Highly conjugated multiporphyrins: synthesis, spectroscopic and electrochemical properties

Bio-inspired strategies for next-generation perovskite solar mobile power sources

Smart electronic devices are becoming ubiquitous due to many appealing attributes including portability, long operational time, rechargeability and compatibility with the user-desired form factor. Integration of mobile power sources (MPS) based on photovoltaic technologies with smart electronics will continue to drive improved sustainability and independence. With high efficiency, low cost, flexibility and lightweight features, halide perovskite photovoltaics have become promising candidates for MPS. Realization of these photovoltaic MPS (PV-MPS) with unconventionally extraordinary attributes requires new 'out-of-box' designs. Natural materials have provided promising designing solutions to engineer properties under a broad range of boundary conditions, ranging from molecules, proteins, cells, tissues, apparatus to systems in animals, plants, and humans optimized through billions of years of evolution. Applying bio-inspired strategies in PV-MPS could be biomolecular modification on crystallization at the atomic/meso-scale, bio-structural duplication at the device/system level and bio-mimicking at the functional level to render efficient charge delivery, energy transport/utilization, as well as stronger resistance against environmental stimuli (e.g., self-healing and self-cleaning). In this review, we discuss the bio-inspired/-mimetic structures, experimental models, and working principles, with the goal of revealing physics and bio-microstructures relevant for PV-MPS. Here the emphasis is on identifying the strategies and material designs towards improvement of the performance of emerging halide perovskite PVs and strategizing their bridge to future MPS.

Access to Corrole-Appended Persubstituted Benzofurans by a Multicomponent Reaction: The Dual Role of p-Chloranil

A multicomponent reaction among dipyrranes, aryl-propargyl aldehydes, and p-chloranil leading to 10-(benzofuran-2-yl)corroles is described. p-Chloranil was identified as a crucial reagent playing a twofold role: an oxidant taking part in the formation of the corrole macrocycle and a component undergoing heteroannulation to the incipient 10-arylethynylcorrole. A series of corroles bearing persubstituted benzofuran-2-yl moieties have been synthesized, and their fundamental electronic properties have been studied via UV-vis absorption and fluorescence spectroscopies.

Self-assembly of an alkynylpyrene derivative for multi-responsive fluorescence behavior and photoswitching performance

Highly emissive fluorophores based on polyaromatic hydrocarbons with tunable emission properties and aggregated structures play a very important role in relevant functional studies. In this study, a novel alkynylpyrene derivative 1 was synthesized, which exhibits unimolecular to excimer emission in methanol with an increasing concentration accompanied by the formation of nanovesicles via the π-π stacking, hydrogen bond and hydrophobic interaction. The self-assembly behavior as well as emission properties of 1 in aprotic polar solvents (ACN, acetone, DMF and DMSO) can also be adjusted by the volume fraction of the poor solvent H2O, which can induce 1 self-assembly to excimer state and could be applied in information transfer. Moreover, upon visible light irradiation, photoswitchable performance of nanovesicles of 1 was observed in which the emission markedly changes from yellow to blue; this is attributed to the cycloaddition reaction of alkynyl groups and singlet oxygen, which can be generated without the addition of external photosensitizers. The multi-responsive and fluorescence behavior of the alkynylpyrene derivative show that the self-assembly can be used to expand the development of this type of fluorophores, and the novel photoinduced tunability of the fluorescence emission provides an effective strategy to obtain high-performance transmitting and sensing materials.

Spectroscopic characterization of free-base hydroxy(arylethynyl)porphyrins in acidic and basic media

The addition of arylethynyl groups to the porphyrin macrocycle represents an effective strategy with which to enhance the light-harvesting properties of porphyrins. We now extend this modification to arylethynyl porphyrins with two or four [Formula: see text]-hydroxyphenyl substituents. Arylethynyl porphyrins bearing four, but not two, [Formula: see text]-hydroxyphenyl substituents show evidence of aggregation under acidic conditions. Under basic conditions, deprotonation of the peripheral hydroxyphenyl substituents results in substantially red-shifted spectral features and enhanced absorption in the Q-band region. When the hydroxyphenyl groups are appended to the porphyrin macrocylce via the ethynyl spacers, the spectral shifts observed upon deprotonation are significantly enhanced relative to those observed for hydroxyphenylporphyrins, highlighting the role of expanded conjugation in altering porphyrin photophysics.

