Thiophene-based helicenes : eclectic scaffolds in organometallic chemistry

Helicenes are ortho-annulated polycyclic aromatic compounds, endowed with an inherently chiral \u3c0-conjugated system that are intensively studied in different areas of science.1 Among helicenes, thiophene-based helicenes are emerging as an intriguing and promising class of screw-shaped structures, thanks to the presence of the thiophene rings, which confer peculiar chemical, structural, and electronic features.2 For several years, we have been interested in the synthesis and functionalization of tetrathia[7]helicenes (7-TH, Figure 1), which are configurationally stable heterohelicenes, potentially very interesting for applications in optoelectronics,3 catalysis,4 and biology.5 In particular, transition metal-based 7-TH systems are an extremely appealing class of complexes, in which the coordination of metals with the \u3c0-helical ligand, bearing proper coordinating groups, provides unusual chiral architectures. Indeed, the selective functionalization of 2 and 13 positions of the 7-TH scaffold allows the introduction of a variety of substituents, including those with efficient coordinating ability (e.g. cyano, phosphane, phosphine oxide). In this communication we report our recent studies on the synthesis and characterization of 7-TH-based organometallic complexes, and their potential applications in optoelectronics and catalysis

Synthesis and characterization of a tetrathia[7]helicenebased rhenium(I) complex

Tetrathia[7]helicenes (7-TH), formed by thiophene and benzene rings ortho-fused in an alternating fashion, are emerging as one of the most popular class of chiral helical-shaped molecules, thanks to their peculiar electronic and chiroptical properties suitable for manifold applications in different areas of science.1 In particular, transition metal-based 7-TH systems are an extremely appealing class of complexes, in which the coordination of metals with the \uf070-helical ligand, bearing appropriate coordinating functionalities, provides original chiral architectures. Indeed, the effective functionalization of the \uf061-position(s) of the terminal thiophene ring(s) of the 7-TH scaffold allows the introduction of a variety of substituents, including those with efficient coordinating ability (e.g. cyano2, phosphane3, phosphine oxide4). For example, Rh(I)5 and Au(I)6 complexes based on 7-TH phosphanes have been successfully used in the homogenous transition metal catalysis. In our ongoing studies on 7-TH-based organometallic complexes, we have focused on a novel field of investigation concerning the development of rhenium-based polynuclear complexes containing 7-TH phosphine oxide ligands. In this communication, we describe the synthesis and the characterization of a novel dinuclear rhenium(I) complex (Figure 1), along with the elucidation of its tridimensional structure by single crystal X-ray diffraction studies

The 9p21 Rs 1333040 polymorphism is associated with coronary microvascular obstruction in ST-segment elevation myocardial infarction treated by primary angioplasty

Background: Microvascular obstruction (MVO) after primary percutaneous coronary intervention (pPCI) leads to higher incidence of both early and late complications. A number of single nucleotide polymorphisms in 9p21 chromosome have been shown to affect angiogenesis in response to ischaemia. In particular, Rs1333040 with its three genotypic vriants C/C, T/C and T/T might influence the occurrence of MVO after pPCI. Methods: We enrolled ST-elevation myocardial infarction (STEMI) patients undergoing pPCI. The Rs1333040 polymorphism was evaluated by polymerase chain reaction-restriction fragment length polymorphism using restriction endonucleases (Bsml). Two expert operators unaware of the patients' identity performed the angiographic analysis; collaterals were assessed applying Rentrop's classification. Angiographic MVO was defined as a post-pPCI Thrombolysis In Myocardial Infarction (TIMI)<3 or TIMI 3 with myocardial blush grade 0 or 1, whereas electrocardiographic MVO was defined as ST segment resolution Results: Among our 133 STEMI patients (mean age 63 +/- 11 years, men 72%), 35 (26%) and 53 (40%) respectively experienced angiographic or electrocardiographic MVO. Angiographic and electrocardiographic MVO were different among the three variants (p= 0.03 and p=0.02 respectively). In particular, T/T genotype was associated with a higher incidence of both angiographic and electrocardiographic MVO compared with C/C genotype (p=0.04 and p=0.03 respectively). Moreover, Rentrop score <2 detection rate differed among the three genotypes (p=0.03). In particular T/T genotype was associated with a higher incidence of a Rentrop score <2 as compared with C/C genotype (p= 0.02). Conclusion: Rs1333040 polymorphism genetic variants portend different MVO incidence. In particular, T/T genotype is related to angiographic and electrocardiographic MVO and to worse collaterals towards the culprit artery

Dirhenium Coordination Complex Endowed with an Intrinsically Chiral Helical-Shaped Diphosphine Oxide

A one-pot, multicomponent strategy was used to synthesize the first example of the dirhenium carbonyl coordination complex 2, in which the two metal atoms are connected through a chiral helical-shaped diphosphine oxide. Thanks to the flexibility of the helix of helicene 1, complex 2 was isolated in quite a good yield as a stable compound. It was characterized by analytical and spectroscopic techniques as well as by single-crystal X-ray analysis, which confirmed the chemical structure and the peculiar architecture of 2. In addition, computational studies were in agreement with the transitions observed in the experimental UV\u2013vis spectrum, revealing the presence of two bands with maxima at about 520 (metal-to-ligand charge transfer) and 400 nm (IL

