Amerigo Beneduci

Electrofluorochromism in π-conjugated ionic liquid crystals

Materials in which photoluminescence is modulated by redox processes are known as electrofluorochromic. Intrinsically switchable fluorophores, incorporating both redox and fluorescent moieties, could be ideal electrofluorochromic materials if they possess high fluorescence quantum yields in at least one of their redox states. Fluorescent liquid crystals with redox active centres could combine the above requirements with the advantage to work in bulk anisotropic phases. However, electrofluorochromic liquid crystals have not been reported yet because their synthesis is challenging due to aggregation-caused fluorescent quenching. Here we show the first examples of electrofluorochromic π-conjugated ionic liquid crystals based on thienoviologens. These ordered materials, combining ionic and electronic functions, are highly fluorescence in the bulk state (quantum yield>60%). Their direct electrochemical reduction leads to fast and reversible bulk electrofluorochromic response in both columnar and smectic phases allowing for fluorescence intensity modulation and colour tuning.

Highly routinely reproducible alignment of 1H NMR spectral peaks of metabolites in huge sets of urines.

A method to obtain high reproducibility of (1)H NMR chemical shift of peaks of biofluid metabolites, by simple acidification with HCl is evaluated. Biofluid (1)H NMR analysis is indeed spoiled by a strong chemical shift dependence of metabolite peaks on parameters such as ionic strength, concentration of some earth alkali cations and, mostly, on pH of samples. The resulting chemical shift variations, as large as 0.1 ppm, generate misalignments of homogeneous peaks, artifacts and misinterpretations. Reproducible alignment is essential in (1)H NMR based metabonomics, where peak misalignments prevent even very wide bins (i.e., 0.04 ppm, as elsewhere proposed) from being used to integrate spectral data for multivariate statistical analysis. Here is demonstrated that routine acidification with HCl to 1.2≤pH≤2.0 ensures highly reproducible peak alignment of urine (1)H NMR spectra. In this respect, simple inspection of citrate peaks in the urine can be used to measure pH, as it will be extensively discussed, in that at such low pH they show no dependency on other urine components as reported at higher pH. Under these conditions, in as many as 493 urine samples, in which concentrations of Ca(2+), Mg(2+), K(+), Na(+), Cl(-), phosphate, and creatinine and ionic strength measured by means of well standardized conventional procedures, showed very wide ranges, peaks align within a SD always lower than 0.002 ppm, thus allowing the use of integration bins at least five times narrower than 0.04 ppm.

Metabonomics and population studies: Age-related amino acids excretion and inferring networks through the study of urine samples in two Italian isolated populations

The study of two different Italian isolated populations was combined with a metabonomic approach to better understand tubular handling of amino acids. Levels of amino acids and metabolites have been analyzed by Nucleic Magnetic Resonance and expressed as ratio vs urinary creatinine concentration (mmol/mol). For most of the amino acids there is an age-related U shape pattern of excretion, with the peaks during childhood and old age, and a significant reduction in the adult age. Hierarchical cluster analysis has clearly identified three groups clustering the same amino acids: His, Thr and Ala (group one); Gly and Phe (group two) and a third larger one. Results have been further confirmed by factor and regression analysis, and used to confirm and, in some cases, infer new amino acids networks. As a matter of facts, the identification of strong evidences for clustering of urine excretion of several neutral amino acids suggests the predominant impact of relevant and common transporters

Microwave induced shift of the main phase transition in phosphatidylcholine membranes.

Numerous experimental evidence show that exposure of biological systems to extremely high frequency microwaves may induce significant effects even at low powers. These effects are thought to occur via nonthermal mechanisms involving primarily the interaction of microwaves with phospholipid membrane structures. However, no conclusive experimental evidence that biomembranes exhibit remarkable sensitivity to this radiation has been provided up to now. Here, deuterium nuclear magnetic resonance spectroscopy is used to study the effects of microwaves on 1,2-Dimyristoyl-sn-glycero-3-phosphatidylcholine/(2)H(2)O multilamellar vesicles that serve as biomimetic membranes. Here we show that, if the membrane is brought into close proximity to the transition point, microwaves induce a reduction of water ordering at the membrane interface, an upward shift of the main phase transition temperature and a broadening of the transition region. A deep dosimetric analysis shows that the above effects are nonthermal, indicating the need for a nonthermal hypothesis to explain them. This study suggests that exposure to high-frequency microwaves can have far reaching consequences on active biological systems.

