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1.
Inorg Chem ; 59(3): 1959-1966, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31950821

RESUMO

A series of heterometallic Ln-Cr clusters with the formulas [Ln5Cr2(H2L)2(OAc)6(µ3-OH)6(H2O)15](ClO4)7·xH2O (Ln = Gd and x = 33 for 1 and Ln = Dy and x = 21 for 2) and [Ln8Cr4(H2L)4(OAc)8(µ3-OH)16(µ4-O)1(H2O)8](Cl)(ClO4)5·10H2O (Ln = Gd for 3 and Ln = Dy for 4) was obtained through the reaction of the acetate ligands 2,2-dimethylolpropionic acid (H3L) and Ln(ClO4)3 in the presence of chromium salts with different anions under the same high pH conditions. X-ray analysis revealed that compound 1 contained a metal unit [Gd3Cr2] displaying the pentagonal bipyramid configuration and that compound 3 was templated by Cl- and ClO4- as a mixed anion template featuring a quadrangular structure. In compound 3, the 12 metal atoms were arranged in a wheel-shaped metal skeleton [Gd8Cr4], which was produced by 4 tetrahedral metal units [Gd3Cr] sharing vertices. The introduction of the mixed anion template increased the number of metal atoms in the Ln-Cr clusters. Magnetic calculations indicated that there was weak antiferromagnetic Gd···Cr coupling and weak ferromagnetic Gd···Gd coupling in 1, whereas both Gd···Cr and Gd···Gd in 3 exhibited weak antiferromagnetic interactions. Magnetothermal studies showed that compounds 1 and 3 displayed magnetic entropy changes of 25.2 J kg-1 K-1 at 5 K and 7 T and 33.8 J kg-1 K-1 at 2 K and 7 T, respectively.

2.
Chem Commun (Camb) ; 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31967118

RESUMO

The exquisite combination of hetreometallic [TbIIINiII(COO)3(H2O)] clusters with a designed hexatopic ligand generates one highly robust three-dimensional heterometallic TbIII/NiII-organic framework material {[TbNi(HTDP)(H2O)]·3DMF·2H2O}n (NUC-2; H6TDP = 2,4,6-tri(2,4-dicarboxyphenyl)pyridine). Gas adsorption measurements reveal that the activated NUC-2 exhibits ultrahigh C2H2 adsorption capacity but negligible uptake of C2H4, which is ascribed to its high stability and ultrahigh functional internal surface. Furthermore, dynamic breakthrough experiments confirm that NUC-2 can effectively fulfill the separation of a C2H2/C2H4 (1 : 99) mixture. Such excellent performance makes NUC-2 a promising adsorbent for practical C2H2/C2H4 separation and provides new insights into heterometallic MOFs for gas separation.

3.
Nat Commun ; 10(1): 5510, 2019 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-31796745

RESUMO

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. Herein, we report the synthesis of a nanosized complex, [Fe(Tp)(CN)3]8[Fe(H2O)(DMSO)]6 (abbreviated as [Fe14], Tp-, hydrotris(pyrazolyl)borate; DMSO, dimethyl sulfoxide), which has a fluctuating valence due to two mobile d-electrons in its atomic layer shell. The rate of electron transfer of [Fe14] complex demonstrates the Arrhenius-type temperature dependence in the nanosized spheric surface, wherein high-spin centers are ferromagnetically coupled, producing an S = 14 ground state. The electron-hopping rate at room temperature is faster than the time scale of Mössbauer measurements (<~10-8 s). Partial reduction of N-terminal high spin FeIII sites and electron mediation ability of CN ligands lead to the observation of both an extensive electron transfer and magnetic coupling properties in a precisely atomic layered shell structure of a nanosized [Fe14] complex.

4.
Chem Sci ; 10(18): 4862-4867, 2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31183036

RESUMO

Isomerization is highly important in all aspects of science, yet it is rarely observed in nanoscience. Here, we synthesized a unique triple core-shell Ag84 nanocluster displaying isomerism, which is controlled by different carboxylic acids and a one-way transformation (SD/Ag84a → SD/Ag84b). The innermost core is a rare Ag10 nanocluster which comprises an Ag6 octahedral unit as seen in face-centred cubic (fcc) silver metal and four capped Ag atoms. It templates two crescent-shaped polyoxometalate (W7O26)10- shells which are then enclosed in a shell of silver shaped as rugby balls. The organic ligands (iPrS-, n PrCOO- and PhCOO-) finally shield the metallic clusters. Due to slight differences in structure at two poles and the steric hindrance of n PrCOO- and PhCOO-, SD/Ag84a and SD/Ag84b adopt the shapes of flat-headed and cuspidal prolate spheres, respectively. Interestingly, PhCOOH is dominant over n PrCOOH whereby crystals of SD/Ag84b were isolated if PhCOOH is added during the synthesis of SD/Ag84a. This demonstrates that PhCOOH not only alters the organic coats but also induces metal shell re-organization. This work reveals carboxylate-controlled skeletal isomerism in silver nanoclusters for the first time, thus deepening the understanding of silver nanocluster assembly, flexibility and reactivity.

