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1.
Dalton Trans ; 52(45): 16791-16801, 2023 Nov 21.
Artículo en Inglés | MEDLINE | ID: mdl-37902968

RESUMEN

Two LnIII complexes Ln(HTMSA)3(H2O)2·5.5H2O (Ln = Dy (1) and Tb (2), H2TMSA = 5-azotriazolyl-3-methoxysalicylaldehyde) and two MnII-LnIII clusters [Mn(H2O)6][MnLn2(TTMSA)4(HTTMSA)2(H2O)6]·4H2O (Ln = Dy (3) and Tb (4), H2TTMSA = 5-azotetrazolyl-3-methoxysalicylaldehyde) have been synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that 1 and 2 are isostructural complexes in which the LnIII ions are surrounded by six oxygen atoms from three chelate HTMSA ligands and two oxygen atoms from two coordinated water molecules forming a distorted square-anti-prismatic geometry. In complexes 3 and 4, the MnII ions adjust two LnIII mononuclear anion clusters into tri-nuclear LnIII-MnII-LnIII anion clusters, with an additional [Mn(H2O)6]2+ as a counter ion to maintain the electroneutrality of the compound. Magnetic studies reveal that all the complexes 1-4 show nonzero out-of-phase signals, indicating single-molecule magnet behavior. The photoluminescence spectra of all the complexes were investigated and are discussed in detail.

2.
Dalton Trans ; 51(33): 12661-12669, 2022 Aug 23.
Artículo en Inglés | MEDLINE | ID: mdl-35938501

RESUMEN

Based on the uncommon Kramers ions CeIII, SmIII and YbIII, complexes [Ce(dppbO2)2Cl3] (1, dppbO2 = 1,2-bis(diphenylphosphino)benzene dioxide), [Sm(dppbO2)2Cl3] (2) and [Yb(dppbO2)2Cl2]Cl (3) toward single-ion magnets were obtained and fully characterized. Complexes 1 and 2 are isostructural seven-coordinate with distorted geometries between a capped trigonal prism and a capped octahedron, while 3 is six-coordinate with an octahedral geometry. Dynamic magnetic property measurements reveal their field induced slow magnetic relaxation behaviours. Fits to the temperature dependent relaxation time (τ) result in effective barriers of 38(2), 11.7(2) and 20.2(6) cm-1 for 1, 2 and 3, respectively, as well as relatively low Raman exponents (3.4(2) for 1 and 2.1(1) for 3). Ab initio calculations were then performed and they indicated that the first excited Kramers doublets (KDs) for 1, 2 and 3 lie at ca. 291, 63.5 and 137 cm-1, respectively, which are much higher than the fitting results. Combining the significant transverse magnetic moments between the ground state KDs and the first excited KDs, we thus attribute the dominant relaxation pathway of the three compounds to a Raman process, while quantum tunnelling of magnetization and direct relaxation processes may coexist. In this case, the obtained effective barriers in a high temperature region for 1 and 3 are actually the energies of the vibrational modes, which lead to second-order Raman processes with exponential temperature dependence.

3.
Dalton Trans ; 51(13): 5195-5202, 2022 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-35274652

RESUMEN

Due to the small differences in the chemical properties of facial (fac) and meridional (mer) stereoisomers, selective synthesis of one of the isomers is challenging, especially for lanthanide complexes. By using a flexible bidentate phosphine oxide ligand, we managed to isolate three stereoisomeric 2D and 3D coordination polymers, in which six-coordinate Dy(III) ions possess fac- or mer-Cl3O3 coordination environments. Structural studies indicate that the stereochemistry differences result from their various supramolecular interactions (e.g., hydrogen bonding and π⋯π stacking). Magnetic property measurements reveal the different static and dynamic magnetic behaviours of the three stereoisomers. Ab initio CASSCF calculations were then performed which indicated that their distinct magnetic behaviours arise from their fac/mer configurations. Compared to fac-Dy(III), mer-Dy(III) possesses more axial ground-state KDs and higher first excited KDs.


Asunto(s)
Disprosio , Elementos de la Serie de los Lantanoides , Cristalografía por Rayos X , Disprosio/química , Elementos de la Serie de los Lantanoides/química , Polímeros/química , Estereoisomerismo
4.
Chem Asian J ; 14(9): 1467-1471, 2019 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-30865374

RESUMEN

Two isostructural mononuclear CoII complexes, [Co(xantpo)(NCE)2 ] (E=S (1) and O (2); xantpo=9,9-dimethyl-4,5-bis(diphenylphosphoryl) xanthene), supported by a bidentate phosphine oxide ligand are reported. The cobalt complexes exhibit characteristic tetrahedral structures coordinated with two oxygen and two nitrogen atoms. Magnetic property measurements show their similar static magnetic behaviours but very different dynamic magnetic behaviours. Both complexes show field-induced slow magnetic relaxation behaviours, but the relaxation of 2 is much slower than that of 1. Fittings to the magnetic data and ab initio CASSCF calculations reveal significant changes in the zero field splitting (ZFS) parameters (D and E), which can be attributed to the small geometrical changes of the Co ions and the different ligand field strength of the two terminal ligands.

