Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 24
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Chemistry ; 26(33): 7497-7503, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32298000

RESUMO

Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels-Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0 =0.72; half-life, t1/2 =3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels-Alder reaction, which featured a biradical character at the ground state (y0 =0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels-Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.

2.
Angew Chem Int Ed Engl ; 59(14): 5756-5764, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-31860759

RESUMO

Magnetic hysteresis is demonstrated for monolayers of the single-molecule magnet (SMM) Dy2 ScN@C80 deposited on Au(111), Ag(100), and MgO|Ag(100) surfaces by vacuum sublimation. The topography and electronic structure of Dy2 ScN@C80 adsorbed on Au(111) were studied by STM. X-ray magnetic CD studies show that the Dy2 ScN@C80 monolayers exhibit similarly broad magnetic hysteresis independent on the substrate used, but the orientation of the Dy2 ScN cluster depends strongly on the surface. DFT calculations show that the extent of the electronic interaction of the fullerene molecules with the surface is increasing dramatically from MgO to Au(111) and Ag(100). However, the charge redistribution at the fullerene-surface interface is fully absorbed by the carbon cage, leaving the state of the endohedral cluster intact. This Faraday cage effect of the fullerene preserves the magnetic bistability of fullerene-SMMs on conducting substrates and facilitates their application in molecular spintronics.

3.
Angew Chem Int Ed Engl ; 59(14): 5637-5642, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-31867754

RESUMO

Three unprecedented helical nanographenes (1, 2, and 3) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X-ray crystallographic analysis. The embedded azulene unit in 2 possesses a record-high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis-spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps (2: 1.88 eV; 3: 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in-situ EPR/Vis-NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties.

4.
Adv Sci (Weinh) ; 6(20): 1901352, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31637168

RESUMO

A new class of single-molecule magnets (SMMs) based on Dy-oxide clusterfullerenes is synthesized. Three isomers of Dy2O@C82 with C s(6), C 3v(8), and C 2v(9) cage symmetries are characterized by single-crystal X-ray diffraction, which shows that the endohedral Dy-(µ2-O)-Dy cluster has bent shape with very short Dy-O bonds. Dy2O@C82 isomers show SMM behavior with broad magnetic hysteresis, but the temperature and magnetization relaxation depend strongly on the fullerene cage. The short Dy-O distances and the large negative charge of the oxide ion in Dy2O@C82 result in the very strong magnetic anisotropy of Dy ions. Their magnetic moments are aligned along the Dy-O bonds and are antiferromagnetically (AFM) coupled. At low temperatures, relaxation of magnetization in Dy2O@C82 proceeds via the ferromagnetically (FM)-coupled excited state, giving Arrhenius behavior with the effective barriers equal to the AFM-FM energy difference. The AFM-FM energy differences of 5.4-12.9 cm-1 in Dy2O@C82 are considerably larger than in SMMs with {Dy2O2} bridges, and the Dy∙∙∙Dy exchange coupling in Dy2O@C82 is the strongest among all dinuclear Dy SMMs with diamagnetic bridges. Dy-oxide clusterfullerenes provide a playground for the further tuning of molecular magnetism via variation of the size and shape of the fullerene cage.

5.
Chem Commun (Camb) ; 55(86): 13000-13003, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31608903

RESUMO

Variable temperature X-ray diffraction studies on two single crystals containing M3N@C80, i.e., Ho2LuN@C80·NiOEP·2(C6H6) and Lu3N@C80·NiOEP·2(C6H6), (NiOEP = Nickel octaethylporphyrin) unravelled the temperature dependent rotation of the M3N cluster and C80 cage on the static NiOEP molecule.

