Gadolinium(III) Complexes of dota‐Derived N‐Sulfonylacetamides (H4(dota‐NHSO2R)=10‐{2‐[(R)sulfonylamino]‐2‐oxoethyl}‐1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic Acid): A New Class of Relaxation Agents for Magnetic Resonance Imaging Applications

Four new ligands for lanthanide ions based on the H₃do3a (=1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid) structure and bearing one N‐sulfonylacetamide arm were synthesized, i.e., H₄dota‐NHSO₂R=10‐{2‐[(R)sulfonylamino]‐2‐oxoethyl}‐1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acids 1a – e . A ¹⁵N‐NMR study of the ¹⁵N‐labelled Eu³⁺ complex of one such ligands, 1d , showed that the coordination of the N‐sulfonylacetamide arm involves the carbonyl O‐atom rather than the N‐atom. The relaxometric properties of the corresponding Gd³⁺ complexes were investigated as a function of pH and temperature. These complexes have relaxivities in the range 4.5–5.3 mM ^?1 s^?1, at 20 MHz and 25°, and are characterized by a single H₂O molecule in their inner coordination sphere. The mean residence lifetime of this molecule is relatively long (500–700 ns) compared to other anionic complexes. The slow rate of H₂O exchange can be justified by the extensive delocalization of the negative charge on the N‐sulfonylacetamide arm. The long residence time of the coordinated H₂O allowed the observation of the effect of the prototropic exchange on the relaxivity. The study of the interaction between the complex [Gd( 1e )]‐ and HSA revealed a weak affinity constant highlighting the importance of a localized negative charge on the complex to promote a strong interaction with the protein.     

An electrochemically driven molecular shuttle controlled and monitored by C60

Herein we describe a fullerene rotaxane, in which shuttling between two well-defined and distant co-conformations is both induced and monitored by the C60 stopper.     

Effect of temperature and surfactant type on the stability and aggregation behavior of styrene-acrylate copolymer colloids

The colloidal stability, aggregation kinetics, and cluster structure of two styrene-acrylate copolymer latexes, stabilized with an aliphatic sulfonate and an aliphatic carboxylate surfactant, respectively, have been investigated experimentally in the temperature range between 283 and 323 K. The main objective of this study is to investigate the role of temperature and surfactant type on the aggregation kinetics and cluster structure. For this, the values of the Fuchs stability ratio and the time evolutions of the average radius of gyration, hydrodynamic radius, and structure factor of the clusters have been determined using static and dynamic light scattering techniques at different temperatures. It is found that although the two latexes exhibit a somewhat different dependence of the colloidal stability on temperature, all of the values of the average radius of gyration (or hydrodynamic radius) measured at different temperatures and surfactant types, which are plotted as a function of a properly defined dimensionless time, collapse to form a single master curve. Similarly, all of the measured average structure factors also collapse to form a single master curve when they are plotted as a function of the wavevector normalized using the average radius of gyration. These results indicate that, at least for the conditions investigated in this work, the aggregation mechanism and cluster structure are independent of temperature and surfactant type.     

Propagation velocity of the reaction front in addition polymerization systems

Traveling polymerization fronts in unstirred solutions of methylmethacrylate, methacrylic acid, or acrylamide with some free radicals initiators (through thermal decomposition) have been observed experimentally. A local heating of the initial reactant mixture, under suitable conditions, leads to a reaction front that propagates along the space coordinate with a constant velocity. In this article, a physical interpretation of this phenomenon is provided through a mathematical model that accounts for the depolimerization reaction and is based on the constant pattern approach. Moreover, an approximate explicit analytic expression for the velocity of propagation of the polymerization front is proposed. The theoretical values are compared with those measured experimentally as a function of the initiator concentration for different addition polymerization systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35:1047–1059, 1997     

Reaction of N,N'-dialkyldithiodianilines with β-ketoesters. A new synthesis of N-alkyl-2-acyl-3-oxo-3,4-dihydro-1,4-benzothiazines

The title compounds 3a-j together with the N-alkylacylketene S,N-acetals 12a-j were obtained by reaction of N,N'-dialkyldithiodianilines with β-ketoesters compounds. A possible reaction pathway is suggested.     

