Juan Niclós

Bio: Juan Niclós is an academic researcher from University of Granada. The author has contributed to research in topics: Denticity & Square pyramidal molecular geometry. The author has an hindex of 11, co-authored 17 publications receiving 369 citations.

Mixed‐Ligand Complexes of Copper(II) with α‐Hydroxycarboxylic Acids and 1,10‐Phenanthroline

Abstract: Eight new two-ligand complexes of copper(II) with 1,10-phenanthroline and one of four different α-hydroxy-carboxylic acids (glycolic, lactic, mandelic and benzylic) were prepared. The complexes of general formula [Cu(HL)2(phen)] · nH2O (HL = monodeprotonated acid) (1–4) were characterized by elemental analysis, IR, electronic and EPR spectroscopy, magnetic measurements and thermo-gravimetric analysis. The complexes of general formulae [Cu(HL)(phen)2](HL) · H2L · nSolv [1 a (HL = HGLYO–, n = 1, Solv = MeCN) and 3 a (HL = HMANO–, n = 0)] and [Cu(L)(phen)(OH2)] · nH2O [2 a (L = LACO2–, n = 4) and 4 a (L = BENO2–, n = 2)] were characterized by X-ray diffractometry. In all these latter a pentacoordinated copper atom has a basically square pyramidal coordination polyhedron, the distortion of which towards a trigonal bipyramidal configuration has been evaluated in terms of the parameter τ. In 1 a and 3 a there are three forms of α-hydroxycarboxylic acid: a monodentate monoanion, a monoanionic counterion, and a neutral molecule lying in the outer coordination sphere; in 2 a and 4 a the α-hydroxycarboxylic acid is a bidentate dianion coordinating through carboxyl and hydroxyl oxygens. Gemischtliganden-Komplexe von Kupfer(II) mit α-Hydroxycarbonsauren und 1,10-Phenanthrolin Acht neue Zweiligand-Komplexe von Kupfer(II) mit 1,10-Phenanthrolin und einer von vier α-Hydroxycarbonsauren (Glykol-, Milch-, Mandel-, Benzilsaure) wurden dargestellt. Die Komplexe mit der allgemeinen Formel [Cu(HL)2(phen)] · nH2O (HL = monodeprotonierte Saure) (1–4) wurden elementaranalytisch, durch IR-, UV/Vis- und EPR-Spektroskopie, magnetische Messungen sowie thermogravimetrisch charakterisiert. Die Komplexe [Cu(HL)(phen)2](HL) · H2L · nSolvens [1 a (HL = HGLYO–, n = 1, Solvens = MeCN) und 3 a (HL = HMNO–, n = 0] und [Cu(L)(phen)(OH2)] · nH2O [2 a (L = LACO2–, n = 4) und 4 a (L = BENO2–, n = 2)] wurden rontgenographisch charakterisiert. In allen letztgenannten Komplexen bildet das funffach koordinierte Kupferatom ein im wesentlichen quadratisch-pyramidales Koordinationspolyeder, die Verzerrung zu einer trigonal-bipyramidalen Konfiguration wird uber den Parameter τ definiert. In 1 a und 3 a liegen die α-Hydroxycarbonsaure in drei Formen vor: als einzahniges Monoanion, als monoanionisches Gegenion und als neutrales Molekul in der auseren Koordinationssphare; in 2 a und 4 a ist die α-Hydroxycarbonlsaure ein zweizahniges Dianion, das uber die Carboxyl- und Hydroxyl-Sauerstoffatome koordiniert.

