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Oscillating reactions are among the most intriguing phenomena in chemistry, but many questions on their mechanisms still remain unanswered, due to their intrinsic complexity and to the low sensitivity of the most common spectroscopic techniques toward the reaction brominated species. In this work, we investigate the cerium ion-catalyzed Belousov-Zhabotinsky (BZ) oscillating reaction by means of time-resolved X-ray absorption spectroscopy (XAS), in combination with UV-vis spectroscopy and unsupervised machine learning, multivariate curve resolution, and kinetic analyses. Altogether, we provide new insights into the collective oscillatory behavior of the key brominated species involved in the classical BZ reaction and measure previously unreported oscillations in their concentrations through Br K-edge XAS, while simultaneously tracking the oscillatory Ce 4+ -to-Ce 3+ transformation by coupling XAS with UV-vis spectroscopy. Our work evidences the potential of the XAS technique to investigate the mechanisms of oscillatory chemical systems whose species are often not detectable with conventional experimental methods.

Brønsted basicity is a fundamental chemical property featured by several kinds of inorganic and organic compounds. In this Review, we treat a particularly high basicity resulting from the mechanical entanglement involving two or more molecular subunits in catenanes and rotaxanes. Such entanglement allows a number of basic sites to be in close proximity with each other, highly increasing the proton affinity in comparison with the corresponding, non-entangled counterparts up to obtain superbases, properly defined as mechanically interlocked superbases. In the following pages, the development of this kind of superbases will be described with a historical perusal, starting from the initial, serendipitous findings up to the most recent reports where the strong basic property of entangled molecular units is the object of a rational design., (© 2024. The Author(s).)

The use of Activated Carboxylic Acids (ACAs) allows the time-controlled operation of dissipative chemical systems based on the acid-base reaction by providing both the stimulus that temporarily drives a physicochemical change and, subsequently, the counter-stimulus with a single reagent addition. However, their application is inherently limited to acid-sensitive systems. To overcome this limitation, we herein develop a straightforward device for the transduction of the acid-base stimuli delivered by an ACA into a voltage signal that, in turn, is used to control voltage-sensitive circuits that are not pH-responsive by themselves. The signal transductor can be easily assembled from common laboratory equipment and employs aqueous solutions of readily available chemicals. Furthermore, the operator can simply and intuitively tune the amplitude of the voltage signal, as well as its duration and offset by varying the concentration of the chemical species involved in the transduction process., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Chiral oxygenated aliphatic moieties are recurrent in biological and pharmaceutically relevant molecules and constitute one of the most versatile types of functionalities for further elaboration. Herein we report a protocol for straightforward and general access to chiral γ -lactones via enantioselective oxidation of strong nonactivated primary and secondary C( sp 3 )-H bonds in readily available carboxylic acids. The key enabling aspect is the use of robust sterically encumbered manganese catalysts that provide outstanding enantioselectivities (up to >99.9%) and yields (up to 96%) employing hydrogen peroxide as the oxidant. The resulting γ -lactones are of immediate interest for the preparation of inter alia natural products and recyclable polymeric materials.

The dissipative translocation of the Zn 2+ ion between two prototypical coordination complexes has been investigated by combining X-ray absorption and 1 H NMR spectroscopy. An integrated experimental and theoretical approach, based on state-of-the-art Multivariate Curve Resolution and DFT based theoretical analyses, is presented as a means to understand the concentration time evolution of all relevant Zn and organic species in the investigated processes, and accurately characterize the solution structures of the key metal coordination complexes. Specifically, we investigate the dissipative translocation of the Zn 2+ cation from hexaaza-18-crown-6 to two terpyridine moieties and back again to hexaaza-18-crown-6 using 2-cyano-2-phenylpropanoic acid and its para -chloro derivative as fuels. Our interdisciplinary approach has been proven to be a valuable tool to shed light on reactive systems containing metal ions that are silent to other spectroscopic methods. These combined experimental approaches will enable future applications to chemical and biological systems in a predictive manner.

The adoption of a supramolecular approach in catalysis promises to address a number of unmet challenges, ranging from activity (unlocking of novel reaction pathways) to selectivity (alteration of the innate selectivity of a reaction, e.g. selective functionalization of C-H bonds) and regulation (switch ON/OFF, sequential catalysis, etc.). Supramolecular tools such as reversible association and recognition, pre-organization of reactants and stabilization of transition states upon binding offer a unique chance to achieve the above goals disclosing new horizons whose potential is being increasingly recognized and used, sometimes reaching the degree of ripeness for practical use. This review summarizes the main developments that have opened such new frontiers, with the aim of providing a guide to researchers approaching the field. We focus on artificial supramolecular catalysts of defined stoichiometry which, under homogeneous conditions, unlock outcomes that are highly difficult if not impossible to attain otherwise, namely unnatural reactivity or selectivity and catalysis regulation. The different strategies recently explored in supramolecular catalysis are concisely presented, and, for each one, a single or very few examples is/are described (mainly last 10 years, with only milestone older works discussed). The subject is divided into four sections in light of the key design principle: (i) nanoconfinement of reactants, (ii) recognition-driven catalysis, (iii) catalysis regulation by molecular machines and (iv) processive catalysis.