Recent Advances in Nanotechnology for the Treatment of Melanoma

Melanoma is one of the most aggressive forms of skin cancer, with few possibilities for therapeutic approaches, due to its multi-drug resistance and, consequently, low survival rate for patients. Conventional therapies for treatment melanoma include radiotherapy, chemotherapy, targeted therapy, and immunotherapy, which have various side effects. For this reason, in recent years, pharmaceutical and biomedical research has focused on new sito-specific alternative therapeutic strategies. In this regard, nanotechnology offers numerous benefits which could improve the life expectancy of melanoma patients with very low adverse effects. This review aims to examine the latest advances in nanotechnology as an innovative strategy for treating melanoma. In particular, the use of different types of nanoparticles, such as vesicles, polymers, metal-based, carbon nanotubes, dendrimers, solid lipid, microneedles, and their combination with immunotherapies and vaccines will be discussed.     

Some Novel Cobalt Diphenylphosphine Complexes: Synthesis,Characterization, and Behavior in the Polymerization of 1,3-Butadiene

Some novel cobalt diphenylphosphine complexes were synthesized by reacting cobalt(II) chloride with (2-methoxyethyl)diphenylphosphine, (2-methoxyphenyl)diphenylphosphine, and 2-(1,1-dimethylpropyl)-6-(diphenylphosphino)pyridine. Single crystals suitable for X-ray diffraction studies were obtained for the first two complexes, and their crystal structure was determined. The novel compounds were then used in association with methylaluminoxane (MAO) for the polymerization of 1,3-butadiene, and their behavior was compared with that exhibited in the polymerization of the same monomer by the systems CoCl₂(PⁿPrPh₂)₂/MAO and CoCl₂(PPh₃)₂/MAO. Some significant differences were observed depending on the MAO/Co ratio used, and a plausible interpretation for such a different behavior is proposed.     

Synthesis and Spectroscopic Characterization of Thienopyrazine-Based Fluorophores for Application in Luminescent Solar Concentrators (LSCs)

Organic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very challenging undertaking. Here, we report a simple and easy way to prepare three symmetrical donor–acceptor–donor (DAD) organic-emitting materials based on a thienopyrazine core. The central core in the three dyes was modified with the introduction of aromatic substituents, aiming to affect their optical properties. The fluorophores were characterized by spectroscopic studies. In all cases, visible-NIR emissions with large Stokes shifts were found, highlighting these molecules as promising materials for the application in LSCs.     

Wavy graphene sheets from electrochemical sewing of corannulene

The presence of non-hexagonal rings in the honeycomb carbon arrangement of graphene produces rippled graphene layers with valuable chemical and physical properties. In principle, a bottom-up approach to introducing distortion from planarity of a graphene sheet can be achieved by careful insertion of curved polyaromatic hydrocarbons during the growth of the lattice. Corannulene, the archetype of such non-planar polyaromatic hydrocarbons, can act as an ideal wrinkling motif in 2D carbon nanostructures. Herein we report an electrochemical bottom-up method to obtain egg-box shaped nanographene structures through a polycondensation of corannulene that produces a new conducting layered material. Characterization of this new polymeric material by electrochemistry, spectroscopy, electron microscopy (SEM and TEM), scanning probe microscopy, and laser desorption-ionization time of flight mass spectrometry provides strong evidence that the anodic polymerization of corannulene, combined with electrochemically induced oxidative cyclodehydrogenations (Scholl reactions), leads to polycorannulene with a wavy graphene-like structure.

A bottom-up synthesis of wavy graphene structures obtained through an anodic polymerization process, combined with an electrochemically triggered oxidative cyclodehydrogenation, of the bowl-shaped polyaromatic hydrocarbon corannulene.     

Light‐Controlled Regioselective Synthesis of Fullerene Bis‐Adducts

Multi‐functionalization and isomer‐purity of fullerenes are crucial tasks for the development of their chemistry in various fields. In both current main approaches—tether‐directed covalent functionalization and supramolecular masks—the control of regioselectivity requires multi‐step synthetic procedures to prepare the desired tether or mask. Herein, we describe light‐responsive tethers, containing an azobenzene photoswitch and two malonate groups, in the double cyclopropanation of [60]fullerene. The formation of the bis‐adducts and their spectroscopic and photochemical properties, as well as the effect of azobenzene photoswitching on the regiochemistry of the bis‐addition, have been studied. The behavior of the tethers depends on the geometry of the connection between the photoactive core and the malonate moieties. One tether lead to a strikingly different adduct distribution for the E and Z isomers, indicating that the covalent bis‐functionalization of C₆₀ can be controlled by light.