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1.
Chemistry ; 30(42): e202400420, 2024 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-38563635

RESUMO

A diradical with engineered g-asymmetry was synthesized by grafting a nitroxide radical onto the [Y(Pc)2]⋅ radical platform. Various spectroscopic techniques and computational studies revealed that the electronic structures of the two spin systems remained minimally affected within the diradical system. Fluid-solution Electron Paramagnetic Resonance (EPR) experiments revealed a weak exchange coupling with |J| ~ 0.014 cm-1, subsequently rationalized by CAS-SCF calculations. Frozen solution continuous-wave (CW) EPR experiments showed a complicated and power-dependent spectrum that eluded analysis using the point-dipole model. Pulse EPR manipulations with varying microwave powers, or under varying magnetic fields, demonstrated that different resonances could be selectively enhanced or suppressed, based on their different tipping angles. In particular, Field-Swept Echo-Detected (FSED) spectra revealed absorptions of MW power-dependent intensities, while Field-Swept Spin Nutation (FSSN) experiments revealed two distinct Rabi frequencies. This study introduces a methodology to synthesize and characterize g-asymmetric two-spin systems, of interest in the implementation of spin-based CNOT gates.

2.
J Am Chem Soc ; 145(4): 2461-2472, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36656167

RESUMO

A mixed-ligand phthalocyanine/porphyrin yttrium(III) radical double-decker complex (DD) was synthesized using the custom-made 5,10,15-tris(4-methoxyphenyl)-20-(4-((trimethylsilyl)ethynyl)phenyl)porphyrin. The trimethylsilyl functionality was then used to couple two such complexes into biradicals through rigid tethers. Glaser coupling was used to synthesize a short-tethered biradical (C1) and Sonogashira coupling to synthesize longer-tethered ones (C2 and C3). Field-swept echo-detected (FSED), saturation recovery, and spin nutation-pulsed electron paramagnetic resonance experiments revealed marked similarities of the magnetic properties of DD with those of the parent [Y(pc)2]• complex, both in the solid state and in CD2Cl2/CDCl3 4:1 frozen glasses. FSED experiments on the biradicals C2 and C3 revealed a spectral broadening with respect to the spectra of DD and [Y(pc)2]• assigned to the effect of dipolar interactions in solution. Apart from the main resonance, satellite features were also observed, which were simulated with dipole-dipole pairs of shortest distances, suggesting spin delocalization on the organic tether. FSED experiments on C1 yielded spectral line shapes that could not be simulated as the integration of the off-resonance echoes was complicated by field-dependent modulations. While, for all dimers, the on-resonance spin nutation experiments yielded Rabi oscillations of the same frequencies, off-resonance nutations on C1 yielded Rabi oscillations that could be assigned to a MS = -1 to MS = 0 transition within a S = 1 multiplet. The DFT calculations showed that the trans conformation of the complexes was significantly more stable than the cis one and that it induced a marked spin delocalization over the rigid organic tether. This "spin leakage" was most pronounced for the shortest biradical C1.

3.
Phys Chem Chem Phys ; 23(26): 14415-14421, 2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-34180472

RESUMO

A 16-line pattern has been theoretically predicted, but hitherto not reported, for the Electron Paramagnetic Resonance (EPR) spectrum of antiferromagnetically coupled CuII triangles experiencing isotropic exchange of isosceles magnetic symmetry. Now, the crystallization of such a triangular species and its X-ray structure determination in a polar space group, R3 (No. 146), has enabled its single crystal EPR study. Its detailed magnetic susceptibility, and X- and Q-band, powder and single crystal EPR spectroscopic study reveals the effect of molecular structure and of Dzyaloshinskii-Moriya interactions (DMI) on the g‖, g⊥ and A‖ parameters of the spectrum; DMI is considered for the first time in such a context. Moreover, careful analysis of the spectrum allows the deconvolution of two slightly different cocrystallized magnetic species.

