Enhanced Photocatalytic CO2 Reduction through Hydrophobic Microenvironment and Binuclear Cobalt Synergistic Effect in Metallogels.

Assemblies that mimic natural lipid bilayers are theoretically efficient for photocatalytic CO2 reduction; however, such an approach has not been yet explored. Herein, metallogels (LG/Nico-Co) based on the co-assembly of L-glutamic acid lipid (LG/Nico) and cobalt ions exhibited excellent photocatalytic CO2 reduction, with 208 724 µmol g-1 CO production within 24 h and 90 % CO/H2 selectivity, or 166 826 µmol g-1 CO production within 12 h and 46 % CO/H2 selectivity, depending on the water content of the solvent. The alkyl chains of LG/Nico provide a hydrophobic microenvironment for efficient gas transfer, and the assembled bilayers induce a synergistic effect between two adjacent Co ions for catalyzing the CO2 reduction reaction. These architectures present new alternatives for the development of highly efficient photocatalytic soft matter based on the assembly of small amphiphilic molecules.

Perspectives on Ligand Properties of N-Heterocyclic Carbenes in Iron Porphyrin Complexes.

There has been considerable research interest in the ligand nature of N-heterocyclic carbenes (NHCs). In this work, two six-coordinate NHC iron porphyrin complexes [FeII(TTP)(1,3-Me2Imd)2] (TTP = tetratolylporphyrin, 1,3-Me2Imd = 1,3-dimethylimidazol-2-ylidene) and [FeIII(TDCPP)(1,3-Me2Imd)2]ClO4 (TDCPP = 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin) are reported. Single-crystal X-ray characterizations demonstrate that both complexes have strongly ruffled conformations and relatively perpendicular ligand orientations which are forced by the sterically bulky 1,3-Me2Imd NHC ligands. Multitemperature (4.2-300 K) and high magnetic field (0-9 T) Mössbauer and low-temperature (4.0 K) EPR spectroscopies definitely confirmed the low-spin states of [FeII(TTP)(1,3-Me2Imd)2] (S = 0) and [FeIII(TDCPP)(1,3-Me2Imd)2]ClO4 (S = 1/2). The similarity of 1,3-Me2Imd and imidazole, as well as the well-established correlations between the ligand nature and spectroscopic characteristics of [FeII,III(Porph)(L)2]0,+ (Porph: porphyrin; L: planar base ligand) species, allowed direct comparisons between the pair of ligands which revealed for the first time that NHC has a stronger π-acceptor ability than imidazoles, in addition to its very strong σ-donation.

Multipolar Porphyrin-Triazatruxene Arrays for Two-Photon Fluorescence Cell Imaging.

Two-photon excited fluorescent (TPEF) materials are highly desirable for bioimaging applications owing to their unique characteristics of deep-tissue penetration and high spatiotemporal resolution. Herein, by connecting one, two, or three electron-deficient zinc porphyrin units to an electron-rich triazatruxene core via ethynyl π-bridges, conjugated multipolar molecules TAT-(ZnP)n (n=1-3) were developed as TPEF materials for cell imaging. The three new dyes present high fluorescence quantum yields (0.40-0.47) and rationally improved two-photon absorption (TPA) properties. In particular, the peak TPA cross section of TAT-ZnP (436 GM) is significantly larger than that of the ZnP reference (59 GM). The δTPA values of TAT-(ZnP)2 and TAT-(ZnP)3 further increase to 1031 and up to 1496 GM, respectively, indicating the effect of incorporated ZnP units on the TPA properties. The substantial improvement of the TPEF properties is attributed to the formation of π-conjugated quadrapole/octupole molecules and the extension of D-π-A-D systems, which has been rationalized by density function theory (DFT) calculations. Moreover, all of the three new dyes display good biocompatibility and preferential targeting ability toward cytomembrane, thus can be superior candidates for TPEF imaging of living cells. Overall, this work demonstrated a promising strategy for the development of porphyrin-based TPEF materials by the construction and extension of D-π-A-D multipolar array.

