Abstract
Emission from the triplet state of an organo-lanthanide complex is observed only when the energy transfer to the lanthanide ion is absent. The triplet state lifetime under cryogenic ...conditions for organo-lanthanide compounds usually ranges up to tens of milliseconds. The compound
LaL1(TTA)
3
reported herein exhibits 77 K phosphorescence observable by the naked eye for up to 30 s. Optical spectroscopy, density functional theory (DFT) and time-dependent DFT techniques have been applied to investigate the photophysical processes of this compound. In particular, on-off continuous irradiation cycles reveal a charging behaviour of the emission which is associated with triplet-triplet absorption because it shows a shorter rise lifetime than the corresponding decay lifetime and it varies with illumination intensity. The discovery of the behaviour of this compound provides insight into important photophysical processes of the triplet state of organo-lanthanide systems and may open new fields of application such as data encryption, anti-counterfeiting and temperature switching.
Mn2+ complexes of 2,4‐pyridyl‐disubstituted bispidine ligands have emerged as more biocompatible alternatives to Gd3+‐based MRI probes. They display relaxivities comparable to that of commercial ...contrast agents and high kinetic inertness, unprecedented for Mn2+ complexes. The chemical structure, in particular the substituents on the two macrocyclic nitrogens N3 and N7, are decisive for the conformation of the Mn2+ complexes, and this will in turn determine their thermodynamic, kinetic and relaxation properties. We describe the synthesis of four ligands with acetate substituents in positions N3, N7 or both. We evidence that the bispidine conformation is dependent on N3 substitution, with direct impact on the thermodynamic stability, kinetic inertness, hydration state and relaxivity of the Mn2+ complexes. These results unambiguously show that (i) solely a chair‐chair conformation allows for favorable inertness and relaxivity, and (ii) in this family such chair‐chair conformation is accessible only for ligands without N3‐appended carboxylates.
Mn(II) complexes with acetate‐substituted bispidine ligands can adopt different conformations depending on the N3 substituent. Complexes in chair‐chair conformation display high relaxivity and strong kinetic inertness, both very important for their potential use as MRI contrast agents. In contrast, the boat‐chair conformers undergo fast dissociation and do no retain good relaxivity.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Supported by experimental work, wavefunction theory (WFT) calculations and density functional theory (DFT) calculations employing a range of functionals have been performed for two lanthanide ...complexes to investigate, in gas and solution phases, the representations of frontier orbitals and the orbital transitions between singlet states. The orbital transitions calculated using CASSCF/NEVTP2 served as reference. Functionals with a higher proportion of Hartree-Fock exchange gave better agreement with WFT. The choice of functional is therefore important for understanding the nature of orbital transitions and this is especially relevant in formulating antenna-metal ion energy transfer (ET) mechanisms.
Including experimental work, WFT and DFT calculations employing a range of functionals were performed for two lanthanide complexes to investigate, in different phases, the frontier orbitals and the orbital transitions between singlet states.
The aggregation caused quenching (ACQ) of photoluminescence in porphyrins, which is attributed to strong π–π (C⋯C/C⋯H) interactions in the solid state, often leads to a decrease in photoluminescence, ...short electron lifetimes ( τ PL ) and inferior performance in photocatalytic hydrogen evolution (PHE). To address this issue, we explore self-assembled Pt( ii )-tetrakis(pentafluorophenyl)porphyrin (SA-PtPFTPP) and Pt( ii )-tetraphenylporphyrin (SA-PtTPP) as candidates. We find that SA-PtPFTPP via F⋯F interaction effectively restricts ACQ in the solid state, whereas SA-PtTPP shows noticeable ACQ due to intermolecular π–π (C⋯C/C⋯H) interactions. Compared with SA-PtTPP, SA-PtPFTPP demonstrates a longer τ PL value and higher photoluminescence quantum yield. Moreover, SA-PtPFTPP exhibits more efficient charge separation and better dispersibility in water with a low water contact angle. The favorable photophysical properties of SA-PtPFTPP enable a direct electron transfer from the photoexcited porphyrin moiety to the proton in cocatalyst-free PHE. As a result, SA-PtPFTPP shows a much higher PHE rate ( η H 2 ) of 400.0 μmol g −1 h −1 compared to SA-PtTPP (5.0 μmol g −1 h −1 ) under heterogeneous conditions. Importantly, SA-PtPFTPP also demonstrates high photostability under prolonged irradiation, as evidenced by the consistent η H 2 production in each photocycle and unchanged morphology before and after light irradiation. This research provides a valuable insight into the design of self-assembled porphyrins with hindered ACQ, offering potential applications in cocatalyst-free PHE.
Multifunctional porphyrin–peptide conjugates with different propensities for self‐assembly into various supramolecular nanoarchitectures play important roles in advanced materials and biomedical ...research. However, preparing prefunctionalized core porphyrins by traditional low‐yielding statistical synthesis and purifying them after peptide ligation through many rounds of HPLC purification is tedious and unsustainable. Herein, we report a novel integrated solid‐phase synthetic protocol for the construction of porphyrin moieties from simple aldehydes and dipyrromethanes on resin‐bound peptides directly to form mono‐, cis/trans‐di‐, and trivalent porphyrin–peptide conjugates in a highly efficient and controllable manner; moreover, only single final‐stage HPLC purification of the products is needed. This efficient strategy enables the rapid, greener, and substrate‐controlled diversity‐oriented synthesis of multivalent porphyrin–(long) peptide conjugate libraries for multifarious biological and materials applications.
