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1.
Inorg Chem ; 2021 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-34637309

RESUMO

The multistep synthesis of original antennas incorporating substituted [2.2]paracyclophane (pCp) moieties in the π-conjugated skeleton is described. These antennas, functionalized with an electron donor alkoxy fragment (A1) or with a fused coumarin derivative (A2), are incorporated in a triazacyclonane macrocyclic ligand L1 or L2, respectively, for the design of Eu(III), Yb(III), and Gd(III) complexes. A combined photophysical/theoretical study reveals that A1 presents a charge transfer character via through-space paracyclophane conjugation, whereas A2 presents only local excited states centered on the coumarin-paracyclophane moiety, strongly favoring triplet state population via intersystem crossing. The resulting complexes EuL1 and YbL2 are fully emissive in red and near-infrared, respectively, whereas the GdL2 complex acts as a photosensitizer for the generation of singlet oxygen.

2.
Nanoscale ; 13(32): 13795-13808, 2021 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-34477654

RESUMO

Light-activated functional materials capable of remote control over duplex and G-quadruplex (G4) nucleic acids formation at the cellular level are still very rare. Herein, we report on the photoinduced macrocyclisation of a helicenoid quinoline derivative of binaphthol that selectively provides easy access to an unprecedented class of extended heteroaromatic structures with remarkable photophysical and DNA/RNA binding properties. Thus, while the native bisquinoline precursor shows no DNA binding activity, the new in situ photochemically generated probe features high association constants to DNA and RNA G4s. The latter inhibits DNA synthesis by selectively stabilizing G4 structures associated with oncogenic promoters and telomere repeat units. Finally, the light sensitive compound is capable of in cellulo photoconversion, localizes primarily in the G4-rich sites of cancer cells, competes with a well-known G4 binder and shows a clear nuclear co-localization with the quadruplex specific antibody BG4. This work provides a benchmark for the future design and development of a brand-new generation of light-activated target-selective G4-binders.


Assuntos
Corantes Fluorescentes , Quadruplex G , DNA , Ligantes , Telômero
3.
ACS Appl Mater Interfaces ; 13(30): 36465-36474, 2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34309377

RESUMO

Two-dimensional (2D) van der Waals (vdW) heterostructures currently have attracted much attention in widespread research fields where semiconductor materials are key. With the aim of gaining insights into photocatalytic materials, we use density functional theory (DFT) calculations within the HSE06 functional to analyze the evolution of optoelectronic properties and high-frequency dielectric constant profiles of various 2D MoO3-xSx/MoS2 heterostructures modified by chemical and physical approaches. Although the MoO3/MoS2 heterostructure is a type III heterojunction associated with a metallic character, we found that exchanging the terminal oxo atoms of the MoO3-xSx single layer (SL) with sulfur enables shifting its CB position above the VB position of the MoS2 SL. This trend gives rise to a type II heterojunction where the band gap and charge transfer within the two layers are driven continuously by the S concentration in the MoO3-xSx SL. This fine-tuning leads to a versatile type II heterostructure proposed to provide a direct Z-scheme system valuable for photocatalytic water splitting.

4.
J Phys Chem B ; 125(30): 8572-8580, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34291941

RESUMO

Singlet-triplet interconversions (intersystem crossing, ISC) in organic molecules are at the basis of many important processes in cutting-edge photonic applications (organic light-emitting devices, photodynamic therapy, etc.). Selection rules for these transitions are mainly governed by the spin-orbit coupling (SOC) phenomenon. Although the SOC relies on complex relativistic phenomena, theoreticians have, with time, developed increasingly sophisticated and efficient approaches to gain access to a satisfactory evaluation of its magnitude. However, recent works have highlighted the remarkable and somehow unexpected efficiency of dimers of small conjugated molecules in terms of ISC quantum yields, whose origin has not been completely investigated. In this work, we bring a coupled experimental and theoretical analysis of the origin of the unusually large ISC efficiency on a series of such dimers that differ by their nature (covalent or supramolecular). We show that considering the dynamical nature of the SOC, and especially its dependence on angular orientations between the dimer subunits sometimes overlooked in the literature, it is necessary to rationalize some counterintuitive experimental observations. This combined experimental and theoretical work paves the way for new molecular engineering rules for SOC control.


