Maria Teresa Garland

Crystal structures and luminescent properties of terbium(III) carboxylates

Abstract Single crystals of three terbium(III) carboxylates of formulae [Tb2(CH3COO)6(H2O)4]·4H2O (1), [Tb2(CF3COO)6(H2O)6] (2) and [Tb(Hoda)3]·H2oda·H2O (3) (H2oda=2,2′-oxydiacetic acid) were obtained and their structures determined by X-ray crystallography. Compounds 1 and 2 are dimeric, in the former the terbium atoms are bound by two tridentate carboxylates in the μ2-bridging mode, whereas in the latter the bridging is fourfold with all carboxylates in the syn–syn coordination mode. Compound 3 is mononuclear containing three tridentate Hoda anions, and consecutive units are linked by a network of H-bonds involving the interstitial molecules. The luminescence spectra of the carboxylates were analyzed in the solid state and in aqueous solution. Comparison of the emission lifetimes in H2O and D2O allowed the determination of the average value for q, the number of coordinated water molecules, being 9.2 for 1 and 2 and 3.6 for 3, respectively. The quenching effect of Cu(II) on the luminescence of the terbium(III) carboxylates was evaluated through the emission decay constants. From the addition of Cu(II) to an aqueous solution of 3, single crystals of polymeric [{Cu3Tb2(oda)6(H2O)6}·12H2O]n (4) were isolated with completely quenched luminescence. Compound 4 exhibits an overall antiferromagnetic interaction.

Molecular structure and magnetic properties of [Gd(LH4)(NO3)2(H2O)]NO3(H2O)2, [Sm(LH4)(NO3)2(H2O)]NO3 (H2O)1.5(CH3OH)0.5 and [Cu2(LH2)(H2O)2](NO3)2 complexes (LH4: Schiff base ligand derived from 4-methyl-2,6-diformylphenol and 1,3-diaminopropanol)

Abstract Novel lanthanide(III) complexes (Ln=Gd (1), Sm (2), La (3)) of the macrocyclic ligand LH4 have been prepared and characterized. The binuclear copper(II) complex (Cu2(LH2)(H2O)2)(NO3)2 (4), has been obtained by transmetalation of complex 3 with Cu(CF3COO)2. The macrocyclic Schiff base ligand (LH4) is formed by the condensation of two molecules of 4-methyl-2,6-diformylphenol with two molecules of 1,3-diaminopropanol in the presence of the lanthanide ions. The alcohol group of the macrocycle does not coordinate to the copper(II) centers of the binuclear complex. However, one of the secondary alcohol groups of the ligand coordinates in an asymmetric mode to the lanthanide ion in the corresponding three complexes. The X-ray crystal structures of (Gd(LH4)(NO3)2(H2O))(NO3)(H2O)2 (1), (Sm(LH4)(NO3)2(H2O))(NO3)(H2O)1.5(CH3OH)0.5 (2), and (Cu2(LH2)(H2O)2)(NO3)2 (4) have been determined. Magnetic susceptibility measurements in the 5–300 K range were obtained for these complexes.

Synthesis and characterization of zinc(II) oxydiacetate (oda) complexes. Crystal structures of [{Zn(oda)·0.3H2O}n], [Zn(oda)(bipy)(H2O)]·2.5H2O and [Zn(oda)(phen)(H2O)]·1.5H2O (bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline)

Three novel zinc(II) oxydiacetate (oda) compounds [{Zn(oda)·0.3H2O}n]1, [Zn(oda)(bipy)(H2O)]·2.5H2 O 2(bipy = 2,2′-bipyridine) and [Zn(oda)(phen)(H2O)]·1.5H2O 3(phen = 1,10-phenanthroline) have been synthesized and their structures determined by single-crystal X-ray diffraction methods. Compound 1 consists of polymeric sheets formed by ZnO5 units bridged by carboxylate groups in anti-syn conformation along the z axis; 2 and 3 are mononuclear with the zinc atoms in distorted octahedral ZnN2O4 co-ordination geometries. Thermal decomposition of the compounds under an oxygen atmosphere affords ZnO at ca. 500 °C.