Electrocatalytic Reduction of Bromothiophenes on Gold and Silver Electrodes: an Example of Synergism in Electrocatalysis

The reductive cleavage of C\u2013Br bonds on silver electrodes can be regarded as an ideal model of dissociative electron transfer (DET) in electrocatalytic conditions, modulated by many factors, among which the molecular structure is of particular relevance. A detailed mechanistic study based on a large set of compounds with different molecular structures allowed us a full rationalization of the process for the case of aryl bromides in acetonitrile. [1] Now we are extending this research to heteroaromatic halides, in which the heteroatom not only makes the aromatic ring asymmetric from the perspective of the electron density but also can have its own specific interactions with the electrode surface, in addition to those of the halide ions. [2] As a first approach, we have selected the mono-, di-, tri- and tetra-bromothiophene series, plus a series of substituted bromothiophenes together with the corresponding bromobenzenes as benchmarks, investigating (by CV, supported by EIS in selected cases) the electrochemical reduction of the whole family: (i) on glassy carbon, GC, assumed as a non-catalytic reference electrode accounting for intrinsic reactivity; (ii) on the highly catalytic silver electrode; (iii) on gold electrode, showing in former halide cases lower catalytic effects than silver but having the highest affinity for the sulphur atom in the thiophene ring. While the results on GC and on Ag are fully consistent with the formerly studied aryl bromide case on the same two electrodes [1] the catalytic effects of Au appear to be neatly modulated by the relative position of the Br leaving group with respect to the sulphur atom. This feature is quite evident and reproducible in the whole series (including polysubstituted cases provided by our organic partner group), and points to the S atom acting as an asymmetrically anchoring group for the molecule on the Au surface. [1] S. Arnaboldi, A. Gennaro, A.A. Isse, P.R. Mussini (2015) Electrochimica Acta, 158, 427-436 [2] S. Arnaboldi, A. Bonetti, E. Giussani, P.R. Mussini, T. Benincori, S. Rizzo, A.A. Isse, A. Gennaro (2014) Electrochemistry Communications, 38, 100-10

Thiahelicene-based inherently chiral films for enantioselective electroanalysis

Chiral electroanalysis could be regarded as the highest recognition degree in electrochemical sensing, implying the ability to discriminate between specular images of an electroactive molecule, particularly in terms of significant peak potential difference. A groundbreaking strategy was recently proposed, based on the use of \u201cinherently chiral\u201d molecular selectors, with chirality and key functional properties originating from the same structural element. Large differences in peak potentials have been observed for the enantiomers of different chiral molecules, also of applicative interest, using different selectors, all of them based on atropisomeric biheteroaromatic scaffolds of axial stereogenicity. However, helicene systems also provide inherently chiral building blocks with attractive features. In this paper the enantiodiscrimination performances of enantiopure inherently chiral films obtained by electrooxidation of a thiahelicene monomer with helicoidal stereogenicity are presented for the first time. The outstanding potentialities of this novel approach are evaluated towards chiral probes with different chemical nature and bulkiness, in comparison with a representative case of the so far exploited class of inherently chiral selectors with axial stereogenicity. It is also verified that the high enantiodiscrimination ability holds as well for electron spins, as for atropisomeric selectors

Fischer carbene mediated covalent grafting of a peptide nucleic acid on gold surfaces and IR optical detection of DNA hybridization with a transition metalcarbonyl label

Amine-reactive surfaces comprising N-hydroxysuccinimide ester groups as well as much more unusual Fischer alkoxymetallocarbene groups were generated on gold-coated surfaces via self-assembled monolayers of carboxy- and azido-terminated thiolates, respectively. These functions were further used to immobilize homothymine peptide nucleic acid (PNA) decamer in a covalent fashion involving the primary amine located at its N-terminus. These stepwise processes were monitored by polarization modulation reflection - absorption infrared spectroscopy (PM-RAIRS) that gave useful information on the molecular composition of the organic layers. PNA grafting and hybridization with complementary DNA strand were successfully transduced by quartz crystal microbalance (QCM) measurements. Unfortunately, attempts to transduce the hybridization optically by IR in a label-free fashion were inconclusive. Therefore we undertook to introduce an IR reporter group, namely a transition metalcarbonyl (TMC) entity at the 5\u2032 terminus of complementary DNA. Evidence for the formation of PNA-DNA heteroduplex was brought by the presence of \u3bd(C 61O) bands in the 2000 cm-1 region of the IR spectrum of the gold surface owing to the metalcarbonyl label

