Berta Covelo

One-dimensional fluorescent stacking structure based on zinc mixed-complex salt encapsulated within an ‘ice-like’ three-dimensional hydrogen-bonded water network

Self-assembly of the fluorescent mixed-complex salt [Zn(HL)(phen)2][Zn(L)(HL)(phen)]·13H2O (1) [HL = methyllactato(−1) and L = methyllactato(−2)] created an ‘ice-like’ three-dimensional open framework by hydrogen-bonded crystallisation water molecules that encapsulates an infinite stacking chains result of the intercalation of phenanthroline ligands of complex ions.

Three new modes of adenine-copper(II) coordination: interligand interactions controlling the selective N3-, N7- and bridging μ-N3,N7metal-bonding of adenine to different N-substituted iminodiacetato-copper(II) chelates

Abstract The reaction of Cu2CO3(OH)2, various N-substituted-iminodiacetic acids [RN(CH2CO2H)2)] and adenine (AdeH) in water yields crystalline samples of mixed-ligand copper(II) complexes of formulas [Cu(A)(N7AdeH)(H2O)]·H2O (A=N-methyl- or N-ethyl-iminodiacetato(2−); compounds 1 and 2, respectively), [Cu(B)(N3AdeH)(H2O)]·H2O (B=N-benzyl- or N-(p-methylbenzyl)-iminodiacetato(2−); compounds 3 and 4, respectively) as well as [Cu4(pheida)4(μ-N3,N7AdeH)2(H2O)4]·2H2O (pheida=N-phenethyl-iminodiacetato(2−)). Crystal structures of the acid H2pheida and compounds 1–5 are reported. H2pheida acid exhibits a typical zwitterionic structure. Copper(II) compounds were also studied by TG analysis (with FT-IR study of the evolved gasses), IR, electronic and ESR spectra and magnetic susceptibility data. The N-alkyl- or N-benzyl-like-iminodiacetato(2−) ligands (A or B) give complexes with Cu(II)/(A or B)/AdeH equimolar ratio, whereas pheida yields an unexpected tetranuclear compound with a 2:2:1 Cu(II)/pheida/AdeH molar ratio. In 1 and 2 AdeH binds to the metal by N7, whereas in 3 and 4 the N3 atom is used. An unexpected bridging μ-N3,N7AdeHdicopper(II) binding mode is found in the tetra-nuclear compound 5 (without interligand π,π-stacking interactions). These AdeHCu(II) binding modes have not been referred in the literature before. The difference in AdeHCu(II) binding modes in compounds 1 or 2 and 3 or 4 is rationalised on the basis of the absence or presence of a flexible N-benzyl-like substituent in the iminodiacetato(2−) ligand skeleton, which prevents or permits the interligand π,π-stacking interactions.

Solid state coordination chemistry of copper(II)/α-hydroxycarboxylato/2,2′-bipyridine systems

Abstract Four new two-ligand complexes of copper(II) with 2,2′-bipyridine and one of three different α-hydroxycarboxylic acids (lactic, H2LACO; 2-methyllactic, H2MLACO; and mandelic, H2MANO) were prepared. Complexes 1–3 of general formula [Cu(HL)2(bipy)]·nH2O (HL=monodeprotonated acid), were characterized by elemental analysis, IR, electronic and EPR spectroscopy, magnetic measurements and thermogravimetric analysis. Complexes 1 (HL=HLACO, n=2), 2 (HL=HMLACO, n=1) and 3a (the result of attempted recrystallization of 3, of formula [Cu(HMANO)(bipy)2](HMANO)·H2MANO·CH3CN were studied by X-ray diffractometry. The copper atom is in an elongated, tetragonally distorted octahedral environment in 1 and 2 and in 3a has a coordination polyhedron intermediate between a square pyramid and a trigonal bipyramid, as evaluated in terms of the parameter τ. In 1 and 2 the α-hydroxycarboxylato ligand is bidentate and monoanionic but in 3a there are three forms: a monodentate monoanion, a monoanionic counterion, and a neutral molecule.

