Роль семьи в процессе первичной социализации в отечественной и зарубежной литературе

A series of 5,15 push–pull <i>meso</i>-diarylzinc­(II) porphyrinates, carrying one or two −COOH or −COOCH₃ acceptor groups and a −OCH₃ or a −N­(CH₃)₂ donor group, show in <i>N</i>,<i>N</i>-dimethylformamide and CHCl₃ solutions a negative and solvent-dependent second-order nonlinear-optical (NLO) response measured by the electric-field-induced second-harmonic generation (EFISH) technique, different from the structurally related zinc­(II) porphyrinate carrying a −N­(CH₃)₂ donor group and a −NO₂ acceptor group, where a still solvent-dependent but positive EFISH second-order response was previously reported. Moreover, when a −N­(CH₃)₂ donor group and a −COOH acceptor group are part of a sterically hindered 2,12 push–pull β-pyrrolic-substituted tetraarylzinc­(II) porphyrinate, the EFISH response is positive and solvent-independent. In order to rationalize these rather intriguing series of observations, EFISH measurements have been integrated by electronic absorption and IR spectroscopic investigations and by density functional theory (DFT) and coupled-perturbed DFT theoretical and ¹H pulsed-gradient spin-echo NMR investigations, which prompt that the significant concentration effects and the strong influence of the solvent nature on the NLO response are originated by a complex whole of different aggregation processes induced by the −COOH group

Les calmars géants

8 páginas, 6 figurasPeer reviewe

Nonlinear-Optical Properties of α‑Diiminedithiolatonickel(II) Complexes Enhanced by Electron-Withdrawing Carboxyl Groups

We report the synthesis, characterization, nonlinear-optical (NLO) properties, and density functional theory (DFT) calculations for three nickel diiminedithiolate complexes [Ni­(4,4′-R₂carboxy-bpy)­(L)] [R = methyl, L = 1,2-benzenedithiolate (bdt), <b>1</b>; R = ethyl, L = 5,6-dihydro-1,4-dithine-2,3-dithiolate (dddt), <b>2</b>; R = ethyl, L = 1-(<i>N</i>-methylindol-5-yl)­ethene-1,2-dithiolate (mi-5edt), <b>3</b>]. The crystal structure of <b>1</b> shows a square-planar coordination for the nickel ion and bond distances consistent with a diiminedithiolate description for the complex. For all complexes, the cyclic voltammetry measurements show two reversible reduction processes (−1.353/–1.380 V and −0798/–0.830 V, respectively) and an anodic wave (+0.372/+0.601 V). The UV–vis spectra present a band around 600–700 nm (ε = 4880–6000 dm³ mol^–1 cm^–1) mainly attributed to a charge-transfer highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) transition, which shows a large negative solvatochromic shift, characteristic of push–pull complexes, and is responsible for the NLO properties of these molecules. The charge-transfer character of this electronic transition is confirmed by DFT calculations, with the HOMO mainly centered on the dithiolate moiety and the LUMO on the bpy ligand, with important contribution given by the carboxyl groups (≈13%). Small contributions from the nickel­(II) ion are present in both of the frontier orbitals. The carboxyl groups enhance the optical properties of this class of complexes, confirmed by comparison with the corresponding unsubstituted compounds. The second-order NLO properties have been measured by an electric-field-induced second-harmonic-generation technique using a 10^–3 M solution in <i>N</i>,<i>N</i>-dimethylformamide and working with a 1.907 μm incident wavelength, giving for μβ_1.907 (μβ₀) values of −1095 (−581), −2760 (−954), and −1650 (−618) × 10^–48 esu for <b>1</b>–<b>3</b>, respectively. These values are among the highest in the class of square-planar push–pull complexes, similar to those found for dithionedithiolate compounds. Moreover, spectroelectrochemical experiments demonstrate the possibility of using these complexes as redox-switchable NLO chromophores

Nonlinear-Optical Properties of α‑Diiminedithiolatonickel(II) Complexes Enhanced by Electron-Withdrawing Carboxyl Groups

