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1.
Inorg Chem ; 63(22): 10207-10220, 2024 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-38767574

RESUMO

We prepared polyoxomolybdates with methylammonium countercations from methylammonium monomolybdate, (CH3NH3)2[MoO4], through two dehydrative condensation methods, acidifying in the aqueous solution and solid-state heating. Discrete (CH3NH3)10[Mo36O112(OH)2(H2O)14], polymeric ((CH3NH3)8[Mo36O112(H2O)14])n, and polymeric ((CH3NH3)4[γ-Mo8O26])n were selectively isolated via pH control of the aqueous (CH3NH3)2[MoO4] solution. The H2SO4-acidified solution of pH < 1 produced "sulfonated α-MoO3", polymeric ((CH3NH3)2[(MoO3)3(SO4)])n. The solid-state heating of (CH3NH3)2[MoO4] in air released methylamine and water to produce several methylammonium polyoxomolybdates in the sequence of discrete (CH3NH3)8[Mo7O24-MoO4], discrete (CH3NH3)6[Mo7O24], discrete (CH3NH3)8[Mo10O34], and polymeric ((CH3NH3)4[γ-Mo8O26])n, before their transformation into molybdenum oxides such as hexagonal-MoO3 and α-MoO3. Notably, some of their polyoxomolybdate structures were different from polyoxomolybdates produced from ammonium molybdates, such as (NH4)2[MoO4] or (NH4)6[Mo7O24], indicating that countercation affected the polyoxomolybdate structure. Moreover, among the tested polyoxomolybdates, (CH3NH3)6[Mo7O24] was the best negative staining reagent for the observation of the SARS-CoV-2 virus using transmission electron microscopy.

2.
Chemistry ; 29(63): e202302303, 2023 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-37553318

RESUMO

Synthetic strategies to access high-valent iridium complexes usually require use of π donating ligands bearing electronegative atoms (e. g. amide or oxide) or σ donating electropositive atoms (e. g. boryl or hydride). Besides the η5 -(methyl)cyclopentadienyl derivatives, high-valent η1 carbon-ligated iridium complexes are challenging to synthesize. To meet this challenge, this work reports the oxidation behavior of an all-carbon-ligated anionic bis(CCC-pincer) IrIII complex. Being both σ and π donating, the diaryl dipyrido-annulated N-heterocyclic carbene (dpa-NHC) IrIII complex allowed a stepwise 4e- oxidation sequence. The first 2e- oxidation led to an oxidative coupling of two adjacent aryl groups, resulting in formation of a cationic chiral IrIII complex bearing a CCCC-tetradentate ligand. A further 2e- oxidation allowed isolation of a high-valent tricationic complex with a triplet ground state. These results close a synthetic gap for carbon-ligated iridium complexes and demonstrate the electronic tuning potential of organic π ligands for unusual electronic properties.

3.
Angew Chem Int Ed Engl ; 59(50): 22446-22450, 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-32856378

RESUMO

The structural phase of a metal oxide changes with temperature and pressure. During phase transitions, component ions move in multidimensional metal-oxygen networks. Such macroscopic structural events are robust to changes in particle size, even at scales of around 10 nm, and size effects limiting these transitions are particularly important in, for example, high-density memory applications of ferroelectrics. In this study, we examined structural transitions of the molecular metal oxide [Na@(SO3 )2 (n-BuPO3 )4 MoV 4 MoVI 14 O49 ]5- (Molecule 1) at approximately 2 nm by using single-crystal X-ray diffraction analysis. The Na+ encapsulated in the discrete metal-oxide anion exhibited a reversible order-disorder transition with distortion of the Mo-O molecular framework induced by temperature. Similar order-disorder transitions were also triggered by chemical pressure induced by removing crystalline solvent molecules in the single-crystal state or by substituting the countercation to change the molecular packing.

