Relationship between solid state structure and solution stability of copper(ii)-hydroxypyridinecarboxylate complexes

The complementary solid state/solution studies of the systematic series of bioactive ligands 3-hydroxy- 1-methyl-4-pyridinecarboxylate (L1), 3-hydroxy-1,2,6-trimethyl-4-pyridinecarboxylate (L2), 4-hydroxy-1- methyl-3-pyridinecarboxylate (L3), 4-hydroxy-1,6-dimethyl-3-pyridinecarboxylate (L4), 4-hydroxy-1-(2- hydroxyethyl)-6-methyl-3-pyridinecarboxylate (L5) and 4-hydroxy-1-(2-carboxyethyl)-6-methyl-3- pyridinecarboxylate (L6) with copper(II) have been performed in order to design efficient chelating drugs for the treatment of metal overloading conditions. Single crystals of [Cu(L1)2(H2O)]3H2O (1) (monomer) with axial water coordination, [Cu2(L2)4]6H2O (2) and [Cu2(L3)4]4H2O (3) (cyclic dimers), where pyridinolato and carboxylato oxygens, respectively, act as linkers between adjacent copper complexes, [Cu(L4)2]n3H2O (4) (1D polymer) and [Cu3(L5)6]18H2O (5) (trimer), constructed using two square-pyramidal and one elongated octahedral Cu(II) complexes have been determined by SXRD. The bidentate coordination mode of the ligands has been found preferentially with cis arrangements in 1 and 2 and trans arrangements in 3\u20135. The solution speciation and complex stability of aqueous solutions have been studied by pH-dependent electron paramagnetic resonance spectroscopy resulting in the detection of solely monomeric [CuL]+ and [CuL2] complexes. The stability order obtained for the [CuL]+ complexes could be correlated with the deprotonation constants of their hydroxyl group (log bLH) reflecting that the higher acidity increases the complex stability in the order L2 o L1 E L6 o L4 E L5 o L3. This stability order elucidates the different axial linkers in the cyclic dimers 2 and 3. DFT quantum-chemical calculations support the effect of the electron distribution on the established stability order

Online coupled TG-FTIR and TG/DTA-MS analyses of the evolved gases from dichloro(thiourea) tin(II)

Identification and monitoring of gaseous species released during thermal decomposition of title compound 1, dichloro(thiourea) tin(II), Sn(tU)Cl-2, [thiourea (tu), (NH2)(2)C=S] in flowing air atmosphere have been carried out by both online coupled TG-FTIR and simultaneous TG/DTA - MS evolved gas -analysis (EGA) instruments. The first gaseous products of 1, evolved from 170 degreesC, are cyanamide (NH2CN), carbonyl sulphide (COS), carbon disulfide (CS2) and water (H2O). At 240 degreesC isothiocyanic acid (HNCS) becomes the main product, accompanied by CS2, hydrogen cyanide (HCN) and traces of hydrogen chloride (HCI) according to EGA-FTIR analysis. Ammonia (NH3) occurs first only above 250 degreesC, while sulfur dioxide (SO2) formation is not observed till 400 degreesC. Air oxidation products of tin sulphides and organic residues, such as SO2, carbon dioxide (CO2) and NH2CN, occur suddenly at 425 degreesC together with a very sharp exothermic heat effect. All species identified by FTIR gas cells are confirmed by mass spectrometry, except HNCS. Evolution of H2S has not been observed at any stage of the degradation of 1 by either of the EGA methods. (C) 2004 Elsevier B.V. All rights reserved

Comparative online coupled TG-FTIR and TG/DTA-MS analyses of the evolved gases from thiourea complexes of SnCl2.

Identification and monitoring of gaseous species released during thermal decomposition of title compound 1, Sn-2(tu)(5)Cl(4)(.)2H(2)O (tu stands for thiourea (NH2)(2)C=S)) in flowing air atmosphere have been carried out up to 600 degreesC by both online coupled TG-EGA-FTIR and simultaneous TG/DTA-EGA-MS apparatuses. The first gaseous products of the dehydrated 1, evolved around 190 degreesC, are carbonyl sulphide (COS), carbon disulfide (CS2), and cyanamide (NH2CN). At 240 degreesC isothiocyanic acid, HNCS becomes the main product, accompanied by CS2, ammonia (NH3) a small amount of hydrogen cyanide (HCN) and traces of hydrogen chloride (HCI), according to EGA-FTIR spectroscopic analysis. At 250 degreesC formation of sulphur dioxide (SO2) has been observed by EGA-mass spectrometry. SO2 as air oxidation product of tin sulphides, formed in the previous stages, occurs also around 430 degreesC, while gaseous oxidation products of the organic residues, such as CO2 and NH2CN are released at 515 degreesC. Both oxidation processes are accompanied by an exothermic heat effect. All species identified by FTIR gas cell are also confirmed by mass spectrometry, except HNCS. (C) 2004 Elsevier B.V. All rights reserved

Supramolecular morphotropy of calixarene inclusion compounds

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