5.
J Am Chem Soc ; 141(17): 6822-6826, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30986355

RESUMO

Due to the structural advantages displayed by Metal-Organic Frameworks (MOFs), integrating Valence Tautomerism (VT) systems within MOFs could be an effective strategy in order to break through the constraints of the traditional ones. Herein, we report the first successful integration of a VT system into a MOF termed VT-MOF-1. The structural characteristics of VT-MOF-1, such as dinuclear cobalt-catechol clusters and solvent-accessible pores, are both innovative and novel, potentially yielding new vitality within VT field. In addition, VT-MOF-1 exhibits specific behaviors responsive to temperature and different solvent molecules as n-butanol, tert-butanol, and isopropyl alcohol. The entropy values and configurations of the solvent molecules might be responsible for the tunable sensing behaviors.

6.
Chem Sci ; 10(2): 564-568, 2019 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-30713652

RESUMO

Controlled trapping atom-precise ultrasmall silver nanoparticles into silver nanoclusters is challenging; thus only limited progress has been made in this area. We are therefore inspired to isolate two novel silver nanoclusters, Ag10@Ag70 (SD/Ag80a and SD/Ag80b; SD = SunDi), where a novel fcc-structured Ag10 kernel built from two single-edge opened Ag6 octahedra by sharing one edge is trapped. The bioctahedral Ag10 kernel is locked by a pair of Mo7O26 10- anions to form an inner Ag10@(Mo7O26)2 core which is further encapsulated by an outer Ag70 shell to form three-shell Ag10@(Mo7O26)2@Ag70 nanoclusters. Notably, the bioctahedral Ag10 kernel has not been observed in silver nanoclusters ever before, thus representing a new embryo state of silver nanoparticles. SD/Ag80a emits in the near infrared (NIR) region (λ em = 730 nm) at low temperature. This work will deepen our understanding on the atomic-level growth of silver nanoparticles and complicated three-shell self-assembly involving polyoxometalate (POM) and two different silver nanoclusters.

7.
J Am Chem Soc ; 140(44): 14581-14585, 2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30347976

RESUMO

Herein, we report the construction of a neutral, radical-rich, cobalt valence tautomeric triangle, which consists of two types of radical groups including tetrazine-based bridges and semiquinone anions at high temperature and has traits of high intensity and density of sensing sites. The mechanism of the Valence Tautomerism process within the triangle has been illustrated as one electron transfer, preceding a two electrons transfer along with the phenomenon of spin flipping.

8.
Chem Sci ; 9(38): 7498-7504, 2018 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-30319749

RESUMO

A hierarchical tandem assembly - coordination, oligomerisation and supramolecular organization - is identified using MALDI-TOF of the solid products of the solvothermal reaction of 5,5'-pyridyl-3,3'-bi-1H-pyrazole with CuSO4·5H2O in CH3OH-CH3CN. The initial coordination leads to a [3×3] [CuI4CuII5(L)6] (SO4)·2CH3OH (Cu9 ) grid followed by oligomerisation to a 3×[3×3] [CuI6CuII21(L)18(CN)6(SO4)](SO4)2·8CH3CN (Cu27 ) grid through bridging sulfate and in situ generated cyanide with time and subsequent supramolecular organization. The isolated silvery lustrous crystals, Cu9 and Cu27 , are good electrical conductors, with conductivities of 3.2 × 10-2 and 5.4 × 10-3 S cm-1, respectively, due to the mixed valency. Their magnetic properties are dominated by antiferromagnetic interactions. DFT and band structure calculations confirm their valence distribution and semiconducting behavior. The planarity of the large 3×[3×3] Cu27 and its electro-activity renders it suitable for the development of large surface area molecular devices.

