In-Core N4-Coordination of Palladium(II) in Dinaphthoporphycene: Synthesis, Structure, and Photophysical Studies

Dinaphthoporphycene (DNP) has emerged as a versatile ligand undergoing large out-of-plane distortion to form a cis-bimetallic complex with Pd(II) using Pd(OAc)₂ and out-of-plane monometallic complexes with Pd(acac)₂ and PtCl₂(PhCN)₂. Herein, we are finally able to synthesize the in-core complex with Pd(II) using PdCl₂(PhCN)₂ or PdCl₂. The crystal structure shows the palladium ion resides slightly above the N4-core, with the Pd(II) dimensionally dissenting with the typical square planarity displayed by the reported in-core DNP complexes with Ni(II) and Cu(II) ions. The deformed complex displays a blue shift in the absorption spectra compared to DNP and its metallo-derivatives. PdDNP exhibits a moderate singlet oxygen generation ability (18%).

3,6,13,16-Tetraalkylporphycenes: Synthesis and Exploration of Effect of Alkyl Groups on Structure, Photophysical Properties, and Basicity

Two new 3,6,13,16-tetraalkylporphycenes were synthesized following rational approach. The reason behind lower yield of the desired β,β'-bipyrroles was unraveled. The σ-donating effect of alkyl-substituents was more profound than reported positional...

3,6,13,16-Tetrasubstituted Porphycene: The Missing Link in Porphycene Chemistry

We have introduced the first 3,6,13,16-tetrasubstituted porphycene as its tetramethoxy analogue. This substitution pattern is one of the most general patterns yet missing in this isomeric porphyrin chemistry. This porphycene exhibits intense fluorescence along with the ability to coordinate with divalent metal ions; in particular, it forms the first stable Zn(II) complex among the tetrasubstituted porphycenes. Notably, the molecular structure of Zn1•Py displays supramolecular chirality.

2,7,12,17-Tetra(2,5-thienylene)-substituted porphycenes

We report syntheses of thiophene and dithiophene-substituted porphycenes (ThPc and DThPc) at 2,7,12,17-positions by McMurry coupling. The crystal structure of ThPc revealed that the porphycene plane shows a highly planar structure, and the dihedral angles between the porphycene core and thiophene are relatively small at 21[Formula: see text] and 18[Formula: see text]. ThPc and DThPc exhibit red-shifted and broadened absorption because of the extension of [Formula: see text] conjugations through porphycene to the substituted thiophenes. We found that introduction of thiophene units onto porphycene results in decreasing the HOMO–LUMO differences effectively.

Engineering NiO/NiFe LDH Intersection to Bypass Scaling Relationship for Oxygen Evolution Reaction via Dynamic Tridimensional Adsorption of Intermediates

Oxygen evolution reaction (OER) is a pivotal reaction in many technologies for renewable energy, such as water splitting, metal-air batteries, and regenerative fuel cells. However, this reaction is known to be kinetically sluggish and proceeds at rather high overpotential due to the universal scaling relationship, namely, the adsorption energies of intermediates are linearly correlated and cannot be optimized simultaneously. Several approaches have been proposed to break the scaling relationship by introducing additional active sites; however, positive experimental results are still absent. Herein, a different solution is suggested on the basis of dynamic tridimensional adsorption of the OER intermediates at NiO/NiFe layered double hydroxide intersection, by which the adsorption energy of each intermediate can be adjusted independently, so as to bypass the scaling relationship and achieve high catalytic performance. Experimentally, the OER overpotential is reduced to ≈205 mV at current density of 30 mA cm^-2 , which represents the best performance achieved by state-of-the-art OER catalysts.

Designing Squaraines to Control Charge Injection and Recombination Processes in NiO-based Dye-Sensitized Solar Cells

Herein, the synthesis of a new family of squaraines (SQs) and their application in p-type dye-sensitized solar cells (DSSCs) is presented. In particular, two sets of SQs were designed featuring either two or four anchoring carboxylic groups combined with either oxygen or dicyanovinyl central groups. The SQs were characterized by using a joint theoretical, photophysical, and electrochemical approach. Importantly, the presence of different central groups forces a frozen cis (dicyanovinyl group) or a trans (oxygen group) SQ conformation. Based on the latter, the current work enables a direct comparison between cis and trans isomers as well as the impact of a different number of anchors. Considering their electron-accepting and light-harvesting character, they were tested in NiO-based DSSCs. Photocurrent-voltage, incident photon-to-current conversion efficiency (IPCE), and electrochemical impedance spectroscopy measurements were performed. By virtue of their different symmetry, stereochemistry, and number of carboxylic groups, altered adsorption behavior onto NiO electrodes as well as diverse charge injection and charge recombination dynamics were noted under operation conditions. SQs with four linkers in a frozen cis isomerism show the best charge collection properties among the investigated SQs, providing a valuable guideline for the molecular design of future SQs for p-type DSSCs. In addition, we assembled tandem DSSCs featuring SQ/NiO photocathodes and N719/TiO₂ photoanodes. The IPCE of the resulting tandem DSSCs implies light harvesting throughout most of the visible part of the solar spectrum owing to the complementary absorption features of SQ and N719.