4.
Phys Chem Chem Phys ; 23(36): 20268-20274, 2021 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-34486006

RESUMO

We built a broadband Electron Paramagnetic Resonance (EPR) spectrometer capable of field- and frequency sweep experiments under field-, microwave amplitude- and microwave frequency-modulation detection modes (HM, AM, and FM, respectively). The spectrometer is based on a coplanar waveguide (CPW) architecture, with the sample being deposited on top of the transmission line. We tested the functionality of this spectrometer by measuring a standard 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH) sample, and complex (NnBu4)2[Cu3(µ3-Cl)2(µ-pz)3Cl3] (1), drop-casted on the CPW. Complex 1 had been previously studied by conventional X-band EPR spectroscopy (Chem. - Eur. J., 2020, 26, 12769-1784), and comparison with the past studies validated the functionality of the spectrometer and confirmed the stability of the sample upon deposition. Moreover, our results highlighted the importance of surface effects and of the orientation of the microwave magnetic component B1 on the lineshapes of the recorded spectra.

5.
J Am Chem Soc ; 141(50): 19765-19775, 2019 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-31762270

RESUMO

Two molecular spin qubits are studied with pulsed electron paramagnetic resonance (EPR) spectroscopy under electric fields to assess their magnetoelectric (ME) couplings and electric spin control. [Fe3O(PhCOO)6(py)3]ClO4·py (Fe3) is characterized by strong Dzyaloshinskii-Moriya interactions (DMI) which induce important magnetoanisotropy, whereas the DMI in [Cr3O(PhCOO)6(py)3]ClO4·0.5py (Cr3) is 1-2 orders of magnitude weaker. Fe3 is observed to demonstrate a clear ME effect, whose intensity shows an unprecedented dependence on the molecular orientation within the electric field E (electroanisotropy) and on the relative orientations of the molecular z axis, the Zeeman field B0 and E (magnetoelectric anisotropy). The electric control in Fe3 is shown to be coherent, and the ME effect exhibits complex dynamics characterized by saturation and oscillatory effects. On the other hand, Cr3 exhibits no discernible ME effect, which correlates well with its negligible DMI.

6.
Inorg Chem ; 58(11): 7537-7544, 2019 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-31091082

RESUMO

Two trinuclear CuII pyrazolato complexes with a Cu3(µ3-E)-core (E = O2- or OH-) and terminal nitrite ligands in two coordination modes were characterized crystallographically, spectroscopically, and electrochemically. One-electron oxidation of the µ3-O species produces a delocalized, mixed-valent, formally CuII2CuIII-nitrite, but no nitrate. In contrast, under reducing conditions-addition of PhSH as an electron and proton donor-both complexes mediate the reduction of nitrite, releasing NO.

7.
Phys Chem Chem Phys ; 21(35): 19575-19584, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31464324

RESUMO

Spectral broadenings due to Dzyaloshinskii-Moriya interactions (DMI) were assessed with respect to the decoherence they induce through increased spin-spin interactions, as the role of DMI in developing magnetoelectric spin-chirality qubits is gaining recognition. The structurally related spin triangles [Fe3O(PhCOO)6(py)3]ClO4·py (Fe3) and [Cr3O(PhCOO)6(py)3]ClO4·0.5py (Cr3) were studied as frozen py-d5 solutions with various pulsed Electron Paramagnetic Resonance (EPR) spectroscopy experiments, and under identical experimental conditions. Field-swept Hahn echo experiments revealed a match with continuous-wave (CW) spectra, while variable-temperature saturation/inversion recovery and Hahn echo decay experiments were used to extract the thermal evolutions of the spin-lattice relaxation and phase-memory times (T1 and Tm, respectively). Nutation experiments revealed Rabi oscillations demonstrating that the spins of the complexes could be coherently manipulated. Careful comparisons of Tm times confirmed hyperfine interactions with the magnetic nuclei of the metal ions as an intrinsic source of decoherence. Comparisons of Rabi damping times revealed that DMI-induced spectral broadenings play a discernible but moderate role as an extrinsic source of decoherence for the nutation experiments and that they are not particularly detrimental to spin manipulations.

8.
Chemistry ; 24(56): 14896-14900, 2018 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-30136321

RESUMO

Single-crystal EPR experiments show that the highly symmetric antiferromagnetic half-integer spin triangle [Fe3 O(O2 CPh)6 (py)3 ]ClO4 ⋅py (1, py=pyridine) possesses a ST =1/2 ground state exhibiting high g-anisotropy due to antisymmetric exchange (Dzyaloshinskii-Moriya) interactions. EPR experiments under static electric fields parallel to the triangle's plane (i.e., perpendicular to the magnetic z-axis) reveal that this ground state couples to externally applied electric fields. This magnetoelectric coupling causes an increase in the intensity of the intradoublet EPR transition and does not affect its resonance position when B0 ∥z. The results are discussed on the basis of theoretical models correlating the spin chirality of the ground state with the magnetoelectric effect.