9.
Chem Commun (Camb) ; 54(84): 11905-11908, 2018 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-30283966

RESUMO

Compared to emissive silver-thiolate clusters, their alkynyl cousins are, however, usually luminescence silent. Herein we report a novel silver-alkynyl cluster based NbO-type framework (SD/Ag18) showing unprecedented triple emission spanning from the visible to near-infrared (NIR) region. It is a 3D framework constructed from a [Cl@Ag16] cluster based unit, which is further quadruply bridged by the surrounding four Ag atoms through AgAg interactions, giving a 4-connected NbO topology. Although SD/Ag18 exhibits weak orange-red emission at room temperature, its emission becomes strong upon cooling, with three emission maxima at 524, 647 and 1036 nm, respectively, covering both the visible and NIR regions. The visible emissions involve triplet alkynyl-to-metal charge transfer mixed with a cluster-centered state, whereas the participation of cPrC[triple bond, length as m-dash]C- in the frontier orbitals of the cluster may be responsible for the NIR emission. The unusual emissions, especially in the NIR-II region, are observed, for the first time, in silver complexes.

10.
Nat Commun ; 9(1): 3353, 2018 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-30135431

RESUMO

Photocatalytic reduction of CO2 is a promising approach to achieve solar-to-chemical energy conversion. However, traditional catalysts usually suffer from low efficiency, poor stability, and selectivity. Here we demonstrate that a large porous and stable metal-organic framework featuring dinuclear Eu(III)2 clusters as connecting nodes and Ru(phen)3-derived ligands as linkers is constructed to catalyze visible-light-driven CO2 reduction. Photo-excitation of the metalloligands initiates electron injection into the nodes to generate dinuclear {Eu(II)}2 active sites, which can selectively reduce CO2 to formate in a two-electron process with a remarkable rate of 321.9 µmol h-1 mmolMOF-1. The electron transfer from Ru metalloligands to Eu(III)2 catalytic centers are studied via transient absorption and theoretical calculations, shedding light on the photocatalytic mechanism. This work highlights opportunities in photo-generation of highly active lanthanide clusters stabilized in MOFs, which not only enables efficient photocatalysis but also facilitates mechanistic investigation of photo-driven charge separation processes.

11.
Inorg Chem ; 57(14): 8639-8645, 2018 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-29962201

RESUMO

Two enantiomeric pairs of new 3d-4f heterometallic clusters have been built from two enantiomer Schiff base derivatives, labeled as R-/ S-H2L, in situ obtained from the condensation reactions with o-vanillin and R-/ S-2-phenylglycinol. The formulas of the series clusters are [Mn6Ln2(µ3-OH)4(µ4-O)(Ac)4(H2O)2( R-L)6]·NO3·OH (Ln = Dy (1R), Gd (2R)), [Mn6Ln2(µ3-OH)4(µ4-O)(Ac)4(H2O)2( S-L)6]·NO3·OH (Ln = Dy (1S), Gd (2S)), whose crystal structures and magnetic properties have been characterized. Structural analysis indicated that the above clusters consisted of a [Mn6Ln2] core, featuring a sandwich configuration. The results of magnetic measurements showed the presence of slow magnetic relaxation with the effective energy barrier of 14.85 K in two Dy derivatives under the condition of zero-dc field, while the significant magnetocaloric effect of Gd analogues was found in a wide temperature range.

12.
Chem Commun (Camb) ; 54(33): 4104-4107, 2018 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-29451292

RESUMO

Magnetic cooling is a highly efficient refrigeration technique with the potential of replacing expensive and rare helium-3 in the field of ultra-low temperature cooling. However, the visualization of a cryogen at an extremely low temperature and in a strong magnetic field is challenging, but it is crucial for the precise positioning and in situ thermal probe measurements in potential practical applications. Here, the activation of a red-emissive Mn(ii) ion using 3d/4f chemistry produces a luminescent molecule cooler, [Gd5Mn2(LOMe)2(OH)4(Ac)6(MeOH)10Cl2]Cl3·2MeOH (1), with the core of an Mn(ii)-anchored heptanuclear [GdIII5MnII2] pyramid. The photoluminescence (PL) of the Mn2+ emission, with a large Stokes shift (λem ∼ 690 nm) from 4T1(4G) → 6A1(6S), shows not only a sensitive temperature sensing property but also reversible mechanoluminescence (ML). More attractively, these findings reveal a considerable magnetocaloric effect (MCE) coupled with a tunable emission window, opening up new opportunities in the multifunctional applications of PL, ML, and the MCE involving red-light sources, thermometers, and stress imaging. In particular, this provides a novel resolution to design visualized PL coolers.