The understanding of reactive processes involving organic substrates is crucial to chemical knowledge and requires multidisciplinary efforts for its advancement. Herein, we apply a combined multivariate, statistical and theoretical analysis of coupled time-resolved X-ray absorption (XAS)/UV-Vis data to obtain detailed mechanistic information for on the C-H bond activation of 9,10-dihydroanthracene (DHA) and diphenylmethane (Ph2CH2) by the nonheme FeIV-oxo complex [N4Py·FeIV(O)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) in CH3CN at room temperature. Within this approach, we determine the number of key chemical species present in the reaction mixtures and derive spectral and concentration profiles for the reaction intermediates. From the quantitative analysis of the XAS spectra the transient intermediate species are structurally determined. As a result, it is suggested that, while DHA is oxidized by [N4Py·FeIV(O)]2+ with a hydrogen atom transfer-electron transfer (HAT-ET) mechanism, Ph2CH2 is oxidized by the nonheme iron-oxo complex through a HAT-radical dissociation pathway. In the latter process, we prove that the intermediate FeIII complex [N4Py·FeIII(OH)]2+ is not able to oxidize the diphenylmethyl radical and we provide its structural characterization in solution. The employed combined experimental and theoretical strategy is promising for the spectroscopic characterization of transient intermediates as well as for the mechanistic investigation of redox chemical transformations on the second to millisecond time scales.

In this work, we obtain detailed mechanistic and structural information on bimolecular chemical reactions occurring in solution on the second to millisecond time scales through the combination of a statistical, multivariate and theoretical analysis of time-resolved coupled X-ray Absorption Spectroscopy (XAS) and UV-Vis data. We apply this innovative method to investigate the sulfoxidation of p-cyanothioanisole and p-methoxythioanisole by the nonheme Fe IV oxo complex [N4Py·Fe IV (O)] 2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) in acetonitrile at room temperature. By employing statistical and multivariate techniques we determine the number of key chemical species involved along the reaction paths and derive spectral and concentration profiles for the reaction intermediates. From the quantitative analysis of the XAS spectra we obtain accurate structural information for all reaction intermediates and provide the first structural characterization in solution of complex [N4Py·Fe III (OH)] 2+ . The employed strategy is promising for the spectroscopic characterization of transient species formed in redox reactions.

Sterically hindered imine-based non-heme complexes 4 and 5 rapidly self-assemble in acetonitrile at 25 °C, when the corresponding building blocks are added in solution in the proper ratios. Such complexes are investigated as catalysts for the H 2 O 2 oxidation of a series of substrates in order to ascertain the role and the importance of the ligand steric hindrance on the action of the catalytic core 1, previously shown to be an efficient catalyst for aliphatic and aromatic C-H bond oxidation. The study reveals a modest dependence of the output of the oxidation reactions on the presence of bulky substituents in the backbone of the catalyst, both in terms of activity and selectivity. This result supports a previously hypothesized catalytic mechanism, which is based on the hemi-lability of the metal complex. In the active form of the catalyst, one of the pyridine arms temporarily leaves the iron centre, freeing up a lot of room for the access of the substrate., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Predictability is a key requirement to encompass late-stage C-H functionalization in synthetic routes. However, prediction (and control) of reaction selectivity is usually challenging, especially for complex substrate structures and elusive transformations such as remote C(sp 3 )-H oxidation, as it requires distinguishing a specific C-H bond from many others with similar reactivity. Developed here is a strategy for predictable, remote C-H oxidation that entails substrate binding to a supramolecular Mn or Fe catalyst followed by elucidation of the conformation of the host-guest adduct by NMR analysis. These analyses indicate which remote C-H bonds are suitably oriented for the oxidation before carrying out the reaction, enabling prediction of site selectivity. This strategy was applied to late-stage C(sp 3 )-H oxidation of amino-steroids at C15 (or C16) positions, with a selectivity tunable by modification of catalyst chirality and metal., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, we propose a method to directly determine the mechanism of the reaction between the nonheme complex Fe II (tris(2-pyridylmethyl)amine) ([Fe II (TPA)(CH 3 CN) 2 ] 2+ ) and peracetic acid (AcOOH) in CH 3 CN, working at room temperature. A multivariate analysis is applied to the time-resolved coupled energy-dispersive X-ray absorption spectroscopy (EDXAS) reaction data, from which a set of spectral and concentration profiles for the reaction key species is derived. These "pure" extracted EDXAS spectra are then quantitatively characterized by full multiple scattering (MS) calculations. As a result, structural information for the elusive reaction intermediates [Fe III (TPA)(κ 2 -OOAc)] 2+ and [Fe IV (TPA)(O)(X)] +/2+ is obtained, and it is suggested that X = AcO - in opposition to X = CH 3 CN. The employed strategy is promising both for the spectroscopic characterization of reaction intermediates that are labile or silent to the conventional spectroscopic techniques, as well as for the mechanistic understanding of complex redox reactions involving organic substrates.