A practical integrated solid‐phase synthetic protocol is reported for the direct construction of porphyrin moieties on resin‐bound peptides from simple aldehyde and dipyrromethane building blocks. Monovalent, cis/trans‐divalent, and trivalent porphyrin–(long) peptide conjugate products can be formed by this method in a highly efficient and controllable manner.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We introduce a new and highly efficient synthetic protocol towards multifunctional fluorescent cyclopeptides by solid‐phase peptide macrocyclization via dipyrrin construction, with full scope of ...proteinogenic amino acids and different ring sizes. Various bicyclic peptides can be created by dipyrrin‐based crosslinking and double dipyrrin‐ring formation. The embedded dipyrrin can be either transformed to fluorescent BODIPY and then utilized as cancer‐selective targeted protein imaging probe in vitro, or directly employed as a selective metal sensor in aqueous media. This work provides a valuable addition to the peptide macrocyclization toolbox, and a blueprint for the development of multifunctional dipyrrin linkers in cyclopeptides for a wide range of potential bioapplications.
A facile and highly efficient synthetic protocol towards multifunctional fluorescent cyclopeptides by solid‐phase peptide macrocyclization via dipyrrin staple construction is introduced, where the dipyrrin moiety serves as a novel multifunctional staple linker for targeted protein imaging and selective metal sensing.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Traditional fluorescent peptide chemical syntheses hinge on the use of limited fluorescent/dye-taggable unnatural amino acids and entail multiple costly purifications. Here we describe a facile and ...efficient protocol for in situ construction of dipyrrins on the N-terminus with 20 natural and five unnatural amino acids and the lysine's side chain of selected peptides/peptide drugs through Fmoc-based solid-phase peptide synthesis. The new strategy enables the direct formation of boron–dipyrromethene (BODIPY)–peptide conjugates from simple aldehyde and pyrrole derivatives without pre-functionalization, and only requires a single-time chromatographic purification at the final stage. As a model study, synthesized EBNA1-targeting BODIPY1–Pep4 demonstrates intact selectivity in vitro , responsive fluorescence enhancement, and higher light cytotoxicity due to the photo-generation of cytotoxic singlet oxygen. This work offers a novel practical synthetic platform for fluorescent peptides for multifaceted biomedical applications.
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IJS, KILJ, NUK, UL, UM, UPUK
Corroles have attracted increasing research interests in recent decades owing to their unique properties over porphyrins. However, the relatively inefficient and tedious synthetic procedures of ...corrole building blocks with functional groups for bioconjugation hindered their bioapplications. Herein, we report a highly efficient protocol to synthesize corrole‐peptide conjugates with good yields (up to 63 %) without using prepared corrole building blocks. By condensing two −COOH‐bearing‐dipyrromethane molecules onto an aldehyde group on resin‐bound peptide chains in a controllable manner, a series of desired products with long (up to 25 residues) and bioactive peptide chains were obtained with at most one chromatographic purification. The synthesized compounds exhibited potential applications as chelators for metal ions for biomedical applications, as building blocks for supramolecular materials, as well as targeted fluorescent probes.
Solid‐phase peptide synthesis: An efficient and practical protocol is reported to functionalize peptides by corrole motifs without using prepared corrole building blocks. The synthesized corrole‐peptide conjugates displayed their multifunctionality for metal chelating, aggregation, as well as targeted imaging.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
An oxidative cascade cyclization of β-keto esters has been developed for the construction of the tricyclic picrotoxane motif in a single step, and DFT calculations suggested a possible cationic ...cyclization mechanism. This cascade cyclization can be operated on a 20 g scale to obtain a 77% total yield of the tricyclic products, which in turn can be converted to versatile intermediates for further elaboration to picrotoxanes and their structurally related compounds.
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IJS, KILJ, NUK, PNG, UL, UM
Two homometallic ytterbium dimers are prepared and their solution‐state photoluminescence and upconversion properties are investigated. Both complexes exhibit two‐photon cooperative luminescence ...upconversion in the visible region (λem ≈ 510 nm) upon excitation into the near‐infrared Yb 2F5/2 ← 2F7/2 absorption band at 980 nm. This miniaturization of the cooperative luminescence phenomenon down to just two Yb ions unequivocally proves the mechanistic origins of this process. Time‐resolved measurements and excited‐state modeling indicate the presence of a slow recombination of two singly excited ions Yb*Yb* into a virtual excited state, which ultimately gives rise to the observed emission at ≈510 nm.
Cooperative luminescence upconversion is observed for two discrete dimeric Yb complexes in solution with green emission being observed upon near‐infrared excitation at 980 nm. Kinetic experiments reveal a slow energy transfer step able to compete with the non‐radiative deactivation of Yb*, finally leading to a virtual doubly excited state.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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