6 research outputs found
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 −COOCH<sub>3</sub> acceptor groups and a −OCH<sub>3</sub> or a −N(CH<sub>3</sub>)<sub>2</sub> donor group, show
in <i>N</i>,<i>N</i>-dimethylformamide and CHCl<sub>3</sub> 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(CH<sub>3</sub>)<sub>2</sub> donor group and a −NO<sub>2</sub> acceptor group, where a
still solvent-dependent but positive EFISH second-order response was
previously reported. Moreover, when a −N(CH<sub>3</sub>)<sub>2</sub> 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 <sup>1</sup>H 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
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<sup>II</sup> 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
Physicochemical Investigation of the Panchromatic Effect on β‑Substituted Zn<sup>II</sup> Porphyrinates for DSSCs: The Role of the π Bridge between a Dithienylethylene Unit and the Porphyrinic Ring
Three novel dyes based on Zn<sup>II</sup> 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 TiO<sub>2</sub> units. The small energetic overlap between
the LUMO and the TiO<sub>2</sub> 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/TiO<sub>2</sub> 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/TiO<sub>2</sub> 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<sup>–</sup>/I<sub>3</sub><sup>–</sup>-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 TiO<sub>2</sub> interface. We have found that
charge injection yields into TiO<sub>2</sub> are quite similar for
both dyes and that the regeneration efficiencies by I<sup>–</sup>, 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 TiO<sub>2</sub> 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 TiO<sub>2</sub>. 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 TiO<sub>2</sub> 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
Zn<sup>2+</sup> 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)<sub>2</sub>]<sup>+/2+</sup>, exceeds the performance reached by Co<sup>2+/3+</sup> and I<sup>–</sup>/I<sub>3</sub><sup>–</sup> 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 TiO<sub>2</sub> photoanode but also by a lower electron injection efficiency and a less successful hole transfer to the electrolyte, leading to increased charge recombination