José M. Seco

A chiral diamondoid 3D lanthanum metal–organic framework displaying blue-greenish long lifetime photoluminescence emission

The compound [La(pmtz)(TzC)(H2O)3](H2O) (pmtz = 5-(pyrimidyl)-tetrazolato, TzC = 5-carboxylato-tetrazolato) has been prepared under hydrothermal conditions and exhibits a 3D diamondoid network. This three-dimensional metal–organic framework has channels with hosted water molecules inside and shows an intense blue-greenish long lifetime photoluminescence emission at room temperature in the solid state with two lifetime decay values of 0.26 and 27 ms.

Synthesis, X-ray crystal structure and spectroscopic, magnetic and EPR studies of copper(II) dimers with methoxy-di-(2-pyridyl)methoxide as bridging ligand

Abstract The binuclear complexes [{Cu(bipy)}2{μ-[(NC5H4)2C(OMe)O]}2]X2·1/2H2O, X−=PF6− (1) or ClO4− (2) and [{Cu(phen)}2{μ-[(NC5H4)2C(OMe)O]}2]X2·2[(NC5H4)2CO], X−=PF6− (3) or ClO4− (4) have been synthesized by the reaction of [{Cu(NN)}2(μ-OH)2]X2·nH2O and di-2-pyridylketone in methanol. The compounds were characterized by conductance measurements and IR and electronic spectroscopies. The X-ray crystal structure of compounds 1, 3 and 4 show the presence of two [(NC5H4)2C(OMe)O−] uninegative tridentate N,O,N-donor η1:η2:η1:μ2 ligands per dimer. The coordination sphere of Cu(II) is a very distorted octahedron. All four compounds are ferromagnetic, with a superexchange parameter 2J=10.0, 10.1, 16.7 and 15.8 cm−1 for compound 1, 2, 3 and 4, respectively. Zero field splitting parameters (D, E) and g values have been calculated from the spin triplet state signals positions in the EPR spectra.

2-Anilinopyridinate of Cu(I) and adducts of 2-anilinopyridine and metal acetates.: Crystal structure of Cu2(μ-OAc)4(PhNHpy)2

Abstract The adducts of M(OAc)2·nH2O (M=Cu, Co, Ni, Zn) with 2-anilinopyridine, M(OAc)2(PhNHpy), have been synthesized and characterized. The X-ray crystal structure of Cu2(μ-OAc)4(PhNHpy)2 shows the dimer structure of Cu2(μ-OAc)4(H2O)2 with the PhNHpy ligand in the axial positions of the water molecules. It is antiferromagnetic (2J=−286 cm−1). Signals of the triplet state are observed in its EPR spectrum and the zero field splitting parameter (D=0.33 cm−1) has been calculated. The electronic spectra and the strong antiferromagnetism of the cobalt (2J=−324 cm−1) and nickel (2J=−382 cm−1) compounds allow to propose also a dimeric structure for them. By excess of ligand, in the anionic form, the Cu(I) compound Cu(PhNpy) was obtained for which a dinuclear structure with a lineal coordination in Cu(I) is proposed.

Luminescence and magnetic properties of three metal–organic frameworks based on the 5-(1H-tetrazol-5-yl)isophthalic acid ligand

Three new metal–organic frameworks based on 5-(1H-tetrazol-5-yl)isophthalic acid complexes {[Cd4(TZI)2(OH)2(H2O)4](H2O)6}n (1), {[Zn2(TZI)(OH)(H2O)2](H2O)}n (2) and {[Co8(TZI)3(OH)5((N3)2(H2O)8](H2O)8}n (3) have been synthesized in situ by hydrothermal reactions of the 5-cyano-1,3-benzenedicarboxylic acid ligand with cadmium, zinc and cobalt metallic(II) salts in the presence of sodium azide in water. Compounds 1 and 2 display intense photoluminescence properties in the solid state at room temperature, while 3 exhibits an antiferromagnetic interaction between cobalt(II) ions with a J value of −3.8 cm−1. The in situ hydrothermal syntheses reveal new possibilities for the formation of new MOFs to construct new materials with fascinating structures and potential applications.

Controlling interpenetration for tuning porosity and luminescence properties of flexible MOFs based on biphenyl-4,4′-dicarboxylic acid

Four new compounds based on zinc(II) or cadmium(II) metal ions and elongated dicarboxylate and bipyridine ligands, namely, {[Cd3(μ4-bpdc)3(H2O)2]·DMF}n (1), {[Zn3(μ4-bpdc)3(μ-bpdb)]·5DMF}n (2), {[Zn2(μ4-bpdc)2(μ-bpdb)]·7DMF}n (3), and {[Zn4(μ4-bpdc)3(DMF)(μ4-O)(H2O)]·7DMF·3H2O}n (4), (where bpdc = biphenyl-4,4′-dicarboxylate, bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, DMF = dimethylformamide) have been synthesised under solvothermal conditions and structurally characterised by single crystal X-ray diffraction. The crystal structures range from 2D (in 1) to 3D (2, 3, and 4) systems according to the coordination mode acquired by the bpdc ligand and the presence of an ancillary linker. Compound 1 consists of stacked Cd-bpdc neutral layers containing isolated small voids. The coordination of the bpdb ligand (2 and 3) or the formation of a tetrahedral Zn4O cluster (in 4) generates highly open 3D architectures that share the structural feature of being doubly interpenetrated. A careful computational analysis on the crystal structures permits unravelling their void systems. Moreover, characterising the photoluminescence emission of the compounds at variable excitation wavelengths provides an opportunity to couple the luminescence response with their porosity, which could signify the potential utility of these materials as photofluorescent sensors for small adsorbates.