13.
Inorg Chem ; 57(5): 2577-2583, 2018 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-29465993

RESUMO

By utilizing a preselected functional ligand produced by 1 H-imidazole-4,5-dicarboxylic acid, three isostructural lanthanide coordination polymers (CPs), denoted as {[Ln2(OH)2(L)2]·(DMF)·(H2O)4} n (Ln = Gd (1), Eu (2), Dy (3); L = 1-(4-carboxybenzyl)imidazole-4-carboxylic acid), containing a 1D infinite [Ln4(OH)4] subchain have been successfully constructed. The highly connected mode between the multifunctional ligand and 1D building units is responsible for the exceptional chemical stability of three lanthanide CPs. In addition, a study of the magnetic properties reveals that 1 displays a large magnetic entropy change (-Δ Sm = 30.33 J kg-1 K-1 with T = 2 K and Δ H = 7 T). Furthermore, genetic algorithm and quantum Monte Carlo methods were combined to simulate the magnetic coupling parameters of compound 1, shedding light on the effect of linking bridges on magnetic propagation. 2 shows intense luminescence in the range of 350-710 nm. Comparably, magnetic studies of 3 reveal the existence of a metamagnetic transformation from an antiferromagnetic interaction to a ferromagnetic interaction along with a decrease in temperature. Through fitting of the results of HF-EPR measurements, a component of the g tensor is obtained, g|| = 16.4(5), indicating the large anisotropy of 3.

14.
J Am Chem Soc ; 139(50): 18178-18181, 2017 12 20.
Artigo em Inglês | MEDLINE | ID: mdl-29200280

RESUMO

Nanoscale inorganic wheel-shaped structures are one of the most striking types of molecular aggregations. Here, we report the synthesis of a gigantic lanthanide wheel cluster containing 140 Gd3+ atoms. As the largest lanthanide cluster reported thus far, {Gd140} features an attractive wheel-like structure with 10-fold symmetry. The nanoscopic molecular wheel possesses the largest diameter of 6.0 nm and displays high stability in solution, which allows direct visualization by scanning transmission electron microscopy. The newly discovered lanthanide {Gd140} cluster represents a new member of the molecular wheel family.

15.
Angew Chem Int Ed Engl ; 56(38): 11475-11479, 2017 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-28719109

RESUMO

The largest Ln-Fe metal cluster [Gd12 Fe14 (µ3 -OH)12 (µ4 -OH)6 (µ4 -O)12 (TEOA)6 (CH3 COO)16 (H2 O)8 ]⋅(CH3 COO)2 (CH3 CN)2 ⋅(H2 O)20 (1) and the core-shell monodisperse metal cluster of 1 a@SiO2 (1 a=[Gd12 Fe14 (µ3 -OH)12 (µ4 -OH)6 (µ4 -O)12 (TEOA)6 (CH3 COO)16 (H2 O)8 ]2+ ) were prepared. Experimental and theoretical studies on the magnetic properties of 1 and 1 a@SiO2 reveal that encapsulation of one cluster into one silica nanosphere not only effectively decreases intermolecular magnetic interactions but also significantly increases the zero-field splitting effect of the outer layer Fe3+ ions.

16.
Dalton Trans ; 46(14): 4786-4795, 2017 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-28345728

RESUMO

By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt-carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 63 cobalt-carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of -/+/- for syn-anti carboxylate bridges and -/-/- for syn-syn carboxylate bridges. Through HF-EPR measurements performed on polycrystalline samples over the frequency range of 60-260 GHz and field range of 0-12 T, the effective g-values of 1 and 2 were all larger than 2.00, and the signs of their D values were probably positive.

17.
Chemistry ; 22(49): 17619-17626, 2016 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-27730682

RESUMO

Cu(CF3 COO)2 reacts with tert-butylacetylene (tBuC≡CH) in methanol in the presence of metallic copper powder to give two air-stable clusters, [CuI15 (tBuC≡C)10 (CF3 COO)5 ]⋅tBuC≡CH (1) and [CuI16 (tBuC≡C)12 (CF3 COO)4 (CH3 OH)2 ] (2). The assembly process involves in situ comproportionation reaction between Cu2+ and Cu0 and the formation of two different clusters is controlled by reactants concentration. The clusters consist of Cu15 and Cu16 cores co-stabilized by strong by σ- and π-bonded tert-butylethynide and CF3 COO- (together with methanol molecule in 2). Their stabilities in solution were confirmed using electrospray ionization mass spectrometry in which the cluster core remains intact for 1 in chloroform and acetone, and for 2 in acetonitrile. Strong thermochromic luminescence in the near infrared (NIR) region was observed in the solid-state. Of particular interest, the emission maximum of 1 is red-shifted from 710 nm at 298 K to 793 nm at 93 K, along with a 17-fold fluorescence enhancement. In contrast, 2 exhibits red shift from 298 to 123 K followed by blue shift from 123 to 93 K. The emission wavelength was correlated with the structural parameters using variable-temperature X-ray single-crystal analyses. The rich cuprophilic interaction plays a significant role in the formation of 3 LMCT (tBuC≡C→Cux ) excited state mixed with cluster-centered (3 CC) characters, which can be considerably influenced by temperature, leading to thermochromic luminescence. The present work provides 1) a new synthetic protocol for the high-nuclear CuI -alkynyl clusters; 2) a comprehensive insight into the mechanism of thermochromic luminescence; 3) unusual emissive materials with the characters of NIR and thermochromic luminescence simultaneously.

