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Over the past two decades, the chirality-induced spin selectivity (CISS) effect was reported in several experiments disclosing a unique connection between chirality and electron spin. Recent theoretical works have highlighted time-resolved Electron Paramagnetic Resonance (trEPR) as a powerful tool to directly detect the spin polarisation resulting from CISS. Because of the absence of interfaces with conducting electrodes, such spectroscopic evidence could provide a clear understanding of how CISS works at the intramolecular level. Experimental results have demonstrated the potential of this approach for detecting a spin-polarised photoinduced electron transfer (ET) in hybrid systems comprising a CdSe quantum dot as an electron donor (D) connected by a chiral linker (χ) to a fullerene derivative as an electron acceptor (A). However, the study of the ET process in fully organic D-χ-A dyads holds tremendous potential for the unambiguous detection of CISS. Here, we report a first attempt performed using novel D-χ-A dyads, comprising pyrene (D) and fullerene (A) connected by chiral saturated peptide bridges (χ) of different length and electric dipole moment. The dyads are investigated by an array of techniques, including cyclic voltammetry, optical spectroscopies, and trEPR. Despite the promising energy alignment of the electronic levels and the evidence of luminescence quenching, trEPR does not detect a significant ET highlighting the challenges of spectroscopic detection of CISS. However, the analysis allows the formulation of guidelines for the design of chiral organic model systems suitable to directly probe CISS-polarised ET.

The removal of Diclofenac sodium from waste waters has a high relevance since it belongs to the therapeutic group most commonly found in wastes. An aromatic-free and low-impact technology that efficiently entraps aqueous pollutants is highly desirable. We synthesised two Boc-protected and aromatic-free tripeptides (Boc-L-Ala-Aib-L-Val-OH and Boc-L-Val-Aib-L-Val-OH) and studied their ability to form gels with mixtures of water and alcohols, such as methanol, ethanol and 2-propanol. Boc-L-Ala-Aib-L-Val-OH forms a strong hydrogel in 2-propanol/water mixtures able to trap up to 97.8% of Eosin Y model molecule and up to 92.0% of Diclofenac sodium from aqueous solutions. The hydrogel is also thixotropic, thermoreversible and biocompatible. This outcome is very encouraging and paves the way to a new approach for developing new materials using aromatic-free hydrogels, useful for water remediation.

It is well assessed that the charge transport through a chiral potential barrier can result in spin-polarized charges. The possibility of driving this process through visible photons holds tremendous potential for several aspects of quantum information science, e.g., the optical control and readout of qubits. In this context, the direct observation of this phenomenon via spin-sensitive spectroscopies is of utmost importance to establish future guidelines to control photo-driven spin selectivity in chiral structures. Here, we provide direct proof that time-resolved electron paramagnetic resonance (EPR) can be used to detect long-lived spin polarization generated by photoinduced charge transfer through a chiral bridge. We propose a system comprising CdSe QDs, as a donor, and C60, as an acceptor, covalently linked through a saturated oligopeptide helical bridge (\c{hi}) with a rigid structure of ~ 10{\AA}. Time-resolved EPR spectroscopy shows that the charge transfer in our system results in a C60 radical anion, whose spin polarization maximum is observed at longer times with respect to that of the photogenerated C60 triplet state. Notably, the theoretical modeling of the EPR spectra reveals that the observed features may be compatible with chirality-induced spin selectivity and identifies which parameters need optimization for unambiguous detection of the phenomenon. This work lays the basis for the optical generation and direct manipulation of spin polarization induced by chirality., Comment: 45 pages, 5 main-text figures, 1 main-text table

Physical hydrogels are supramolecular materials obtained by self-assembly of small molecules called gelators. Aromatic amino acids and small peptides containing aromatic rings are good candidates as gelators due to their ability to form weak bonds as π-π interactions and hydrogen bonds between NH and CO of the peptide chain. In this paper we show our results in the preparation of a transparent hydrogel that was obtained by self-assembly of a fluorine-containing dipeptide that relies on the additional formation of halogen bonds due to the fluorine atoms contained in the dipeptide. We used Boc-D-F2Phe-L-Oxd-OH (F2Phe = 3,4-difluorophenylalainine, Oxd = 4-methyl-5-carboxy-oxazolidin-2-one) that formed a strong and transparent hydrogel in 0.5% w/w concentration at pH = 4.2. The formation of a hydrogel made of unnatural fluorinated amino acids may be of great interest in the evaluation of patients with parkinsonian syndromes and may be used for controlled release.