Sinteza i kristalna struktura 1,2,3,4-tetrahidro-9-aminoakridin-tetrahlorocinkata(II) monohidrata

In the reaction of ZnCl(2) with tacrine hydrochloride in water novel tetracoordinated (C(13)H(15)N(2))(2)[ZnCl(4)]-H(2)O complex was obtained and characterized by elemental analysis, molar conductivity and X-ray analysis. The complex crystallizes in the space group P-1 of the triclinic crystal system. The structure contains two crystallographically different molecules of protonated tacrine present as counter cations, the [ZnCl(4)](2-) complex anion and one water solvent molecule. The counter cations slightly differ in the puckering of the cyclohexene ring. The molecules of protonated tacrine are involved in different intermolecular hydrogen bonds. In the crystal, the hydrogen bonding generates a 3D assembly. In the crystal, pi center dot center dot center dot pi stacking interactions between the rings of protonated tacrine were evidenced. The [ZnCl(4)](2-) complex anion has a distorted tetrahedral geometry. Three out of the four Cl atoms are involved in intermolecular hydrogen bonding. The intermolecular H-bond interactions involving the Cl atoms affect the Zn-CI bond lengths.U reakciji ZnCl2 sa takrin-hidrohloridom u vodi, dobijen je novi tetrakoordinovani (C13H15N2)2[ZnCl4]?H2O kompleks koji je okarakterisan pomoću elementalne analize, molarne provodljivosti i rendgenske strukturne analize. Kompleks kristališe u prostornoj grupi P?1 trikliničnog kristalnog sistema. Struktura sadrži dva kristalografski različita molekula protonovanog takrina koji su prisutni kao kontra-katjoni, [ZnCl4]2 kompleksni anjon i molekul kristalne vode. Molekuli katjona se neznatno razlikuju u stepenu nabiranja cikloheksenovog prstena. Molekuli protonovanog takrina su uključeni u različite intermolekulske vodonične veze. Intermolekulsko vodonično vezivanje u kristalu generiše 3D molekulski skup pi...pi interakcije između prstenova protonovanog takrina su primećene u kristalu. [ZnCl4]2- ima distorgovanu tetraedarsku geometriju. Tri od četiri Cl atoma su uključena u intermolekulske vodonične veze. Intermolekulske vodonične interakcije koje uključuju Cl atome utiču na dužinu Zn-Cl veza

Sinteza, NMR i DFT proračunavanja i ispitivanje antimikrobne aktivnosti Zn(II) kompleksa sa N-benziloksikarbonil-S-alaninom

In this study, the first complexes of Zn(II) with the N-benzyloxycarbonyl-S-alaninato ligand (N-Boc-S-ala) were synthesized. The new complexes were characterized by elemental analysis, conductometric measurements, IR. (1)H-NMR, (13)C-NMR and 2D-NMR spectroscopy. On the basis of the experimental data, tetrahedral geometry of the Zn(II) complexes was proposed. A very good agreement between the NMR and DFT calculated data was obtained. Investigation of antimicrobial activity of the newly synthesized complexes was also performed. It was established that [Zn(N-Boc-S-ala)(2)] was selective and acts only on Candida aibicans.U ovom radu su sintetizovani prvi kompleksi Zn(II) sa N-benziloksikarbonil-S-alaninato ligandom (N-Boc-S-ala). Kompleksi su okarakterisani elementalnom analizom, konduktometrijskim merenjem, IR, 1H-NMR, 13C-NMR i 2D-NMR spektroskopijom. Tetraedarska geometrija Zn(II) kompleksa pretpostavljena je na osnovu eksperimentalnih podataka. Dobijeno je veoma dobro slaganje između NMR i DFT podataka. Ispitivana je antimikrobna aktivnost novosintetizovanih kompleksa. Ustanovljeno je da je [Zn(N-Boc-S-ala)2] kompleks selektivan i da deluje samo na gljivu Candida albicans