6.
Acc Chem Res ; 52(10): 2981-2993, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31571482

RESUMO

A characteristic phenomenon of lanthanide-fullerene interactions is the transfer of metal valence electrons to the carbon cage. With early lanthanides such as La, a complete transfer of six valence electrons takes place for the metal dimers encapsulated in the fullerene cage. However, the low energy of the σ-type Ln-Ln bonding orbital in the second half of the lanthanide row limits the Ln2 → fullerene transfer to only five electrons. One electron remains in the Ln-Ln bonding orbital, whereas the fullerene cage with a formal charge of -5 is left electron-deficient. Such Ln2@C80 molecules are unstable in the neutral form but can be stabilized by substitution of one carbon atom by nitrogen to give azafullerenes Ln2@C79N or by quenching the unpaired electron on the fullerene cage by reacting it with a chemical such as benzyl bromide, transforming one sp2 carbon into an sp3 carbon and yielding the monoadduct Ln2@C80(CH2Ph). Because of the presence of the Ln-Ln bonding molecular orbital with one electron, the Ln2@C79N and Ln2@C80(R) molecules feature a unique single-electron Ln-Ln bond and an unconventional +2.5 oxidation state of the lanthanides. In this Account, which brings together metallofullerenes, molecular magnets, and lanthanides in unconventional valence states, we review the progress in the studies of dimetallofullerenes with single-electron Ln-Ln bonds and highlight the consequences of the unpaired electron residing in the Ln-Ln bonding orbital for the magnetic interactions between Ln ions. Usually, Ln···Ln exchange coupling in polynuclear lanthanide compounds is weak because of the core nature of 4f electrons. However, when interactions between Ln centers are mediated by a radical bridge, stronger coupling may be achieved because of the diffuse nature of radical-based orbitals. Ultimately, when the role of a radical bridge is played by a single unpaired electron in the Ln-Ln bonding orbital, the strength of the exchange coupling is increased dramatically. Giant exchange coupling in endohedral Ln2 dimers is combined with a rather strong axial ligand field exerted on the lanthanide ions by the fullerene cage and the excess electron density localized between two Ln ions. As a result, Ln2@C79N and Ln2@C80(CH2Ph) compounds exhibit slow relaxation of magnetization and exceptionally high blocking temperatures for Ln = Dy and Tb. At low temperatures, the [Ln3+-e-Ln3+] fragment behaves as a single giant spin. Furthermore, the Ln-Ln bonding orbital in dimetallofullerenes is redox-active, which allows its population to be changed by electrochemical reactions, thus changing the magnetic properties because the change in the number of electrons residing in the Ln-Ln orbital affects the magnetic structure of the molecule.

7.
Angew Chem Int Ed Engl ; 58(33): 11350-11354, 2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31132204

RESUMO

Despite recent successes in preparing three-dimensional crystals of empty fullerenes, such as C60 and C70 , 3D endohedral fullerene crystals, and especially hollow nanostructures, have been scarcely reported. A universal approach has now been developed to prepare shape-tunable 3D crystals of several metal nitride clusterfullerenes, including cubes and dice (hollow cubes with holes at the center of each face), which can be readily switched by changing the volume ratio of good (mesitylene) and poor (isopropanol) solvents. Synchrotron-based soft X-ray nano-computed tomography was used to unambiguously identify the interior microstructure of the dice-shaped crystals of Tb3 N@C80 , and especially the depth of the hole at each face, confirming that the dice has a solid center and the holes are not interconnected. Owing to the enhanced light absorption, the dice-shaped crystals exhibit enhanced photoluminescence relative to that of the cubes.

8.
Org Lett ; 21(5): 1354-1358, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30785760

RESUMO

Two novel nonhexagonal ring fused NBN-dibenzophenalenes (NBN-penta and NBN-hepta) were designed and synthesized. X-ray analysis reveals the planar structure of NBN-penta, while NBN-hepta displays a double-helical structure. Both compounds possess higher oxidation potential compared to the NBN-type zigzag-edged polycyclic aromatic hydrocarbons. The resultant NBN-penta and NBN-hepta exhibit global aromatic character based on X-ray analysis and DFT calculations. Furthermore, single crystal transistors of NBN-penta and NBN-hepta were fabricated, manifesting their promising potential in organic electronics.

9.
Nat Commun ; 10(1): 571, 2019 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-30718550

RESUMO

Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln2@C80(CH2Ph) dimetallofullerenes (Ln2 = Y2, Gd2, Tb2, Dy2, Ho2, Er2, TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal-metal bonding orbital. Tb2@C80(CH2Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln2@C80(CH2Ph) is redox active, enabling electrochemical tuning of the magnetism.

