New strategies for the synthesis of partially fluorinated acrylic polymers as possible materials for the protection of stone monuments

The conservation of the cultural heritage requires the development of new materials having specific characteristics that encompass particular attention to durability and efficacy. We approached this problem by synthesizing polyacrylic esters containing variable amounts of fluorine in the α-position of the main chain. These products were obtained from the copolymerisation of ammonium 2-fluoroacrylate and acrylic acid. The polyacrylic acids were esterified using different procedures. The polyester characteristics vary in relation to the polymerisation procedures and degree of esterification. The best esterification results, were obtained using a reaction catalyzed by BF₃ or TMSCl. These materials show good properties and are of potential interest for their use as protective agents for stone conservation.     

Gold nanoparticles stabilized by modified halloysite nanotubes for catalytic applications

A highly sustainable prototype of a flow system based on gold nanoparticles (4.2 nm) supported on thiol‐functionalized halloysite nanotubes (HNTs) was developed for catalytic applications. The catalytic performances were evaluated using the reduction of 4‐nitrophenol to 4‐aminophenol as a model system. Under the best experimental conditions (0.0001 mol%, 1.97 × 10^?8 mg of Au nanoparticles), an impressive apparent turnover frequency value up to 2 204 530 h^?1 was achieved and the halloysite‐based catalyst showed full recyclability even after ten cycles. The high catalytic activity confirms the importance of the use of HNTs as support for Au nanoparticles that can exert a synergistic effect both as medium for transfer of electrons from borohydride ions to 4‐nitrophenol and by modulating interfacial electron transfer dynamics. With the application of flow technology, the obtained heterogeneous HNT@Au catalyst was fully recovered and reused for at least one month.     

A test case for time-dependent density functional theory calculations of electronic circular dichroism: 2-chloro-4-methoxy-6- [(R)-1-phenylethylamino]-1,3,5- triazine

The three-dimensional structure of an optically active substituted s-triazine derivative, 2-chloro-4-methoxy-6-[(R)-1-phenylethylamino]-1,3,5-triazine, has been studied by conformational analysis using density functional theory (DFT) both in vacuo and in acetonitrile solution in the polarizable continuum model integral equation formalism framework. Time-dependent DFT methods have been used to investigate the molecular electronic CD and absorption UV spectra. Comparison with experimental results allowed the reliability of the theoretical predictions to be enhanced and suggested a possible interpretation of the measured data. Electronic Supplementary Material The online version of this article doi:contains supplementary material, which is available to authorized users.     

Strategies for improving the water solubility of new antitumour nitronaphthylbutadiene derivatives

Different nitronaphthylbutadienes have been previously proved to have antitumour activity. The main drawback of these derivatives is their low water solubility. With the aim of facilitating the administration of these new drugs we have synthesized the hexyl (2Z,4E)-2-methylsulfanyl-5-(1-naphthyl)-4-nitro-2,4-pentadienoate analogue (1-Naph-NHCB) which is demonstrated to be easily included into cyclodextrins and/or entrapped into liposomes. Its antitumour activity was revealed to be almost comparable with that of the previously studied methyl analogue ester (1-Naph-NMCB). On the other hand, in vitro studies with different cancer cell lines showed that the cytotoxic activity of both 1-Naph-NMCB and 1-Naph-NHCB were fully preserved and in some cases also enhanced when entrapped into liposomal carriers.     

Strain estimates for small-ring cyclic allenes and butatrienes

Isodesmic and homodesmic equations at the B3LYP/6-311+G(d,p)+ZPVE level of theory have been used to estimate strain for the homologous series of cyclic allenes and cyclic butatrienes. A simple fragment deformation approach also has been applied and appears to work better for the larger rings. For the cyclic allene series, estimates for allene functional group strain (kcal/mol) include: 1,2-cyclobutadiene, 65; 1,2-cyclopentadiene, 51; 1,2-cyclohexadiene, 32; 1,2-cycloheptadiene, 14; 1,2-cyclooctadiene, 5; 1,2-cyclononadiene, 2; 1,2,4-cyclohexatriene, 34; and bicyclo[3.2.1]octa-2,3-diene, 39. For cyclic butatrienes, functional group strain estimates include: 1,2,3-cyclobutatriene, >100; 1,2,3-cyclopentatriene, 80; 1,2,3-cyclohexatriene, 50; 1,2,3-cycloheptatriene, 26; 1,2,3-cyclooctatriene, 17; and 1,2,3-cyclononatriene, 4. Barriers to interconversion of enantiomers in cyclic allenes are reduced with increasing strain. Newly predicted values include: 1,2-cyclopentadiene <1 kcal/mol and bicyclo[3.2.1]octa-2,3-diene, 7.4 kcal/mol. Estimated levels of strain parallel the known reactivity of these substances.