18.
Inorg Chem ; 55(10): 4757-63, 2016 05 16.
Artigo em Inglês | MEDLINE | ID: mdl-27110839

RESUMO

Two 3d-4d heteropolynuclear clusters with Ag-Zn ratios of 9:2 and 9:4 were stepwise constructed from a robust nonanuclear silver cluster. Their crystal structures consist of a common bucket-shaped [Ag9(mba)9](9-) (H2mba = 2-mercaptobenzoic acid) core with different numbers of Zn(II) connected by different exo-oriented carboxylates. Most fascinating is the observation of emission (∼703 nm) in the near-infrared (NIR) region at 300 K that may be compared to the related Ag9Zn3 cluster with aliphatic polyamine as auxiliary ligand that emits from the visible (∼580 nm). The shift is associated with the change of ligand field of the 2,2'-bipyridine. The emission intensity and lifetime were dramatically enhanced along with the slight bathochromic shift upon cooling from 300 K to 80 K. The results raise two significant issues: (a) the structural and electronic effects of the secondary metal binding to the metalloligand and the factors influencing the heteropolynuclear cluster assembly and (b) the use of NIR fluorescence, introduced by integrating two luminophores into one heteropolynuclear entity, in detecting free-moving zinc in biological systems both in vivo and in vitro.

19.
Angew Chem Int Ed Engl ; 55(14): 4532-6, 2016 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-26923173

RESUMO

Monodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core-shell structure of the monodisperse molecule magnet of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]@SiO2 (1 a@SiO2 ) was prepared by encapsulating one high-nuclearity lanthanide-transition-metal compound of [Gd52 Ni56 (IDA)48 (OH)154 (H2 O)38 ]⋅(NO3 )18 ⋅164 H2 O (1) (IDA=iminodiacetate) into one silica nanosphere through a facile one-pot microemulsion method. 1 a@SiO2 was characterized using transmission electron microscopy, N2 adsorption-desorption isotherms, and inductively coupled plasma-atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J1 =0.25 cm(-1) , J2 =-0.060 cm(-1) , J3 =-0.22 cm(-1) , J4 =-8.63 cm(-1) , g=1.95, and z J=-2.0×10(-3)  cm(-1) for 1, and J1 =0.26 cm(-1) , J2 =-0.065 cm(-1) , J3 =-0.23 cm(-1) , J4 =-8.40 cm(-1) g=1.99, and z J=0.000 cm(-1) for 1 a@SiO2 . The z J=0 in 1 a@SiO2 suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres.

20.
Chemistry ; 21(51): 18847-54, 2015 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-26541877

RESUMO

The encapsulation of carbonate derived from atmospheric CO2 has resulted in an icosanuclear heteropolyoxocopperate, isolated as a metal-organic 1D chain, 2D sheet, or 3D framework, in which the Cu20 nanocluster represents the first eight-capped α-Keggin polyoxometalate with the late-transition-metal Cu(II) as the polyatom, CO3(2-) as the heteroanion, and OH(-) and suc(2-) or glu(2-) (H2suc=succinic acid; H2glu=glutaric acid) as the terminal ligands, which suggests a conceptual similarity to classical polyoxometalates. Even in the presence of competitive SO4(2-) in the assembly system, the CO3(2-) anion is still captured as a template to direct the formation of the Cu20 nanocluster, which indicates the stronger templation ability of CO3(2-) compared with SO4(2-). When other aliphatic dicarboxylates, such as glutaric acid, were used as ligands, the CO3(2-)-templated Cu20 nanocluster was maintained and acted as a cluster building unit (CBU) to be linked by two glutarate bridges to generate a distinct 1D metal-organic chain. This report presents not only a rare example of a huge anion-templated transition-metal cluster, but also its use as a robust CBU to construct novel coordination architectures. Variable-temperature magnetic susceptibility studies revealed that an antiferromagnetic interaction exists within the Cu20 nanocluster. The correlation between the coordination structure and the electron paramagnetic resonance spectra recorded of both powder and single-crystal samples are discussed in detail.

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