Maria Ignazia Pilo

Rollover cyclometalation is a distinctive variant of classical cyclometalation where a chelated heterocyclic ligand undergoes internal rotation, releasing one donor atom from coordination and subsequently activating a remote C─H bond with high regioselectivity. The resulting rollover complexes bear an uncoordinated donor atom that confers unique reactivity unavailable to conventional cyclometalated species. The discovery of rollover cyclometalation represents a remarkable example of serendipity in organometallic chemistry, a reaction observed multiple times over decades before being recognized as a distinct and valuable transformation. First appearing in the literature in 1975 and formally named in 1985, rollover cyclometalation involves an unconventional ligand rearrangement to form a new metallacycle. This review traces the serendipitous discovery narrative, emphasizing how early researchers observed the reaction without recognizing its novelty, and examines how subsequent mechanistic studies established rollover cyclometalation as a distinct reaction class. The review explores the reaction’s broad scope beyond 2,2′‐bipyridine, its novel features including reversible retro‐rollover processes, mechanistic insights in gas‐ and condensed‐phase, and growing applications in catalysis, materials science, and novel metallodrugs. This discovery exemplifies Thomas Kuhn’s observation that scientific (r)evolutions often begin with anomalies that challenge existing frameworks, demonstrating how preparedness and systematic investigation can transform unexpected observations into transformative knowledge.

Antimicrobial resistance (AMR) is one of the most urgent public health problems worldwide; multidrug resistance (MDR) is also of concern. In an effort to find new classes of antibiotics, recent studies have found that coordination compounds of noble metals show promising biological effects both in vitro and in vivo, deserving attention as a new class of possible antimicrobial agents. Metal ions in biological systems can essentially have two roles: structural or functional. In the former, the metal ion serves to stabilize structures, especially proteins, while in the latter, the metal is involved in bio-site reactivity (essentially in metallo-enzymes). Two new complexes with 2-(1-ethyl-benzyl)pyridine (py^eb), one monodentate adduct and one cyclometalated ([Au(py^eb)Cl₃] and [Au(py^eb-H)Cl₂], respectively), have been synthesized, characterized, and tested against Gram-positive and Gram-negative bacteria, as well as yeasts, revealing promising antibacterial and antibiofilm properties. The two complexes have been thoroughly characterized by means of 1D and 2D NMR spectroscopy, as well as by cyclic voltammetry, conductivity measurements, FT-IR, and elemental analysis. The study showed that the two derivatives are structurally and chemically different, with the cyclometalated complex being chemically and electrochemically more stable. Antimicrobial assays demonstrated that solutions of the monodentate adduct and of the cyclometalated complex have inhibitory and antibiofilm effects against the pathogenic bacteria E. coli, K. pneumoniae, S. aureus, and S. pyogenes but were unable to reveal a fungicidal effect on C. albicans. A preliminary study was conducted to assess the anti-cancer activity of the compounds, and treatments with the gold compounds also resulted in a significant reduction in the metabolic activity of HT29 colon cancer cells.

Two half-sandwich Ru complexes, including an η-coordinated p -cymene ring along with an η-coordinated 3-R-thiophene ring (R = methyl or n -octyl), have been investigated and their antimicrobial activity has been explored.

Two Pt(II) rollover cyclometalated complexes, [Pt(bpy^Ph−H)(DMSO)Me] (1) and [Pt(bpy^Ph−H)(DMSO)Cl] (2), where bpy^Ph−H is the C₃‐deprotonated 6‐phenyl‐2,2’‐bipyridine, were reacted with aqueous ammonia in acetone at room temperature. In the case of the electron‐poor complex 2 simple substitution of DMSO by NH₃ gave the amino complex [Pt(bpy^Ph−H)(NH₃)Cl] (4), whereas the electron‐rich complex 1 produced the rare acetimine complex [Pt(bpy^Ph−H)(HN=CMe₂)Me] (3), which was isolated and characterized. Complex 3 is stable both in solution and in the solid state, in the presence of air and water. The result is noteworthy, as the condensation product of acetone and ammonia, acetimine, is not stable under mild conditions. The reaction likely requires a Pt(II) electron‐rich complex and the presence of a carbon donor in trans position. An analogous reaction occurs with methylamine, allowing the synthesis of the secondary imine complex [Pt(bpy^Ph−H)(MeN=CMe₂)Me], 5. Starting from this finding a series of cyclometalated acetimine complexes [Pt(N C)(HN=CMe₂)Me] were isolated and characterized with other classical and rollover cyclometalated ligands with an array of different electronic and steric properties, indicating a possible extension of the reaction to various cyclometalated ligands. A preliminary study on the antimicrobial and antitumor properties of complex 3, taken as a model for this class, showed no significant effects against Gram‐positive, Gram‐negative bacteria, or yeasts, but found activity in vitro against HT29 colon cancer cell line.