Coordination polymers of copper(II) based on mixed N- and O-donor ligands: the crystal structures of [CuL2(4,4′-bipy)]n (L=lactate or 2-methyllactate)

The neutral polymeric complexes of copper(II) [CuL 2 (4,4′-bipy)] n , where L is an α-hydroxycarboxylato ligand, lactate in 1 , 2-methyllactate in 2 , were prepared and characterised structurally. The copper atom is in an elongated tetragonally distorted octahedral environment in both compounds. Both α-hydroxycarboxylato ligands are O , O ′-bidentate chelating monoanions and 4,4′-bipyridine acts as an N , N ′-bis(monodentate) bridging ligand creating a linear polymeric arrangement. The polymeric chains are interconnected by O hydroxyl H⋯O carboxy hydrogen bonds in a way that creates cavities that differ in size between 1 and 2 . Spectroscopic data are presented and discussed.

Metal chelates of N-(2-pyridylmethyl)iminodiacetate(2-) ion (pmda). Part I. Two mixed-ligand copper(II) complexes of pmda with N,N-chelating bases. Synthesis, crystal structure and properties of H2pmda·0.5H2O, [Cu(pmda)(pca)]·3H2O (pca=α-picolylamine) and [Cu(pmda)(Hpb)]·5H2O (Hpb=2-(2′-pyridyl)benzimidazole)

N -(2-Pyridylmethyl)iminodiacetic acid hemi-hydrate (H2pmda/0.5H2O) was prepared and characterized by X-ray crystallography (final R 1 � /0.042). The zwitterion H2pmda 9 is intra -stabilized by a trifurcated hydrogen bond. Intermolecular carboxyliccarboxylate hydrogen bonds and the parallel inter-ligand p,p-stacking (3.57(2) A u ) between pyridyl rings from pairs of adjacent zwitterions generate 2D frameworks (bi-layers with the carboxyl groups towards the external surfaces and py � /pmda rings towards the inside). In the crystal, the bi-layered structures are connected by equivalent hydrogen bonds, which link each water molecule to two symmetry related O-carboxylate atoms from the adjacent external faces of two 2D frameworks. The compounds [Cu(pmda)(pca)]/3H2 O( 1) and [Cu(pmda)(Hpb)]/5H2 O( 2) were obtained by stoichiometric reaction of Cu2(CO3)(OH)2, H2pmda/0.5H2O and a-picolylamine (pca) or 2-(2?-pyridyl)benzimidazole (Hpb), respectively, and characterized by single crystal X-ray diffractometry. Compound 2 was also studied by TG analysis (with FTIR study of the evolved gasses in the pyrolysis), magnetic susceptibility at 80 � /300 K range, and FTIR, electronic, ESR spectra. In 1 and 2 the copper(II) atom exhibits a distorted octahedral coordination (type 4� /1� /1) and pmda acts as tripodal tetra-dentate ligand. However, pmda displays different coordination roles. The pmda supplies two N ,O -meridional and two trans -apical N (py),O -donors in 1, whereas links the metal by three N ,N (py),O -meridional and one O -apical atoms in 2 .N op,p-stacking of pyridyl � /(pmda) rings is observed in these complexes. The pyridyl � /(pca) ring of 1 is not involved in ring � /ring stacking interactions, but compound 2 recognizes itself by a roughly antiparallel p,p-stacking of adjacent Hpb ligands (5.38, 3.41(2) A u ) forming pairs of complex units. # 2002 Elsevier Science Ltd. All

From copper(II) carboxylate to copper(II) 4-pyridylsulfonate coordination polymers as a consequence of the copper(II)-assisted oxidative cleavage of the 4,4′-dipyridyldisulfide ligand