Assuntos
Fotoquimioterapia , Dimerização
5.
Nat Commun ; 12(1): 3485, 2021 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-34108487

RESUMO

When periodically packing the intramolecular donor-acceptor structures to form ferroelectric-like lattice identified by second harmonic generation, our CD49 molecular crystal shows long-wavelength persistent photoluminescence peaked at 542 nm with the lifetime of 0.43 s, in addition to the short-wavelength prompt photoluminescence peaked at 363 nm with the lifetime of 0.45 ns. Interestingly, the long-wavelength persistent photoluminescence demonstrates magnetic field effects, showing as crystalline intermolecular charge-transfer excitons with singlet spin characteristics formed within ferroelectric-like lattice based on internal minority/majority carrier-balancing mechanism activated by isomer doping effects towards increasing electron-hole pairing probability. Our photoinduced Raman spectroscopy reveals the unusual slow relaxation of photoexcited lattice vibrations, indicating slow phonon effects occurring in ferroelectric-like lattice. Here, we show that crystalline intermolecular charge-transfer excitons are interacted with ferroelectric-like lattice, leading to exciton-lattice coupling within periodically packed intramolecular donor-acceptor structures to evolve ultralong-lived crystalline light-emitting states through slow phonon effects in ferroelectric light-emitting organic crystal.

6.
J Org Chem ; 86(8): 5901-5907, 2021 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-33793231

RESUMO

The pallado-catalyzed cyanation of benzothioxanthene imide (BTXI) derivatives is explored herein. Once optimized on the monobromo BTXI, mild reaction conditions were successfully applied to the dibromo derivative affording two regioisomers that have been isolated and structurally solved. Additional hydrogen-deuterium exchange experiments were carried out to support a proposed mechanism involving the formation of a five-membered palladacycle intermediate in the bay area. As well as impacting the structural, photo physical and electrochemical properties of the BTXI core, nitrile moieties were successfully used as orthogonal protecting groups, thus opening doors to new design principles.


Assuntos
Nitrilas , Paládio , Catálise , Hidrogênio
7.
Phys Chem Chem Phys ; 23(4): 2853-2859, 2021 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-33470995

RESUMO

Graphitic carbon nitrides (g-CNs) have become popular light absorbers in photocatalytic water splitting cells. Early theoretical work on these structures focused on fully polymerized g-C3N4. Experimentally, it is known that the typically employed melamine polycondensation does not go toward completion, yielding structures with ∼15 at% hydrogen. Here, we study the conformational stability of "melon", with the [C6N9H3]n structural formula using DFT. Referencing to a 2D melon sheet, B3LYP-dDsC and PBE-MBD computations revealed the same qualitative trend in stability of the 3D structures, with several of them within 5 kJ mol-1 per tecton. Fina's orthorhombic melon is the most stable of the studied conformers, with Lotsch' monoclinic melon taking an intermediate value. Invoking a simple Wannier-Mott-type approach, Fina's and Lotsch' structures exhibited the lowest optical gaps (2.8 eV), within the error margin of the experimental value (2.7 eV). All conformers yielded gaps below that of the monolayer's (3.2 eV), suggesting Jelley-type ("J") aggregation effects.

8.
Angew Chem Int Ed Engl ; 60(5): 2446-2454, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33089921

RESUMO

Long-lived room temperature phosphorescence from organic molecular crystals attracts great attention. Persistent luminescence depends on the electronic properties of the molecular components, mainly π-conjugated donor-acceptor (D-A) chromophores, and their molecular packing. Here, a strategy is developed by designing two isomeric molecular phosphors incorporating and combining a bridge for σ-conjugation between the D and A units and a structure-directing unit for H-bond-directed supramolecular self-assembly. Calculations highlight the critical role played by the two degrees of freedom of the σ-conjugated bridge on the chromophore optical properties. The molecular crystals exhibit RTP quantum yields up to 20 % and lifetimes up to 520 ms. The crystal structures of the efficient phosphorescent materials establish the existence of an unprecedented well-organization of the emitters into 2D rectangular columnar-like supramolecular structure stabilized by intermolecular H-bonding.