9.
Inorg Chem ; 57(21): 13259-13269, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30353727

RESUMO

Magnetic susceptibility and X-band electron paramagnetic resonance (EPR) studies have been carried out on the highly symmetric [Cr3O(PhCOO)6(py)3](ClO4)·0.5py (1; py = pyridine), whose cation exhibits a D3 h crystallographically imposed molecular symmetry. While magnetic susceptibility data can be interpreted with an equilateral magnetic model described by the effective multispin Hamiltonian H = -2 J(S1·S2 + S2·S3 + S3·S1), EPR data require an isosceles model described by the multispin Hamiltonian H = -2 J( S1· S2 + S2· S3) - 2 J' S3· S1, where Δ J = J - J' ≠ 0. Moreover, EPR data reveal the interplay of antisymmetric exchange (or Dzyaloshinskii-Moriya) interactions, described by a 2G(S1 × S2 + S2 × S3 + S3 × S1) term, which induce significant anisotropy to the ST = 1/2 ground state of 1, as well as an important broadening of the g⊥ resonance ( g strain). Through careful analysis of these data and in conjunction with neutron scattering data, this g strain can be deconvoluted into distributions of the individual spin-Hamiltonian parameters Δ J and |G|. This method of analysis provides simultaneous estimates of the central values and distribution profiles of the spin-Hamiltonian parameters, which are shown not to be described by monodisperse values.

10.
Phys Chem Chem Phys ; 20(25): 17234-17244, 2018 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-29901059

RESUMO

The X-ray crystal structure of the CuII complex [Cu3(µ3-OH)(µ-pz)3(PhCOO)3]- (pz- = pyrazolato anion) shows an isosceles triangular core, further forming a hexanuclear H-bonded aggregate. Cleavage of the H-bonds in solution results in isolated trinuclear species. Analysis of variable temperature magnetic susceptibility data of a powder sample shows an antiferromagnetically-coupled Cu3-core with a doublet ground state and isotropic exchange parameters (Jave = -355 cm-1, Hiso = -JijSiSj). The fitting of magnetic data requires the inclusion of antisymmetric exchange, AE (HAE = Gij·Si × Sj) with Gz = 31.2 cm-1 and no detectable inter-Cu3 isotropic exchange. X-band EPR spectroscopy in a frozen tetrahydrofuran solution of the compound indicates isolated Cu3-species with g‖,eff = 2.25, g⊥,eff = 1.67. The small value of g⊥,eff (≪2.0) is consistent with the presence of AE in agreement with the analysis of the magnetic measurements. The parallel component exhibits a hyperfine pattern corresponding to one I = 3/2 nucleus with A‖ = 425 MHz. This implies a specific exchange coupling scheme obeying the order |J12| = |J13| < |J23| consistent with the crystallographically determined two long and one short CuCu distances. The role of AE in modulating the hyperfine parameters in antiferromagnetic Cu3 clusters is studied. EPR spectra at X- and Q-band were performed with powder samples of the cluster at liquid helium temperatures. The spectra in both bands are consistent with two interacting Sa,b = 1/2 species in the point dipolar approximation. Fitting of the spectra reveals that each spin is characterized by g‖ = 2.24, g⊥ = 1.65 which is in agreement with an isolated Cu3 cluster in the ground state. The determined inter-spin distance of 4.4-4.5 Å is very close to the distance between the Cu(1) and Cu(1)' sites of the two trimeric units as imposed crystallographically (4.3 Å). This constitutes further verification of the specific exchange coupling scheme within each trimer. Magnetostructural correlations previously adopted for antiferromagnetically coupled Cu3 clusters are discussed in the light of the combined magnetic measurements and EPR spectroscopy.

