New series of mononuclear ß-diketonate cerium(III) field induced single-molecule magnets.

Five new ß-diketonate Ce3+ mononuclear complexes, [Ce(Btfa)3(H2O)2] (1), [Ce(Btfa)3(phen)] (2), [Ce(Btfa)3(bipy)] (3), [Ce(Btfa)3(terpy)] (4) and [Ce(Btfa)3(bathophen)(DMF)] (5), where Btfa- = 4,4,4-trifluoro-1-phenyl-1,3-butanedionate, phen = 1,10-phenanthroline, bipy = 2,2'-bipyridyl, terpy = 2,2':6',2''-terpyridine and bathophen = 4,7-diphenyl-1,10-phenanthroline, have been synthesized and structurally characterized through X-ray diffraction of single crystals. The central Ce3+ atom displays a coordination number of 8 for 1, 2 and 3 and of 9 for 4 and 5. Under a 0 T external magnetic field, none of the given compounds exhibits single molecule magnet (SMM) behaviour. However, a small magnetic field, between 0.02 and 0.1 T, is enough for all the compounds to exhibit slow relaxation of the magnetization. A comprehensive magnetic analysis, with experimental magnetic data and ab initio calculations, was undertaken for all the complexes, and the study highlights the significance of the different spin relaxation mechanisms that must be considered for a Ce3+ lanthanide ion.

Magnetic and optical studies of a new family of multidimensional and multiproperty PO-lanthanide(III) derived systems.

A new family of lanthanide compounds has been synthesized using 1,2-bis(diphenylphosphino)ethane dioxide (dppeO2) as an O-donor ligand through the phosphoryl group to lanthanide(III) cations and structurally, magnetically and optically studied. Depending on the lanthanide, two different topologies appear: the two-dimensional structure [LnIII(dppeO2)1.5(NO3)3(H2O)0.5]n (Ln = Ce (1), Sm (2) and Dy (6)) and the one-dimensional structure [Ln(dppeO2)(NO3)3DMF]n (Ln = Eu (3), Gd (4) and Tb (5)). Some of the Ln-derived complexes have been used as structural probes, while others have been synthesized to use the specific characteristics of each cation to take advantage of their magnetic/luminescence properties. Complex 6 presents slow relaxation of the magnetization while 2, 3 and 5 present emitting properties in the visible range.

Modulation of the magnetic and photophysical properties in 3d-4f and 4f-4f' heterobimetallic complexes involving a tetrathiafulvalene-based ligand.

The reaction between the 2-(1-(2,6-di(pyrazol-1-yl)-4-methylpyridyl)-4,5-(4,5-bis(propylthio)-tetrathiafulvalenyl)-1H-benzimidazol-2-yl)-pyridine ligand (L), 1 equivalent of Ln(hfac)3·2H2O/Dy(tta)3·2H2O (hfac- = 1,1,1,5,5,5-hexafluoroacetylacetonate, tta- = 2-thenoyltrifluoroacetonate) and M(hfac)2·2H2O leads to the formation of heteroleptic 3d-4f dinuclear complexes of formula [MLn(hfac)5(L)]n (M(II) = Cd, Zn, Co, Mn, Ni and Ln(III) = Dy, Yb, Nd) and [ZnDy(tta)2(hfac)3(L)]·(CH2Cl2). Their X-ray structures reveal that the two coordination sites are occupied by one Ln(III) ion and one M(II) transition metal respectively. The M(II) ions are coordinated to the benzoimidazolylpyridine (bzip) moiety in a N2O4 coordination sphere, while the Ln(III) ions are coordinated to the 2,6-di(pyrazol-1-yl)-4-pyridine (dpp) moiety in a N3O6 surrounding. When Dy(III) ion is used a field-induced Single-Molecule Magnet (SMM) behavior is detected with a magnetic relaxation time slightly dependent to the nature of the vicinal divalent transition metal. On the other hand, when the Yb(III) is used, intense, moderated or quenched 2F5/2 → 2F7/2 NIR luminescence is observed when the Yb(III) ion is respectively associated with the Zn(II), Mn(II) and Ni(II)/Co(II) ion. The emission intensity can be modulated in function of the metal-to-ligand charge transfer and d-d transition intensities. The replacement of the divalent transition metal by a trivalent lanthanide leads to the formation of heteroleptic 4f-4f' dinuclear complexes of formula [Ln2-xLn'x(hfac)6(L)]·a(CH2Cl2)·b(C6H14) and [Dy1.11Nd0.89(tta)3(hfac)3(L)]. The coordination selectivity is based on the radius. Among the 4f-4f' series, the Dy(III) derivatives displayed such ion in N2O6 eight-coordinated sphere allowing the observation of SMM behavior. The three compounds [Dy1.21Nd0.79(hfac)6(L)]·2(CH2Cl2)·(C6H14), [Yb1.04Nd0.96(hfac)6(L)] and [YbPr(hfac)6(L)] displayed respectively Nd(III), modarated Yb(III) and intense Yb(III) NIR emissions.

Insights into the Spin Dynamics of Mononuclear Cerium(III) Single-Molecule Magnets.