Mixed-ligand complexes of zinc(II) with α-hydroxycarboxylates and aromatic N-N donor ligands: Synthesis, crystal structures and effect of weak interactions on their crystal packing

Abstract: Several new two-ligand complexes of zinc(II) with the aromatic N,N-donor ligands 2,2-bipyridine or 1,10-phenanthro- line and one of three different α-hydroxycarboxylates (HL) derived of the α-hydroxycarboxylic acids (H2L) (2-methyllactic, H2mL; mandelic, H2M or benzilic, H2B) were prepared. The compounds of formula (Zn(HL)2(NN))·nH2 O( HL HM, HB) were isolated as white powders and characterized by elemental analysis, IR spec- troscopy and thermogravimetric analysis. The complexes of general formula (Zn(HL)(NN)2)(HL)·nH2 O( HL HmL, HM) and (Zn(HB)2(NN)2), were obtained as single crystals and were charac- terized by elemental analysis, IR spectroscopy, thermogravimetric analysis and X-ray diffractometry. In all cases, the zinc atom is in

Synthesis, Characterization, and Properties of Some Copper(II) Complexes of 2‐Pyridineformamide Thiosemicarbazone (HAm4DH)

Abstract: Reactions between different copper(II) salts and 2-pyridineformamide thiosemicarbazone (HAm4DH) in neutral ethanolic media led to the formation of complexes with the formulae [Cu(HAm4DH)X2] (X = Cl or Br) (1, 2) and [Cu(HAm4DH)2]X2 (X = NO3 or ClO4) (3, 4). The same reactions carried out in the presence of triethylamine gave rise to new complexes with the general formulae [Cu(Am4DH)X] (X = Cl, Br, AcO, or NO3) (5–8), [Cu(H2O)(Am4DH)](ClO4) (9), and [Cu(Am4DH)2] (10), many of which were isolated with different molecules of crystallization and contain a deprotonated thiosemicarbazone (Am4DH). These complexes were characterized by elemental analysis, and different spectroscopic and magnetic techniques. The thermal and redox behavior of the complexes was also evaluated. Complexes 1, 2, 5, and 6 show better nuclease activity than [Cu(phen)2]2+. Inaddition, crystals were isolated in the cases of [Cu(HAm4DH)Cl2]2 (5a), 1∞[Cu(Am4DH)Cl] (5b), 1∞[Cu(Am4DH)Br] (6a), and [Cu(HAm4DH)(H2O)(ClO4)2]·MeOH·H2O (9a) and these structures were analyzed by X-ray diffraction. Compound 5a has a dimeric structure with chlorine bridges and shows weak antiferromagnetism (J = –12.2 cm–1). Complexes 5b and 6a are one-dimensional polymers formed through halogen bridges and the deprotonated thiosemicarbazone in the thiolate form. In compound 9a the copper(II) is in a distorted octahedral environment with two ClO4 units coordinated to the metal center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Supramolecular Self-Assembly of M-IDA Complexes Involving Lone-Pair···π Interactions: Crystal Structures, Hirshfeld Surface Analysis, and DFT Calculations [H2IDA = iminodiacetic acid, M = Cu(II), Ni(II)]

Abstract: Mononuclear copper(II) and nickel(II) complexes, [(C5H6N2)Cu(IDA)(H2O)] (1) and (C5H7N2)2[Ni(IDA)2(H2O)] (2) [H2IDA = iminodiacetic acid; C5H6N2 = 4-aminopyridine; C5H7N2 = protonated 2-aminopyridine], have been synthesized, and their crystal structures were solved using single crystal X-ray diffraction data. A detailed analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions, which are crucial in building different supramolecular architectures. Molecules are linked by a combination of N–H···O, O–H···O and C–H···O hydrogen bonds into two-dimensional framework, whose formation is readily analyzed in terms of substructures of lower dimensionality with zero finite zero-dimensional dimeric units as the building blocks within the structures. Moreover, the aromatic molecules that are engaged in lone pair···π interactions with the noncoordinated carbonyl moieties play a crucial role in stabilizing the self-assembly process observed for both complexes. Intricate...

Reversible coordinative bonds in molecular recognition.

Abstract: Metal complexes with open coordination sites have found wide use in molecular recognition. They serve as binding sites in the development of chemosensors to study metalloenzyme function in bioinorganic chemistry or to direct supramolecular self-assembly. Lewis-acidic metal complexes can target a large variety of Lewis basic functional groups, which makes them very suitable for the design of synthetic receptors. Coordination to metal ions occurs typically with large enthalpies compared to those for hydrogen bond formation, salt-bridges, or dipole-dipole interactions.