10.
Chem Sci ; 8(9): 6451-6465, 2017 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29263779

RESUMO

A method for the selective synthesis of sulfide clusterfullerenes Dy2S@C2n is developed. Addition of methane to the reactive atmosphere reduces the formation of empty fullerenes in the arc-discharge synthesis, whereas the use of Dy2S3 as a source of metal and sulfur affords sulfide clusterfullerenes as the main fullerene products along with smaller amounts of carbide clusterfullerenes. Two isomers of Dy2S@C82 with Cs(6) and C3v(8) cage symmetry, Dy2S@C72-Cs(10528), and a carbide clusterfullerene Dy2C2@C82-Cs(6) were isolated. The molecular structure of both Dy2S@C82 isomers was elucidated by single-crystal X-ray diffraction. SQUID magnetometry demonstrates that all of these clusterfullerenes exhibit hysteresis of magnetization, with Dy2S@C82-C3v(8) being the strongest single molecule magnet in the series. DC- and AC-susceptibility measurements were used to determine magnetization relaxation times in the temperature range from 1.6 K to 70 K. Unprecedented magnetization relaxation dynamics with three consequent Orbach processes and energy barriers of 10.5, 48, and 1232 K are determined for Dy2S@C82-C3v(8). Dy2S@C82-Cs(6) exhibits faster relaxation of magnetization with two barriers of 15.2 and 523 K. Ab initio calculations were used to interpret experimental data and compare the Dy-sulfide clusterfullerenes to other Dy-clusterfullerenes. The smallest and largest barriers are ascribed to the exchange/dipolar barrier and relaxation via crystal-field states, respectively, whereas an intermediate energy barrier of 48 K in Dy2S@C82-C3v(8) is assigned to the local phonon mode, corresponding to the librational motion of the Dy2S cluster inside the carbon cage.

11.
Nat Commun ; 8: 16098, 2017 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-28706223

RESUMO

Increasing the temperature at which molecules behave as single-molecule magnets is a serious challenge in molecular magnetism. One of the ways to address this problem is to create the molecules with strongly coupled lanthanide ions. In this work, endohedral metallofullerenes Y2@C80 and Dy2@C80 are obtained in the form of air-stable benzyl monoadducts. Both feature an unpaired electron trapped between metal ions, thus forming a single-electron metal-metal bond. Giant exchange interactions between lanthanide ions and the unpaired electron result in single-molecule magnetism of Dy2@C80(CH2Ph) with a record-high 100 s blocking temperature of 18 K. All magnetic moments in Dy2@C80(CH2Ph) are parallel and couple ferromagnetically to form a single spin unit of 21 µB with a dysprosium-electron exchange constant of 32 cm-1. The barrier of the magnetization reversal of 613 K is assigned to the state in which the spin of one Dy centre is flipped.

12.
Angew Chem Int Ed Engl ; 56(7): 1830-1834, 2017 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-28079303

RESUMO

Fused-pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non-IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused-pentagons, making it difficult to access the single-atom properties. Herein, we report the syntheses and isolations of novel non-IPR mononuclear clusterfullerenes MNC@C76 (M=Tb, Y), in which one pair of strained fused-pentagon is stabilized by a mononuclear cluster. The molecular structures of MNC@C76 (M=Tb, Y) were determined unambiguously by single-crystal X-ray diffraction, featuring a non-IPR C2v (19138)-C76 cage entrapping a nearly linear MNC cluster, which is remarkably different from the triangular MNC cluster within the reported analogous clusterfullerenes based on IPR-obeying C82 cages. The TbNC@C76 molecule is found to be a field-induced single-molecule magnet (SMM).

13.
J Am Chem Soc ; 138(44): 14764-14771, 2016 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-27755875

RESUMO

Clusterfullerenes are capable of entrapping a variety of metal clusters within carbon cage, for which the entrapped metal cluster generally keeps its geometric structure (e.g., bond distance and angle) upon changing the isomeric structure of fullerene cage, and whether the properties of the entrapped metal cluster is geometry-dependent remains unclear. Herein we report an unusual triangular monometallic cluster entrapped in fullerene cage by isolating several novel terbium cyanide clusterfullerenes (TbNC@C82) with different cage isomeric structures. Upon varying the isomeric structure of C82 cage from C2(5) to Cs(6) and to C2v(9), the entrapped triangular TbNC cluster exhibits significant distortions as evidenced by the changes of Tb-C(N) and C-N bond distances and variation of the Tb-C(N)-N(C) angle by up to 20°, revealing that the geometric structure of the entrapped triangular TbNC cluster is variable. All three TbNC@C82 molecules are found to be single-ion magnets, and the change of the geometric structure of TbNC cluster directly leads to the alternation of the magnetic relaxation time of the corresponding TbNC@C82 clusterfullerene.