4.
Inorg Chem ; 58(14): 9187-9194, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31241906

RESUMO

A study of the single-crystal-to-single-crystal transformation induced by temperature variation for the chain polymer Cu(II) complex with nitronyl nitroxide showed that an increase in the hydrostatic pressure of up to ∼0.07 GPa completely changes the intracrystalline displacements of molecules relative to one another. This, in turn, significantly affects the interaction energy of the unpaired electrons of the paramagnetic centers and hence the form of the temperature dependence of the magnetic susceptibility χT. The cooling of crystals under normal conditions causes a rearrangement of the intrachain exchange clusters {>N-•O-Cu(II)-O•-N<} accompanied by a shortening of the distances between the paramagnetic centers. This changes the character of exchange interactions and generates multistage spin transitions. An increase in the hydrostatic pressure leads to a drastic change in the O···O distances between the nitroxyl fragments of adjacent chains, an increase in the antiferromagnetic exchange between them, and complete suppression of spin transitions.

5.
Angew Chem Int Ed Engl ; 58(27): 9184-9187, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31070833

RESUMO

We report the development of a molecular ferroelectric material inspired by the hexamethylenetetramine (hmta) non-centrosymmetric molecular rotator. The bromide salt of diprotonated hmta (hmtaH2 ) crystalized as (hmtaH2 )(NH4 )Br3 in a metal-free ABX3 perovskite-type structure, in which the A and B sites are occupied by hmtaH2 2+ and ammonium cations, respectively. The compound crystallized in the Pma2 polar space group. A distorted polar perovskite structure formed owing to the distortion of {(NH4 )Br6 } octahedrons that are stabilized through the formation of NH⋅⋅⋅Br hydrogen bonds and the orientational ordering of positive charges on the non-centrosymmetric hmtaH2 molecules. This spontaneous polarization exhibited ferroelectric behavior with a nominally high Curie temperature (>400 K), in which the electrical switching of polarization originates from the rotation of the hmtaH2 unit.

6.
Angew Chem Int Ed Engl ; 58(13): 4169-4172, 2019 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-30673160

RESUMO

Artificial ion channels are of increasing interest because of potential applications in biomimetics, for example, for realizing selective ion permeability through the transport and/or exchange of selected ions. However, selective ion transport and/or exchange in the crystalline state is rare, and to the best of our knowledge, such a process has not been successfully combined with changes in the physical properties of a material. Herein, by soaking single crystals of Li2 ([18]crown-6)3 [Ni(dmit)2 ]2 (H2 O)4 (1) in an aqueous solution containing K+ , we succeeded in complete ion exchange of the Li+ ions in 1 with K+ ions in the solution, while maintaining the crystalline state of the material. This ion exchange with K+ was selectively conducted even in mixed solutions containing K+ as well as Na+ /Li+ . Furthermore, remarkable changes in the physical properties of 1 resulted from the ion exchange. Our finding enables not only the realization of selective ion permeability but also the development of highly sensitive biosensors and futuristic ion exchange agents, for example.

7.
Angew Chem Int Ed Engl ; 57(41): 13429-13432, 2018 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-30088326

RESUMO

Continual progress has been achieved in information technology through unrelenting miniaturisation of the single memory bit in integrated ferromagnetic, ferroelectric, optical, and related circuits. However, as miniaturisation approaches its theoretical limit, new memory materials are being sought. Herein, we report a unique material exhibiting single-molecule electric polarisation switching that can operate above room temperature. The phenomenon occurs in a Preyssler-type polyoxometalate (POM) cluster we call a single-molecule electret (SME). It exhibits all the characteristics of ferroelectricity but without long-range dipole ordering. The SME affords bi-stability as a result of the two potential positions of localisation of a Tb3+ ion trapped in the POM, resulting in extremely slow relaxation of the polarisation and electric hysteresis with high spontaneous polarisation and coercive electric fields. Our findings suggest that SMEs can potentially be applied to ultrahigh-density memory and other molecular-level electronic devices operating above room temperature.

