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1.
Inorg Chem ; 58(2): 1184-1190, 2019 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-30592220

RESUMO

A series of heterometallic formate framework templated by amines were solvothermally prepared. They feature the formula of [AI][CrMII(HCO2)6] (AI = NH4H2OI and M = Mn for 1, AI = CH3NH3I and M = Fe for 2, AI = CH3NH2CH3I and M = Co for 3, AI = CH3NH3I and M = Ni for 4). The title compounds exhibit isostructural niccolite architectures with differences only in the host metal ions and guest amines. Tunable ferromagnetic (FO) strength was realized in the resulting framework under the guidance of orthogonal magnetic orbital analysis of CrIII (t2g3eg) and MII (t2g3eg2 for MnII, t2g4eg2 for FeII, t2g5eg2 for CoII, t2g6eg2 for NiII) ions. The magnetic ordering temperatures derived from the experimental magnetic measurements for 1-4 are lower than 2, 10.3, 7.6, and 22.0 K, respectively. Notably, thanks to the weak FO coupling between CrIII and MnII ions, compound 1 displays a large magnetocaloric effect bearing the maximum of magnetic entropy change (-Δ Smmax) up to 43.9 J kg-1 K-1 with Δ H = 7 T and T = 3.5 K, larger than most reported transition metal-based complexes and commercial gadolinium gallium garnet (Gd3Ga5O12) (-Δ Smmax = 38.4 J kg-1 K-1 with Δ H = 7 T). From 1, 2/3, to 4, an enhancement of the magnetic ordering temperature is observable due to the increasing strength of FO interactions between CrIII and MII ions. Our work provides a successful instance to modulate the strength of FO exchange via analyzing the orthogonal magnetic orbitals of heterometallic ions.

2.
Nanoscale ; 10(41): 19286-19289, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30325384

RESUMO

Herein, a gas-sensitive functional nanomaterial was constructed by confining Tb(acac)3(H2O)2 (acac = acetylacetone) in the space of the metal organic framework ZIF-8. This functional nanomaterial can realize a gas-solid state aldol condensation reaction, even at room temperature and without the use of a catalyst. In the reaction process, formaldehyde (FA) gas molecules can invalidate the antenna effect of the acac ligands, and it can therefore act as an ultrasensitive FA gas remover and detector (limit of detection value = 49 ppb).

3.
Inorg Chem ; 56(16): 9555-9562, 2017 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-28758753

RESUMO

Introducing another chromophore into a luminescent MOF is a potential way to assembling novel dual-emissive luminescent materials. Putting the chromophore, for which luminescence can be enhanced by Zn2+ ion, into MOF-5 by the "bottle around ship" strategy is a simple but efficient synthesis method to realize such dual-emissive materials. According to this strategy, a novel dual-emissive luminescent composite material [Zn2(HL)3]+@MOF-5 was constructed by loading the [La3(HL)2L2(NO3)3H2O] (1) (H2L = 7,7'-(ethane-1,1'-diyl)8-hydro-quinoline) into MOF-5, in which the [Zn2(HL)3]+ anions were transformed from 1 with the existence of Zn2+. The dual-emissive composite materials show excellent luminescence with two emissions of MOF-5 at 410 nm and [Zn2(HL)3]+ at 524 nm. Furthermore, by combining characteristics of MOF-5 and the guest chromophore, the composite material is highly selectively sensitive toward Al3+ and monoethanolamine, which makes [Zn2(HL)3]+@MOF-5 a potential self-calibrated fluorescence sensor.

4.
Dalton Trans ; 46(26): 8593-8597, 2017 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-28640292

RESUMO

A 63 2D layer complex [Mn3Cl3(L3)]n·H2O (1) (L = pyrimidine-2-carboxylate) was obtained by assembling 2-cyanopyrimidine and manganese chloride, in which the L ligands were generated in situ. In 1 six-membered Mn rings were constructed from MnII ions and L ligands, which were connected to each other by double chloride anions affording a 2D layer. When the chloride anions in 1 were substituted partly by formate, [Mn4Cl3L4(HCO2)]n (2) was obtained. In 2, the L ligands bridge MnII to give a 1D chain, which was further connected by the double chloride anions and Cl/formate bridges to form a two-fold interpenetrated srs-net. Interestingly, 2 exhibits an obvious SHG response of approximately 0.8 times that of KDP. Furthermore, 2 is an antiferromagnet with a field induced spin flop transition.