11.
Inorg Chem ; 56(23): 14540-14555, 2017 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-29160703

RESUMO

The preparation and properties of novel ruthenium carbon-rich complexes [(Ph-C≡C-)2-nRu(dppe)2(-C≡C-bipyM(hfac)2)n] (n = 1, 2; M = CuII, MnII; bipy = 2,2'-bipyridin-5-yl) characterized by single-crystal X-ray diffraction and designed for molecular magnetism are reported. With the help of EPR spectroscopy, we show that the neutral ruthenium system sets up a magnetic coupling between two remote paramagnetic CuII units. More specifically, these copper compounds are unique examples of bimetallic and linear heterotrimetallic compounds for which a complete rationalization of the magnetic interactions could be made for exceptionally long distances between the spin carriers (8.3 Å between adjacent Cu and Ru centers, 16.6 Å between external Cu centers) and compared at two different redox states. Surprisingly, oxidation of the ruthenium redox-active metal coupling unit (MCU), which introduces an additional spin unit on the carbon-rich part, leads to weaker magnetic interactions. In contrast, in the simpler parent complexes bearing only one paramagnetic metal unit [Ph-C≡C-Ru(dppe)2-C≡C-bipyCu(hfac)2], one-electron oxidation of the ruthenium bis(acetylide) unit generates an interaction between the Cu and Ru spin carriers of magnitude comparable to that observed between the two far apart Cu ions in the above corresponding neutral trimetallic system. Evaluation and rationalization of this coupling with theoretical tools are in rational agreement with experiments for such complex systems.

12.
Inorg Chem ; 55(9): 4183-98, 2016 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-27054464

RESUMO

The coordination of two heterofunctional P,P,S ligands of the N-functionalized DPPA-type bearing an alkylthioether or arylthioether N-substituent, (Ph2P)2N(CH2)3SMe (1) and (Ph2P)2N(p-C6H4)SMe (2), respectively, toward cobalt dichloride was investigated to examine the influence of the linker between the PNP nitrogen and the S atoms. The complexes [CoCl2(1)]2 (3) and [CoCl2(2)]2 (4) have been isolated, and 3 was shown by X-ray diffraction to be a unique dinuclear, zwitterion containing one CoCl moiety bis-chelated by two ligands 1 and one CoCl3 fragment coordinated by the S atom of a thioether function. The FT-IR, UV-vis, and EPR spectroscopic features of 3 were analyzed as the superposition of those of constitutive fragments identified by a retrosynthetic-type analysis. A similar approach provided insight into the nature of 4 for which no X-ray diffraction data could be obtained. A comparison between the spectroscopic features of 4 and of its constitutive fragments, [CoCl(2)2]PF6 (7) and [H2']2[CoCl4] (8) (2' = NH2(p-C6H4)SMe), and between those of 4 and 3 suggested that 4 could either have a zwitterionic structure, similar to that of 3, or contain a tetrahedral dicationic bis-chelated Co center associated with a CoCl4 dianion. Magnetic and EPR studies and theoretical calculations were performed. Doublet spin states were found for the pentacoordinated complexes [CoCl(1)2]PF6 (5) and 7 and anisotropic quadruplet spin states for the tetrahedral complexes [CoCl3(H1')] (6) (1' = NH2(CH2)3SMe) and 8. A very similar behavior was observed for 3 and 4, consisting in the juxtaposition of noninteracting doublet and quadruplet spin states. Antiferromagnetic interactions explain the formation of dimers for 6 and of layers for 8. The EPR signatures of 3 and 4 correspond to the superposition of low-spin nuclei in 5 and 7 and high-spin nuclei in 6 and 8, respectively. From DFT calculations, the solid-state structure of 4 appears best described as zwitterionic, with a low-spin state for the Co1 atom.

13.
Nucleic Acids Res ; 42(15): e117, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24981512

RESUMO

Site-directed spin labeling is emerging as an essential tool to investigate the structural and dynamical features of RNA. We propose here an enzymatic method, which allows the insertion of a paramagnetic center at a specific position in an RNA molecule. The technique is based on a segmental approach using a ligation protocol with T4 RNA ligase 2. One transcribed acceptor RNA is ligated to a donor RNA in which a thio-modified nucleotide is introduced at its 5'-end by in vitro transcription with T7 RNA polymerase. The paramagnetic thiol-specific reagent is subsequently attached to the RNA ligation product. This novel strategy is demonstrated by introducing a paramagnetic probe into the 55 nucleotides long RNA corresponding to K-turn and Specifier Loop domains from the Bacillus subtilis tyrS T-Box leader RNA. The efficiency of the coupling reaction and the quality of the resulting spin-labeled RNA were assessed by Mass Spectrometry, Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR). This method enables various combinations of isotopic segmental labeling and spin labeling schemes, a strategy that will be of particular interest to investigate the structural and dynamical properties of large RNA complexes by NMR and EPR spectroscopies.