Mechanisms underlying reductant-induced reactive oxygen species formation by anticancer copper(II) compounds.

Abstract: Intracellular generation of reactive oxygen species (ROS) via thiol-mediated reduction of copper(II) to copper(I) has been assumed as the major mechanism underlying the anticancer activity of copper(II) complexes. The aim of this study was to compare the anticancer potential of copper(II) complexes of Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone; currently in phase II clinical trials) and its terminally dimethylated derivative with that of 2-formylpyridine thiosemicarbazone and that of 2,2′-bipyridyl-6-carbothioamide. Experiments on generation of oxidative stress and the influence of biologically relevant reductants (glutathione, ascorbic acid) on the anticancer activity of the copper complexes revealed that reductant-dependent redox cycling occurred mainly outside the cells, leading to generation and dismutation of superoxide radicals resulting in cytotoxic amounts of H2O2. However, without extracellular reductants only weak intracellular ROS generation was observed at IC50 levels, suggesting that cellular thiols are not involved in copper-complex-induced oxidative stress. Taken together, thiol-induced intracellular ROS generation might contribute to the anticancer activity of copper thiosemicarbazone complexes but is not the determining factor.

Syntheses, Structures, and Photoluminescence of Five New Metal−Organic Frameworks Based on Flexible Tetrapyridines and Aromatic Polycarboxylate Acids

Abstract: Solvothermal reactions of tetrakis(4-pyridyloxymethylene)methane (TPOM) with deprotonated 1,4-benzenedicarboxylate (H2bdc) or 5-hydroxyisophthalic acid (5-OH-H2bdc) in the presence of nitrates of cadmium, zinc, and cobalt in H2O or H2O/DMF produced five new complexes, namely, {[Cd2(TPOM)(bdc)2]·(H2O)5(DMF)}n (1), {[Zn2(TPOM)(bdc)2]·(H2O)4}n (2), {[Zn2(TPOM)(bdc)2]·(H2O)}n (3), {[Co2(TPOM)(5-OH-bdc)2(H2O)2]·(H2O)5}n (4), and {[Cd2(TPOM)(5-OH-bdc)2]·(H2O)2}n (5). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complex 1 reveals a 2-fold interpenetrating three-dimensional (3D) framework with pcu topology constructed from binuclear Cd clusters and TPOM ligands. In addition, the experiment of single-crystal-to-single-crystal (SC-SC) structural transformations upon guest exchange was tested. Zn complexes 2 and 3 possess different 3D frameworks and are prepared from TPOM and H2bdc under different reaction conditions. In complexes 4 and 5, TPOM and ...

Six new metal-organic frameworks based on polycarboxylate acids and V-shaped imidazole-based synthon: syntheses, crystal structures, and properties.

Abstract: Solvothermal reactions of 4,4′-bis(imidazol-1-yl)diphenyl ether (BIDPE) with deprotonated 5-hydroxy-isophthalic acid (5-OH-H2bdc), and benzene-1,3,5-tricarboxylic acid (H3btc) in the presence of cadmium(II), zinc(II), cobalt(II), nickel(II), and manganese(II) salts in H2O or H2O/DMF produced six new complexes, namely, [Cd(BIDPE)(5-OH-bdc)·H2O]n (1), [Co(BIDPE)(5-OH-bdc)·H2O]n (2), [Zn3(BIDPE)3(5-OH-bdc)3·4H2O]n (3), [Ni(BIDPE)2(5-OH-bdc)(H2O)·3H2O]n (4), {[Mn2(BIDPE)2(5-OH-bdc)2]n (5), and [Ni(BIDPE)2(Hbtc)(H2O)]n (6). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Compounds 1 and 2 reveal the same two-dimensional (2D) sheets with a 32-membered [(Cd/Co)2(BIDPE)2] metallocyclic ring constructed from BIDPE and 5-OH-H2bdc with Cd or Co salts. For compound 3, six identical 2D sheets are polycatenated in parallel to form a rare 2D → 2D framework; it displays ferroelectric behavior with a remnant electric polarization (Pr) of 0.033 μC/cm2 and an ...