Enantioselective voltammetry in chiral ionic liquid media

Enantioselective voltammetry in chiral ionic liquid media P. R. Mussini1*, S. Arnaboldi1, M. Longhi1, I.F. Buzzi1, S. Grecchi1, F. Sannicol\uf21, Simona Rizzo2, Voichita Michali1, E. Licandro1, S. Cauteruccio1, T. Bellini3, G. Zanchetta3, A. Gennaro,4 A.A. Isse4, C. Chiappe5, L. Guazzelli5 1 Universit\ue0 degli Studi di Milano, Dip. di Chimica, Via Golgi 19, 20133 Milano, Italy 2 Istituto di Scienze e Tecnologie Molecolari, CNR, via Golgi 19, 20133 Milano, Italy 3 Universit\ue0 degli Studi di Milano, Dip. di Biotecnologie Mediche e Medicina Traslazionale, Via Fratelli Cervi 93, 20090 Segrate (MI), Italy 4 Universit\ue0 degli Studi di Padova, Dip.di Scienze Chimiche, Via Marzolo 1, 35131 Padova, Italy 5 Universit\ue0 degli Studi di Pisa, Dip. di Farmacia, via Bonanno 33, 56126 Pisa, Italy. *[email protected] Chiral media enabling enantiorecognition of chiral probes on achiral electrodes (in terms of significantly different peak potentials for the two probe enantiomers) represent an attractive target in voltammetry. Concerning possible ad hoc strategies, (a) on one hand, transmission of the chiral information should be more and more efficient with increasing structural order at the chiral medium| charged electrode interphase, and it has been recently shown that ionic liquid|electrode interphases are extremely well organized for many layers [1]; (b) on the other hand, outstanding enantioselection performances have been recently observed on electrode surfaces consisting in "inherently chiral" oligomer films, in which chirality originates from the whole main molecular backbone (also determining the material electroactivity), on account of a tailored torsion with high racemization barrier [2-6]. Combining both approaches, we recently developed two "inherently chiral" ionic liquids, consisting of dialkylated bicollidinium salts, with an atropisomeric bipyridinium cation featuring at least one octyl chain and bistrifilimidate counteranions.[7] They show high enantioselectivity in terms of wide potential differences for the enantiomers of a chiral probe when tested even as low concentration additives in commercial achiral ionic liquids. Importantly, similar ability (increasing with additive concentration) was also shown by other selectors of the same family, having shorter alkyl chains and/or different counteranions, and thus solid at room temperature but easier to synthesize [7]. Using such chiral selectors as additives in an achiral ionic liquid rather than as bulk media is even more attractive, since only a small quantity of the enantiopure selector is needed and a low melting point is no more required, but only sufficient solubility in the achiral ionic liquid. For instance, this allowed us to successfully exploit as additives for chiral voltammetry in ionic liquids other inherently chiral selectors based on different stereogenic elements, i.e., a bibenzimidazole atropisomeric scaffold [8,9] and a helicene one. The study provides further evidence of the general validity of the "inherent chirality" strategy, since large potential differences are observed on achiral electrodes for the enantiomers of chiral probes even of very different structure and electroactivity (like in our parallel research on inherently chiral electrodes), and possibly even in experiments with more than one chiral probe. Work is also in progress to better elucidate the process, including evaluation of the twisting power of our selectors as well as comparison with a family of ionic liquids and additives having cations derived from the natural pool, in which chirality originates from one or more stereocentres. References [1] Langmuir 2016, 32, 9507-9512. [2] Angew. Chem. Int. Ed. 2014, 53, 2623 [3] Chem. Eur. J. 2014, 20, 15298. [4] Chem. Sci. 2015, 6,1706. [5] Chem. Eur. J. 2016 , 22,10839. [6] Anal. Bioanal. Chem. 2016, 408, 7243. [7] Angew. Chem. Int. Ed. 2017, 56, 2079. [8] Electrochim. Acta 2015, 179, 250-262. [9] Electrochem. Comm. 2018, accepted. Acknowledgment. The support of Fondazione Cariplo/Regione Lombardia "Avviso congiunto per l\u2019incremento dell\u2019attrattivit\ue0 del sistema di ricerca lombardo e della competitivit\ue0 dei ricercatori candidati su strumenti ERC - edizione 2016\u201d (Project 2016-0923) to our chiral electrochemistry and electroanalysis research is gratefully acknowledged

Internet of Things for Sustainability: Perspectives in Privacy, Cybersecurity, and Future Trends

In the sustainability IoT, the cybersecurity risks to things, sensors, and monitoring systems are distinct from the conventional networking systems in many aspects. The interaction of sustainability IoT with the physical world phenomena (e.g., weather, climate, water, and oceans) is mostly not found in the modern information technology systems. Accordingly, actuation, the ability of these devices to make changes in real world based on sensing and monitoring, requires special consideration in terms of privacy and security. Moreover, the energy efficiency, safety, power, performance requirements of these device distinguish them from conventional computers systems. In this chapter, the cybersecurity approaches towards sustainability IoT are discussed in detail. The sustainability IoT risk categorization, risk mitigation goals, and implementation aspects are analyzed. The openness paradox and data dichotomy between privacy and sharing is analyzed. Accordingly, the IoT technology and security standard developments activities are highlighted. The perspectives on opportunities and challenges in IoT for sustainability are given. Finally, the chapter concludes with a discussion of sustainability IoT cybersecurity case studies