π-Extended diketopyrrolopyrrole–porphyrin arrays: one- and two-photon photophysical investigations and theoretical studies

Diketopyrrolopyrrole–porphyrin conjugates show remarkable NIR emission properties, high two-photon absorption cross-sections and significant singlet oxygen production efficiency.

Excited-state localization and energy transfer in pyrene core dendrimers with fluorene/carbazole as the dendrons and acetylene as the linkages

Multi-scale theoretical model and spectra simulation for dendrimers combining TD-DFT/DFT and semi-empirical methods.

A systematic theoretical study of the electronic structures of porphyrin dimers: DFT and TD-DFT calculations on diporphyrins linked by ethane, ethene, ethyne, imine, and azo bridges

Theoretical calculations of the geometries, electronic structures and electronic absorption spectra of a series of covalently-linked porphyrin dimers are reported. The diporphyrins comprise 5,10,15-triphenylporphyrinatozinc(II) (ZnTriPP) units linked through the meso carbons by two-atom bridges, namely 1,2-ethanediyl (1), trans-1,2-ethenediyl (2), ethynediyl (3), 1,2-iminomethenediyl (4), and transdiazenediyl (5). The structures were optimised in toluene solvent by Density Functional Theory (DFT), using the integral equation formalism variant of the polarizable continuum model. The calculations were performed using the B3LYP functional and the 6-31G(d,p) basis set. The complete molecules were modelled, with no substitution of smaller groups on the periphery. In parallel, the compounds 2–5 were prepared by known or novel synthetic routes, to enable comparisons of experimental electronic absorption spectra with those calculated using time dependent-DFT at the same level of theory. As the ethane dimer 1 is not yet synthetically accessible, the model monomer meso-2-phenylethylZnTriPP was used for comparisons with the theoretical predictions. The results form a self-consistent set, enabling for the first time legitimate comparisons of the electronic structures of the series, especially regarding the degree to which the porphyrin p-systems interact by conjugation across the bridges. The theoretical calculations of the electronic transitions match the observed spectra in toluene to a remarkable degree, especially with respect to the peak maximum of the Q band, which represents to a large degree the energy of the HOMO–LUMO transition. The imine 4 is intrinsically polar due to the asymmetric bridge, and the HOMO is located almost exclusively on the ZnTriPP unit attached to the nitrogen of the imine, and the LUMO on the C-attached ring. Thus the Q-band transition is mapped as a comprehensive charge-transfer from the former ring to the latter. This may have consequences for the non-linear optical properties of the system. The azoporphyrin 5 exhibits the largest splittings between the interacting MOs via the conjugated bridge, vindicating a prediction by Anderson and co-workers in 2002, and confirmed experimentally by our synthesis of 5. The collected results also indicate that this level of theory is more thanadequate as a model with which to handle these large delocalised molecules.

New synthesis of zinc tetrakis(arylethynyl)porphyrins and substituent effects on their redox chemistry

Sonogashira coupling of zinc 5,10,15,20-tetraethynylporphyrin with various phenyl iodides under mild conditions afforded good yields of the corresponding zinc porphyrins. This method is applicable to a variety of aryl iodides including meso-substituted iodoporphyrin to form a conjugated star-shaped multiporphyrin. The UV-Vis spectra show that peak broadening, red shifts, and changes in the oscillator strength of absorptions increase with the extension of pi-conjugation. In the electrochemical measurements, the first oxidation of porphyrins 4-9 occurs at potentials in the range +0.89 to +1.08 V, which are comparable to that of ZnTPP (TPP = tetraphenylporphyrin). The first reduction was observed at potentials from -0.73 to -0.89 V, which is anodically shifted by 390-550 mV as compared to that of ZnTPP, and the second reduction occurs at potentials in the range -1.12 to -1.33 V. The para-substituted tetrakis(phenylethynyl)porphyrins show substituent effects on their redox chemistry and exhibit only slight substituent effects in their emission and absorption maxima.