A discrete dinuclear Cu(II)–Gd(III) complex derived from a Schiff base ligand, [CuGd(ems)(NO3)3H2O]Cu(ems) (ems: N,N′-ethylene-bis-5-methoxy salicylaldiimine)

Abstract A Cu(II)–Gd(III) heteronuclear complex with N,N′-ethylene-bis-5-methoxy salicylaldiimine (ems) as ligand has been synthesized. The complex crystallizes in the monoclinic system C2/c space group. The structure consists of two different discrete molecules: a mononuclear unit containing a single Cu(II) center, and a dinuclear one containing both a nine coordinated Gd(III) plus a four coordinated Cu(II) cation [CuGd(H2O)(NO3)(ems)]. The complex was characterized by magnetic susceptibility and electron paramagnetic resonance. The Cu(II)–Gd(III) complex presents a ferromagnetic interaction (J=1.88 cm−1); its effective magnetic moment was found to increase with decreasing temperature. Both electronic and structural parameters are shown to influence the magnitude of the magnetic interaction.

New homobinuclear carboxylate-bridged gadolinium(III) complexes

Abstract Two novel gadolinium(III) trans-2-butenoate dimeric compounds [Gd2(O2CCHCHCH3)6(H2O)4]·2H2O (1) and [Gd2(O2CCHCHCH3)6(phen)2]·2H2O (2) have been synthesized via hydrothermal routes. Compound 1 consists of two independent dimers in the unit cell, one is doubly bridged (η2:η1:μ2) and the other quadruply bridged (two η1:η1:μ2 and two η2:η1:μ2). Compound 2 is dimeric with a quadruply bridged core (two η1:η1:μ2 and two η2:η1:μ2). Magnetic measurements for 2 show that there is a weak antiferromagnetic intramolecular Gd⋯Gd interaction.

Coordination mode of some polypyridyl ligands towards the platinum(II) complexes [Pt(dppf)(H2O)2](CF3SO3)2 (dppf=1,1′-bis(diphenylphosphino)ferrocene) and [Pt(Me2SO)2Cl2]. Crystal structure of the seven-membered chelate ring complex [Pt(dpq)Cl2] (dpq=2,3-di(2-pyridyl)quinoxaline)

Abstract A series of novel platinum(II) complexes were isolated through the reaction of the polypyridyl ligands 2,3,7,8-tetra(2-pyridyl)pyrazino[2,3-g]quinoxaline (tpq), 2,3-di(2-pyridyl)pyrazine (dpp), 2,3-di(2-pyridyl)quinoxaline (dpq) and 6,7-dimethyl-2,3-di(2-pyridyl)quinoxaline (ddpq) with the heterobimetallic complex [Pt(dppf)(H2O)2](CF3SO3)2 or with the dimethyl sulfoxide complex [Pt(Me2SO)2Cl2]. The di-platinum complex [{Pt(dppf)}2(tpq)](CF3SO3)4 and the mono-platinum compounds [Pt(dppf)(L)](CF3SO3)2 (L=dpp, ddpq) and [Pt(L)Cl2] (L=dpq, ddpq) were synthesized. As shown by 1H NMR spectroscopy, in these complexes the bridging tpq and the mononucleating ligands dpp, dpq and ddpq present an uncommon bidentate chelate mode; they are bonded to the Pt(II) centres only by the means of their pyridyl nitrogen atoms. This behaviour was corroborated through the X-ray crystallographic study of the [Pt(dpq)Cl2] derivative. The redox properties of the three new dppf-based complexes, in dichloromethane solution, show in all cases that they undergo ferrocene-based (dppf) oxidations and that the primary cathodic processes are tpq-centered in the tpq complex and platinum(II)-centered in the dpp and ddpq complexes.

SYNTHESIS AND X-RAY CRYSTAL DETERMINATION OF FOUR NOVEL LANTHANIDE(III) OXYDIACETATE COMPLEXES

Abstract Four newlanthanide oxydiacetates [{Y(Hoda)3}·H2oda·H2O] (1), [{Y2(oda)3(H2O)4·2H2O}n] (2), [{LaGd(oda)3(H2O)3·6H2O}n] (3) and [{LaY (oda)3(H2O)3·6H2O}n] (4) (oda = O2CCH2OCH2CO2) have been synthesized and their structures determined by singlecrystal X-ray methods. Compound 1 is monometallic with distorted YO9 units formed via coordination of three tridentate Hoda ligands. Compound 2 consists of polymeric sheets of YO9 units formed via coordination of three tridentate oda ligands bridged through carboxylate groups to YO8 units. Compounds 3 and 4 are isomorphous heterobimetallic three-dimensional networks of LnO9 units (Ln Gd or Y) formed via coordination of three tridentate oda ligands bridged to the larger radius La (III) in LaO9 units through carboxylate groups.