9.
ACS Appl Mater Interfaces ; 12(49): 55157-55168, 2020 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-33217234

RESUMO

This paper aims at designing chromophores with efficient aggregation-induced emission (AIE) properties for two-photon fluorescence microscopy (2PFM), which is one of the best-suited types of microscopy for the imaging of living organisms or thick biological tissues. Tetraphenylethylene (TPE) derivatives are common building blocks in the design of chromophores with efficient AIE properties. Therefore, in this study, extended TPE AIEgens specifically optimized for two-photon absorption (2PA) are synthesized and the resulting (E/Z) isomers are separated using chromatography on chiral supports. Comparative characterization of the AIE properties is performed on the pure (Z) and (E) isomers and the mixture, allowing us, in combination with powder X-ray diffraction and solid-state NMR, to document a profound impact of crystallinity on solid-state fluorescence properties. In particular, we show that stereopure AIEgens form aggregates of superior crystallinity, which in turn exhibit a higher fluorescence quantum yield compared to diastereoisomers mixtures. Preparation of stereopure organic nanoparticles affords very bright fluorescent contrast agents, which are then used for cellular and intravital two-photon microscopy on human breast cancer cells and on zebrafish embryos.


Assuntos
Compostos de Anilina/química , Meios de Contraste/química , Imagem Óptica/métodos , Estilbenos/química , Animais , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Embrião não Mamífero/anatomia & histologia , Feminino , Corantes Fluorescentes/química , Humanos , Isomerismo , Células MCF-7 , Microscopia de Fluorescência por Excitação Multifotônica , Nanopartículas/química , Peixe-Zebra/crescimento & desenvolvimento
10.
Phys Chem Chem Phys ; 22(22): 12373-12381, 2020 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-32309827

RESUMO

In spite of their remarkable luminescence properties, benzothioxanthene imide (BTXI, an imide containing rylene chromophores) derivatives have been largely overlooked compared to their perylene bisimide and naphthalene bisimide counterparts. Thus, their detailed photophysics are much less understood. In this paper, we show how relatively simple structural modifications of the backbone of BTXIs can lead to impressive variations in their inter-system crossing kinetics. Thus, through rational engineering of their structure, it is possible to obtain a triplet formation quantum yield that reaches unity, making BTXI a promising class of compounds for triplet-based applications (photodynamic therapy, electroluminescence, etc.).

11.
Phys Chem Chem Phys ; 22(13): 7031-7038, 2020 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-32195492

RESUMO

We uncover the existence of several competitive mechanisms of water oxidation on the ß-CoOOH (10-14) surface by going beyond the classical 4-step mechanism frequently used to study this reaction at the DFT level. Our results demonstrate the importance of two-site reactivity and of purely chemical steps with the associated activation energies. Taking the electrochemical potential explicitly into account leads to modifications of the reaction energy profiles finally leading to the proposition of a new family of mechanisms involving tetraoxidane intermediates. The two-site mechanisms revealed in this work are of key importance to rationalize and predict the impact of dopants in the design of future catalysts.

12.
Chemistry ; 25(38): 9026-9034, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-30972809

RESUMO

Two trispicolinate 1,4,7-triazacyclonane (TACN)-based ligands bearing three picolinate biphotonic antennae were synthetized and their Yb3+ and Gd3+ complexes isolated. One series differs from the other by the absence (L1 )/presence (L2 ) of bromine atoms on the antenna backbone, offering respectively improved optical and singlet-oxygen generation properties. Photophysical properties of the ligands, complexes and micellar Pluronic suspensions were investigated. Complexes exhibit high two-photon absorption cross-section combined either with NIR emission (Yb) or excellent 1 O2 generation (Gd). The very large intersystem crossing efficiency induced by the combination of bromine atom and heavy rare-earth element was corroborated with theoretical calculations. The 1 O2 generation properties of L2 Gd micellar suspension under two-photon activation leads to tumour cell death, suggesting the potential of such structures for theranostic applications.

13.
Phys Chem Chem Phys ; 19(19): 12321-12330, 2017 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-28453012

RESUMO

The investigation of the BiCuOCh (Ch = S, Se and Te) semiconductor family for thermoelectric or photovoltaic materials is a topic of increasing research interest. These materials can also be considered for photochemical water splitting if one representative having a bandgap, Eg, at around 2 eV can be developed. With this aim, we simulated the solid solutions Bi1-xRExCuOS (RE = Y, La, Gd and Lu) from pure BiCuOS (Eg ∼ 1.1 eV) to pure RECuOS compositions (Eg ∼ 2.9 eV) by DFT calculations based on the HSE06 range-separated hybrid functional with the inclusion of spin-orbit coupling. Starting from the thermodynamic stability of the solid solution, several properties were computed for each system including bandgaps, dielectric constants, effective masses and exciton binding energies. We discussed the variation of these properties based on the relative organization of Bi and RE atoms in their common sublattice to offer a physical understanding of the influence of the RE doping of BiCuOS. Some compositions were found to give appropriate properties for water splitting applications. Furthermore, we found that at low RE fractions the transport properties of BiCuOS are improved that can find applications beyond water splitting.

14.
Inorg Chem ; 56(1): 414-423, 2017 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-27977170

RESUMO

S-doped sodalite minerals of the Na8Al6Si6O24(Cl,S)2 formula, also known as hackmanites, are computationally investigated for the first time, in order to understand their photochromic properties. With combined periodic boundary conditions and embedded cluster-type approaches, this paper brings a theoretical overview of the photochromism mechanism, also called tenebrescence in geology. Time-dependent density functional theory (TD-DFT) calculations of sodalite systems containing electrons trapped in Cl vacancies showed an absorption spectrum and a simulated color in agreement with experiment. This modeling highlights the huge effect of the F center's environment such as the direct contribution of the ß cage on the trapped electron and a strong vibronic coupling of the absorption spectrum. TD-DFT and post-Hartree-Fock (SAC-CI) calculations were also operated on S22--containing systems in order to determine the exact mechanism of coloration and discoloration, supporting that the key step is a direct through-space charge transfer between the S22- ion and a Cl vacancy. The geometry modification induced by this charge transfer leads to a large electronic reorganization stabilizing the F center, thus explaining the high stability of the colored state of the mineral.

15.
Inorg Chem ; 55(19): 9586-9595, 2016 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-27618579

RESUMO

A tris-cyclometalated iridium complex that bears two ligands functionalized by peripheral carbazole groups combines an intense solid state emission and a significant two-photon absorption cross section in the near-infrared. After incorporation into a physiological micellar suspension, it can be used for the intravital two-photon fluorescence microscopy of cerebral vasculature.


Assuntos
Carbazóis/química , Complexos de Coordenação/química , Corantes Fluorescentes/química , Irídio/efeitos da radiação , Animais , Encéfalo/irrigação sanguínea , Encéfalo/diagnóstico por imagem , Carbazóis/síntese química , Complexos de Coordenação/síntese química , Fluorescência , Corantes Fluorescentes/síntese química , Raios Infravermelhos , Microscopia Intravital , Irídio/química , Camundongos , Fótons
16.
J Phys Chem Lett ; 6(3): 395-400, 2015 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-26261954

RESUMO

Metallocene (MCp2) wires have recently attracted considerable interest in relation to molecular spintronics due to predictions concerning their half-metallic nature. This exciting prospect is however hampered by the little and often-contradictory knowledge we have concerning the metallocene self-assembly and interaction with a metal. Here, we elucidate these aspects by focusing on the adsorption of ferrocene on Cu(111) and Cu(100). Combining low-temperature scanning tunneling microscopy and density functional theory calculations, we demonstrate that the two-dimensional molecular arrangement consists of vertical- and horizontal-lying molecules. The noncovalent T-shaped interactions between Cp rings of vertical and horizontal molecules are essential for the stability of the physisorbed molecular layer. These results provide a fresh insight into ferrocene adsorption on surfaces and may serve as an archetypal reference for future work with this important variety of organometallic molecules.

17.
Phys Chem Chem Phys ; 17(3): 2199-209, 2015 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-25483273

RESUMO

Since the discovery of their excellent performance as the light-absorbing semiconducting component in photovoltaic cells, the PbX3CH3NH3 (X = I, Br, Cl) perovskites have received renewed attention. The five polymorphs stable above 200 K - the tetragonal phases for X = I, Br, Cl and the cubic phases for X = I, Br - were studied using periodic DFT calculations involving hybrid functionals (PBE0 and HSE), employing Gaussian-type orbitals as well as plane waves and including relativistic effects (spin-orbit coupling). The influence of the halogen substitution and of the crystal phase on these properties is analysed by comparing the properties obtained in this study to the experimental ones and to the theoretical ones computed using other methods. We show that an accurate treatment of these systems requires the description of dispersion forces and spin-orbit coupling. The different time scales for the electronic and vibrational components of the polarizability inspire the hypothesis that several interfacial charge transfer mechanisms are encountered in the working principle of the photovoltaic devices involving these perovskite materials. The heavy elements in the structure (Pb, I) play a major role in the high polarizability and the low effective charge carrier masses and hence in the low exciton binding energies and the high charge mobility. This systematic work on the PbX3CH3NH3 family offers to theoreticians an overview of the landscape of quantum chemical methods to enable a reasonable choice of methodology for studying these systems.

18.
Phys Chem Chem Phys ; 16(28): 14435-44, 2014 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-24499921

RESUMO

Transition metal complexes, typically Ru-based complexes, are the most efficient dyes used in dye-sensitized solar cells. The absorption spectra of these molecules generally involve numerous electronic transitions, which are not equivalent for the conversion of the light into electricity. In the present manuscript, an analysis of each electronic transition of selected inorganic complexes is performed based on the variation of the electronic density upon light absorption. To this end, a series of indices recently proposed in the literature is applied. The main conclusions of this work are twofold: from a methodological point of view, global hybrid functionals confirm their robustness for studying the electronic transitions of these compounds and from an application oriented point of view it is clear that the most intense transitions are not necessarily the most efficient ones for the light conversion.

19.
J Phys Chem Lett ; 4(6): 1044-50, 2013 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-26291375

RESUMO

Density functional theory (DFT) and time-dependent DFT are useful computational approaches frequently used in the dye-sensitized solar cell (DSSC) community in order to analyze experimental results and to clarify the elementary processes involved in the working principles of these devices. Indeed, despite these significant contributions, these methods can provide insights that go well beyond a purely descriptive aim, especially when suitable computational approaches and methodologies for interpreting and validating the computational outcomes are developed. In the present contribution, the possibility of using recently developed computational approaches to design and interpret the macroscopic behavior of DSSCs is exemplified by the study of the performances of three new TiO2-based DSSCs making use of organic dyes, all belonging to the expanded pyridinium family.

20.
Acc Chem Res ; 45(8): 1268-77, 2012 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-22497694

RESUMO

Since dye-sensitized solar cells (DSSCs) appeared as a promising inexpensive alternative to the traditional silicon-based solar cells, DSSCs have attracted a considerable amount of experimental and theoretical interest. In contrast with silicon-based solar cells, DSSCs use different components for the light-harvesting and transport functions, which allow researchers to fine-tune each material and, under ideal conditions, to optimize their overall performance in assembled devices. Because of the variety of elementary components present in these cells and their multiple possible combinations, this task presents experimental challenges. The photoconversion efficiencies obtained up to this point are still low, despite the significant experimental efforts spent in their optimization. The development of a low-cost and efficient computational protocol that could qualitatively (or even quantitatively) identify the promising semiconductors, dyes, and electrolytes, as well as their assembly, could save substantial experimental time and resources. In this Account, we describe our computational approach that allows us to understand and predict the different elementary mechanisms involved in DSSC working principles. We use this computational framework to propose an in silico route for the ab initio design of these materials. Our approach relies on a unique density functional theory (DFT) based model, which allows for an accurate and balanced treatment of electronic and spectroscopic properties in different phases (such as gas, solution, or interfaces) and avoids or minimizes spurious computational effects. Using this tool, we reproduced and predicted the properties of the isolated components of the DSSC assemblies. We accessed the microscopic measurable characteristics of the cells such as the short circuit current (J(sc)) or the open circuit voltage (V(oc)), which define the overall photoconversion efficiency of the cell. The absence of empirical or material-related parameters in our approach should allow for its wide application to the optimization of existing devices or the design of new ones.

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