Complexation behaviour of caffeic, ferulic and p-coumaric acids towards aluminium cations: a combined experimental and theoretical approach

Here we have studied the complexation of caffeic, ferulic and p-coumaric acids with Al(III) under physiological conditions (i.e. at 37 °C and in 0.16 M NaCl). Solubility and protonation constants of these hydroxycinnamic acids were firstly determined in order to evaluate the competition of the ligands for the Al(III) and H+ ions. Speciation analysis made by potentiometric titrations and supported by UV and 1H-NMR data shows that a pH-dependent complexation occurs at 1 : 1 and 2 : 1 ligand-to-Al(III) ratios. Notably, these data combined with computational (DFT) results unequivocally indicate that the complexation site is the carboxylate group of the ligands thus excluding any involvement of the phenolic sites.

Electro-optical Properties of Neutral and Radical Ion Thienosquaraines.

Thienosquaraines are an interesting class of electroactive dyes that are useful for applications in organic electronics. Herein, the redox chemistry and electrochromic response of a few newly synthesized thienosquaraines are presented. These properties are compared to those of the commercial 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine. The stability of the radical ions formed in electrochemical processes strongly affects these properties, as shown by cyclic voltammetry, in situ spectroelectrochemistry, and quantum chemical calculations. Furthermore, all of the dyes show aggregation tendency resulting in panchromatic absorption covering the whole UV/Vis spectral range.

Switching from columnar to calamitic mesophases in a new class of rod-like thienoviologens

Here we report the synthesis and the liquid crystalline properties of a new class of thienoviologen salts of the dication series 4,4′-(2,2′-bithiophene-5,5′-diyl)bis(1-alkylpyridinium)++ (mV++s) having different alkyl-chain lengths (m = 9–11). As determined by DSC, polarized optical microscopy and X-ray diffraction analyses, the anion of the salt plays a crucial role in disclosing the liquid crystalline nature of the mV++s. It is shown that the bis(triflimide) salts, mV(NTf2)2s, exhibit a unique bimesomorphic behaviour, self-segregating into columnar rectangular and/or smectic phases. Despite the rod-like shape of these π-extended viologen dications, columnar phases are obtained by the self-assembly of disk-like structures formed by the association of dications into dimers through bridging interacting anions. Interestingly, the bimesomorphism allows “switching” from a columnar to a calamitic phase and vice versa by changing the temperature and/or the alkyl-chain length. In particular, as the length of the alkyl chains increases from m = 9, where a stable rectangular columnar mesophase is observed, to m = 10, an incipient calamitic mesomorphism takes place which manifests itself with the formation of a lamello-columnar mesophase. This ultimately evolves toward a smectic A phase for m = 11.

Millimeter Wave Radiations Affect Membrane Hydration in Phosphatidylcholine Vesicles

A clear understanding of the response of biological systems to millimeter waves exposure is of increasing interest for the scientific community due to the recent convincing use of these radiations in the ultrafast wireless communications. Here we report a deuterium nuclear magnetic resonance spectroscopy (2H-NMR) investigation on the effects of millimeter waves in the 53–78 GHz range on phosphocholine bio-mimetic membranes. Millimeter waves significantly affect the polar interface of the membrane causing a decrease of the heavy water quadrupole splitting. This effect is as important as inducing the transition from the fluid to the gel phase when the membrane exposure occurs in the neighborhood of the transition point. On the molecular level, the above effect can be well explained by membrane dehydration induced by the radiation.

n-Type Columnar Liquid Crystal Combining Ionic and Electronic Functions

The research in the field of electronic and photonic devices based on ordered organic semiconducting materials has been boosted by the development of new multifunctional materials. The order characterizing liquid crystals has been exploited for improving charge mobility performances. However, while in the last decade much effort has been addressed to the synthesis of hole-conducting materials (p-type), less attention has been paid on the development of electron-conducting ones (n-type). Here we show the bulk multifunctional properties of a π-conjugated thienoviologen ionic liquid crystal which exhibits strong electron acceptor character. Notably, the combination of its optical properties with high ionic conductivities and fast intermolecular electron transport, leads to unique bulk electrochromic functions.

Reduced OFF-axis haze in polymer-dispersed liquid crystals

ABSTRACT Polymer-dispersed liquid crystals (PDLCs) are composite materials formed by micron-sized droplets of liquid crystals (LCs) dispersed in a polymer matrix, which can be turned from an opaque state to a transparent one by application of a suitable electric field. PDLCs have been proposed in applications related to the control of light transmittance on large surfaces (light shutters, displays, rear mirrors). Despite several advantages, PDLCs’ main drawback is haze, i.e. the fast decay of transmission at large viewing angles. In this paper, a method for achieving highly transparent PDLC devices over a wide range of viewing angles is proposed. The method is based on the use of PDLCs with tilted elongated LC droplets and driven by opportune electric fields, which are experimentally calculated and able to ensure an almost constant value for OFF-axis transmittance. Graphical Abstract