Acid- and hydrogen-bonding-induced switching between 22-π and 18-π electron conjugations in 2-aminothiazolo[4,5-c]porphycenes

2-Aminothiazolo[4,5-c]porphycenes undergo a 22-π to 18-π electron conjugation switch in the presence of acids and strong H-bonding solvents.

Porphycene dimer-based non-fullerene acceptor for organic solar cell

Porphycene dimers connected by [Formula: see text]-phenylene (DPc– m P) and 2,5-thienylene (DPc–T) linkages have been synthesized from 2,7,12,17-tetrahexyl-3-iodoporphycene by palladium-catalyzed cross-couplings. The crystal structures of porphycene dimers revealed that meta-phenylene linkage provides a highly twisted structure with the dihedral angel of 103° between two porphycene units, while thienylene linkage provides a nearly planar structure of two porphycene units. These porphycene dimers showed strong absorption thorough the visible to NIR regions and HOMO and LUMO energy levels of them are suitable as [Formula: see text]-type materials of organic solar cells (OSCs) in combination with P3HT as a [Formula: see text]-type material. The hole and electron mobilities of the blended films of the porphycene dimers and P3HT obtained by space-charge-limited-current (SCLC) method were 3.7 × 10[Formula: see text] and 0.26 × 10[Formula: see text] cm2.V[Formula: see text].s[Formula: see text] for DPc– m P :P3HT, and 3.2 × 10[Formula: see text] and 0.027 × 10[Formula: see text] cm2.V[Formula: see text].s[Formula: see text] for DPc–T :P3HT. Atomic force microscopy (AFM) and thin-film X-ray diffraction analysis (XRD) measurements indicated that the blended films of the porphycene dimers and P3HT formed amorphous films with smooth and low-roughness surfaces, whereas the blended film of porphycene monomer and P3HT created the highly crystalline film with huge domain structures. The OSCs composed of porphycene dimers and P3HT showed power conversion efficiencies of 0.08% was twice as high as that of monomer-based OSC.

Optimizing CuO p-type dye-sensitized solar cells by using a comprehensive electrochemical impedance spectroscopic study

We introduce a novel and comprehensive approach for the evaluation and interpretation of electrochemical impedance spectroscopy (EIS) measurements in p-type DSSCs. In detail, we correlate both the device performance and EIS figures-of-merit of a series of devices in which, the calcination temperature, film thickness, and electrolyte concentration have been systematically modified. This new approach enables the separation of the different processes across the dye/semiconductor/electrolyte interface, namely the unfavorable charge recombination and the favorable electron injection/regeneration processes. In addition, studies on non-sensitized CuO and NiO electrodes provide insights into their affinity towards a reaction with the electrolyte - CuO is far less reactive towards the polyiodide species. Overall, this work underlines the superior features of CuO with respect to NiO for p-DSSCs and demonstrates a comprehensive optimization of the CuO-based DSSCs with respect to the device architecture by the aid of EIS analysis.

Spectroscopy and Tautomerization Studies of Porphycenes

Tautomerization in porphycenes, constitutional isomers of porphyrins, is strongly entangled with spectral and photophysical parameters. The intramolecular double hydrogen transfer occurring in the ground and electronically excited states leads to uncommon spectroscopic characteristics, such as depolarized emission, viscosity-dependent radiationless depopulation, and vibrational-mode-specific tunneling splittings. This review starts with documentation of the electronic spectra of porphycenes: Absorption and magnetic circular dichroism are discussed, together with their analysis based on the perimeter model. Next, photophysical characteristics are presented, setting the stage for the final part, which discusses the developments in research on tautomerism. Porphycenes have been studied in different experimental regimes: molecules in condensed phases, isolated in supersonic jets and helium nanodroplets, and, recently also on the level of single molecules investigated by optical and scanning probe microscopies. Because of the rich and detailed information obtained from these diverse investigations, porphycenes emerge as very good models for studying the complex, multidimensional phenomena involved in the process of intramolecular double hydrogen transfer.