E. Carolina Sañudo

An azido -CuII -triazolate complex with utp-type topological network, showing spin-canted antiferromagnetism

An azido-metal-1,2,4-triazolate coordination polymer, [Cu(trz)(N(3))](n) (trz = 1,2,4-triazolate) was synthesized using hydrothermal methods; the complex has a rare three-dimensional non-interpenetrated utp or (10,3)-d topological network structure and exhibits spin-canted antiferromagnetism at low temperature.

Heterobridged dinuclear, tetranuclear, dinuclear-based 1-d, and heptanuclear-based 1-D complexes of copper(II) derived from a dinucleating ligand: syntheses, structures, magnetochemistry, spectroscopy, and catecholase activity.

The work in this paper presents syntheses, characterization, crystal structures, variable-temperature/field magnetic properties, catecholase activity, and electrospray ionization mass spectroscopic (ESI-MS positive) study of five copper(II) complexes of composition [Cu(II)(2)L(μ(1,1)-NO(3))(H(2)O)(NO(3))](NO(3)) (1), [{Cu(II)(2)L(μ-OH)(H(2)O)}(μ-ClO(4))](n)(ClO(4))(n) (2), [{Cu(II)(2)L(NCS)(2)}(μ(1,3)-NCS)](n) (3), [{Cu(II)(2)L(μ(1,1)-N(3))(ClO(4))}(2)(μ(1,3)-N(3))(2)] (4), and [{Cu(II)(2)L(μ-OH)}{Cu(II)(2)L(μ(1,1)-N(3))}{Cu(II)(μ(1,1)-N(3))(4)(dmf)}{Cu(II)(2)(μ(1,1)-N(3))(2)(N(3))(4)}](n)·ndmf (5), derived from a new compartmental ligand 2,6-bis[N-(2-pyridylethyl)formidoyl]-4-ethylphenol, which is the 1:2 condensation product of 4-ethyl-2,6-diformylphenol and 2-(2-aminoethyl)pyridine. The title compounds are either of the following nuclearities/topologies: dinuclear (1), dinuclear-based one-dimensional (2 and 3), tetranuclear (4), and heptanuclear-based one-dimensional (5). The bridging moieties in 1-5 are as follows: μ-phenoxo-μ(1,1)-nitrate (1), μ-phenoxo-μ-hydroxo and μ-perchlorate (2), μ-phenoxo and μ(1,3)-thiocyanate (3), μ-phenoxo-μ(1,1)-azide and μ(1,3)-azide (4), μ-phenoxo-μ-hydroxo, μ-phenoxo-μ(1,1)-azide, and μ(1,1)-azide (5). All the five compounds exhibit overall antiferromagnetic interaction. The J values in 1-4 have been determined (-135 cm(-1) for 1, -298 cm(-1) for 2, -105 cm(-1) for 3, -119.5 cm(-1) for 4). The pairwise interactions in 5 have been evaluated qualitatively to result in S(T) = 3/2 spin ground state, which has been verified by magnetization experiment. Utilizing 3,5-di-tert-butyl catechol (3,5-DTBCH(2)) as the substrate, catecholase activity of all the five complexes have been checked. While 1 and 3 are inactive, complexes 2, 4, and 5 show catecholase activity with turn over numbers 39 h(-1) (for 2), 40 h(-1) (for 4), and 48 h(-1) (for 5) in dmf and 167 h(-1) (for 2) and 215 h(-1) (for 4) in acetonitrile. Conductance of the dmf solution of the complexes has been measured, revealing that bridging moieties and nuclearity have been almost retained in solution. Electrospray ionization mass (ESI-MS positive) spectra of complexes 1, 2, and 4 have been recorded in acetonitrile solutions and the positive ions have been well characterized. ESI-MS positive spectrum of complex 2 in presence of 3,5-DTBCH(2) have also been recorded and, interestingly, a positive ion [Cu(II)(2)L(μ-3,5-DTBC(2-))(3,5-DTBCH(-))Na(I)](+) has been identified.

Coordination polymers with pyridine-2,4,6-tricarboxylic acid and alkaline-earth/lanthanide/transition metals: synthesis and X-ray structures