Assuntos
RNA/química , Marcadores de Spin , Bioquímica/métodos , Espectroscopia de Ressonância de Spin Eletrônica , Marcação por Isótopo , Espectroscopia de Ressonância Magnética , RNA/biossíntese , RNA Ligase (ATP) , Tionucleotídeos/biossíntese , Tionucleotídeos/química , Proteínas Virais
14.
Inorg Chem ; 54(13): 6347-55, 2015 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-26068041

RESUMO

With the help of EPR spectroscopy, we show that the diamagnetic [Ru(dppe)2(-C≡C-R)2] system sets up a magnetic coupling between two organic radicals R, i.e., two nitronyl nitroxide or two verdazyl units, which is stronger than that of related platinum organometallic systems. Surprisingly, further oxidation of the ruthenium redox-active metal coupling unit (MCU), which introduces an additional spin unit on the carbon-rich part, leads to the switching off of this interaction. On the contrary, in simpler complexes bearing only one of the organic radical ligands [C6H5-C≡C-Ru(dppe)2-C≡C-R], one-electron oxidation of the transition metal unit generates an interaction between the two spin carriers of comparable magnitude to that observed in the above corresponding neutral systems.

15.
Inorg Chem ; 53(15): 8172-88, 2014 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-25033266

RESUMO

The association of a dithienylethene (DTE) system with ruthenium carbon-rich systems allows reaching sophisticated and efficient light- and electro-triggered multifunctional switches R-[Ru]-C≡C-DTE-C≡C-[Ru]-R, featuring multicolor electrochromism and electrochemical cyclization at remarkably low voltage. The spin density on the DTE ligand and the energetic stabilization of the system upon oxidation could be manipulated to influence the closing event, owing to the noninnocent behavior of carbon-rich ligands in the redox processes. A combination of spectroscopic (UV-vis-NIR-IR and EPR) and electrochemical studies, with the help of quantum chemical calculations, demonstrates that one can control and get a deeper understanding of the electrochemical ring closure with a slight modification of ligands remote from the DTE unit. This electrochemical cyclization was established to occur in the second oxidized state (EEC mechanism), and the kinetic rate constant in solution was measured. Importantly, these complexes provide an unprecedented experimental means to directly probe the remarkable efficiency of electronic (spin) delocalization between two trans carbon-rich ligands through a metal atom, in full agreement with the theoretical predictions. In addition, when no cyclization occurs upon oxidation, we could achieve a redox-triggered magnetic switch.

16.
Inorg Chem ; 53(2): 1184-94, 2014 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-24400974

RESUMO

A series of new hybrid multilayers has been synthesized by insertion-grafting of transition metal (Cu(II), Co(II), Ni(II), and Zn(II)) tetrasulfonato phthalocyanines between layers of Cu(II) and Co(II) simple hydroxides. The structural and spectroscopic investigations confirm the formation of new layered hybrid materials in which the phthalocyanines act as pillars between the inorganic layers. The magnetic investigations show that all copper hydroxide-based compounds behave similarly, presenting an overall antiferromagnetic behavior with no ordering down to 1.8 K. On the contrary, the cobalt hydroxide-based compounds present a ferrimagnetic ordering around 6 K, regardless of the nature of the metal phthalocyanine between the inorganic layers. The latter observation points to strictly dipolar interactions between the inorganic layers. The amplitude of the dipolar field has been evaluated from X-band and Q-band EPR spectroscopy investigation (Bdipolar ≈ 30 mT).