8.
Inorg Chem ; 56(15): 8759-8767, 2017 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-28722450

RESUMO

Herein we report two pentanuclear MnII-substituted sandwich-type polyoxotungstate complexes, [{Mn(bpy)}2Na(H2O)2(MnCl)2{Mn(H2O)}(AsW9O33)2]9- and [{Mn(bpy)}2Na(H2O)2(MnCl){Mn(H2O)}2(SbW9O33)2]8- (bpy = 2,2'-bipyridine), whose structures have been obtained by single-crystal X-ray diffraction (SCXRD), complemented by results obtained from elemental analysis, electrospray ionization mass spectrometry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. They consist of two [B-α-XW9O33]9- subunits sandwiching a cyclic assembly of the hexagonal [{Mn(bpy)}2Na(H2O)2(MnCl)2{Mn(H2O)}]9+ and [{Mn(bpy)}2Na(H2O)2(MnCl){Mn(H2O)}2]10+ moieties, respectively, and represent the first pentanuclear MnII-substituted sandwich-type polyoxometalates (POMs). Both compounds have been synthesized by reacting MnCl2·4H2O with trilacunary Na9[XW9O33]·27H2O (X = AsIII and SbIII) POM precursors in the presence of bpy in a 1 M aqueous sodium chloride solution under mild reaction conditions. SCXRD showed that the alternate arrangement of three five-coordinated MnII ions and two six-coordinated MnII ions with an internal Na cation formed a coplanar six-membered ring that was sandwiched between two [B-α-XW9O33]9- (X = AsIII and SbIII) subunits. The results of temperature-dependent direct-current (dc) magnetic susceptibility data indicated ferromagnetic interactions between Mn ions in the cluster. Moreover, alternating-current magnetic susceptibility measurements with a dc-biased magnetic field showed the existence of a ferromagnetic order for both samples. Electrochemistry studies revealed the presence of redox processes assigned to the Mn centers. They are associated with the deposition of material on the working electrode surface, possibly MnxOy, as demonstrated by electrochemical quartz crystal microbalance experiments.

9.
Inorg Chem ; 56(4): 2042-2049, 2017 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-28182416

RESUMO

We describe the preparation of ε-Keggin-type cobaltomolybdate-based 3D frameworks with sodium cations, NaH9[ε-CoIIMoV8MoVI4O40CoII2], and their characterization by high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy. Atomic-scale HAADF-STEM images of ε-Keggin compounds were obtained for the first time, and positions of Mo and Co were confirmed. Furthermore, clear evidence of the presence of a CoO4 tetrahedron was obtained by X-ray absorption near-edge structure (XANES) analysis. Their characterization clearly revealed that ε-Keggin-type cobaltomolybdate units, [ε-CoMo12O40]n-, constructed by a central CoIIO4 tetrahedron and 12 surrounding MoO6 octahedra, are linked with CoII to form 3D frameworks.

10.
Angew Chem Int Ed Engl ; 56(32): 9367-9370, 2017 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-28621036

RESUMO

Multiferroic materials coupling ferroelasticity and ferromagnetism show strong magnetoelastic effects as magnetization is induced by mechanical stress or alternately strain induced by applying a magnetic field. These effects were reported for inorganic multiferroics such as LaCox Sr1-x O3 . (C6 H5 C2 H4 NH3 )2 FeII Cl4 is the first example of an organic-inorganic perovskite to exhibit such effects below the canted antiferromagnetism at TC =98 K and ferroelasticity at TC =433 K. This is shown by switching the magnetic hysteresis on and off by uniaxial pressure through the strong coupling of the magnetic and elastic domains. The spin-canting direction was controlled by mechanical stress in the heating and cooling cycles. This unique observation gives additional impetus in the search for coupled hysteretic effect in organic-inorganic multiferroics.

11.
Inorg Chem ; 55(6): 3047-57, 2016 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-26893217

RESUMO

We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, T(B) = 7 K) and ferrimagnet (FI, T(C) = 18 K), for one crystal structure of [{Mn(II)(D/L-NH2ala)}3{Mn(III)(CN)6}]·3H2O obtained from [Mn(CN)6](3-) and D/L-aminoalanine, in contrast to one MGS for [{Mn(II)(L-NH2ala)}3{Cr(III)(CN)6}]·3H2O. They consist of three Mn(NH2ala) helical chains bridged by M(III)(CN)6 to give the framework with disordered water molecules in channels and between the M(III)(CN)6. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the ac susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both T(crit) and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn(III)-CN-Mn(II) antiferromagnetic (J1 and J2), the weak Mn(II)-OCO-Mn(II) (J3), and Dzyaloshinkii-Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn(III)(CN)6 and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn(III)(CN)6 in good accordance with the Mn-Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique c axis of the hexagonal space group.