Five coordination polymers 1 {[Cu4(HCO2)6(OH)2(4dpds)2]·2CH2Cl2}n, 2 {[Cu4(CH3CO2)6(OH)2(4dpds)2]}n, 3 {[Cu(4dpds)2(H2O)2](4pySO3)2·2H2O}n, 4 {[Cu(4pySO3)2(4dpds)2]·2H2O}n and 5 {[Cu(4pySO3)2(dmso)2]·2H2O}n (where 4dpds = 4,4′-dipyridyldisulfide, 4pySO3 = 4-pyridylsulfonate) have been obtained during a study into the reactivity of basic copper(II) salts (formate and acetate) with 4,4′-dipyridyldisulfide (4dpds). The coordination polymers 1 and 2 consist of a repeated rhomboid structure in which analogous Cu4(RCO2)6(OH)2 cores are joined by two 4,4′-dipyridyldisulfide bridging ligands to generate two different chain topologies: planar ribbon in 1 and ruffled ribbon in 2. 4-Pyridylsulfonate ions appear as ligands or counterions in the coordination polymers 3, 4 and 5 due to oxidative cleavage of the 4,4′-dipyridyldisulfide under mild conditions. The coordination polymer 3 has been isolated repeatedly in several direct reactions of the copper(II) carboxylates with 4,4′-dipyridyldisulfide. However, the coordination polymers 4 and 5 have been obtained from 1 and 2, respectively, by recrystallization from DMF and DMSO. In compound 4, as in 3, the 4,4′-dipyridyldisulfide has only been partially oxidized to 4-pyridylsulfonate and a proportion of these units remain in the structure as disulfide. However, in 5 the oxidation is complete. The structural analysis of these coordination polymers reveals that, in all cases, weak interactions such as classical and non-classical hydrogen bonds, as well as CH⋯π, S⋯π and S⋯O interactions, join the polymeric chains to generate three-dimensional networks.

Supramolecular architectures of neutral and cationic complexes of transition metals with lactate and 1,10-phenanthroline

The following molecular complexes of transition metals MII with lactato (HL) and 1,10-phenanthroline (phen) ligands were prepared and characterized structurally: [M(HL)2(phen)]·nH2O, MII = Mn, Co, Ni, Cu, Zn; 1–6), [M(HL)(H2O)2(phen)]Cl, (MII = Mn, Co, Ni; 7–9), and [Ni(HL)(H2O)2(phen)]Br (10). These neutral and cationic octahedral complexes have 3-D supramolecular architectures due to weak noncovalent interactions. In the halide compounds, C–H⋯X− hydrogen bonds play a key role in the stabilization of the 3-D network.

The interaction of 2-methyllactic acid (H2mL) with divalent metal cations. The structures of (M(HmL)2(H2O)2), M /Mn(II), Zn(II)

Abstract The mononuclear complexes [M(HmL)2(H2O)2], where M=Mn(II) (1), Ni(II) (2) or Zn(II) (3) and HmL=2-methyllactato, were prepared and characterized by elemental analysis, FT-IR and UV/Vis spectroscopy and room temperature magnetic susceptibility measurements. Their thermal behaviour was also investigated, and compounds 1 and 3 were characterized by X-ray diffractometry. In both cases, the metal ion is hexacoordinated to two (O,O′)-bidentate monoanionic 2-methyllactato ligands and two aqua ligands in a distorted octahedral fashion. The [M(HmL)2(H2O)2] units are connected by hydrogen bonds, forming a two-dimensional network.

Synthesis and characterization of a potassium complex of magneson: [K(HL)(OH2)2]∞ [H2L=4-(4-nitrophenylazo)resorcinol (magneson)]

The synthesis and crystallographic, spectroscopic and thermal characterization of the potassium complex [K(HL)(OH2)2] [H2L=4-(4-nitrophenylazo)resorcinol (magneson)] are reported. In the solid state, the K + ion is heptacoordinated and the ligand binds with three different coordination modes (via a bidentate chelating nitro group, a bridging nitro oxygen and a phenolic oxygen), giving rise to a polymeric structure.

Stabilization of Discrete (H2O)14 Water Clusters in the Supramolecular Crystal Host of [Ni(phen)3](HB)2 · 7H2O (HB−=benzilate)

A discrete tetradecameric water cluster has been observed in the lattice of [Ni(phen)3](HB)2 · 7H2O, HB=benzilate (diphenylglycolate). The cluster, which is based on one cyclic tetramer and two acyclic pentamers, is entrapped in the hydrogen‐bonded layer constructed by the benzilate anions and the water molecules. This layer is located between two hydrophobic layers generated by association of [Ni(phen)3]+ cations through π‐π interactions.