Fraudulent practices concerning honey are growing fast and involve misrepresentation of origin and adulteration. Simple and feasible methods for honey authentication are needed to ascertain honey compliance and quality. Working on a robust dataset and simultaneously investigating honey traceability and adulterant detection, this study proposed a portable FTNIR fingerprinting approach combined with chemometrics. Multifloral and unifloral honey samples (n = 244) from Spain and Sardinia (Italy) were discriminated by botanical and geographical origin. Qualitative and quantitative methods were developed using linear discriminant analysis (LDA) and partial least squares (PLS) regression to detect adulterated honey with two syrups, consisting of glucose, fructose, and maltose. Botanical and geographical origins were predicted with 90% and 95% accuracy, respectively. LDA models discriminated pure and adulterated honey samples with an accuracy of over 92%, whereas PLS allows for the accurate quantification of over 10% of adulterants in unifloral and 20% in multifloral honey.

Conducting polymers are used in a wide range of applications, especially in the design and development of electrochemical sensors. Their main advantage, in this context, is their ability to efficiently modify an electrode surface using the direct polymerization of a suitable monomer in an electrochemical cell, or by physical coating. Additionally, the conducting polymers can be mixed with further materials (metal nanoparticles, carbonaceous materials) to enhance conductivity and analytical features (linear range, limit of detection, sensitivity, and selectivity). Due to their characteristics, conducting polymer-based amperometric sensors are applied to the determination of different organic and inorganic analytes. A view of recent advances in this field focusing on pyrrole, thiophene, and 3,4-ethylenedioxythiophene as starting materials is reported.

Sardinia, located in Italy, is a significant producer of Protected Designation of Origin (PDO) sheep cheeses. In response to the growing demand for high-quality, safe, and traceable food products, the elemental fingerprints of Pecorino Romano PDO and Pecorino Sardo PDO were determined on 200 samples of cheese using validated, inductively coupled plasma methods. The aim of this study was to collect data for food authentication studies, evaluate nutritional and safety aspects, and verify the influence of cheesemaking technology and seasonality on elemental fingerprints. According to European regulations, one 100 g serving of both cheeses provides over 30% of the recommended dietary allowance for calcium, sodium, zinc, selenium, and phosphorus, and over 15% of the recommended dietary intake for copper and magnesium. Toxic elements, such as Cd, As, Hg, and Pb, were frequently not quantified or measured at concentrations of toxicological interest. Linear discriminant analysis was used to discriminate between the two types of pecorino cheese with an accuracy of over 95%. The cheese-making process affects the elemental fingerprint, which can be used for authentication purposes. Seasonal variations in several elements have been observed and discussed.

Discrimination of honey based on geographical origin is a common fraudulent practice and is one of the most investigated topics in honey authentication. This research aims to discriminate honeys according to their geographical origin by combining elemental fingerprinting with machine-learning techniques. In particular, the main objective of this study is to distinguish the origin of unifloral and multifloral honeys produced in neighboring regions, such as Sardinia (Italy) and Spain. The elemental compositions of 247 honeys were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The origins of honey were differentiated using Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and Random Forest (RF). Compared to LDA, RF demonstrated greater stability and better classification performance. The best classification was based on geographical origin, achieving 90% accuracy using Na, Mg, Mn, Sr, Zn, Ce, Nd, Eu, and Tb as predictors.

Free fluoride ions are effective in combating caries in children, and their supplementation in milk has been widely used worldwide for this purpose. Furthermore, it is known that ionic fluoride added to milk is distributed among its components, but little is known about their quantitative relationships. This is likely due to the absence of an analytical protocol aimed at differentiating and quantifying the most important forms of fluorine present in milk. For the first time, a comprehensive protocol made up of six potentiometric methods devoted to quantifying the most important fractions of fluorine in milk (i.e., the free inorganic fluoride, the inorganic bonded fluorine, the caseins-bonded fluorine, the whey-bonded fluorine, the lipid-bonded fluorine, and the total fluorine) has been developed and tested on real samples. Four of the six methods of the procedure are original, and all have been validated in terms of limit of detection and quantification, precision, and trueness. The data obtained show that 9% of all fluorine was in ionic form, while 66.3% of total fluorine was bound to proteins and lipids, therefore unavailable for human absorption. Beyond applications in dental research, this protocol could be extended also to other foods, or used in environmental monitoring.