites, possibly strong basic sites, is detrimental to the regenerability of the spent adsorbent and to the adsorption which could be limited by partial blockage of the AC porosity. Interestingly the regenerability of the alkali-free AC depends only on the volatility of the siloxane.

New template reactions of salicylaldehyde S-methyl-isothiosemicarbazone with 2-formylpyridine promoted by Ni(II) or Cu(II) metal ions

The template reaction between salicylaldehyde S-methyl-isothiosemicarbazone and 2-formylpyridine in presence of nickel(II) or copper(II) salts yields two new coordination compounds with general formula [NiL1]2(1) and [CuL2]2(2) (L1=the dianionic (N1-salicylidene)(N4-(hydroxy(pyridin-2-yl)methyl) S-methyl-isothiosemicarbazide) ligand and L2=the doubly deprotonated (N1-salicylidene)(N4-(picolinoyl) S-methyl-isothiosemicarbazide) ligand). In the complex 1, the formed L1 ligand appears as result of an addition reaction of the precursors, while for 2 a redox mechanism is implicated in the formation of L2. Despite the fact that the initial organic precursors are the same, the resulting ligands obtained in the template reaction are different. In 1, the Ni(II) metal ion adopts a square-planar geometry and the [NiL1] units are forming dimerized chains through weak Ni···Ni interactions (3.336 and 3.632Å). In 2, the Cu(II) metal ions adopt a square-pyramidal geometry and form dinuclear species through weak Cu···O (phenoxo) interactions. The magnetic susceptibility measurements of the complexes reveal the diamagnetic nature of 1 as expected for a square planar Ni(II) complex and a paramagnetic behavior for 2 with weak intra-dimer antiferromagnetic interaction (J/kB=−2.1(1)K).

Iron(II) complexes with novel pentadentate ligands via C–C bond formation between various nitriles and [2,4-bis(2-pyridylmethylimino)pentane]iron(II) perchlorate: synthesis and structures ‡

The iron(II) complex of 2,4-bis(2-pyridylmethylimino)pentane (L1), trans-[FeL1(MeCN)2][ClO4]2·MeCN, was prepared by a template reaction and isolated as pale red crystals. An acetonitrile solution of the complex exhibited a crossover from a low- to a high-spin form above 20 °C. With this complex as precursor, a series of iron(II) complexes with novel pentadentate ligands, 3-(1-alkyl (or aryl)-methyl)-1-imino-2,4-bis(2-pyridylmethylimine) (L2), was prepared using various nitriles such as propionitrile, isobutyronitrile, benzyl cyanide, benzonitrile, 4-fluoro-, 3,4-difluoro-, and pentafluoro-benzonitrile, as well as acetonitrile, as solvents. On formation of L2, the co-ordination mode of the L1 part of the parent compound was converted from trans into cis-β with concomitant C–C bond formation between the central carbon atom of L1 and the carbon atom of the various nitriles. The isolated triimine part in the pentadentate ligands occupies one of the trigonal faces of the distorted octahedron. The resulting complex undergoes rapid intramolecular isomerization at or above room temperature. The crystal structures of the precursor and of three new iron(II) complexes with pentadentate ligands have been determined.

ChemInform Abstract: SPECTROPHOTOMETRIC INVESTIGATIONS OF AQUEOUS SOLUTIONS AT ELEVATED TEMPERATURES

Chemischer InformationsdienstVolume 6, Issue 29 Article ChemInform Abstract: SPECTROPHOTOMETRIC INVESTIGATIONS OF AQUEOUS SOLUTIONS AT ELEVATED TEMPERATURES WILLIM L. DUDENEY, WILLIM L. DUDENEYSearch for more papers by this authorROGER J. IRVING, ROGER J. IRVINGSearch for more papers by this author WILLIM L. DUDENEY, WILLIM L. DUDENEYSearch for more papers by this authorROGER J. IRVING, ROGER J. IRVINGSearch for more papers by this author First published: July 22, 1975 https://doi.org/10.1002/chin.197529099Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue29July 22, 1975 RelatedInformation

Spectrophotometric investigations of aqueous solutions at elevated temperatures

New spectrophotometric data have been obtained for the dissociation of salicylic acid (H2L), over the temperature range 10–85°C, from which values of the first and second thermodynamic dissociation constants (K1 and K2 respectively) of the acid have been calculated.The results substantiate recent conductimetric measurments of K1, which show a shallow maximum in K1 near 40°C. They indicate an increase in K2 with temperature in the range considered but do not agree well with available literature values for this constant.Discrepancies in K2 are attributed largely to systematic errors arising from the low degree of formation of L2–, slight chemical decomposition of this species particularly at higher temperatures, and high ionic strength in the experimental solutions. As a result of these errors it is unlikely that reliable thermodynamic data can be derived from reported determinations of K2.