Intermolecular Chirality Modulation of Binaphthalene-Bridged Bisporphyrins With Chiral Diamines.

A new pair of 2,2'-diamino-1,1'-binaphthyl linked porphyrin dimers, (R)-/(S)-H, were synthesized to study their supramolecular interactions with a pair of chiral diamines ((R)-/(S)-PPDA) by using UV-Vis absorption, fluorescence and NMR titrations. The spectroscopic titrations indicated that sandwich-type 1:1 complexes were formed at low guest concentration and then transformed to 1:2 open complexes at high guest concentration. The supramolecular interactions afforded sensitive circular dichroism responses, and the CD signs of the 1:1 complexes are decided by the stereostructure of chiral diamine guests. Moreover, due to the shortened linking units, (R)-/(S)-H show more sensitive and predicable CD response than the previously reported hosts (R)-/(S)-H1 and this can be reasonably explained by DFT molecular modeling. The present results suggest (R)-/(S)-H are promising for chiral optical sensing.

Ultrathin Phthalocyanine-Conjugated Polymer Nanosheet-Based Electrochemical Platform for Accurately Detecting H2O2 in Real Time.

As a vital biological mediator and a widely used industrial oxidant, the accurate detection of hydrogen peroxide (H2O2) is of significance for both academic purpose and practical applications. Herein, we report a novel approach for the development of a high-performance electrochemical H2O2 sensor constructed by iron phthalocyanine (FePc)-based diyne-linked conjugated polymeric nanosheets (NSs), FePc-CP NSs. The FePc-CP NSs were delaminated from the bulk material via a defect- and disorder-induced synthetic strategy. By the quasi-Langmuir-Shäfer method, the prepared FePc-CP NSs were self-assembled into multilayer films with controllable thickness on electrodes. Owing to the highly exposed active centers on the surfaces, the FePc-CP NS film-modified electrodes exhibited excellent H2O2 determination performance with a wide linear detection range (0.1-1000 µM), a short response time (the response current approached the maximum value within 0.1 s), a low limit of detection (0.017 µM), and excellent sensitivity (97 µA cm-2 mM-1), which are comparable to the best results reported so far for electrochemical H2O2 sensors. In addition, the fabricated electrochemical H2O2 sensor also displayed satisfactory stability, reproducibility, and selectivity. Furthermore, the obtained FePc-CP NS film sensor can be applied in real-time monitoring of H2O2 in commercial orange juice and beer as well as H2O2 secreted from A549 live cells, revealing its application potential toward the accurate detection of H2O2 in real-sample analysis.

Two-Photon Excited FRET Dyads for Lysosome-Targeted Imaging and Photodynamic Therapy.

Two-photon excitable fluorescent dyes with integrated functions of targeted imaging and photodynamic therapy (PDT) are highly desired for the development of cancer theranostic agents. Herein, fluorescence resonance energy transfer (FRET) dyads, AceDAN-H2Por-Lyso (1a) and AceDAN-ZnPor-Lyso (1b), were developed for two-photon excited (TPE) lysosome-targeted fluorescence imaging and PDT of cancer cells. Under one-photon or two-photon excitation, the AceDAN donor can effectively transfer the excited state energy to the porphyrin acceptor via high efficient FRET, leading to the generation of deep-red fluorescence and singlet oxygen for cell imaging and PDT, respectively. 1a and 1b exhibit high photocytotoxicity and low dark cytotoxicity, in addition to strong lysosomal targeting capability in living cells. By taking the advantages of the two-photon absorption properties of the AceDAN donor and the properly distributed S1 and T1 states of the porphyrin acceptor, the AceDAN-porphyrin dyads 1a and 1b have been successfully applied to TPE-fluorescence imaging for tracking the significant morphology changes of cancer cells under two-photon laser irradiation.