5.
Adv Mater ; 29(23)2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28401592

RESUMO

Multiple switchable physical properties have been demonstrated in one single niccolite structural metal-organic framework, [(CH3 CH2 )2 NH2 ][FeIII FeII (HCOO)6 ] (1), including (i) a reversible ferroelastic phase transition triggered by freezing the disordered (CH3 CH2 )2 NH2+ cations, (ii) a thermally switchable dielectric constant transition accompanied by phase transition, and (iii) thermal and positive magnetic field driven magnetic poles reversal at low temperatures, attributed to different responses of the magnetization of FeII and FeIII sublattices to external stimuli. More interestingly, the exchange anisotropy between the two sublattices can also give rise to tunable positive and negative exchange bias fields. Straightforwardly, such diverse demonstrations of bistability in one single material (depending on the specific tuning way) will provide extra freedom and flexibility for the design of switcher devices.

6.
Inorg Chem ; 56(1): 197-207, 2017 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-27935298

RESUMO

A study of the magnetic structure of the [NH2(CH3)2]n[FeIIIMII(HCOO)6]n niccolite-like compounds, with MII = CoII (2) and MnII (3) ions, has been carried out using neutron diffraction and compared with the previously reported FeII-containing compound (1). The inclusion of two different metallic atoms into the niccolite-like structure framework leads to the formation of isostructural compounds with very different magnetic behaviors due to the compensation or not of the different spins involved in each lattice. Below TN, the magnetic order in these compounds varies from ferrimagnetic behavior for 1 and 2 to an antiferromagnetic behavior with a weak spin canting for 3. Structure refinements of 2 and 3 at low temperature (45 K) have been carried out combining synchrotron X-ray and high-resolution neutron diffraction in a multipattern approach. The magnetic structures have been determined from the difference patterns between the neutron data in the paramagnetic and the magnetically ordered regions. These difference patterns have been analyzed using a simulated annealing protocol and symmetry analysis techniques. The obtained magnetic structures have been further rationalized by means of ab initio DFT calculations. The direction of the magnetic moment of each compound has been determined. The easy axis of the MII for compound 1 (FeII) is along the c axis; for compound 2 (CoII), the moments are mainly within the ab plane; finally, for compound 3 (MnII), the calculations show that the moments have components both in the ab plane and along the c axis.

7.
Chem Commun (Camb) ; 52(56): 8722-5, 2016 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-27333437

RESUMO

A new single-chain-magnet (SCM), [Co4(OMe)3(HCO2)2(L)3·DMF]n, (L = 4-(pyridin-4-yl)benzolate) (2), was constructed by changing the spacers of a weak ferromagnetic single-chain magnet [Co8(OMe)6(HCO2)4(isonic)6·H2O]n (1). By contrasting the magnetism of the two complexes, it is found that the longer the linker the stronger the magnetic properties.

8.
Dalton Trans ; 45(7): 2796-9, 2016 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-26795908

RESUMO

A hydrothermal reaction of CuCl2·2H2O, 4,5-diazafluoren-9-one (L) and K3[Fe(CN)6], which is used as an environment friendly cyanide source, produces a two-dimensional copper cyanide complex Cu10(CN)10L4 (1). In the complex, the L ligands act as corner and bridge ligands simultaneously. With the help of the corner ligands, infinite Cu(CN)∞ chains are formed. The chains are further bridged by another type of L ligand forming a 2D layer with a Cu20(CN)18L2 macrocycle, which shows blue photoluminescence related to centered π-π* transitions of the L ligand.

9.
Dalton Trans ; 45(4): 1514-24, 2016 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-26677799

RESUMO

Low-temperature hydrothermal reactions of copper salts with NaN3 and structurally related pyridine-based ligands, 1-(4-pyridyl)pyridinium, 3-chloromethylpyridine, 4-benzylpyridine, and quinoline (L(4)), respectively, led to the formation of four new magnetic complexes, [Cu3(L(1))2(N3)6]n (), [Cu3(L(2))2(N3)6]n (), [Cu(L(3))2(N3)2] (), and [Cu(L(4))(N3)2]n (). In these complexes, L(1), L(2), and L(3) are pyridine, 3-azidomethylpyridine, and 4-benzoylpyridine, being generated in situ by the decomposition, azido substitution, and oxidation reaction of the 1-(4-pyridyl)pyridinium, 3-chloromethylpyridine, and 4-benzylpyridine, respectively. and have similar structures being composed of double end-on azido-bridging planar [Cu3(L)2(N3)6] trinuclear units, which are further linked into a two-dimensional layer by the end-to-end azido bridges of themselves, along with their weak end-on coordination. It is interesting that the only slight differences of geometrical parameters in and have led to distinct magnetic interactions between the trinuclear units, where the former is antiferromagnetic but the latter is ferromagnetic, whereas has a mono-nuclear core structure, which is further extended to a one-dimensional (1D) chain by weakly coordinated end-on azido bridges. consists of unique 1D chains with double end-on azido bridge bonding distorted five-coordinated Cu(ii) centers, and exhibits ferromagnetic intrachain interactions. In the structures of these complexes there also exist weak inter-layer or inter-chain hydrogen bonds, which should also be responsible for some magnetic behavior at low temperature. In addition, primary structural and magnetic comparisons and discussions have also been performed by combining other reported azido-Cu(ii) systems with related pyridyl-based co-ligands. These results show that the selection of synthesis conditions and slight decoration of co-ligands (or geometric differences of them) have important influences on the structures and magnetic properties of resulting metal azido complexes.

