A versatile bis-porphyrin tweezer host for the assembly of noncovalent photoactive architectures: a photophysical characterization of the tweezers and their association with porphyrins and other guests

A bis(Zn(II)-porphyrin) tweezer host with anthracene components as apex and side-arms has been synthesized. Mono- (pyridine) and bidentate (4,4'-bipyridine) guests were used as models for single and double axial coordination inside the cavity, respectively. A series of dipyridylporphyrin guests with different substitution patterns and excited-state energy levels have association constants with the tweezers that are of the order of 10(6) M(-1), which is indicative of complexation with the inside of the cavity. This complexation can only occur upon an important distortion of the cavity that opens the bite by about 30 %. This characteristic, in conjunction with their ability to reduce the bite distance by rotation around single bonds, makes these porphyrin tweezers amongst the most versatile so far reported, with tuning of the bite distance in the range of approximately 5-20 Angstroms. Energy transfer to the free-base guest within the triporphyrin complex is nearly quantitative (95-98 %) and the rates of transfer are consistent with a F?rster mechanism that is characterized by a reduced orientation factor.     

Coordination symmetry-dependent structure restoration function of one-dimensional MOFs by molecular respiration

One-dimensional metal-organic compounds with cis, trans symmetry-controlled counter anions were synthesized (cis compound {[Cu(azpy)(H2O)2(OTs)2]*2H2O*(acetone)} (1) and trans compound {[Cu(H2O)4Cu(azpy)2(OTs)2(H2O)2]*2(OTs)*2H2O*2EtOH} (2)). Only 2, having trans conformation, exhibited a complete structure-restoration effect with a mechanism involving layering of molecular "bricks" of water and solvent molecules.     

Capillary gas-chromatographic determination of spermidine in hair lotion

Biogenic polyamines, such as spermidine (SPD, NH2-(CH2)4-NH-(CH2)3-NH2), are ubiquitous polycationic molecules which play a definitive role in many biological processes such as nucleic acid metabolism, protein synthesis, and cell growth. SPD is commonly used as an ingredient in hair lotions, because it seems to promote hair growth. This work describes a capillary GC method for quantitative determination of SPD in hair lotions using 1,6-diaminohexane as internal standard, a methyl silicone capillary column, and a flame ionisation detector. Aliquots of hair lotion were treated with an alkaline aqueous solution and internal standard was added. The emulsion was extracted with diethyl ether containing ethyl chloroformate. Ether extracts, evaporated to dryness and reconstituted in ethyl acetate, were analysed by capillary GC with flame ionisation detection. Validation took into account the specificity, linearity, precision, and accuracy of the analytical method: these parameters were valid for the quantitative determination of SPD in hair lotion.     

Determination of dimethyl fumarate in desiccant and mouldproof agents using ultrasound-assisted extraction gas chromatography with electron-capture detection

A fast, simple, low cost, and high throughput method has been developed for the determination of dimethyl fumarate (DMF) in desiccant and anti-mould agents employed for protecting clothes, footwear and accessories from humidity and mould. The procedure is based on ultrasound-assisted extraction followed by GC-μECD analysis. The method was conveniently optimized, and the analyte was efficiently extracted from the samples in only 5 min using such a low volume of solvent (ethyl acetate) as 1 mL. Simultaneous extractions could be carried out in also 5 min without loosing efficiency. The method has been validated showing good linearity and selectivity. Precision was satisfactory with RSD of 4–5%. Recovery was evaluated in two real samples at different DMF concentration levels and was >90% in all cases. Limit of detection and quantification were at the ng g⁻¹ level. The proposed procedure was applied to the determination of DMF in several desiccant and anti-mould samples. Although most of them were labelled as “silica gel” all the samples tested with the exception of three presented important amounts of DMF, many of them at the high μg g⁻¹ level. The presence and the high concentrations of this allergenic fungicide in desiccant and anti-mould sachets employed in many consumer products, such as clothes and footwear, should be a matter of concern.     

Synthesis of new cycloalkenyliden-pyrroles by domino reaction

Easily accessible cycloalkenyl-1-diazenes and β-dicarbonyl compounds are converted in one-pot into previously unknown functionalized fused cycloalkenyliden-pyrroles of different sizes. The domino reaction proceeds through a base-catalyzed conjugate addition/cyclization/elimination sequence.     

Recyclable catalytic synthesis of substituted quinolines: copper-catalyzed heterocyclization of 1-(2-aminoaryl)-2-yn-1-ols in ionic liquids

A convenient and simple approach for the recyclable catalytic synthesis of substituted quinolines is presented. The method is based on CuCl₂-catalyzed heterocyclization of readily available 1-(2-aminoaryl)-2-yn-1-ols in BmimBF₄ as the solvent at 100 °C for 15-24 h. The solvent-catalyst system could be successfully recycled up to six times without significant loss of activity.     

A minimax theorem in the presence of unbounded Palais-Smale sequences

In a reflexive Banach space we consider a family of functionals that may admit unbounded Palais-Smale sequences. Under some structural conditions we provide a suitable Deformation Lemma that is obtained by modifying the classical pseudo-gradient flow. This leads to a variant of the minimax principle in the Lusternik-Schnirelman Theory.     

The submillimeter: A spectroscopist’s view

The submillimeter spectral region has undergone an explosive growth in the last decade, not only in its impact on the larger scientific and technological world, but also in the high resolution laboratory spectroscopy that makes much of this success possible. Major astronomical and atmospheric instruments are the most visible evidence, but the impact is much broader. This breadth lays the foundation for the impact of submillimeter spectroscopy to extend beyond the scientific community. In this paper we consider the scientific and technical foundations of submillimeter spectroscopy and show how the underlying physics has made possible current successes and shows the path forward to even greater opportunities.     

Probabilistic Study of the Speed of Approach to Equilibrium for an Inelastic Kac Model

This paper deals with a one-dimensional model for granular materials, which boils down to an inelastic version of the Kac kinetic equation, with inelasticity parameter p>0. In particular, the paper provides bounds for certain distances—such as specific weighted χ-distances and the Kolmogorov distance—between the solution of that equation and the limit. It is assumed that the even part of the initial datum (which determines the asymptotic properties of the solution) belongs to the domain of normal attraction of a symmetric stable distribution with characteristic exponent α=2/(1+p). With such initial data, it turns out that the limit exists and is just the aforementioned stable distribution. A necessary condition for the relaxation to equilibrium is also proved. Some bounds are obtained without introducing any extra condition. Sharper bounds, of an exponential type, are exhibited in the presence of additional assumptions concerning either the behaviour, close to the origin, of the initial characteristic function, or the behaviour, at infinity, of the initial probability distribution function. Research partially supported by Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR grant 2006/134526).