Pyridine-2,4,6-tricarboxylic acid (ptcH(3)) reacts with Cd(II), Mn(II), Ni(II), Mg(II), Ca(II), Sr(II), Ba(II), Dy(III) salts forming different products depending on the reaction conditions. In the presence of pyridine at room temperature the acetate, chloride or nitrate salt of Cd(II) breaks the ligand to form an open framework structure with the empirical formula, {[Cd(Ox)(H(2)O)(2)]H(2)O}(n) (Ox = oxalate), 1. In the absence of pyridine, no crystalline compound could be isolated at room temperature (RT). However, under hydrothermal conditions and in the absence of pyridine, a discrete tetrameric complex with the formula, {[Cd(2)(cda)(2)(H(2)O)(4)](H(2)O)(3)}(2) (cdaH(2) = 4-hydroxypyridine-2,6-dicarboxylic acid), 2, is formed where the carboxylate group at the 4-position of the ligand is reduced to a hydroxyl group. When Ni(II), Mn(II), Mg(II), Ca(II), Sr(II), Ba(II), Dy(III) salts are used in place of Cd(II), no crystalline product could be isolated at RT. But under hydrothermal conditions, coordination polymers ({[Ni(1.5)(ptc)(pip)(0.5)(H(2)O)(4)].H(2)O}(n), (pip = piperazine), 3; {Mn(1.5)(ptc).2H(2)O}(n), 4; {Mg(3)(ptc)(2).8H(2)O}(n), 5; {[Mg(ptc)(H(2)O)(2)].1/2[Mg(H(2)O)(6)].H(2)O}(n), 6; {Ca(1.5)(ptc).2H(2)O}(n), 7; {Sr(1.5)(ptc).5H(2)O}(n), 8; {[Ba(ptc)(H(2)O)][Ba(ptcH(2))H(2)O]}(n), 9; {[Dy(ptc).3H(2)O].H(2)O}(n), 10) are formed. The structures exhibit different dimensionality depending on the nature of the metal ions. In 1 a discrete acyclic water hexamer is also identified. All the compounds are characterized in the solid state by X-ray crystallography, IR and elemental analysis.

From Infinite One-Dimensional Helix to Discrete CuII15 Cluster along with in Situ SN2 Ring-Cleavage of cis-Epoxysuccinic Acid: pH-Controlled Assemblies, Crystal Structures, and Properties

Two Cu(II) coordination complexes {[Cu(ces)(H(2)O)(2)](H(2)O)(0.5)}(n) (1) and [Cu(15)(dhs)(6)(OH)(6)(H(2)O)(10)](H(2)O)(20) (2) have been synthesized from cis-epoxysuccinic acid (cis-H(2)ces) and Cu(II) perchlorate under different pH conditions (ces = cis-epoxysuccinate and dhs = 2,3-dihydroxysuccinate), and fully characterized by IR spectra, elemental analyses, as well as single crystal and powder X-ray diffraction techniques. Notably, when the reaction was performed at pH above about 7.4, a one-dimensional (1-D) helical chain complex 1 is formed, whereas a neutral isolated Cu(15) nanocluster 2 is generated when the pH value is decreased to the range of about 6.6-7.3, being concomitant with in situ S(N)2 ring-cleavage reaction of cis-H(2)ces to form (2S,3S)- and (2R,3R)-H(4)dhs. Further, extended supramolecular architectures are constructed via secondary interactions in both structures. The magnetic properties of 1 and 2 have also been studied in detail, showing that 1 is an antiferromagnetic helical chain of S = 1/2 spins and 2 possesses an S = 3/2 spin ground state.

Metal cages using a bulky phosphonate as a ligand

The synthesis, structure, magnetic and electronic properties of soluble transition metal phosphonate cages utilizing tritylphosphonic acid (TPA) as ligand are reported.

Lanthanide−Organic Coordination Frameworks Showing New 5‑Connected Network Topology and 3D Ordered Array of Single-Molecular Magnet Behavior in the Dy Case

Five isostructural lanthanide-organic coordination frameworks with a unique 3-D 5-connected (4(7).6(3))(4(3).6(5).8(2)) network, namely, [Ln(phen)(L)]n (Ln = Dy for 1, Gd for 2, Ho for 3, Er for 4, and Tb for 5), have been prepared based on bridging 5-hydroxyisophthalic acid (H3L) and chelating 1,10-phenanthroline (phen) coligand. Significantly, the Dy(III) complex 1 is an organized array of single-molecular magnets (SMMs), with frequency-dependent out-of-phase ac susceptibility signals and magnetization hysteresis at 4 K. Further analysis of the magnetic results can reveal that the SMM behavior of 1 should arise from the smaller ferromagnetic interaction between the Dy(III) ions. Complex 1 was also characterized by X-ray absorption spectra, which give the clear X-ray magnetic circular dichroism signal.

New structural form of a tetranuclear lanthanide hydroxo cluster: Dy4 analogue display slow magnetic relaxation.

A series of tetranuclear lanthanide (Ln = Tb, Dy, Ho) hydroxo clusters has been synthesized by reaction of LnCl3·6H2O (Ln = Tb (1), Dy (2), Ho (3)) with o-vanilin based schiff base ligand 2-(2,3 dihydroxpropyl imino methyl) 6-methoxy phenol (H3L) in methanol and in the presence of triethylamine as base. The solid state structures of all the products were established by single crystal X-ray diffraction technique. Magnetism studies reveal that Dy4 analogue exhibits slow magnetic relaxation at low temperatures.

Coordination polymers of Mn2+ and Dy3+ ions built with a bent tricarboxylate: metamagnetic and weak anti-ferromagnetic behavior.