5.
Dalton Trans ; 47(36): 12526-12533, 2018 Sep 18.
Artículo en Inglés | MEDLINE | ID: mdl-29688242

RESUMEN

Herein we investigate salt metathesis reactions of bulky bis(silyl)amide potassium salts [K{N(SiMe2tBu)2}]n, [K{N(SiMe2tBu)(SiiPr3)}]n, [K{N(SiiPr3)2}]n and [K{N(SiPh3)2}]n (1) with AeI2 (Ae = Mg, Ca, Sr) in an effort to synthesise rare homoleptic two-coordinate complexes. Recrystallization of 1 from THF provided structural authentication of the solvated adduct [K{N(SiPh3)2}(THF)3] (1-THF). For Ae = Mg we were able to identify products for three of the four bis(silyl)amides investigated: [Mg{N(SiMe2tBu)2}2(THF)] (2), [Mg{N(SiMe2tBu)(SiiPr3)}2] (3) and [Mg{N(SiPh3)2}2] (4). Complexes 2-4 were isolated in good yields, and on one occasion during recrystallization of 2 a crystal of the heteroleptic complex [Mg{N(SiMe2tBu)2}(I)(THF)2] (5) was identified by XRD. We found that these methodologies were not widely applicable for larger Ae = Ca and Sr, as large quantities of the parent bis(silyl)amines formed in reaction mixtures; however, we were able to isolate the first near-linear Ca(ii) amide [Ca{N(SiiPr3)2}2] (6) from these studies. No Ae-containing products could be isolated from KC8/crown ether reductions of 3, 4 and 6. Complexes 1-4 and 6 were characterised by single crystal XRD, multinuclear NMR and FTIR spectroscopy and elemental analysis, whereas complex 5 was identified by single crystal XRD only.

6.
Dalton Trans ; 47(18): 6361-6369, 2018 May 08.
Artículo en Inglés | MEDLINE | ID: mdl-29658048

RESUMEN

The reactions of {Cr6} horseshoe chains {[nPr2NH2]3[Cr6F11(O2CtBu)10]}2, 1 and precursors of actinides and group IV metals led to a series of ring complexes [nPr2NH2][Cr7TiF6O2(O2CtBu)16], 2, [nPr2NH2][Cr6Ti2F5O3(O2CtBu)16], 3, [Cr6ThF7(O2CtBu)15 (Me2SO)], 4, [(nPr2NH2)2(Cr6Th2F12(O2CtBu)16)], 5 and [nPr2NH2][Cr6U2O2F8(O2CtBu)16(Me2SO)], 6. X-ray structure studies indicate that the {Cr6} chains maintain their structures in these complexes, acting as polydentate fluoride ligands. Their static magnetic properties were measured and fitted by isotropic exchange Hamiltonian. In accordance with 1, the magnetic exchanges between CrIII are antiferromagnetic, while the exchange interactions can be modified by the tetravalent metals. For compound 6, ferromagnetic exchanges JCr-U and JU-U are obtained. EPR spectra of compounds 2-5 were measured at Q band and were simulated. The spectrum of 2 has the same profile as {Cr7Cd} and {Cr7Zn} rings with a ground state S = 3/2. 3, 4 and 5 give similar EPR spectra with S = 0 ground states.

7.
Chem Commun (Camb) ; 53(55): 7820-7823, 2017 Jul 06.
Artículo en Inglés | MEDLINE | ID: mdl-28653076

RESUMEN

Reversible crystal-to-crystal transformation between a linear trinuclear Fe(ii) complex [Fe3(NH2-trz)6(SCN)5(H2O)] (SCN)·4H2O (1, NH2-trz = 4-amino-1,2,4-triazole) and a 1D chain [Fe3(NH2-trz)6(SCN)5]n(SCN)n (1a) and the SCO behaviour change have been studied by X-ray single-crystal diffraction, magnetic measurements and DSC. Complex 1a exhibits one more SCO step at a low temperature.

8.
Dalton Trans ; 44(30): 13480-4, 2015 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-26159885

RESUMEN

A one-dimensional dysprosium(iii)-carboxylate chain in which the Dy(III) ions sit in a pseudo D(2d)-symmetry environment is synthesized and shows different slow magnetic relaxation behaviours depending on the field and dilution effects. Besides, the chiral ligand introduces the additional functions of the Cotton effect and polarization for this compound.