Four novel CeIII mononuclear complexes of formulas [Ce(ntfa)3(MeOH)2] (1), [Ce(ntfa)3(5,5'-Me2bipy)] (2), [Ce(ntfa)3(terpy)] (3), and [Ce(ntfa)3(bipy)2] (4), where ntfa = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionato, 5,5'-Me2bipy = 5,5'-dimethyl-2,2'-dipyridyl, terpy = 2,2':6',2″-terpyridine, and bipy = 2,2'-bipyridine, have been synthesized and structurally characterized with CeIII displaying coordination numbers of 8, 8, 9, and 10, respectively. Magnetic measurements indicate that all the complexes show a field-induced single-ion magnet behavior under a small applied dc field. The magnetic analysis shows the relevance of the different spin relaxation mechanisms in the magnetic relaxation of the CeIII compounds, with special emphasis on the local-mode process. Multiconfigurational calculations were also performed to get more information on the axiality of the compounds.

Magnetic and Luminescence Properties of 8-Coordinate Holmium(III) Complexes Containing 4,4,4-Trifluoro-1-Phenyl- and 1-(Naphthalen-2-yl)-1,3-Butanedionates.

A new series of mononuclear Ho3+ complexes derived from the ß-diketonate anions: 4,4,4-trifluoro-1-phenyl-1,3-butanedioneate (btfa-) and 4,4,4-trifuoro-1-(naphthalen-2-yl)-1,3-butanedionate (ntfa-) have been synthesized, [Ho(btfa)3(H2O)2] (1a), [Ho(ntfa)3(MeOH)2] (1b), (1), [Ho(btfa)3(phen)] (2), [Ho(btfa)3(bipy)] (3), [Ho(btfa)3(di-tbubipy)] (4), [Ho(ntfa)3(Me2bipy)] (5), and [Ho(ntfa)3(bipy)] (6), where phen is 1,10-phenantroline, bipy is 2,2'-bipyridyl, di-tbubipy is 4,4'-di-tert-butyl-2,2'-bipyridyl, and Me2bipy is 4,4'-dimethyl-2,2'-bipyridyl. These compounds have been characterized by elemental microanalysis and infrared spectroscopy as well as single-crystal X-ray difraction for 2-6. The central Ho3+ ions in these compounds display coordination number 8. The luminescence-emission properties of the pyridyl adducts 2-6 display a strong characteristic band in the visible region at 661 nm and a series of bands in the NIR region (excitation wavelengths (λex) of 367 nm for 2-4 and 380 nm for 5 and 6). The magnetic properties of the complexes revealed magnetically uncoupled Ho3+ compounds with no field-induced, single-molecule magnet (SMMs).

Chiral dinuclear Ln(iii) complexes derived from S- and R-2-(6-methoxy-2-naphthyl)propionate. Optical and magnetic properties.

The reaction of LnCl3·6H2O with (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (S-HL), best known as naproxen, and 1,10-phenanthroline (phen) in EtOH allows the isolation of dinuclear chiral compounds S-1-4 of the formula [Ln2(S-L)6(phen)2]·3DMF·H2O [Ln(iii) = Eu (1), Gd (2), Tb (3) and Dy (4)]. The use of the R-enantiomeric species of the HL ligand led to complexes R-1-4 with the formula [Ln2(R-L)6(phen)2]·3DMF·H2O. Compounds R- andS-1, 3 and 4 show strong sensitized metal-centred luminescence in the visible region. Moreover, Dy(iii) complexes R- andS-4 display field-induced single-molecule magnet (SMM) behaviour. For chiral and emissive compounds circularly polarized luminescence (CPL) measurements have also been performed.

µ1,1-R-phenylcyanamido bridges as a new safe synthetic strategy for ferromagnetic molecular clusters.

The reaction of Ni(NO3)2·6H2O with di-2-pyridyl ketone, (py)2CO, and the R-phenylcyanamides 4Cl-3CF3-PhHNCN and 4F-3CF3-PhHNCN in CH3OH or CH3CH2OH allows the isolation of the tetranuclear compounds [(Ni4(µ-py2COOCH3)2(µ3-py2COOH)2(µ1,1-4Cl-3CF3-PhNCN)2(4Cl-3CF3-PhNCN)2]·CH3OH (1), [(Ni4(µ-py2COOCH2CH3)2(µ3-py2COOH)2(µ1,1-4Cl-3CF3-PhNCN)2(4Cl-3CF3-PhNCN)2]·2EtOH (2) and [(Ni4(µ-py2COOCH3)2(µ3-py2COOH)2(µ1,1-4F-3CF3-PhNCN)2(4F-3CF3-PhNCN)2]·4CH3OH (3). {(py)2C(OH)O}(-) and {(py)2C(OR)O}(-) are the monoanions of the gem-diol and hemiketal (R = CH3, CH2CH3) forms of (py)2CO. X-ray diffraction analysis reveals defective double-cubane tetrameric entities in which the Ni(II) atoms are linked by µ1,1-R-phenylcyanamido bridges and two kinds of O-bridges. The molar magnetic susceptibility measurements of 1-3 in the 2-300 K range indicate bulk ferromagnetic coupling.