RIQUALIFICAZIONE ENERGETICA DEGLI EDIFICI DEL WWF

Il lavoro svolto consiste nella valutazione energetica degli edifici dell’oasi della Laguna di Orbetello (Centro di Educazione Ambientale “A. Peccei”) e della sede centrale del WWF Italia a Roma. Per gli edifici dell’oasi, lo studio consiste in primo luogo nell’analisi del fabbisogno energetico degli edifici secondo la normativa vigente; in secondo luogo nella valutazione delle prestazioni delle coperture ventilate presenti, in termini di risparmio di calore entrante nell’edificio in estate; infine vengono proposti alcuni interventi di riqualificazione energetica suddivisi in cinque grandi aree di pertinenza: la messa in efficienza dell’involucro, la messa in efficienza degli impianti termico ed elettrico, lo sfruttamento delle risorse naturali costituite dalla radiazione solare (progetto di un impianto solare termico per la produzione di acqua calda sanitaria e ristrutturazione degli impianti fotovoltaici presenti), dall’acqua (riduzione del fabbisogno idrico, riciclo delle acque grigie, impianto di fitodepurazione) e dal combustibile producibile in loco (sostituzione delle caldaie obsolete presenti con caldaie a cippato). Per ogni intervento è stato proposto un modello di progettazione e dimensionamento degli impianti in gioco, ed è stato quindi dato un prospetto del risaparmio ottenibile in termini di diminuzione del fabbisogno di energia primaria, idrica e di combustibile. Tale procedimento è stato adottato anche per la valutazione energetica della sede centrale WWF di Roma, avvalendosi di opportune modifiche legate al diverso contesto

Thermal stability and degradation of Co(II), Cd(II), and Zn(II) complexes with N-benzyloxycarbonylglycinato ligand

Thermal behavior of Co(II), Cd(II), and Zn(II) complexes with N-benzyloxycarbonylglycinato ligand was investigated using the results of TG, DSC and DTG analysis obtained at different heating rates (2.5 to 30 A degrees C min(-1)), from room temperature to about 900 A degrees C. Mechanisms of complex degradation, as well as enthalpies of the degradation processes were determined. It is shown that thermal stability of investigated complexes correlates with their crystal structures, especially with the presence of crystallization and coordinated water molecules. The values of dehydration enthalpies are discussed and correlated with composition of the complexes. Kissinger's, Ozawa's, and Friedman's isoconversion methods were used for the determination of kinetic parameters: the pre-exponential factor A and the apparent activation energy E (a). For all three complexes and all steps of degradation, the values of kinetics parameters obtained by Kissinger's and Ozawa's methods are in good agreement. The results obtained by Friedman's method showed that some decomposition steps are simple and some others are complex ones

Mixed cobalt(III) complexes with S-tyrosine and 1,3-diaminopropane

Four out of six theoretically possible isomers of the (1,3-diaminopropane)bis(S-tyrosinato)cobalt(III) complex, having the cis(O) configuration, were isolated, and the trans(O) isomer was only defined in the eluate. The isomers were separated on an optically active Sephadex QAE column. Geometrical and absolute configurations of the isomers were determined by electronic absorption, circular dichroic and H-1 NMR spectra. The effect of the aromatic side group of the coordinated S-tyrosinato ligand on the stereoselective formation of the obtained isomers was examined

Mixed cobalt(III) complexes with aromatic amino acids and diamine - Part V. Thermal investigation of (1,2-diaminoethane)bis(S-tyrosinato)cobalt(III) complex diastereomers

Thermal properties of (1,2-diaminoethane)bis(S-tyrosinato)cobalt(III) complex diastereomers are investigated by means of TG technique in 293-873 K temperature range. This is a first thermal study of [Co(S-aa)(2)en](+) (S-aa = anion of S-amino acid; en = 1,2-diaminoethane) complex diastereomers. It is shown that thermal decompositions of these complexes are multi-step degradation processes, which in some cases can be satisfactory separated into individual steps, depending on the molecular symmetry. It is proposed that the degradation processes occur with cleavage of the side chain of one S-tyrosinato ligand, followed by the cleavage of the second side chain by further heating. The proposed pathways of decomposition are in accordance with results of thermal degradation of noncoordinated S-tyrosine [F. Rodante, G. Marrosu, G. Catalani, Thermochim. Acta 194 (1992) 197-213]. In the case of diastereomers which crystallize with water molecules, the departure of both hygroscopic and crystal water occurs before. The corresponding kinetic and thermodynamic parameters of some processes were determined. (c) 2004 Elsevier B.V. All rights reserved