14.
J Am Chem Soc ; 138(1): 207-14, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26645852

RESUMO

So far the entrapped metals for the isolated endohedral metallofullerenes (EMFs) are primarily limited to rare earth metals, whereas except group-IVB metals, whether it is possible to entrap other d-block transition metals remains unclear. Herein we report the successful entrapment of the group-VB transition metal vanadium(V) into fullerene cage, affording the heretofore unknown V-containing EMFs. Two novel V-containing EMFs--V(x)Sc(3-x)N@C80 (x = 1, 2)--were isolated, and their molecular structures were unambiguously determined by X-ray crystallography to be I(h)(7)-C80 cage entrapping the planar VSc2N/V2ScN clusters. V(x)Sc(3-x)N@I(h)(7)-C80 (x = 1, 2) were further characterized by UV-vis-NIR and ESR spectroscopies and electrochemistry, revealing that the electronic and magnetic properties of V(x)Sc(3-x)N@I(h)(7)-C80 (x = 1, 2) are tunable upon varying the number of entrapped V atoms (i.e., x value). The molecular structures and electronic properties of V(x)Sc(3-x)N@I(h)(7)-C80 (x = 1, 2) were further compared with those of the reported analogous EMFs based on lanthanide metals and the adjacent group-IVB transition metal Ti, revealing the peculiarity of the group-VB transition metal V-based EMFs.

15.
Chemistry ; 21(15): 5750-9, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25712246

RESUMO

A large family of dysprosium-scandium (Dy-Sc) mixed-metal nitride clusterfullerenes (MMNCFs), Dy(x)Sc(3-x)N@C2n (x = 1, 2, 2n = 68, 70, 76-86) have been successfully synthesized and isolated. Among these, the C70 and C82-based MMNCFs are two new cages that have never been isolated for MMNCFs. Synthesis of Dy(x)Sc(3-x)N@C2n was accomplished by the "selective organic solid" route using guanidinium thiocyanate as the nitrogen source, and their isolation was fulfilled by recycling HPLC. UV/Vis-NIR spectroscopic study indicates that almost all Dy(x)Sc(3-x)N@C2n MMNCFs are kinetically stable fullerenes with optical band gaps beyond 1 eV. This feature is distinctly different to their counterparts Dy3N@C2n (78≤2n≤88), whose for optical band-gaps are below 1 eV for relatively large cages such as C84 and C86. An FTIR spectroscopic study in combination with DFT calculations enables reasonable assignments of the cage isomeric structures of all isolated Dy(x)Sc(3-x)N@C2n (x = 1, 2, 2n = 68, 70, 76-86) MMNCFs. The carbon cage size distribution of Dy(x)Sc(3-x)N@C2n (2n = 68, 70, 76-86) is compared to the reported Dy3N@C2n (78≤2n≤8) homogeneous NCF and Dy(x)Sc(3-x)N@C2n (78≤2n≤88) MMNCF families, revealing that the medium-sized Dy metal plays a crucial role on the expanded cage size distribution of MMNCFs. As a result, Dy(x)Sc(3-x)N@C2n MMNCFs are the largest MMNCF family reported to date.


Assuntos
Disprósio/química , Fulerenos/química , Escândio/química , Modelos Moleculares
16.
J Am Chem Soc ; 137(8): 3119-23, 2015 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-25659601

RESUMO

The long-sought small-bandgap endohedral fullerene Sc3N@C82 with low kinetic stability has been successfully synthesized and isolated for the first time, for which the molecular structure has been unambiguously determined as Sc3N@C82-C2v(39718) by single crystal X-ray diffraction. The C82-C2v(39718) (or labeled as C82-C2v(9) according to the conventional numbering of the isolated pentagon rule (IPR) isomers based on the Fowler-Monolopoulos spiral algorithm) isomeric cage of Sc3N@C82 agrees well with its most stable isomer previously predicted by DFT computations and is dramatically different to those of the reported counterparts M3N@C82-Cs(39663) (M = Gd, Y) based on a non-IPR C82 isomer, revealing the strong dependence of the cage isomeric structure on the size of the encaged metal for C82-based metal nitride clusterfullerenes (NCFs).