9.
Inorg Chem ; 54(10): 4588-90, 2015 May 18.
Artículo en Inglés | MEDLINE | ID: mdl-25928354

RESUMEN

To test the coordination symmetry effect on the magnetization-reversal barrier trend of Er(III)-based single-ion magnets, the C2v-symmetric organolanthanide anion [Er(Cp)2(O(t)Bu)2](-) has been incorporated with different countercations, resulting in two structures, namely, the discrete [K2(Cp)(18-C-6)2][Er(Cp)2(O(t)Bu)2] (1) and the polymeric [ErK2(Cp)3(O(t)Bu)2(THF)2]n (2), where 18-C-6 = 18-crown-6 ether and Cp = cyclopentadienide. Surprisingly, the polymeric 2 exhibits much stronger field-induced magnetization relaxing behavior compared to the monomeric 1. Such disparate dynamic magnetism is attributable to the subtle coordination environmental perturbations of the central Er(III) ions.

10.
Inorg Chem ; 53(11): 5458-66, 2014 Jun 02.
Artículo en Inglés | MEDLINE | ID: mdl-24826941

RESUMEN

The synthesis, structure and magnetic properties are reported of two disklike mixed-valence cobalt clusters [Co(III)Co(II)6(thmp)2(acac)6(ada)3] (1) and [Co(III)2Co(II)11(thmp)4(Me3CCOO)4(acac)6(OH)4(H2O)4](Me3CCOO)2·H2O (2). Heptanuclear complex 1 was prepared by solvothermal reaction of cobalt(II) acetylacetonate (Co(acac)2), 1,1,1-tris(hydroxymethyl)-propane (H3thmp), and adamantane-1-carboxylic acid (Hada), whereas by substituting Hada with Me3CCO2H, tridecanuclear complex 2 was obtained with an unexpected [Co(III)2Co(II)11] core. The core structures of 1 and 2 are related to each other: that of 1 arranges as a centered hexagon of a central Co(III) ion surrounded by a [Co(II)6] hexagon, while that of 2 can be described as a larger oligomer based on two vertex-sharing [Co(III)Co(II)6] clusters. Variable-temperature direct-current magnetic susceptibility measurements demonstrated overall ferromagnetic coupling between the Co(II) ions within both clusters. The magnetic exchange (J) and magnetic anisotropy (D) values were quantified with appropriate spin-Hamiltonian models and were also supported by density functional theory calculations. The presence of frequency-dependent out-of-phase (χM″) alternating current susceptibility signals at temperatures below 3 K suggested that 2 might be a single-molecule magnet.

11.
Chemistry ; 20(11): 3029-35, 2014 Mar 10.
Artículo en Inglés | MEDLINE | ID: mdl-24532426

RESUMEN

The transformation of Mn(II) glycolates (glc) between the three-dimensional coordination polymer [Mn(glc)2]n (1) and discrete mononuclear phase [Mn(glc)2 (H2O)2] (2) can be reversibly switched by water molecules, which dramatically change the magnetocaloric effect (MCE) of Mn(II) glycolates from the maximum of 6.9 J kg(-1) K(-1) in 1 to 60.3 J kg(-1) K(-1) in 2. This case example reveals that the effect of magnetic coupling on MCE plays a dominant role over that of other factors such as magnetic density for 3d-type magnetic refrigerants.

12.
Chemistry ; 19(51): 17567-77, 2013 Dec 16.
Artículo en Inglés | MEDLINE | ID: mdl-24265054

RESUMEN

A series of heterometallic [Ln(III)(x)Cu(II)(y)] complexes, [Gd2Cu2]n (1), [Gd4Cu8] (2), [Ln9Cu8] (Ln=Gd, 3·Gd; Ln=Dy, 3·Dy), were successfully synthesized by a one-pot route at room temperature with three kinds of in situ carbonyl-related reactions: Cannizzaro reaction, aldol reaction, and oxidation. This strategy led to dysprosium analogues that behaved as single-molecule magnets (SMMs) and gadolinium analogues that showed significant magnetocaloric effect (MCE). In this study a numerical DFT approach is proposed by using pseudopotentials to calculate the exchange coupling constants in three polynuclear [Gd(x)Cu(y)] complexes; with these values exact diagonalization or quantum Monte Carlo simulations have been performed to calculate the variation of the magnetic entropy involved in the MCE. For the [Dy9Cu8] complexes, local magnetic properties of the Dy(III) centers have been determined by using the CASSCF+RASSI method.