Two new coordination polymers have been synthesized with Mn(2+) and Dy(3+) ions using a new bent ether-bridged tricarboxylic acid ligand, o-cpiaH(3) (5-(2-carboxy-phenoxy)-isophthalic acid). The ligand readily reacts with a Mn(2+) salt in presence of pyridine (py) under hydrothermal condition to afford a 3D coordination polymer {[Mn(9)(o-cpia)(6)(py)(3)(3H(2)O)]·H(2)O}(n) (1), that contains two types of polymeric chains. One of them is merely carboxylate bridged Mn(2+) where each metal ion shows both penta- and hexa-coordination. The other chain consists of carboxylate-bridging along with terminally bound pyridines providing both penta- and hexa-coordination to each metal ion. When o-cpiaH(3) is treated with Dy(NO(3))(3).xH(2)O under solvothermal condition, it gives rise to an unusual double layer (6,6) connected 2D coordination polymer {[Dy(o-cpia)]}(n)(2), where each metal ion is hexacoordinated. The double layer 2D sheets are stacked to each other in AA··· fashion through strong C-H···π interactions to generate an overall 3D supramolecular architecture. Both the complexes have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. Variable temperature magnetic susceptibility measurements indicate that 1 exhibits metamagnetic behavior while 2 shows weak antiferromagnetic behavior.

Carboxylate-Free Manganese(II) Phosphonate Assemblies: Synthesis, Structure, and Magnetism

The reaction of manganese(II) salts with organophosphonic acid [t-BuPO(3)H(2) or cyclopentyl phosphonic acid (C(5)H(9)PO(3)H(2))] in the presence of ancillary nitrogen ligands [1,10-phenanthroline (phen) or 2,6-bis(pyrazol-3-yl)pyridine (dpzpy)], afforded, depending on the stoichiometry of the reactants and the reaction conditions, dinuclear, trinuclear, and tetranuclear compounds, [Mn(2)(t-BuPO(3)H)(4)(phen)(2)]·2DMF (1), [Mn(3)(C(5)H(9)PO(3))(2)(phen)(6)](ClO(4))(2)·7CH(3)OH (2), [Mn(3)(t-BuPO(3))(2)(dpzpy)(3)](ClO(4))(2)·H(2)O (3), [Mn(4)(t-BuPO(3))(2)(t-BuPO(3)H)(2)(phen)(6)(H(2)O)(2)](ClO(4))(2) (4), and [Mn(4)(C(5)H(9)PO(3))(2)(phen)(8)(H(2)O)(2)](ClO(4))(4) (5). Magnetic studies on 1, 2, and 4 reveal that the phosphonate bridges mediate weak antiferromagnetic interactions between the Mn(II) ions have also been carried out.

Metal–organic coordination polymers based on a flexible tetrahydrofuran-2,3,4,5-tetracarboxylate ligand: syntheses, crystal structures, and magnetic/photoluminescent properties

The coordination possibilities of flexible heteroalicyclic ligands with transition metals have been explored. Five CuII, MnII, and CdII coordination polymers with the fully deprotonated tetrahydrofuran-2,3,4,5-tetracarboxylate (L) ligand were synthesized and characterized, sometimes incorporating different auxiliary ligands: {[Cu2(L)(H2O)](H2O)1.42}∞ (1), {[Cu2(L)(2bpy)(H2O)2](H2O)2}∞ (2), {[Cu2(L)(phen)(H2O)2](H2O)1.5(CH3OH)0.25}∞ (3), {[Mn2(L)(phen)2(H2O)](H2O)2}∞ (4), and {[Cd2(L)(phen)2(H2O)](H2O)2}∞ (5) (2bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline). The structural analysis related to 1–5 reveals that the fully deprotonated L ligand displays versatile coordination modes, which result in the generation of a fairly complicated three dimensional (3D) framework for 1 with a Schlafli symbol of (43·67)(46·64), two isostructural two dimensional (2D) puckered layers for 2 and 3 with the decorated binodal (3,5)-connected (3·52)2(32·53·64·7) topology, and two isostructural one dimensional (1D) ribbon-like chains for 4 and 5, respectively. The present work indicates that, in comparison with the rigid aromatic multicarboxylate ligands, tetrahydrofuran-2,3,4,5-tetracarboxylate (L), a heteroalicyclic multicarboxylate ligand, has richer coordination modes and a more flexible ring skeleton, which may remain largely unexpected in the process of constructing metal–organic frameworks (MOFs) and make it more difficult to predict and control the final coordination polymers. Magnetic susceptibility measurements demonstrate that complexes 1 and 4 exhibit antiferromagnetic coupling, whereas 2 and 3 show ferromagnetic coupling, with the corresponding J values of −23.62 cm−1 for 1, 5.18 cm−1 for 2, 3.90 cm−1 for 3, and −0.79 cm−1 for 4. Moreover, complex 5 displays solid blue emission originating from an intraligand π → π* transition of the auxiliary phen ligand.