We report the synthesis, characterization, nonlinear-optical (NLO) properties, and density functional theory (DFT) calculations for three nickel diiminedithiolate complexes [Ni­(4,4′-R₂carboxy-bpy)­(L)] [R = methyl, L = 1,2-benzenedithiolate (bdt), <b>1</b>; R = ethyl, L = 5,6-dihydro-1,4-dithine-2,3-dithiolate (dddt), <b>2</b>; R = ethyl, L = 1-(<i>N</i>-methylindol-5-yl)­ethene-1,2-dithiolate (mi-5edt), <b>3</b>]. The crystal structure of <b>1</b> shows a square-planar coordination for the nickel ion and bond distances consistent with a diiminedithiolate description for the complex. For all complexes, the cyclic voltammetry measurements show two reversible reduction processes (−1.353/–1.380 V and −0798/–0.830 V, respectively) and an anodic wave (+0.372/+0.601 V). The UV–vis spectra present a band around 600–700 nm (ε = 4880–6000 dm³ mol^–1 cm^–1) mainly attributed to a charge-transfer highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) transition, which shows a large negative solvatochromic shift, characteristic of push–pull complexes, and is responsible for the NLO properties of these molecules. The charge-transfer character of this electronic transition is confirmed by DFT calculations, with the HOMO mainly centered on the dithiolate moiety and the LUMO on the bpy ligand, with important contribution given by the carboxyl groups (≈13%). Small contributions from the nickel­(II) ion are present in both of the frontier orbitals. The carboxyl groups enhance the optical properties of this class of complexes, confirmed by comparison with the corresponding unsubstituted compounds. The second-order NLO properties have been measured by an electric-field-induced second-harmonic-generation technique using a 10^–3 M solution in <i>N</i>,<i>N</i>-dimethylformamide and working with a 1.907 μm incident wavelength, giving for μβ_1.907 (μβ₀) values of −1095 (−581), −2760 (−954), and −1650 (−618) × 10^–48 esu for <b>1</b>–<b>3</b>, respectively. These values are among the highest in the class of square-planar push–pull complexes, similar to those found for dithionedithiolate compounds. Moreover, spectroelectrochemical experiments demonstrate the possibility of using these complexes as redox-switchable NLO chromophores

Light-Induced Regiospecific Bromination of <i>meso</i>-Tetra(3,5-di-<i>tert</i>-butylphenyl)Porphyrin on 2,12 β‑Pyrrolic Positions

The antipodal introduction of two bromine atoms on the 2,12 β-pyrrolic position of 5,10,15,20-tetra­(3,5-di-<i>tert</i>-butylphenyl)­porphyrin was successfully achieved by a light-induced reaction of the substrate with excess NBS. Complexation with Ni^II of the major regioisomer led to good quality crystals, suitable for X-ray structure determination with unprecedented probability levels. The regiospecific character of the synthetic procedure and the exactness of the bromine atom position assignment were thus confirmed, suggesting an unexpected electrophilic aromatic substitution pathway rather than a free-radical halogenation process. A QTAIM topological analysis on the DFT-optimized wave function of the monosubstituted free-base porphyrin intermediate carrying a bromine atom in C2 β-pyrrolic position confirmed the largest negative charge for the C12 carbon atom in antipodal position, in agreement with the proposed electrophilic aromatic substitution mechanism

New Internal-Charge-Transfer Second-Order Nonlinear Optical Chromophores Based on the Donor Ferrocenylpyrazole Moiety

A series of new N-arylated ferrocenepyrazole structures, carrying different donor or acceptor substituents in the para position of the aryl ring, has been synthesized by the Chan–Lam cross-coupling reaction. The nonplanar geometric molecular structure of some of these chromophores together with their crystal packing was determined by X-ray diffraction, and the HOMO and LUMO energy levels were evaluated by electrochemical and optical measurements and by density functional theoretical (DFT) calculations. By the investigation of solvent effects and time-dependent DFT (TD-DFT) calculations, the intense electronic absorption band around 270–310 nm was confirmed to be an internal-charge-transfer (ICT) band, showing a significant red shift by increasing the electron withdrawing properties of the substituent on the para position of the aryl ring. TD-DFT calculations and electric field induced second harmonic generation (EFISH) measurements of the quadratic hyperpolarizability have shown that also the second-order nonlinear optical (NLO) response of these new ICT chromophores can be tuned by changing the nature of the substituent. Both theoretical μβ and β and experimental EFISH μβ₁₉₀₇ and β₁₉₀₇ values are significant, with a quite satisfactory correlation of the general trend of theoretical μβ and EFISH μβ₁₉₀₇ values. The highest value of EFISH μβ₁₉₀₇ (410 × 10^–48 esu) was measured for the chromophore carrying the strong electron withdrawing NO₂ group

Physicochemical Investigation of the Panchromatic Effect on β‑Substituted Zn^II Porphyrinates for DSSCs: The Role of the π Bridge between a Dithienylethylene Unit and the Porphyrinic Ring

Three novel dyes based on Zn^II porphyrinates combined, in β-pyrrolic position, with the π unit dithienylethylene (DTE) have been synthesized and investigated for application in DSSCs. The panchromatic effect due to elongation of the π-delocalized system through a bridge between the porphyrinic ring and the DTE unit such as the 4-ethynylstyryl (<b>1</b>), ethynyl (<b>2</b>), and ethenyl (<b>3</b>) bonds have been investigated by computational, electrochemical, and photoelectrochemical methods. For all three dyes the π conjugated substituents in the β position produced the expected panchromatic effect with broadened electronic absorption spectra over a wide range of wavelengths and IPCE spectra featuring a broad plateau in the region 430–650 nm. In addition both DFT computational and electrochemical data have shown a smaller HOMO–LUMO energy gap for dye <b>3,</b> when compared to dye <b>2</b> suggesting a slightly more facile conjugation between the porphyrinic core and the DTE unit through the ethenylic bond. Conversely the photoelectrochemical investigation showed improved DSSC performances from <b>3</b> to <b>1</b>. These results have been rationalized by an in-depth DFT computational study of dyes <b>2</b> and <b>3</b> interacting with a cluster of 82 TiO₂ units. The small energetic overlap between the LUMO and the TiO₂ conduction band characterizing the more structurally distorted dye <b>3</b> would suggest low quantum yield of electron injection, while dye <b>2</b> shows a greater interaction between the LUMO of the dye and the semiconductor. Consequently the increased linearity and planarity of the structure of dye <b>1</b> seems to be the origin of its best performance in DSSC. Therefore it appears that the nature of the bridge between the DTE unit and the porphyrinic ring is quite relevant for the efficiency of these dyes for DSSC, due to distortion from the planarity and linearity of the structure of the dye and the consequent changes on the dye π conjugation