X-ray study on the nickel(II)-oxydiacetic system and its 1,10-phenanthroline and 2,2′:6′,2′′ terpyridine complexes

Abstract Three new metal–organic coordination complexes have been prepared and their crystal structures determined: [Ni(oda)(H2O)3]·1.5H2O, [Ni(oda)(phen)(H2O)]·1.5H2O and [Ni(oda)(terpy)]·2H2O (oda=oxydiacetate, phen=1,10-phenanthroline, terpy=2,2′:6′,2′′ terpyridine). The oxydiacetate ligand is tridentate in these compounds, being hinged in the first and nearly planar in the other two. Hydrogen-bonding and π–π interaction is extensive in the solids.

Novel europium and gadolinium compounds in the lanthanide(III) oxydiacetate series

Abstract Three new lanthanide oxydiacetate compounds have been prepared and their structures determined by single crystal X-ray methods: {[Ln2(oda)3(H2O)2]·5H2O}n (Ln=Eu, Gd) and [Eu(oda)(Hoda)(H2O)]·2H2O. The former are orthorhombic and Ama2, with LnO8 and LnO9 cores bridged by anti–anti carboxylate ligands and the latter is mononuclear containing a EuO9 core. Luminescence spectra of the europium complexes in the solid state are presented.

1-D polymers with alternate Cu2 and Ln2 units (Ln = Gd, Er, Y) and carboxylate linkages.

Three isostructural Cu 2Ln 2 1-D polymers [Cu 2Ln 2L 10(H 2O) 4.3H 2O] n where Ln = Gd ( 1), Er ( 2), and Y ( 3) and HL= trans-2-butenoic acid, were synthesized and characterized by X-ray crystallography, electron paramagnetic resonance, and magnetic measurements. Pairs of alternate Cu 2 and Ln 2 dinuclear units are combined into a linear array by a set of one covalent eta (2):eta (1):mu 2 carboxylate oxygen and two H bonds, at Cu...Ln distances of ca. 4.5 A. These units exhibit four eta (1):eta (1):mu 2 and two eta (2):eta (1):mu 2 carboxylate bridges, respectively. Magnetic measurements between 2 and 300 K, fields B 0 = mu 0 H between 0 and 9 T, and electron paramagnetic resonance (EPR) measurements at the X-band and room temperature are reported. The magnetic susceptibilities indicate bulk antiferromagnetic behavior of the three compounds at low temperatures. Magnetization and EPR data for 1 and 3 allowed evaluation of the exchange couplings between both Cu and Gd ions in their dinuclear units and between Cu and Gd neighbor ions in the spin chains. The data for the isolated Cu 2 units in 3 yield g || = 2.350 and g [symbol: see text] = 2.054, J Cu-Cu = -338 (3) cm (-1) for the exchange coupling [ H ex(1,2) = - J 1-2 S1 x S2], and D 0 = -0.342 (0.003) cm (-1) and E 0 = 0.003 (0.001) cm (-1) for the zero-field-splitting parameters of the triplet state arising from anisotropic spin-spin interactions. Considering tetranuclear blocks Gd-Cu-Cu-Gd in 1, with the parameters for the Cu 2 unit obtained for 3, we evaluated ferromagnetic interactions between Cu and Gd neighbors, J Cu-Gd = 13.0 (0.1) cm (-1), and between Gd ions in the Gd 2 units, J Gd-Gd = 0.25 (0.02) cm (-1), with g Gd = 1.991. The bulk antiferromagnetic behavior of 1 is a consequence of the antiferromagnetic coupling between Cu ions and of the magnitude, |J Cu-Gd|, of the Cu-Gd exchange coupling. Compound 2 displays a susceptibility peak at 15 K that may be interpreted as the combined result from antiferromagnetic couplings between Er (III) ions in Er 2 units and their coupling with the Cu 2 units.