13.
Chemistry ; 19(44): 14876-85, 2013 Oct 25.
Artículo en Inglés | MEDLINE | ID: mdl-24105852

RESUMEN

The comprehensive study reported herein provides compelling evidence that anion templates are the main driving force in the formation of two novel nanoscale lanthanide hydroxide clusters, {Gd38(ClO4)6} (1) and {Gd48Cl2(NO3)} (2), characterized by single-crystal X-ray crystallography, infrared spectroscopy, and magnetic measurements. {Gd38(ClO4)6}, encapsulating six ClO4(-) ions, features a cage core composed of twelve vertex-sharing {Gd4} tetrahedrons and one Gd⋅⋅⋅Gd pillar. When Cl(-) and NO3(-) were incorporated in the reaction instead of ClO4(-), {Gd48Cl2(NO3)} is obtained with a barrel shape constituted by twelve vertex-sharing {Gd4} tetrahedrons and six {Gd5} pyramids. What is more, the cage-like {Gd38} can be dynamically converted into the barrel-shaped {Gd48} upon Cl(-) and NO3(-) stimulus. To our knowledge, it is the first time that the linear M-O-M' fashion and the unique µ8-ClO4(-) mode have been crystallized in pure lanthanide complex, and complex 2 represents the largest gadolinium cluster. Both of the complexes display large magnetocaloric effect in units of J kg(-1) K(-1) and mJ cm(-3) K(-1) on account of the weak antiferromagnetic exchange, the high N(Gd)/M(W) ratio (magnetic density), and the relatively compact crystal lattice (mass density).

14.
Chem Commun (Camb) ; 49(81): 9341-3, 2013 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-23999586

RESUMEN

A ferromagnetic intramolecular dipolar interaction is observed and verified by both experimental studies and ab initio calculations on a dinuclear holmium(III) complex [Ho2(H2cht)2Cl4(H2O)(MeCN)]·MeCN.

15.
Chemistry ; 19(40): 13504-10, 2013 Sep 27.
Artículo en Inglés | MEDLINE | ID: mdl-23959529

RESUMEN

Two kinds of inorganic gadolinium(III)-hydroxy "ladders", [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd2(OH)2(suc)2(H2O)]n·2nH2O (1) and [Gd6(OH)8(suc)5(H2O)2 ]n·4n H2O (2), respectively. Such coordination polymers could be regarded as alternating inorganic-organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg(-1) K(-1) for complex 1 and 48.0 J kg(-1) K(-1) for complex 2. The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm(-3) K(-1) for complexes 1 and 2, respectively.

16.
Chem Commun (Camb) ; 49(73): 8081-3, 2013 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-23912749

RESUMEN

Two unprecedented wheel-shaped nanoscale clusters {Co(II)16Ln(III)24} (Ln = Dy and Gd), with a diameter and a thickness of 3.0 nm and 2.0 nm, respectively, were obtained from the self-assembly of Co(NO3)2, Ln(NO3)3 and a pyridyl-functionalized ß-diketone ligand. Notably, the gadolinium species exhibited a relatively large magnetocaloric effect.

17.
Dalton Trans ; 42(31): 11262-70, 2013 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-23811798

RESUMEN

Four single-phase isostructural mononuclear complexes (HNEt3)[DyxYb1-x(bpyda)2]·3H2O (x = 1 (1), 0 (2), 0.367 (3), 0.135 (4), bpyda = 2,2'-bipyridine-6,6'-dicarboxylate) show characteristics of controllable slow relaxation and photoluminescence. The molecular hybrids 3 and 4 exhibit the Orbach process for the DyIII component and a mixture of direct and Raman processes for the YbIII component. The presence of paramagnetic YbIII enhances the relaxation time of the DyIII component, originating from the suppression of the direct process/QTM. The correlation between photoluminescence, static susceptibilities and dynamic magnetic relaxation in the hybrid species was also analysed by comparing the energy gap between the ground and first excited states to the energy barrier.

18.
Chemistry ; 19(37): 12254-8, 2013 Sep 09.
Artículo en Inglés | MEDLINE | ID: mdl-23794500

RESUMEN

Supertetrahedral clusters: A family of lanthanide oxide supertetrahedral T3{Ln20} clusters (Ln = Tb, Dy, Ho, Er; see figure) were obtained from the solvothermal reaction of lanthanide(III) salts with polytriazolate ligands that could be methylated and oxidized in situ.

19.
Chem Commun (Camb) ; 49(58): 6549-51, 2013 Jul 25.
Artículo en Inglés | MEDLINE | ID: mdl-23765169

RESUMEN

Two 3d-4f nanomagnets, [Dy(III)2Cu(II)7] (1) and [Gd(III)6Cu(II)12] (2), are synthesized under a two-step in situ reaction of picolinaldehyde. Not only the final adduct (hemiacetal), but also the intermediate (gem-diol) are "visualized" by X-ray single crystal diffraction. The Dy complex behaves as a single-molecule magnet, while the Gd complex exhibits a significant magnetocaloric effect. Theoretical calculations are employed to obtain the orientation of the magnetic moments and the magnetic exchange.

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