12.
Inorg Chem ; 55(1): 300-6, 2016 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-26671258

RESUMO

All five coordinating atoms of the amino-acid dianion L-aspartate (L-asp = NH2CH(COO)CH2COO(2-)) are found to be involved in coordination with Mn(II) in the presence of [Cr(III)(CN)6](3-) to self-assemble into a chiral three-dimensional cyanide-bridged K3[Mn(L-asp)]6[Cr(CN)6]·2H2O containing the highest ratio of Mn:Cr of 6:1. It adopts the chiral P3 (no. 143) space group consisting of zigzag Mn-OCO-Mn chains sharing edges of hexagonal channels with central [Cr(CN)6](3-), while K(+) and H2O occupy another parallel star-shaped channel. Its magnetic susceptibility above 100 K is dominated by the nearest neighbor (Mn-Cr at 5.08 and 5.31 Å) antiferromagnetic (AF) exchange interactions (θ = -15(1) K) and below 40 K by further AF interaction between Mn and Mn at 5.32 Å. It finally reaches a steady value at 4.5 K, where a bifurcation of the zero-field-cooled and field-cooled magnetizations is observed in small fields (<1 kOe). The isothermal magnetization is linear in field and deviating toward saturation above 60 kOe at 2 K. No imaginary component of the ac susceptibilities is observed. This behavior is associated with long-range antiferromagnetic order of a helical or conic nature where the magnetic sublattices are numerous [2n × (6Mn + 1Cr)], leading to a domain of sufficient size to allow for the presence of the bifurcation. A model is proposed based on the local anisotropy and symmetry multiplicity of the space group.

13.
Inorg Chem ; 55(17): 8292-300, 2016 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-27509227

RESUMO

A new series of heterometallic 3d-4f sandwich type phosphotungstates, [Ln{PCo2W10O38(H2O)2}2](11-) (Ln = Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), and Lu(III), denoted 1a-10a, respectively), have been synthesized by a one-pot reaction procedure on reacting the dilacunary K14[P2W19O69(H2O)]·24H2O precursor with Ln(NO3)3·nH2O and Co(NO3)2·6H2O in an aqueous potassium chloride solution. All the compounds were isolated as potassium salts and further characterized with different analytical techniques such as single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectrometry, elemental analysis by inductively coupled plasma atomic emission spectroscopy, magnetic measurement, and thermogravimetric analysis. Single-crystal X-ray diffraction analysis of the compounds reveals that all these compounds are isostructural and crystallized in the orthorhombic crystal system in space group Iba2. The polyanions contain the α-1,5 isomer of dicobalt-substituted α-Keggin phosphotungstate, which sandwiched lanthanoid cation and formed novel heterometallic dimer species. The temperature-dependent magnetic susceptibilities of 1a, 2a, 4a, and 7a-10a indicate the dominant contribution of the ferromagnetic interaction between Co(II) and Co(II) within the cluster, while the antiferromagnetic interaction between Co(II) and Ln(III) dominates for 3a, 5a, and 6a. The isothermal magnetizations of 1a-10a show a gradual increase in magnetization at low fields and do not reach saturation even at 50 kOe.