Mixed cobalt(III) complexes with S-tyrosine and 1,3-diaminopropane

Four out of six theoretically possible isomers of the (1,3-diaminopropane)bis(S-tyrosinato)cobalt(III) complex, having the cis(O) configuration, were isolated, and the trans(O) isomer was only defined in the eluate. The isomers were separated on an optically active Sephadex QAE column. Geometrical and absolute configurations of the isomers were determined by electronic absorption, circular dichroic and H-1 NMR spectra. The effect of the aromatic side group of the coordinated S-tyrosinato ligand on the stereoselective formation of the obtained isomers was examined

NH...pi interactions stabilize the most-hindered rotamer of the (S)-tyrosinato side group in bis[(S)-tyrosinato](diamine)cobalt(III) complexes: An NMR spectroscopic and DFT study

Conformational analysis based on an analysis of the vicinal alpha- and beta-proton coupling constants of (S)-tyrosinato ligands in diastereomers of a bis[(S)-tyrosinato](1,3-diaminopropane)cobalt(III) complex is used to calculate the mol fractions of the three most stable rotamers (t, g, h) of the (S)-tyrosinato ligand's side groups in D2O solution. The results of this conformational analysis indicate a population increase in the sterically least favorable rotamer h in diastereomers of Cl-molecular symmetry (complexes 5 and 6). The TOCSY spectrum of complex 6 in aqueous solution shows an exceptionally small chemical shift of one NH2 proton from the coordinated diamine, which is explained by an interligand NH center dot center dot center dot pi interaction. These findings demonstrate the persistence of this weak, noncovalent interaction in water solution. DFT calculations for complex 6, whose diamine ring is in a chair conformation, indicate that the complex with an h conformation in both its (S)-tyrosinato ligand side-residues, which yields the most frequent NH center dot center dot center dot pi interactions, represents an energy minimum. The fact that coordinated 1,3-diaminopropane in the examined complex 6 is in a chair conformation in aqueous solution is proved by the NMR analysis. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005

Kinetics and mechanism of degradation of Co(II)-N-benzyloxycarbonylglycinato complex

The kinetics of multi-step thermal degradation of Co(II) complex with N-benzyloxycarbonyl glycinato ligand [Co(N-Boc-gly)(2)(H2O)(4)]center dot 2H(2)O, in non-isothermal conditions was studied using isoconversional and non-isoconversional methods. The degradation of complex occurs in three well-separated steps involving the loss of water molecules in first step followed by two degradation steps of dehydrated complex. The dependence of Arrhenius parameters on conversion degree showed that all observed steps of thermal degradation are very complex, involving more than one elementary step, as can be expected for most solid-state heterogeneous reactions with solid reactants and solid and gaseous products. It was shown that step 1, corresponding to the dehydration, involves a series of competitive dehydration steps of differently bound water molecules complicated by diffusion. Second step involves two parallel reactions related to the loss of two identical C6H5CH2O-ligand fragments complicated by the presence of products in gaseous state. Further degradation in step 3 corresponds to complex process with a change in the limiting stage, in this case from the kinetic to the diffusion regime, connected with the presence of gaseous products diffusing through the solid product

Synthesis and absolute configuration of novel mono- and dinuclear cobalt(III) complexes containing S-phenylalanine

Two diastereomers of bis(1,3-diaminopropane)(S-phenylalaninato)cobalt(III) were prepared by reaction of S-phenylalanine with carbonatobis(1,3-diaminopropane)cobalt(III). The diastereomers were separated on an optically active Sephadex QAE column and their absolute configurations assigned by means of circular dichroism. In addition, H-1 NMR spectra of the diastereomers were analyzed in terms of the population of the three predominant rotamers of the coordinated S-phenylalaninato ligand. One out of 24 theoretically possible diastereomers of the dinuclear species di-mu-hydroxo-tetrakis(S-phenylalaninato)dicobalt(III) was obtained by direct synthesis and its absolute configuration deduced from CD spectra