Supramolecular hierarchy among halogen and hydrogen bond donors in light-induced surface patterning

Halogen bonding, a noncovalent interaction possessing several unique features compared to the more familiar hydrogen bonding, is emerging as a powerful tool in functional materials design. Herein, we unambiguously show that one of these characteristic features, namely high directionality, renders halogen bonding the interaction of choice when developing azobenzene-containing supramolecular polymers for light-induced surface patterning. The study is conducted by using an extensive library of azobenzene molecules that differ only in terms of the bond-donor unit. We introduce a new tetrafluorophenol-containing azobenzene photoswitch capable of forming strong hydrogen bonds, and show that an iodoethynyl-containing azobenzene comes out on top of the supramolecular hierarchy to provide unprecedented photoinduced surface patterning efficiency. Specifically, the iodoethynyl motif seems highly promising in future development of polymeric optical and photoactive materials driven by halogen bonding

Fluorine-induced J-aggregation enhances emissive properties of a new NLO push-pull chromophore

A new fluorinated push-pull chromophore with good second-order NLO properties even in concentrated solution shows solid state intermolecular aryl-fluoroaryl interactions leading to J-aggregates with intense solid state luminescence. This journal is \ua9 the Partner Organisations 2014

Confined space design by nanoparticle self-assembly

Nanoparticle (NP) self-assembly has led to the fabrication of an array of functional nanoscale systems, having diverse architectures and functionalities. In this perspective, we discuss the design and application of NP suprastructures (SPs) characterized by nanoconfined compartments in their self-assembled framework, providing an overview about SP synthetic strategies reported to date and the role of their confined nanocavities in applications in several high-end fields. We also set to give our contribution towards the formation of more advanced nanocompartmentalized SPs able to work in dynamic manners, discussing the opportunities of further advances in NP self-assembly and SP research

Photochemistry of transition metal complexes (2019-2020)

This Chapter aims to summarise the major advances achieved over 2019 and 2020 in the field of photochemistry and photocatalysis by transition metal compounds. In the last years, one of the central research themes has been the development of efficient photocatalytic complexes based on earth-abundant metals as a potential eco-friendly, resource-efficient, and sustainable photochemical approach. Nevertheless, second- and third-row metal complexes still represent key building blocks in the design of new photocatalysts in organic transformations, biomedical applications, as well as in green chemistry fields

Halogen bonding as a key interaction in the self-assembly of iodinated diphenylalanine peptides

The diphenylalanine peptide FF (H2N-Phe-Phe-COOH) is a simple building-block that has been extensively studied for multiple purposes. Among the many possible mutations finalized to tailor specific functions and properties of FF-based materials, halogenation was marginally considered despite the huge changes it confers to molecular self-assembly. Here, we report a detailed study on the role of halogenation, specifically iodination, in the aggregation behavior of iodine-modified FF dipeptides. Single-crystal X-ray structures of mono-iodinated—F(I)F—and bis-iodinated—F(I)F(I)—diphenylalanine reveal that halogen atoms exert a key role in the packing features of these compounds. Specifically, halogen bonding provides additional stability to the dry interfaces formed by the aromatic rings, providing a contribution in the solid-state packing of these dipeptides. The structural evidence of halogen bonding as crucial noncovalent interaction confirms the great potential of halogenation as supramolecular tool for peptide-based systems

Phenyl cation: a versatile intermediate

Phenyl cations are short-lived electrophiles and can be smoothly generated by photolysis of aromatic halides (chlorides, fluorides) and esters (sulfonates, sulfates and phosphates) in protic media. Indeed, the heterolytic cleavage of an Arylsingle bondLG bond (LG = leaving group; X, OR) allows for the generation of a triplet aryl cation (3Ar+) that chemoselectively reacts with π-bond nucleophiles to perform transition metal-free arylations. Aryl cations can be also exploited in the generation of other high energy intermediates, such as diradicals (including ortho-arynes and α,n-didehydrotoluenes), potentially useful for medicinal applications. Since the generation of phenyl cations is always accompanied by the release of a strong acid (e.g. sulfonic acids), the phenyl cation precursors are actually non ionic photoacid generators (PAGs) that find useful applications in nanolithography

Photoluminescent nanocluster-based probes for bioimaging applications

In the continuous search for versatile and better performing probes for optical bioimaging and biosensing applications, many research efforts have focused on the design and optimization of photoluminescent metal nanoclusters. They consist of a metal core composed by a small number of atoms (diameter < 2–3 nm), usually coated by a shell of stabilizing ligands of different nature, and are characterized by molecule-like quantization of electronic states, resulting in discrete and tunable optical transitions in the UV–Vis and NIR spectral regions. Recent advances in their size-selective synthesis and tailored surface functionalization have allowed the effective combination of nanoclusters and biologically relevant molecules into hybrid platforms, that hold a large potential for bioimaging purposes, as well as for the detection and tracking of specific markers of biological processes or diseases. Here, we will present an overview of the latest combined imaging or sensing nanocluster-based systems reported in the literature, classified according to the different families of coating ligands (namely, peptides, proteins, nucleic acids, and biocompatible polymers), highlighting for each of them the possible applications in the biomedical field. Graphical abstract: [Figure not available: see fulltext.