Second-order rate constants of the aminolysis of 2-cyano-2-phenylpropanoic anhydride 3 by a series of N-methylanilines differently substituted in the aromatic moiety (4a-d) were measured in dichloromethane. The common reaction product of aminolysis is 2-cyano-2-phenylpropanoic acid 1, which is known to be an effective fuel for acid-base driven molecular machines, but cannot be used in molar excess with respect to the machine. The motivation behind the kinetic study has been the prospect of using the aminolysis of 3 to supply the machine with fuel at a rate that is never so high as to overfeed the system, thus avoiding the malfunction of the machine with concomitant waste of fuel. Knowledge of the kinetic parameters dictated the choice of 4c as the best nucleophile in the lot for feeding acid 1 into a catenane-based molecular machine at a rate that ensured a correct operation.

This work aimed to render phenomenologically autonomous the otherwise stepwise operation of a catenane-based molecular switch, which is chemically triggered by the decarboxylation of 2-cyano-2-phenylpropanoic acid (2). Given that any amount of 2 in stoichiometric excess with respect to the catenane is consumed in a side reaction, the authors resorted to the corresponding anhydride 5, the slow hydrolysis of which, due to adventitious water in dichloromethane, continuously produces in situ the actual fuel 2. As a consequence, the machine does not require a reloading after each cycle, but switches back and forth as long as fuel is present., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Time-resolved X-ray absorption (XAS) and UV-vis spectroscopies with millisecond resolution are used simultaneously to investigate oxidation reactions of organic substrates by nonheme iron activated species. In particular, the oxidation processes of arylsulfides and benzyl alcohols by a nonheme iron-oxo complex have been studied. We show for the first time that the pseudo-first-order rate constants of fast bimolecular processes in solution (milliseconds and above) can be determined by time-resolved XAS technique. By following the Fe K-edge energy shift, it is possible to detect the rate of iron oxidation state evolution that matches that of the bimolecular reaction in solution. The kinetic constant values obtained by XAS are in perfect agreement with those obtained by means of the concomitant UV-vis detection. This combined approach has the potential to provide unique insights into reaction mechanisms in the liquid phase that involve changes of the oxidation state of a metal center, and it is particularly useful in complex chemical systems where possible interferences from species present in solution could make it impossible to use other detection techniques.

Substrate-selectivity stemming from recognition is a key feature of enzymes that has been seldom observed in artificial catalysts. Herein, we report a recognition-driven, substrate-selective C-H oxidation that inverts the intrinsic reactivity of the competing C-H bonds. Analysis of this selectivity highlights an unexpectedly high reactivity enhancement imparted by intramolecularity.

It is well-known that while RIS allows the management of all input and output data of a Radiology service, PACS plays a major role in the management of all radiologic images. However, the two systems should be closely integrated: scheduling of a radiologic exam requires direct automated integration with the system of image management for retrieval of previous exams and storage of the exam just completed. A modern information system of integration of data and radiologic images should be based on an automated work flow management in al its components, being at the same time flexible and compatible with the ward organization to support and computerize each stage of the working process. Similarly, standard protocols (DICOM 3.0, HL7) defined for interfacing with the Diagnostic Imaging (D.I.) department and the other components of modules of a modern HIS, should be used. They ensure the system to be expandable and accessible to ensure share and integration of information with HIS, emergency service or wards. Correct RIS/PACS integration allows a marked improvement in the efficiency of a modern D.I. department with a positive impact on the daily activity, prompt availability of previous data and images with sophisticated handling of diagnostic images to enhance the reporting quality. The increased diffusion of internet and intranet technology predicts future developments still to be discovered.

One of the major and demanding problems in the management of a modern department of Radiology is undoubtedly the organization of a radiologic archive. Its management has been increasingly difficult in last years both for the increase in procedures and the number of radiologic exams. At the Radiology department of UCSC, since some years, this problem has been tackled. Major objectives have been identified in focusing on responsibilities, global management and planning of radiologic film retrieval and archiving integrated with health care activities (scheduling of admissions and exam appointments, reporting, discharge). Based on these assumptions, the archive has been divided into 3 sections, each dynamically integrated with the others. The 3 archives should be integrated with RIS and supported by information technology. RIS is considered the starting point of the process. In fact the system ensures communication to the archiving workstation and to the radiology room of patient admission and consequent execution of the exam which involves image production. This user-friendly procedure enables consistent information between RIS and archiving system and correct association of images to the patient medical report, for subsequent consultation.

Until recently Radiology Information Systems (RISs) were considered a set of separate, often heterogeneous applications at the functional, technological and architectural level. In last years, the need for an integrated methodological approach and an engineering vision of the system design has become the most important aspect in the implementation of RISs. Based on this approach, the fundamental organizational, operational and clinical objectives of an advanced RIS together with the major critical factors of success, are presented. Such objectives and requirements have constituted the starting basis for the implementation of the DREAM (Distributed radiological environment advanced and multimedia) system, the result of the collaboration of the "Università Cattolica del S. Cuore, Policlinico A. Gemelli" of Rome and "GESI-Gestione Sistemi per l'Informatica". An overview of the main functional characteristics, the most qualifying aspects of the system and the methodological approach followed in its implementation, are reported.