17.
Chemphyschem ; 14(5): 958-69, 2013 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-23401358

RESUMO

The electronic structure of polyanions of sterically encumbered triisopropylsilyl-substituted linear and cyclic oligo(phenyleneethynylene)s (Monomer, Trimer, Pentamer, and Triangle) is investigated by electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and UV/Vis-near-infrared (NIR) spectroscopies, cyclic voltammetry, and theoretical calculations (DFT). Increasing anion orders are generated sequentially in vacuo at room temperature by chemical reaction with potassium metal up to the pentaanion. The relevance of these compounds acting as electron reservoirs is thus demonstrated. Even-order anions are EPR silent, whereas the odd species exhibit different signatures, which are identified after comparison of the measured hyperfine couplings by ENDOR spectroscopy with those predicted by DFT calculations. With increasing size of the oligomers the electron spin density is first distributed over the backbone carbon atoms for the monoanions, and then further localized at the outer phenyl rings for the trianion species. Examination of the UV/Vis-NIR spectra indicates that the monoanions (T(.-) , P(.-) ) exhibit two transitions in the Vis-NIR region, whereas a strong absorption in the IR region is solely observed for higher reduced states. Electronic transitions of the neutral monoanions and trianions are redshifted with increasing oligomer size, whereas for a given oligomer a blueshift is observed upon increasing the charge, which suggests a localization of the spin density.

18.
Chem Commun (Camb) ; 57(87): 11505-11508, 2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34652347

RESUMO

FID-detected nutations of the antiferromagnetic crystal form of [Y(pc)2]˙ demonstrated that its radical spin can be coherently driven in its magnetically condensed undeuterated phase and at room temperature. Liquid-helium nutations revealed additional Rabi oscillations assigned to transitions within higher-multiplicity states of finite-sized chain fragments.

19.
J Am Chem Soc ; 132(16): 5638-51, 2010 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-20359227

RESUMO

In this work, we report the synthesis and the electronic properties of the unique highly conjugated molecular wires trans-[Cl-(dppe)(2)Ru=C=C=(Ph)C-CH=(CH(3))C-C[triple bond]C-(X)(2)Ru-C=C-C(CH(3))=CH-C(Ph)=C=C=Ru(dppe)(2)Cl](n+) (n = 2, X = dppe ([3a](OTf)(2)) and dppm ([3b](OTf)(2)) with three similar metal centers spanned by two odd-numbered unsaturated C(7) chains providing a 28 A long conjugated path and displaying five well-separated redox states (n = 0-4). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV-vis-NIR-IR spectroelectrochemistry. The electronic and physical properties of the different states were further rationalized with the help of DFT-based calculations. Upon one-electron reduction (n = 1), the single electron is delocalized over the two carbon chains through the central metal atom to an extent driven by the rotations within and between the chains. The second reduction (n = 0) involves the whole carbon-rich conjugated path of the molecule in a spin polarized scheme: one electron is delocalized over each chain, and the two electrons are antiferromagnetically coupled with a coupling on the order of kT. Interestingly, oxidation processes strongly involve both the metal atoms and the bridging ligands. The combined investigations reveal that the mono-oxidized system (n = 3) presents a spin density uniformly distributed between the metal atoms and the carbon atoms of the chains, whereas in the second oxidation state (n = 4) the compounds show a strong antiferromagnetic coupling on the order of 4 kT between the two single electrons localized in two distinct delocalized spin orbitals implying all the carbon atoms of the bridges and the three metal atoms. Thus, for the first time, electronic communication was fully evidenced and tuned in homonuclear trimetallic oligomeric carbon-rich systems in either an oxidation or a reduction process.

20.
RSC Adv ; 10(63): 38233-38243, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-35517541

RESUMO

Mesoporous TiO2 films with enhanced photocatalytic activity in both UV and visible wavelength ranges were developed through a non-conventional atomic layer deposition (ALD) process at room temperature. Deposition at such a low temperature promotes the accumulation of by-products in the amorphous TiO2 films, caused by the incomplete hydrolysis of the TiCl4 precursor. The additional thermal annealing induces the fast recrystallisation of amorphous films, as well as an in situ acidic treatment of TiO2. The interplay between the deposition parameters, such as purge time, the amount of structural defects introduced and the enhancement of the photocatalytic properties from different mesoporous films clearly shows that our easily upscalable non-conventional ALD process is of great industrial interest for environmental remediation and other photocatalytic applications, such as hydrogen production.

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