Influence of Porphyrinic Structure on Electron Transfer Processes at the Electrolyte/Dye/TiO₂ Interface in PSSCs: a Comparison between meso Push–Pull and β‑Pyrrolic Architectures

Time-resolved photophysical and photoelectrochemical investigations have been carried out to compare the electron transfer dynamics of a 2-β-substituted tetraarylporphyrinic dye (ZnB) and a 5,15-meso-disubstituted diarylporphyrinic one (ZnM) at the electrolyte/dye/TiO₂ interface in PSSCs. Although the meso push–pull structural arrangement has shown, up to now, to have the best performing architecture for solar cell applications, we have obtained superior energy conversion efficiencies for ZnB (6.1%) rather than for ZnM (3.9%), by using the I^–/I₃^–-based electrolyte. To gain deeper insights about these unexpected results, we have investigated whether the intrinsic structural features of the two different porphyrinic dyes can play a key role on electron transfer processes occurring at the dye-sensitized TiO₂ interface. We have found that charge injection yields into TiO₂ are quite similar for both dyes and that the regeneration efficiencies by I^–, are also comparable and in the range of 75–85%. Moreover, besides injection quantum yields above 80%, identical dye loading, for both ZnB and ZnM, has been evidenced by spectrophotometric measurements on transparent thin TiO₂ layers after the same adsorption period. Conversely, major differences have emerged by DC and AC (electrochemical impedance spectroscopy) photoelectrochemical investigations, pointing out a slower charge recombination rate when ZnB is adsorbed on TiO₂. This may result from its more sterically hindered macrocyclic core which, besides guaranteeing a decrease of π-staking aggregation of the dye, promotes a superior shielding of the TiO₂ surface against charge recombination involving oxidized species of the electrolyte

Coupling of Zinc Porphyrin Dyes and Copper Electrolytes: A Springboard for Novel Sustainable Dye-Sensitized Solar Cells

The combination of β-substituted Zn²⁺ porphyrin dyes and copper-based electrolytes represents a sustainable route for economic and environmentally friendly dye-sensitized solar cells. Remarkably, a new copper electrolyte, [Cu­(2-mesityl-1,10-phenanthroline)₂]^+/2+, exceeds the performance reached by Co^2+/3+ and I^–/I₃^– reference electrolytes

A Multitechnique Physicochemical Investigation of Various Factors Controlling the Photoaction Spectra and of Some Aspects of the Electron Transfer for a Series of Push–Pull Zn(II) Porphyrins Acting as Dyes in DSSCs

A multitechnique physicochemical comparative investigation involving TDDFT theoretical calculations, steady-state and time-resolved electronic absorption spectra, and electrochemical and photoelectrochemical investigations was carried out on a family of push–pull porphyrinic sensitizers ([5-(4′-carboxy-phenylethynyl)-15-(4″-methoxy-phenylethynyl)-10,20-bis(3,5-di-<i>tert</i>-butylphenyl)porphyrinate]Zn(II) (<b>1</b>) and [5-(4′-carboxy-phenylethynyl)-15-(4″-<i>N</i>,<i>N</i>-dimethylamino-phenylethynyl)-10,20-bis(3,5-di-<i>tert</i>-butylphenyl)porphyrinate]Zn(II) (<b>2</b>) and the new fluorinated porphyrinic dye [5-(4′-carboxy-2′,3′,5′,6′-tetrafluorophenylethynyl)-15-(4″-<i>N</i>,<i>N</i>-dimethylamino-phenylethynyl)-10,20-bis(3,5-di-<i>tert</i>-butylphenyl)porphyrinate]Zn(II) (<b>3</b>)) with the aim of identifying the structurally related electronic properties at the basis of efficient interfacial charge separation. We found for all dyes a photoconversion nearly twice more effective for the B band than for the Q band, which could not be explained only by considerations based on the electron collection efficiency but also by a more energetically favorable electron injection from the S2 excited state. The lower photoconversion of the fluorinated dye <b>3</b>, when compared to dyes <b>1</b> and <b>2</b>, was explained not only by a more difficult absorption on the TiO₂ photoanode but also by a lower electron injection efficiency and a less successful hole transfer to the electrolyte, leading to increased charge recombination