10.
Chem Commun (Camb) ; 51(83): 15336-9, 2015 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-26343266

RESUMO

Linking magnetically frustrated triangular FeO units by divalent metal ions (M(II) = Fe(II) for 1, Mn(II) for 2) gives isostructural 1D spin chains. Strong antiferromagnetic interactions were found in these complexes with significant frustrations but very interesting ferrimagnetic like transition and metamagnetism were found in mixed valence 1. By comparing the magnetic behaviours with isostructural complex 3 (with M(II) = Mg(II)), it is proposed that the spins of Fe(II) ions and Mn(II) ions have ferromagnetic and antiferromagnetic contributions respectively.

11.
Dalton Trans ; 44(22): 10289-96, 2015 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-25965673

RESUMO

The structure and magnetism of three cobalt(ii)-azide complexes, [Co(N3)2(bepy)2]n (), [Co2(N3)4(vipy)4]n (), and [Co(N3)2(bipy)]n () were tuned by three structurally related 4-substituent pyridines, 4-benzylpyridine (bepy), 4-vinyl pyridine (vipy), and 4,4'-bipyridine (bipy) as co-ligands in solvothermal reactions. With flexible benzyl as a substituent group of the pyridine co-ligand, a one-dimensional (1D) complex with double end-to-end (EE) azide-bridging Co(ii) chain is formed. While using a rigid but small vinyl group as the substituent, a distinct Co(ii)-azide chain with alternate double end-on (EO) and double EE azide bridges was obtained. Finally, when another pyridine group was used instead of the substituent incapable of coordinating in and , a bipyridine, it gave rise to a chiral complex with a three-dimensional (3D) diamondoid Co(ii)-azide framework further reinforced by the bipy ligand. Magnetic studies indicate antiferromagnetic interactions between the Co(ii) ions in the three complexes, but interestingly, weak antiferromagnetism origin of spin canting exists in at low temperatures.

12.
Inorg Chem ; 54(11): 5249-56, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-25978293

RESUMO

Three new Gd(III) based coordination polymers [Gd2(C2H6SO)(SO4)3(H2O)2]n (1), {[Gd4(HCOO)2(SO4)5(H2O)6]·H2O}n (2), and [Gd(HCOO)(SO4)(H2O)]n (3) were obtained by modifying gadolinium sulfate. With the gradual increase of the volume ratio of HCOOH and DMSO in synthesis, the formate anions begin to coordinate with metal centers; this results in the coordination numbers of sulfate anion increasing and the contents of water and DMSO molecules decreasing in target complexes. Accordingly, spin densities both per mass and per volume were enhanced step by step, which are beneficial for the magneto-caloric effect (MCE). Magnetic studies reveal that with the more formate anions present, the larger the negative value of magnetic entropy change (-ΔSm) is. Complex 3 exhibits the largest -ΔSm = 49.91 J kg(-1) K(-1) (189.51 mJ cm(-3) K(-1)) for T = 2 K and ΔH = 7 T among three new complexes.

13.
Chem Commun (Camb) ; 51(39): 8288-91, 2015 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-25877906

RESUMO

Metal formate frameworks [A][CrMn(HCOO)6] (A = CH3NH2CH3(+) for 1 and CH3NH3(+) for 2) with a large MCE were obtained, directed by the heterometallic strategy in which very weak magnetic interactions were achieved. A switch from antiferromagnetism to ferromagnetism occurs when replacing the CH3NH2CH3(+) cation with CH3NH3(+). The magnetic entropy change (-ΔSm) reached 48.20 J kg(-1) K(-1) for 2, which is the largest among the known polymeric 3d complexes.

14.
Chem Commun (Camb) ; 51(22): 4627-30, 2015 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-25692186

RESUMO

In our efforts to fabricate magnetically frustrated materials, a feasible vertices augmentation method was successfully used to construct a 4-fold interpenetrating three dimensional metal-organic framework (MOF) with rare topology by linking [Fe3(µ3-O)(µ-O2CCH3)6](+) triangular moieties through the pure anti,anti acetate ligands. Strong antiferromagnetic interactions were found to exist between the neighboring Fe(III) ions without long-range magnetic ordering above 2.2 K, indicating the strong geometric spin frustration nature of this MOF.