Four new trinuclear {Cu3(µ3-OH)(oximate)3}²âº clusters: crystal structure and magnetic behaviour.

Four new triangular copper(II) complexes with the fragment {Cu3(µ3-OH)(oximate)3}(2+) and formulae [Cu3(µ3-OH)(µ-Cl)(Py2CNO)3((t)BuPO3H)]·4H2O (1), [Cu3(µ3-OH)(µ-Br)(Py2CNO)3((t)BuPO3H)]·3.5H2O (2), [Cu3(µ3-OH)(µ-Br)(PhPyCNO)3((t)BuPO3H)(MeOH)]·1.5 MeOH (3), [Cu3(µ3-OH)Cl2(PhPyCNO)3]·0.5H2O (4), (Py2CNO = di(2-pyridyl)ketoximate, PhPyCNO = phenyl(2-pyridyl)ketoximate, (t)BuPO3H2 = tert-butylphosphonic acid) are reported. The magnetic properties of compounds 1-4 were studied. The compounds were found to exhibit strong antiferromagnetic coupling and antisymmetric exchange interaction.

Hexanuclear copper(II) cages built on a central {µ3-O···H···µ3-O} moiety, 1,3-bis(dimethylamino)-2-propanolato and capping R-phosphonates: crystal structures, magnetic behavior, and DFT studies.

The syntheses, structural characterization, and magnetic behavior of two new hexanuclear copper(II) complexes derived from R-phosphonic acids and 1,3-bis(dimethylamino)-2-propanol (Hbdmap) with formulas [Cu(6)(µ-bdmap)(3)(µ(3)-Ph-PO(3))(2)(µ(3)-O···H···µ(3)-O)(ClO(4))(2)(H(2)O)]·5H(2)O (1) and [Cu(6)(µ-bdmap)(3)(µ(3)-t-Bu-PO(3))(2)(µ(3)-O···H···µ(3)-O)(µ(1,3)-dca)(dca)(H(2)O)]·6H(2)O (2) (Ph-H(2)PO(3) = phenylphosphonic acid, t-Bu-H(2)PO(3) = tert-butylphosphonic acid, dca = dicyanamide) are reported. Compounds 1 and 2 are hexanuclear 3.111 R-phosphonate(2-)/1,3-bis(dimethylamino)-2-propanolato(1-) cages including in the center the [µ(3)-O···H···µ(3)-O](3-) unit. The temperature dependence of the magnetic properties of 1 and 2 clearly indicates an overall strong antiferromagnetic coupling confirmed by DFT calculations.

Polynuclear copper(II) complexes of di-2-pyridyl ketone derivatives and tert-butylphosphonic acid: crystal structures and magnetic behaviour.

The syntheses, structural characterization, and magnetic behavior of four new copper(II) complexes derived from tert-butylphosphonic acid and di-2-pyridyl ketone with formulae [Cu{(py)(2)C(OH)(2)}](C(4)H(9)PO(3)H)(2).(H(2)O)(2) (1), [Cu(2)(mu(2)-C(4)H(9)PO(3)H){(py)(2)C(OCH(2)CH(3))O}(mu(2)-NO(3))(NO(3))(H(2)O)](n).(H(2)O)(n) (2), [Cu(4)(mu(2)-C(4)H(9)PO(3)H)(2)(mu(4)-C(4)H(9)PO(3))(2){(py)(2)C(OCH(3))O}(2)].2H(2)O (3) and Na[Cu(6)(mu(3)-C(4)H(9)PO(3))(3){(py)(2)C(OCH(3))O}(3)(mu(6)-NO(3))(NO(3))(3)] (4) (C(4)H(9)PO(3)H(2) = tert-butylphosphonic acid, (py)(2)C(OH)(2) = bis(2-pyridyl)methanediol, {(py)(2)C(OCH(2)CH(3))O}(-) = bis(2-pyridyl)ethoxymethanolato {(py)(2)C(OCH(3))O}(-) = bis(2-pyridyl)methoxymethanolato, are reported. 1 is a mononuclear compound, with tert-butylhydrogenphosphonate in the anionic form. 2 is a nitrate bridged monodimensional compound with 2.110 tert-butylhydrogenphosphonate bridging ligands. 3 is a tetranuclear compound with 2.110 tert-butylhydrogenphosphonate and 3.111 tert-butylphosphonate bridging ligands and 4 is a hexanuclear compound with 3.111 tert-butylphosphonate bridging ligands. The magnetic properties of 2-4 are reported.

Calibrating the coordination chemistry tool chest: metrics of bi- and tridentate ligands.

Bi- and multidentate ligands form part of the tools commonly used for designing coordination and supramolecular complexes with desired stereochemistries. Parameters and concepts usually employed include the normalized bite of bidentate ligands, their cis- or trans-coordinating ability, their rigidity or flexibility, or the duality of some ligands that can act in chelating or dinucleating modes. In this contribution we present a structural database study of over one hundred bi- and tridentate ligands that allows us to parametrize their coordinating properties and discuss the relevance of such parameters for the choice of coordination polyhedron or coordination sites.