Synthesis and spectroscopic, magnetic and EPR studies of di-μ-hydroxo-bis[(NN)(N-phenyl-2-pyridinamine)copper(II)]hexaflourophosphate, with NN=2,2′-bipyridine or 1,10-phenanthroline.: X-ray crystal structure of the 2,2′-bipyridine complex

Abstract Binuclear complexes [{Cu(NN)(PhNHpy)}2(μ-OH)2](PF6)2, where NN=2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen), have been synthesized and characterized by chemical analysis, conductance measurements and IR and electronic spectroscopy. The X-ray crystal structure of [{Cu(bipy)(PhNHpy)}2(μ-OH)2](PF6)2 shows a distorted square-planar pyramidal coordination for Cu(II), defined by two nitrogen atoms of bipy, two bridging oxygen atoms and the pyridinic nitrogen atom of the ligand. Magnetic susceptibility measurements (in the 4.8–290 K range) reveal coupling which is antiferromagnetic for the bipy complex (2J=−24.2 cm−1) and slightly ferromagnetic for the phen complex (2J=3.3 cm−1). The EPR spectra show the expected triplet signals.

Slow relaxation of magnetization in 3D-MOFs based on dysprosium dinuclear entities bridged by dicarboxylic linkers

Three novel metal–organic-frameworks (MOFs) based on dysprosium as the metal and dicarboxylic ligands have been solvothermally synthesized with the aim of studying and modulating their magnetic properties according to the variation of the distances between metal centers. These materials display intense photoluminescence properties in the solid state at room temperature. In addition, a very interesting property of compound 1 is that it exhibits slow relaxation of magnetization with an activation energy barrier of 32 K. Magneto-structural correlations have been analyzed.

Efficient hydridoirida-β-diketone-catalyzed hydrolysis of ammonia- or amine-boranes for hydrogen generation in air

The dihydridoirida-β-diketone [IrH2{(PPh2(o-C6H4CO))2H}] (2) has been used as a homogeneous catalyst for the hydrolysis of ammonia- or amine-boranes to generate up to 3 equivalents of hydrogen in the presence of air. When using 0.5 mol% loading of 2, dimethylamine-borane is hydrolysed completely within 8 min at 30 °C and maintains its activity in consecutive runs. Ammonia-borane or tert-butylamine-borane is hydrolysed completely within 32 or 25 min respectively. Triethylamine-borane fails to be hydrolysed. Kinetic studies suggest a sequence of two consecutive first-order reactions, in which an intermediate builds up and finally falls, with the first step being the rate controlling step. ΔH1(‡) are in the range 65-85 kJ mol(-1) and negative values of ΔS1(‡) are obtained. A multinuclear NMR study of the catalyzed reaction shows the formation of a resting state (A) of the active catalyst proposed to be of the hydridodiacyl type [IrH(PPh2(o-C6H4CO))2(solvent)] with a hydride trans to the acyl group. In the absence of substrate a dormant species (B) is formed. By the reaction of hydridoirida-β-diketones with ammonia, the hydridoirida-β-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH))H}] (3) and the hydridobis(acylphosphane)aminoiridium(III) complex [IrH(PPh2(o-C6H4CO))2(NH3)] (4), with a hydride trans to phosphane, are formed. Aromatic amines such as aniline or anisidines afford cationic [IrH{(PPh2(o-C6H4CO))2H}(C6H4RNH2)]ClO4 (R = H (6); p-MeO (7); o-MeO (8)) hydridoirida-β-diketones with a coordinated amine group trans to the hydride. The dormant species B is proposed to be of the hydridobis(acylphosphine)aminoiridium(III) type with a hydride trans to the amine group.

Effect of π–π stacking interactions on the emission properties of cadmium metal–organic frameworks based on 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene

Five multidimensional cadmium metal–organic frameworks based on the luminescent 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene linker and flexible dicarboxylate ligands have been synthesized by conventional routes. These MOFs show fascinating structures and display, in the solid state and at room temperature, intense and hypsochromic photoluminescence properties when packed as a 3D network and bathochromic photoluminescence properties when arranged as 2D networks, as compared to the emission properties of the free luminescent 4-bpdb ligand. DFT calculations have revealed the establishment of destabilizing π–π stacking interactions between pyridyl rings of neighbouring 4-bpdb aromatic linkers on the 3D networks synthesized, responsible for the unexpected hypsochromic emission. The absence of π–π stacking interactions in the 2D MOFs yields the expected bathochromic photoluminescence arising from metal coordination with the aromatic ligand.

Multifunctional applications of a dysprosium-based metal–organic chain with single-ion magnet behaviour

A novel metal–organic chain constructed of dysprosium and sodium ions based on 5-aminopyridine-2-carboxylic acid has been synthesized and characterized. The formation of this 1D-MOF is achieved using a soft solvothermal route with dimethylformamide as solvent. This material displays intense photoluminescence properties in the solid state at room temperature and exhibits SIM behavior with frequency dependence of the out-of-phase susceptibility at zero dc field. More interesting, we report here the magnetic field dependent cytotoxicity and multidrug-resistant properties of this 1D-MOF. This multidisciplinary preliminary study of the applications of this metal complex opens up the possibility of further investigations in the fields of metal-based drugs, luminescence and magnetism.