14.
Inorg Chem ; 54(6): 2866-74, 2015 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-25736878

RESUMO

An unusual high magnetic hardness for the layered perovskite-like (C2H5NH3)2[Fe(II)Cl4], in addition to its already found canted antiferromagnetism, ferroelasticity, and ferroelectricity, which are absent for (CH3NH3)2[Fe(II)Cl4], has been observed. The additional CH2 in the ethylammonium compared to methylammonium allows more degrees of freedom and therefore numerous phase transitions which have been characterized by single-crystal structure determinations from 383 to 10 K giving the sequence from tetragonal to orthorhombic to monoclinic (I4/mmm ↔ P42/ncm ↔ Pccn ↔ Pcab ↔ C2/c) accompanied by both tilting and rotation of the FeCl6 octahedra. The magnetic properties on single crystal and powder samples at high temperature are similar for both compounds, but at TN (C2H5NH3)2[Fe(II)Cl4] is a proper canted antiferromagnet unlike the hidden canting observed for (CH3NH3)2[Fe(II)Cl4]. The canting angle is 0.6° toward the c-axis, and thus the moments lie in the easy plane of the iron-chloride layer defined by a critical exponent ß = 0.18. The isothermal magnetizations for the field along the three orthogonal crystallographic axes show wider hysteresis for H ∥ c and is present at all temperature below 98 K. The coercive field increases as the temperature is lowered, and at T < 20 K it is difficult to reverse all the moments with the available 50 kOe of the SQUID for both single crystal and powder samples. The shape of the virgin magnetization after zero-field-cool (ZFC) indicates that the high coercive field is due to domain wall pinning. Thus, there are unusual associated anomalies such as asymmetric hysteresis and history dependence. The difference in magnetic hardness of the two compounds suggests that magnetic, electric, and elastic domains are intricately manifested and therefore raise the key question of how the different domains interact.

15.
Inorg Chem ; 53(4): 2068-75, 2014 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-24471961

RESUMO

In view of renewed interest in multiferroic for molecular systems, we re-examine the structural and magnetic properties of the potentially ferroic layered perovskite-like (CH3NH3)2[Fe(II)Cl4] due to its high-temperature magnetic ordering transition. The structures from several sets of diffraction data of single crystals consist of square-grid layers of corner-sharing FeCl6 octahedra and changes from the high-symmetry I4/mmm (T > 335 K) to the low-symmetry Pccn (T < 335 K). In the former the iron and bridging chlorine atoms are within the layer and the organic cations sit in the middle of each square grid, while in the latter the octahedra are tilted in pairs, two in and two out, progressively by up to 12° and the nitrogen atoms follow their motion to be nearer to the two-in pairs. Crystals are stable up to 450 K and display three phase transitions, two structural at 332 and 233 K and one magnetic at 95 K. The temperature dependences of the dc magnetization (zero-field and field-cooling modes) in different applied fields (10-10,000 Oe) on several aligned single crystals independently reveal a hidden-canted antiferromagnetic ground state of at least four sublattices and not the reported canted antiferromagnetic ground state. A metamagnetic critical field of only 200 Oe transforms it to a canted antiferromagnet. The estimated canting angle is 1.4° in zero field, and it folds to ca. 2.8° in a field of 50 kOe at 2 K. The easy axis is along 010, the hard axis is along 100, and the intermediate and canting axis is 001. Using the available extracted parameters the phase diagram has been constructed. This study provides evidence of a complex and intricate manifestation of the orientation, temperature, and field dependence of the interplay between anisotropy and coherent lengths, which would need further studies.

16.
Angew Chem Int Ed Engl ; 53(42): 11228-31, 2014 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-25082189

RESUMO

In a mixed-valence polyoxometalate, electrons are usually delocalized within the cluster anion because of low level of inter-cluster interaction. Herein, we report the structure and electrical properties of a single crystal in which mixed-valence polyoxometalates were electrically wired by cationic π-molecules of tetrathiafulvalene substituted with pyridinium. Electron-transport characteristics are suggested to represent electron hopping through strong interactions between cluster and cationic π-molecules.