15.
Inorg Chem ; 53(24): 13042-8, 2014 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-25454842

RESUMO

It still remains a great challenge to design and construct framework-structured weak ferromagnets with large canting angle which is an effective approach for high performance magnets. According to the strategy of antisymmetric interaction causing spin canting, we report the design of four cobalt compounds, which were tested by X-ray single crystal diffraction, TGA, PXRD, and magnetic measurement. Single-crystal structure analysis reveals that compound 1 has a 2D structure, complex 2 has a 3,4-connected 3D framework, and complex 3 exhibits a 3D net structure with rare 3,5-connected 2-nodal ß-SnF2 topology and the solvent MeOH trapped in the 3D channels as guests. The magnetic property of 3 is spin canting just as designed, with TN about 4.0 K and large canting angle of 14.8°. Highly stable compound 3 sustains its framework in air for more than 12 months, in which the guest MeOH molecules can be replaced by water to form complex 4.

16.
Chem Asian J ; 9(4): 1116-22, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24519913

RESUMO

Four carboxylate-bridged Gd(III) complexes (1-4) with 1D/2D structures have been synthesized by using the hydrothermal reaction of Gd2O3 with various carboxylate ligands. Compounds 1 and 2 contained the same [2n] Gd(III)-OH ladders, but with different crystallographically independent Gd(III) ions, whilst the structures of compounds 3 and 4 were composed of [Gd4(µ3-OH)2(piv)8(H2O)2](2+) units and 1D ladder Gd(III) chains, respectively. Antiferromagnetic interactions occurred in compounds 1-3, owing to their small Gd-O-Gd angles, whereas ferromagnetic coupling occurred in compound 4, in which the Gd-O-Gd angles were larger. These complexes exhibited a distinct magnetocaloric effect (MCE), which was affected by their different magnetic densities and exchange interactions. Among these compounds, complex 4 presented the largest MCE (-ΔS(m)(max)=43.6 J kg(-1) K(-1)), the lowest M(w)/N(Gd) ratio (the highest magnetic density), and weak ferromagnetic coupling. Therefore, a lower M(w)/N(Gd) ratio and weaker exchange interactions (a smaller absolute value of θ) between Gd(III) ions resulted in a larger MCE for the Gd(III) complexes.

17.
Dalton Trans ; 42(40): 14509-15, 2013 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-23966090

RESUMO

Two M(II) tetranuclear complexes bridged only by azido, Mn4(N3)(7.3)Cl(0.7)L4 (1) and Co4(N3)8L4 (2) in which the four M(II) ions are precisely coplanar bridged only by six azido anions, were obtained by using 4,5-diazafluoren-9-one (L) as a corner ligand. Magnetic studies indicate that ferromagnetic coupling was conducted by the azido anions between M(II) ions. At low temperature, 1 exhibits a large magnetocaloric effect and 2 shows field-induced multiple magnetic relaxations.

18.
Inorg Chem ; 52(16): 9163-5, 2013 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-23895294

RESUMO

An unprecedented decanuclear Gd(III) cluster composed of the [Gd10(µ3-OH)8](22+) core has been hydrothermally synthesized. Magnetic analyses indicate that this complex shows weak antiferromagnetic behavior with a relatively large magnetocaloric effect (-ΔS(m)(max) = 31.22 J kg(-1) K(-1)).


Assuntos
Gadolínio/química , Hidróxidos/química , Campos Magnéticos , Modelos Moleculares , Termodinâmica
19.
Dalton Trans ; 42(23): 8201-4, 2013 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-23629740

RESUMO

A new chiral 3D heterometallic coordination polymer [NaCo2(L)2(N3)·(MeOH)]∞ (1) (L = 2,6-pyridinedicarboxylate) was synthesized and characterized magnetically. Ferro- and antiferromagnetic interactions co-exist in 1, which results in a magnetic phase transition at the high temperature of 29 K.

20.
Inorg Chem ; 52(6): 2862-9, 2013 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-23461619

RESUMO

Three new heterometallic formate coordination polymers formulated as [Na2Co(HCOO)4]∞ (1), [NaCo(HCOO)3]∞ (2), and [Na2Co7(HCOO)16]∞ (3) were obtained by adjusting the solvent and ratio of the reactants. In 1, a (4,4) cobalt formate layer is formed and the sodium ions connect the layers to form a three-dimensional (3D) framework. In 2, each formate ligand binds two Co(2+) and two Na(+) ions with a syn,syn,anti,anti coordination mode to form a chrial network with 4,6-connected topology. 3 is a Na(+)-ion-linked 3D framework based on the cobalt formate layer, which has a 10-membered metal ring. Magnetic studies indicate the existence of ferromagnetic interactions between adjacent Co(2+) ions in 1, while dominating antiferromagnetic couplings in 2 and 3.

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