Synthesis, Mechanism and Catalytic Applications of Pillar[n]arenes

Pillar[n]arenes (P[n] n = 5-15) are a new class of macrocyclic arenes discovered for the first time by Ogoshi in 2008, which attracted a lot of attention due to their unique binding properties towards neutral electron poor compounds. Our research was focused on the enhancement of the yield of the larger macrocycle P[6], starting from three different alkoxy substituted benzene derivatives. Our synthetic approach involved the study of a series of small organic and organometallic cations in the role of a template, such as a cobaltocenium salt, ferrocenium salt, tetramethylammonium chloride and butyl methyl imidazolium salt. Through mass spectroscopy we further investigated the reaction templated by the quaternary ammonium salt and promoted by the presence of FeCl3. We finally tuned the experimental conditions for the conversion of both P[5] and its oligomeric by-products into P[6]. Finally our group studied the catalytic effect of the presence of P[5] in nucleophilic substitution reactions, observing a rate acceleration between 10 and 20 times when the substrates were allyl halides and primary linear amines. This was the first example of the use of pillararenes as real organocatalysts

Pillar[n]arenes: towards higher yielding synthetic routes

An efficient templated approach for the synthesis of pillar[n]arenses (P[n]) bearing different alkoxy substituent has been developed. P[6] was obtained in high yield up to 38% with higher selectivity than P[5] thank to the use of small organic cation binding P[6] better than P[5] as templates

Pillar[n]arenes: towards higher yielding synthetic routes

An efficient templated approach for the synthesis of pillar[n]arenses (P[n]) bearing different alkoxy substituent has been developed. P[6] was obtained in high yield up to 38% with higher selectivity than P[5] thank to the use of small organic cation binding P[6] better than P[5] as templates

Host-guest interaction as driving force for the synthesis of pillar[6]arenes with a close insight into the cyclization mechanism and the templating role of the guest molecules.

3reservedmixedDa Pian, Marta; Fabris, Fabrizio; Scarso, AlessandroDA PIAN, Marta; Fabris, Fabrizio; Scarso, Alessandr

Interpretation of Evidence: The Key to Conveying Information to Court

The advent of new technologies such as DNA typing, the weight of scientific evidence in criminal trials of widespread publicity, and the proliferation of fictional and non-fictional works in popular me - dia have contributed to making forensic science well known, al - though perhaps not as well understood, by the general public. One of the consequences of this popularisation of forensic science was a sharp change in the attitude of investigators, who increasingly tend to delegate to scientists the collection of information necessary to identify the perpetrator of the crime. However, the prominent focus on the search of biological traces or fingerprints, due to their high potential for the personal identification of the individuals present at the crime scene, somewhat fade the interest towards other kinds of evidence, such as trace evidence. This kind of evidence is in fact perceived by judges and lawyers as less informative, because they think that \u201call plastic items are the same\u201d, i.e. that it is impossible to discriminate among mass produced items. The purpose of this pa- per is to stress that, with sound methods for interpreting evidence, it is possible to improve the communication between the scientist and the Court, and to show the real significance of the analytical results, in the context of the case. The analysis of the traces found on a knife used in a murder case were performed by optical microscopy, IR spectroscopy, and UV-visible spectroscopy. The interpretation of evidence was car - ried out according to a Bayesian approach. A description of the interpretation of evidence in a case in which fibres were the key evidence. It is shown that the key aspects for having a high value of the evidence are the circumstances of the case and the reconstruction of the events given by the prosecutor and by the defence, in addition of course to a sound analytical pro- cedure. In other words, it is shown that in some cases the evidential value of fibres or other trace evidence can be very high, sometimes comparable to that of fingerprints or DNA: when properly inter - preted, trace evidence can give key information for solving cases

Insights into the synthesis of pillar[5]arene and its conversion into pillar[6]arene

The synthesis of pillar[5]arenes from p-dialkoxybenzene and formaldehyde in the presence of iron(III) chloride and tetramethylammonium chloride under mild reaction conditions was investigated in detail. For the first time, the presence of linear intermediate oligomers and their conversion into pillar[6]arenes was demonstrated. Incorporation experiments were carried out using methoxy- and ethoxy-functionalized pillar[5]arenes that were reacted respectively with 1,4-diethoxy- and 1,4-dimethoxybenzene, observing the formation of the corresponding co-pillar[6]arene derivatives, PMe[5]Et[1] and PEt[5]Me[1]. An experiment in which methoxy- and ethoxy-functionalized pillar[5]arenes were reacted together led to the major formation of scrambled P[5] derivatives characterized by a bell shape distribution of ethoxy and methoxy aromatic units. Co-Pillar[6]arenes P[6] were also detected by ESI-MS in minor amounts with a similar symmetrical distribution of substituents that allowed the proposal of multiple cleavage events occurring on the same macrocyclic ring forming in solution a series of smaller fragments, whose recombination leads to the observed product distribution of P[5] and P[6] derivatives

Assembly of poly-3-(hexylthiophene) nanocrystals in marginal solvent: The role of PCBM

Poly-3-(hexyl thiophene) (P3HT) represents the benchmark semiconducting polymer for the fabrication of organic photovoltaics (OPVs), where it acts as electron donor component in combination with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as electron acceptor counterpart. The assembly of P3HT under marginal solvent conditions to form dispersions of fibrillar nanocrystals (NCs) is a particularly attractive method for the subsequent fabrication of highly crystalline films, if compared to depositions involving polymer solutions followed by relatively harsh thermal/solvent treatments, which are often incompatible with sensitive substrates. However, the mechanisms that drive the assembly of P3HT to NCs in marginal solvents are not fully understood, while the effects induced by the presence of PCBM during polymer assembly are still debated. In order to shed light into these processes, we systematically investigated the aggregation/crystallization behaviour of P3HT to NCs under different marginal-solvent conditions and in the presence of different relative contents of PCBM. The starting concentration of P3HT was shown to influence assembly kinetics, the micro-/nano-morphology and the photophysical properties of the formed NCs, as demonstrated by combining atomic force microscopy (AFM) and UV–vis adsorption spectroscopy. Polymer assembly to NCs was also highly dependent on the relative concentration of PCBM, within P3HT:PCBM mixtures typically applied in OPVs. In particular, the combination of UV–vis, AFM and wide-angle X-ray scattering (WAXD) highlighted that PCBM confined the aggregation/crystallization process of P3HT NCs, allowing the formation of extended crystallites, while at high concentrations it hindered the formation of NCs slowing down their assembly