17.
J Am Chem Soc ; 134(45): 18656-66, 2012 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-22946479

RESUMO

UV irradiation reversibly switches a new insulating and nonmagnetic molecular crystal, BPY[Ni(dmit)(2)](2) (BPY = N,N'-ethylene-2,2'-bipyridinium; Ni(dmit)(2) = bis(1,3-dithiole-2-thione-4,5-dithiolato)nickelate(III)), into a magnetic conductor. This is possible because the bipyridyl derivative cations (BPY(2+)) trigger a photochemical redox reaction in the crystal to produce a change of ∼10% in the filling of the Ni(dmit)(2) valence band, leaving localized spins on the BPY themselves. In the dark, almost all of the BPY molecules are closed-shell cations, and most of the Ni(dmit)(2) radical anions form spin-singlet pairs; thus, this material is a diamagnetic semiconductor. Under UV irradiation, a photocurrent is observed, which enhances the conductivity by 1 order of magnitude. Electron spin resonance measurements indicate that the UV irradiation reversibly generates carriers and localized spins on the Ni(dmit)(2) and the BPY, respectively. This high photoconductivity can be explained by charge transfer (CT) transitions between Ni(dmit)(2) and BPY in the UV region. In other words, the photoconduction and "photomagnetism" can be described as reversible optical control of the electronic states between an ionic salt (BPY(2+)/[Ni(dmit)(2)](-), nonmagnetic insulator) and a CT complex (BPY(2(1-δ)+)/[Ni(dmit)(2)]((1-δ)-) (δ ≈ 0.1), magnetic conductor) in the solid state.


Assuntos
Compostos Organometálicos/química , Modelos Moleculares , Estrutura Molecular , Níquel/química , Processos Fotoquímicos , Raios Ultravioleta
18.
Dalton Trans ; 51(17): 6682-6686, 2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35411897

RESUMO

The one-dimensional coordination polymers {[CuII(hfac)2]3(m-BNN)}n·nCH2Cl2 (1·CH2Cl2, P1̄) and {[CuII(hfac)2]3(m-BNN)}n (1', P2/n), hfac = hexafluoroacetylacetonate and m-BNN = meta-phenylene bis(nitronyl-nitroxide), were obtained from CH2Cl2 and CHCl3, respectively. 1·CH2Cl2 is transformed to 1 at 335 K. Their magnetic susceptibilities differ in both magnitude and temperature dependence behavior. 1 and 1' undergo a ferroelastic-like phase transition at 110 K and an unidentified one at 37 K. There is a subtle long relaxation of this ferroelastic-like ordered state.

19.
J Phys Chem Lett ; 13(32): 7405-7412, 2022 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-35927064

RESUMO

Semiconductors that emit intrinsic white light are considered next-generation lighting sources. Herein, the broadband emission of one-dimensional (1D) lead halide perovskites, TMAPbBr3-xIx (x = 0, 1, 1.5, 2, 3; TMA+ = tetramethylammonium), is systematically investigated. Lattice distortion causes the conversion of dark excitons to bright self-trapped excitons. Owing to its strongly localized exciton recombination and high absorption probability, TMAPbBr3 is the most viable in this family. A delocalized hole increases the nonradiative recombination rate of excitons in TMAPbBr3-xIx alloys. In 1D TMAPbBr3-xIx perovskites, the vibration mode of the Pb-X bond stretching of the PbX6 octahedra contributes more to the effect on exciton-phonon coupling than the mode of the X-Pb-X angle bending. Pb-X bond stretching and spontaneous polarization can tune exciton binding energy. This systematic study of excitonic behavior in 1D compounds relates the nature of ground states to the unknown excited states and provides the rational design of materials with stable and efficient broadband emission.

20.
RSC Adv ; 12(33): 21280-21286, 2022 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-35975059

RESUMO

Using Na-encapsulated benzo[18]crown-6 (Na)(B18C6) as a counter cation, we successfully magnetically isolated a fluoride-bridging Dy dinuclear complex {[(PW11O39)Dy(H2O)2]2F} (Dy2POM) with lacunary Keggin ligands. (Na)(B18C6) formed two types of tetramers through C-H⋯O, π⋯π and C-H⋯π interactions, and each tetramer aligned in one dimension along the c-axis to form two types of channels. One channel was partially penetrated by a supramolecular cation from the ±a-axis direction, dividing the channel in the form of a "bamboo node". Dy2POM was spatially divided by this "bamboo node," which magnetically isolated one portion from the other. The temperature dependence of the magnetic susceptibility indicated a weak ferromagnetic interaction between the Dy ions bridged by fluoride. Dy2POM exhibited the magnetic relaxation characteristics of a single-molecule magnet, including the dependence of AC magnetic susceptibility on temperature and frequency. Magnetic relaxation can be described by the combination of thermally active Orbach and temperature-independent quantum tunneling processes. The application of a static magnetic field effectively suppressed the relaxation due to quantum tunneling.

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