Assuntos
Fulerenos/química , Estabilidade de Medicamentos , Eletroquímica , Cinética , Modelos Moleculares , Conformação Molecular
17.
Inorg Chem ; 53(10): 5201-5, 2014 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-24786191

RESUMO

The first terbium (Tb)-monometallic cyanide clusterfullerene (CYCF), TbCN@C82, has been successfully synthesized and isolated, whose molecular structure was determined unambiguously as TbCN@C2(5)-C82 by single crystal X-ray diffraction. The C2(5)-C82 isomeric cage represents a new cage capable of encapsulating a monometallic cyanide cluster. The C-N bond length within the encaged TbCN cluster is determined to be 0.94(5) Å, which is smaller by at least 0.17 Å than those of the reported C-N triplet bonds in traditional cyanide/nitrile compounds and cyano coordination complexes. An electronic configuration of [Tb(3+)(CN)(-)](2+)@[C82](2-) was proposed for TbCN@C82.


Assuntos
Cianetos/química , Fulerenos/química , Térbio/química , Cristalografia por Raios X , Modelos Moleculares
18.
Chem Commun (Camb) ; 49(92): 10844-6, 2013 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-24121522

RESUMO

The first Bingel-Hirsch reaction of TiSc2N@Ih-C80 afforded two unconventional singly bonded monoadducts, revealing the dramatically improved reactivity compared to Sc3N@Ih-C80 and obvious change in the addition pattern.


Assuntos
Fulerenos/química , Nitrogênio/química , Escândio/química , Titânio/química , Estrutura Molecular
19.
Sci Rep ; 3: 1487, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23512079

RESUMO

Since the first proposal that fullerenes are capable of hosting atoms, ions, or clusters by the late Smalley in 1985, tremendous examples of endohedral metallofullerenes (EMFs) have been reported. Breaking the dogma that monometallofullerenes (mono-EMFs) always exist in the form of M@C2n while clusterfullerenes always require multiple (two to four) metal cations to stabilize a cluster that is unstable as a single moiety, here we show an unprecedented monometallic endohedral clusterfullerene entrapping an yttrium cyanide cluster inside a popular C82 cage--YCN@C(s)(6)-C82. X-ray crystallography and (13)C NMR characterization unambiguously determine the cage symmetry and the endohedal cyanide structure, unexpectedly revealing that the entrapped YCN cluster is triangular. The unprecedented monometallic clusterfullerene structure unveiled by YCN@C(s)(6)-C82 opens up a new avenue for stabilizing a cluster by a single metal cation within a carbon cage, and will surely stimulate further studies on the stability and formation mechanism of EMFs.

20.
Inorg Chem ; 52(7): 3814-22, 2013 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-23480680

RESUMO

A series of nitrogen-containing inorganic solid compounds with variable oxidation states of nitrogen and counter ions have been successfully applied as new inorganic solid nitrogen sources toward the synthesis of Sc-based metal nitride clusterfullerenes (Sc-NCFs), including ammonium salts [(NH4)xH(3-x)PO4 (x = 0-2), (NH4)2SO4, (NH4)2CO3, NH4X (X = F, Cl), NH4SCN], thiocyanate (KSCN), nitrates (Cu(NO3)2, NaNO3), and nitrite (NaNO2). Among them, ammonium phosphates ((NH4)xH(3-x)PO4, x = 1-3) and ammonium thiocyanate (NH4SCN) are revealed to behave as better nitrogen sources than others, and the highest yield of Sc-NCFs is achieved when NH4SCN was used as a nitrogen source. The optimum molar ratio of Sc2O3:(NH4)3PO4·3H2O:C and Sc2O3:NH4SCN:C has been determined to be 1:2:15 and 1:3:15, respectively. The thermal decomposition products of these 12 inorganic compounds have been discussed in order to understand their different performances toward the synthesis of Sc-NCFs, and accordingly the dependence of the production yield of Sc-NCFs on the oxidation state of nitrogen and counter ion is interpreted. The yield of Sc3N@C80 (I(h) + D(5h)) per gram Sc2O3 by using the N2-based group of nitrogen sources (thiocyanate, nitrates, and nitrite) is overall much lower than those by using gaseous N2 and NH4SCN, indicating the strong dependence of the yield of Sc-NCFs on the oxidation state of nitrogen, which is attributed to the "in-situ" redox reaction taking place for the N2-based group of nitrogen sources during discharging. For NH3-based group of nitrogen sources (ammonium salts) which exhibits a (-3) oxidation states of nitrogen, their performance as nitrogen sources is found to be sensitively dependent on the anion, and this is understood by considering their difference on the thermal stability and/or decomposition rate. Contrarily, for the N2-based group of nitrogen sources, the formation of Sc-NCFs is independent to both the oxidation state of nitrogen (+3 or +5) and the cation.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA