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1.
Angew Chem Int Ed Engl ; 63(12): e202318297, 2024 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-38270341

RESUMO

Two BODIPYs and two boron ß-diketonates were threaded through a macrocycle bearing a 2,2'-biphenol unit, showing thus the ability of boron to act as a gathering atom. The new threaded species were characterized by 1D and 2D NMR spectroscopy as well as by X-ray crystallography for one of them and their properties rationalized with quantum chemistry to unravel the vibronic contributions. The BODIPYs exhibited interesting fluorescence features with quantum yields up to 91 % and enhanced photostability compared to their non-threaded homologues. A rotaxane was synthesized using this threading strategy after stoppering and removing the boron with potassium hydroxide.

2.
Chemistry ; 29(44): e202300584, 2023 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-37218616

RESUMO

Benzene-1,2,4,5-tetrathiolate (btt) has been used as a bridging ligand to prepare a redox active (molybdenocene dithiolene)-based bimetallic complex Cp2 Mo(btt)MoCp2 , which exhibits four successive electron transfers up to the tetracation. Spectro-electrochemical investigations together with DFT and TD-DFT calculations evidence that the two electroactive MoS2 C2 metallacycles are electronically coupled in the monocationic as in the dicationic state. Two salts of the dication [Cp2 Mo(btt)MoCp2 ]2+ have been structurally characterized with PF6 - and HSO4 - counterions, showing different chair or boat conformations associated with variable folding angles of the two MoS2 C2 metallacycles along the S-S hinge. The bis-oxidized dicationic complex exhibits a diradical character, with both radicals essentially localized on the metallacycles and with antiferromagnetic coupling evidenced from magnetic susceptibility measurements.

3.
Inorg Chem ; 62(13): 5067-5080, 2023 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-36541863

RESUMO

Aza-boron-dipyrromethenes (Aza-BODIPYs) are an increasingly studied class of fluorophores. They can be seen as an azadipyrromethene ("aza-DIPY") ligand rigidified by a metalloid, a boron atom. Based on this idea, a series of complexes of group 13 metals (aluminum and gallium) have been synthesized and characterized. The impact of the metal and of the nature of the substituents of aza-DIPY core were investigated. The photophysical and electrochemical properties were determined, and an X-ray structure of an azaGaDIPY was obtained. These data reveal that azaGaDIPY and azaAlDIPY exhibit significant red-shifted fluorescence compared to their analogue aza-BODIPY. Their emission can go up to 800 nm for the maximum emission length and up to NIR-II for the emission tail. This, associated with their electrochemical stability (no metal release whether oxidized or reduced) makes them a promising class of fluorophores for optical medical imaging. Moreover, X-ray structure and molecular modeling studies have shown that this redshift seems to be more due to the geometry around the boron/metal than to the nature of the metal.

4.
Phys Chem Chem Phys ; 25(47): 32699-32708, 2023 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-38014523

RESUMO

Styrylpyrimidines with bulky 9,9-dimethylacridan, phenoxazine and phenothiazine electron-donating fragments were designed. Thermally activated delayed fluorescence (TADF) properties were expected for these structures. These chromophores exhibit peculiar emission properties. For 9,9-dimethylacridan and phenoxazine derivatives, a single emission highly sensitive to the polarity is observed in solution whereas for phenothiazine derivative a dual emission is observed in solution and is attributed to the coexistence of quasi-axial (Qax) and quasi-equatorial (Qeq) conformers. This study intends to understand through theoretical and experimental works, why the studied chromophores do not exhibit TADF properties, contrary to what was expected. The absence of phosphorescence both at room temperature and 77 K tends to indicate the impossibility to harvest triplet states in these systems. Wave-function based calculations show that for both conformers of the three chromophores the S1-T1 splitting is significantly larger than 0.2 eV. The second triplet state T2 of Qeq conformers is found very close in energy to the singlet S1 state, but S1 and T2 states possess similar charge transfer characters. This prevents efficient spin-orbit coupling between the states, which is consistent with the absence of TADF.

5.
J Chem Phys ; 158(7): 074303, 2023 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-36813718

RESUMO

Photochromic molecules are widely studied and developed for their many potential applications. To optimize the required properties through theoretical models, a considerable chemical space is to be explored, and their environment in devices is to be accounted for.. To this end, cheap and reliable computational methods can be powerful tools to steer synthetic developments. As ab initio methods remain costly for extensive studies (in terms of the size of the system and/or number of molecules), semiempirical methods such as density functional tight-binding (TB) could offer a good compromise between accuracy computational cost. However, these approaches necessitate benchmarking on the families of compounds of interest. Thus, the aim of the present study is to evaluate the accuracy of several key features calculated with TB methods (DFTB2, DFTB3, GFN2-xTB, and LC-DFTB2) for three sets of photochromic organic molecules: azobenzene (AZO), norbornadiene/quadricyclane (NBD/QC), and dithienylethene (DTE) derivatives. The features considered here are the optimized geometries, the difference in energy between the two isomers (ΔE), and of the energies of the first relevant excited states. All the TB results are compared to those obtained with DFT methods and state-of-the-art electronic structure calculation methods: DLPNO-CCSD(T) for ground states and DLPNO-STEOM-CCSD for excited states. Our results show that, overall, DFTB3 is the TB method leading to the best results for the geometries and the ΔE values and can be used alone for these purposes for NBD/QC and DTE derivatives. Single point calculations at the r2SCAN-3c level using TB geometries allow circumventing the deficiencies of the TB methods in the AZO series. For electronic transition calculations, the range separated LC-DFTB2 method is the most accurate TB method tested for AZO and NBD/QC derivatives, in close agreement with the reference.

6.
Angew Chem Int Ed Engl ; 62(49): e202313696, 2023 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-37871290

RESUMO

We here present how rebalancing the interplay between H-bonds and dispersive forces (Van der Waals/π-π stacking) may induce or not the generation of kinetic metastable states. In particular, we show that extending the aromatic content and favouring the interchain VdW interactions causes a delay into the cooperative supramolecular polymerization of a new family of toluene bis-amide derivatives by trapping the metastable inactive state.

7.
Angew Chem Int Ed Engl ; 61(6): e202113844, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34813138

RESUMO

By their conformational flexibility, Möbius aromatic hexaphyrins provide a dynamic chirality attractive to develop stimuli responsive systems such as chiroptical switches. A regular [28]hexaphyrin has been equipped with a chiral coordinating arm to achieve transfer of chirality from a fix stereogenic element to the dynamic Möbius one. The arm allows straightforward formation of labile monometallic ZnII complexes with an exogenous ligand, either a carboxylato or an amino with opposite inwards/outwards orientations relative to the Möbius ring. As a corollary, the chiral coordinating arm is constrained over the ring or laterally, inducing opposite P and M Möbius configurations with unprecedented high stereoselectivity (diast. excess greater than 95 %). By tuning the transfer of chirality, these achiral effectors generate electronic circular dichroism spectra with bisignate Cotton effect of opposite signs. Switching between distinct chiroptical states was ultimately achieved in mild conditions owing to ligand exchange, with high robustness (10 cycles).

8.
Chemistry ; 26(36): 8153-8161, 2020 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-32141634

RESUMO

The photophysical properties of a series of conjugated push-pull (iso)quinolines were studied. The compounds were synthesized by well-established and straightforward methodologies. The materials exhibited not only emission solvatochromism in a variety of nonpolar solvents, but also tunable halochromism. Some of the compounds remained moderately luminescent after protonation and had a red emissive form, which was used to obtain white-light emission, both in solution and in thin films, by controlled protonation of the initially blue-green-emitting materials. This methodology has potential applications in the fabrication of white organic light-emitting diodes with two forms of a single emitter in equilibrium.

9.
Phys Chem Chem Phys ; 22(7): 4165-4176, 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32040113

RESUMO

This contribution aims at investigating the branching effect on the steady state, time resolved fluorescence and two-photon absorption (2PA) properties of dimethylamino and diphenylamino substituted styrylpyrimidine derivatives, by means of a combined experimental and theoretical study. In contrast to classical branched molecules with a triphenylamine central core and electron accepting groups at the periphery, here, branched molecules with reverse topology and different symmetries are examined, namely a styrylpyrimidine group is used as the electron withdrawing core and dimethylamino or diphenylamino donors are incorporated at the periphery. Besides, compared to the great majority of existing branched systems, the herein studied molecules do not have C3 symmetry. For this reason, the region of the linear and non-linear optical spectra of the two and three branched chromophores is actually similar. Interestingly, while the one-photon absorption spectra of one-branched systems versus two- or three-branched ones are spectrally shifted, there is almost no spectral shift in the main 2PA spectral region. Meanwhile, there is still an enhancement of both linear and nonlinear optical responses. Overall, here we developed a strategy that enhances the 2PA response while maintaining the spectral position. Specifically, 2PA cross section values as high as 500 GM have been obtained for the diphenylamino A-(π-D)3 molecule in dichloromethane.

10.
Phys Chem Chem Phys ; 19(3): 2044-2052, 2017 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-28009859

RESUMO

Dithienylethenes (DTEs) can be assembled to form supramolecular multiphotochromic systems that are highly functional molecular architectures of potential interest for building complex optoelectronic devices. Yet even simple DTE dimers relying on an organic linker may suffer from a partial photoactivity, i.e., only one of the two switches does isomerise. Experimentally, this limited photochromism has been attributed to an excited state energy transfer (EET) between the two DTEs of the multimer; this EET taking place instead of the desired photoinduced cyclisation of the DTE. However, no clear evidences of this phenomenon have been provided so far. In this work we propose the first rationalisation of this potential parasite photoinduced event using a computational approach based on Time-Dependent Density Functional Theory (TD-DFT) for the calculation of the electronic coupling in DTE dimers. Besides quantifying EET in several systems, we dissect the role of through-bond and through-space mechanisms on this process and clarify their dependence on both the nature and length of the bridge separating the two photochromes. The theoretical data obtained in this framework are in full agreement with the experimental outcomes and pave the way toward a molecular design of coupled, yet fully functionals, DTE-based multiswitches.

11.
Phys Chem Chem Phys ; 18(14): 9358-66, 2016 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-26514279

RESUMO

We investigate with a hybrid SOS-CIS(D)/TD-DFT approach accounting for solvation effects, the structural, electronic and optical properties of recently-proposed PODIPY dyes. Being more soluble in water than the well-known BODIPYs, these new chromogens are particularly appealing, but their characterization remains very limited. It turns out that the selected theoretical protocol could reproduce the experimentally reported differences between PODIPY and BODIPY dyes. Based on this, we have investigated a large number of new PODIPY dyes and determined their theoretical 0-0 energies.

12.
Chem Soc Rev ; 44(11): 3719-59, 2015 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-25921433

RESUMO

Molecular systems encompassing more than one photochromic entity can be used to build highly functional materials, thanks to their potential multi-addressability and/or multi-response properties. Over the last decade, the synthesis and spectroscopic and kinetic characterisation as well as the modeling of a wide range of multiphotochromes have been achieved in a field that is emerging as a distinct branch of photochemistry. In this review, we provide an overview of the available multiphotochromic compounds which use a variety of photoactive building blocks, e.g., diarylethene, azobenzene, spiropyran, naphthopyran or fulgimide derivatives. Their efficiency in terms of multi-responsiveness is discussed and several strategies to circumvent the most common limitation (i.e., the loss of photochromism of one part) are described.

13.
J Comput Chem ; 36(27): 2075-87, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-26280464

RESUMO

We present a parametrization of a self-consistent charge density functional-based tight-binding scheme (SCC-DFTB) to describe gold-organic hybrid systems by adding new Au-X (X = Au, H, C, S, N, O) parameters to a previous set designed for organic molecules. With the aim of describing gold-thiolates systems within the DFTB framework, the resulting parameters are successively compared with density functional theory (DFT) data for the description of Au bulk, Aun gold clusters (n = 2, 4, 8, 20), and Aun SCH3 (n = 3 and 25) molecular-sized models. The geometrical, energetic, and electronic parameters obtained at the SCC-DFTB level for the small Au3 SCH3 gold-thiolate compound compare very well with DFT results, and prove that the different binding situations of the sulfur atom on gold are correctly described with the current parameters. For a larger gold-thiolate model, Au25 SCH3 , the electronic density of states and the potential energy surfaces resulting from the chemisorption of the molecule on the gold aggregate obtained with the new SCC-DFTB parameters are also in good agreement with DFT results.

14.
Phys Chem Chem Phys ; 16(47): 26240-51, 2014 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-25363237

RESUMO

With the help of a computational scheme combining molecular dynamics, DFT and TD-DFT methods, the conformational, electronic and optical properties of a new class of hybrid compounds where a photochromic molecule belonging to the dithienylethene family (DTE) is covalently linked to a Au25 nanocluster (gold nanocluster or GNC) are investigated. We compare two types of hybrid GNC-DTE systems where the aromatic linker between the metallic and the DTE moieties is either a phenyl or a thiophene ring. By examining the perturbation of the DTE electronic structure after grafting upon the GNC, we show that the hybrid system with a phenyl linker should preserve its photochromic activity. For the latter system, we have then studied the possible energy and electron transfer between the GNC and the DTE units. The energy transfer between the two moieties can be a priori discarded while a uni-directional electron transfer should take place from the GNC to the excited DTE. We show that this transfer can be controlled by switching the state of the molecule.

15.
J Phys Chem A ; 118(26): 4695-706, 2014 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-24912128

RESUMO

We present a theoretical study of Aun-dithienylethene hybrid systems (n = 3, 19, 25), where the organic molecule is covalently linked to a nanometer-scaled gold nanoparticle (NP). We aim at gaining insights on the optical properties of such photochromic devices and proposing a size-limited gold aggregate model able to recover the optical properties of the experimental system. We thus present a DFT-based calculation scheme to model the ground-state (conformation, energetic parameters) and excited-state properties (UV-visible absorption spectra) of this type of hybrid systems. Within this framework, the structural parameters (adsorption site, orientation, and internal structure of the photochrome) are found to be slightly dependent on the size/shape of the gold aggregate. The influence of the gold fragment on the optical properties of the resulting hybrid system is then discussed with the help of TD-DFT combined with an analysis of the virtual orbitals involved in the photochromic transitions. We show that, for the open hybrid isomer, the number of gold atoms is the key parameter to recover the photoactive properties that are experimentally observed. On the contrary, for hybrid closed systems, the three-dimensional structure of the metallic aggregate is of high impact. We thus conclude that Au25 corresponds to the most appropriate fragment to model nanometer-sized NP-DTE hybrid device.

16.
Dalton Trans ; 53(23): 9763-9776, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38780397

RESUMO

The synthesis and characterization of two bis(dithiolene) proligands involving heteroatomic linkers such as 1,4-dithiine and dihydro-1,4-disiline between the two protected dithiolene moieties are described. Two bimetallic complexes involving these heteroatomic bridges between two redox active bis(cyclopentadienyl)molybdenum dithiolene moieties have been synthesized and characterized by electrochemistry, spectroelectrochemistry, and their properties rationalized with (TD-)DFT. Cyclic voltammetry experiments show sequential oxidation of the two redox centers with ΔE values between successive one-electron transfers varying according to the nature of the bridge. Depending on the nature of the heteroatomic bridge, the bis-oxidized complexes exhibit either a diradical character with both radicals essentially localized on the metallacycles, or a closed-shell dicationic state.

17.
Chemistry ; 19(39): 13160-7, 2013 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-23939783

RESUMO

Electroactive fused ethylenedithio-tetrathiafulvalene-[4]helicene and -[6]helicenes have been synthesized through a strategy that involved the preparation of 2,3-dibromo-helicene derivatives as intermediates. The dihedral angles between the terminal helicenes, as determined by single-crystal X-ray analysis, are 22.7° and 50.7° for the [4]helicene and [6]helicene, respectively. Their solid-state architectures show interplay between S⋅⋅⋅S and π⋅⋅⋅π intermolecular interactions. The chiroptical properties of the enantiopure EDT-TTF-[6]helicene derivatives have been investigated and supported by TDDFT calculations. Remarkable redox switching of the circular dichroism (CD) signal between the neutral and radical-cation species has been achieved.

18.
Inorg Chem ; 51(15): 8545-56, 2012 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-22799619

RESUMO

The electroactive ligands (2,4-bis-tetrathiafulvalene[6-(dipyridin-2'-ylamino)]-1,3,5-triazine) TTF(2)-tz-dpa (1) and (2-tetrathiafulvalene[4,6-bis-(dipyridin-2'-ylamino)]-1,3,5-triazine) TTF-tz-dpa(2) (2) have been synthesized by palladium cross-coupling catalysis, and the single crystal X-ray structure for 1 was determined. In the solid state the TTF and triazine units are practically coplanar and short intermolecular S···S contacts are established. Two neutral and one tetracationic Zn(II) complexes, formulated as (TTF(2)-tz-dpa)ZnCl(2) (3), [ZnCl(2)(TTF-tz-dpa(2))Zn(H(2)O)Cl(2)] (4), and {[(H(2)O)(2)Zn(TTF-tz-dpa(2))](ClO(4))(2)}(2) (5) have been crystallized and analyzed by single crystal X-ray analysis. A peculiar feature is the evidence for anion-π interactions, as shown by the short Cl···triazine and O(perchlorate)···triazine distances of 3.52 and 3.00 Å, respectively. A complex set of intermolecular π···π, S···S, and hydrogen bonding interactions sustain the supramolecular organizations of the complexes in the solid state. Electronic absorption spectra provide evidence for the intramolecular charge transfer from TTF to triazine, also supported by time-dependent density functional theory (TD DFT) calculations.

19.
Nanoscale ; 13(14): 6786-6797, 2021 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-33690747

RESUMO

The electron flow between a metallic aggregate and an organic molecule after excitation with light is a crucial step on which hybrid photovoltaic nanomaterials are based. So far, designing such devices with the help of theoretical approaches has been heavily limited by the computational cost of quantum dynamics models able to track the evolution of the excited states over time. In this article, we present the first application of the time-dependent density functional tight-binding (TD-DFTB) method for an experimental nanometer-sized gold-organic system consisting of a hexyl-protected Au25 cluster labelled with a pyrene fluorophore, in which the fluorescence quenching of the pyrene is attributed to the electron transfer from the metallic cluster to the dye. The full quantum rationalization of the electron transfer is attained through quantum dynamics simulations, highlighting the crucial role of the protecting ligand shell in electron transfer, as well as the coupling with nuclear movement. This work paves the way towards the fast and accurate theoretical design of optoelectronic nanodevices.

20.
J Chem Theory Comput ; 15(11): 6267-6276, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31633913

RESUMO

We present a benchmark of the performances of the density functional tight-binding model (DFTB) and its time-dependent counterpart (TD-DFTB) in describing both the ground state (GS) and excited state (ES) geometries of a panel of 30 organic molecules. Thanks to high-level wave function reference calculations, we are able to quantitatively assess the strengths and weaknesses of four DFTB models, using either second- or third-order self-consistent charge procedures, as well as different sets of parameters. The performances of the different DFTB models are found to be largely dependent on the type of bond considered, but the global mean absolute error remains acceptable for such "cheap" calculations, as it slightly exceeds the one obtained with DFT (PBE and B3LYP) or CC2 models for the GS of the same set of compounds. When considering the ES of the molecules, the TD-DFTB errors are surprisingly not systematically larger than their GS counterparts. However, the trends, either when going from the GS to the ES or within a homologous chemical series, are less consistently reproduced with TD-DFTB than with the considered ab initio models. This work therefore validates the use of TD-DFTB for describing ES geometries while highlighting that care has to be applied when looking at subtle variations.

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