Photochromic oligothienoacene derivatives with photo-switchable luminescence properties and computational studies

Photochromic thieno[3,2-b]thiophenes and dithieno[3,2-b:2',3'-d]thiophene with photo-switchable luminescence properties have been synthesized using a Suzuki cross-coupling reaction; their electronic structures, and photochromic and luminescence behaviour have also been studied.     

Solidification of molten zinc chloride

Solidification of molten zinc chloride was studied both experimentally and theoretically. By isothermal thermal analysis the time needed for the melt to crystallize at a given temperature ranging between 453 and 553 K was determined and the data obtained were compared with those of a calculated TTT curve. The extremum coordinates (temperature T _N, time t _N) of the curve, critical cooling rate v _CR, interfacial energy σ, and an additional parameter of kinetics barrier for nucleation ɛ were determined as T _N=508 K, t _N=7.29 s, v _CR=11.38 K s⁻¹, σ=0.11956 J m⁻² and ɛ=0.5712. By non-isothermal method the critical cooling rate of glass formation was determined as 1.25 K s⁻¹.     

Field-effect-transistor sensor based on enzyme-functionalized polypyrrole nanotubes for glucose detection

We describe the detection of glucose based on a liquid-ion gated field-effect transistor configuration in which enzyme-functionalized polypyrrole nanotubes are employed as the conductive channel. First of all, carboxylated polypyrrole nanotubes (CPNTs) were successfully fabricated by the chemical polymerization of an intrinsically functionalized monomer (pyrrole-3-carboxylic acid, P3CA) without degradation in major physical properties. The CPNTs possessed not only well-defined functional groups but also electrical properties comparable to nonsubstituted polypyrrole. Importantly, the carboxylic acid functional group can be utilized for various chemical and biological functionalizations. A liquid-ion gated FET sensor was readily constructed on the basis of the chemical functionality of CPNTs. In the first stage, the CPNTs were immobilized onto a microelectrode substrate via covalent linkages. It was noteworthy that the covalent immobilization allowed high-quality contact between the nanotubes and the microelectrodes in the liquid phase. The second stage involved the covalent binding of glucose oxidase (GOx) enzyme to the nanotubes. The covalent functionalization generally provides excellent enzymatic activity and thermal stability. The fabricated FET sensor provided real-time response (an increase in source-drain current) and high sensitivity toward the various concentrations (0.5-20 mM) of glucose. The enzymatic reaction product, hydrogen peroxide, played pivotal roles in modulating the charge transport property of CPNTs.     

Gassman's intramolecular [2 + 2] cationic cycloaddition. formal total syntheses of raikovenal and epi-raikovenal

The first intramolecular version of Gassman's cationic [2 + 2] cycloaddition employing vinyl acetals tethered to an unactivated olefin and its application in the formal syntheses of raikovenal and epi-raikovenal are described.     

Molecular design and preparation of bis-isophthalate electrochromic systems having controllable color and bistability

New electrochromic systems based on bis-isophthalates were designed and prepared. They showed electrochromism behavior by two-electron reduction. The displayed colors showed greatly enhanced bistability and were dependent on the length of the conjugated bridge between the two isophthalate groups. We believe that the connection of two electrochromic systems with a conjugated bridge is a good basic strategy to obtain new bistable electrochromic systems.     

Nanofibrous poly(lactic acid)/hydroxyapatite composite scaffolds for guided tissue regeneration

The production of nanofibrous PLA/HA composite scaffolds is described. The morphological, mechanical, surface, and thermal properties of the composites were extensively investigated. The results show that the mixture of PLA and HA formed smooth nanofibers without lumps. The incorporation of HA increased the mechanical strength of the nanofibers and changed the morphology, increasing the mean fiber diameter and pore size. Surface and internal properties confirmed that HA was homogeneously distributed inside the nanofibers and oriented towards their surface. The nanofiber composites allowed the adhesion and proliferation of pre-osteoblasts for up to 3 weeks.     

Synthesis and structural characterization of monomeric aluminum keto-imine complexes: Catalytic activity toward CO2/styrene oxide coupling and ε-caprolactone ring opening polymerization

A series of benzoylacetone-imine ligands, PhCOCHCMeNHR ( L ¹ H , R = CH₂Ph; L ² H , R = CH₂Ph-4-Me; and L ³ H , R = CH₂Ph-4-OMe), are first synthesized following the condensation of benzoylacetone and 4-substituted benzylamine. Later, reacting L ¹ H – L ³ H with one equivalent of AlMe₃ in toluene, the monomeric Al derivatives are generated, (PhCOCHCMeNR)AlMe₂ ( 1 , R = CH₂Ph; 2 , R = CH₂Ph-4-Me; 3 , R = CH₂Ph-4-OMe). All the ligands and metal derivatives are characterized by ¹H and ¹³C NMR spectroscopy. Single crystal X-ray diffraction analysis reveals the geometry of all ligands and complex 2 . As supporting catalysts, the Al derivatives, 1 – 3 , are effective to initiate the coupling of CO₂ and styrene oxide to form cyclic carbonates. Although employing TBAI (tetra-n-butylammonium iodide), TBAC, tetrabutylammonium chloride, and TBAB (tetra butyl ammonium bromide) as cocatalyst, the optimized catalytic system exhibits the best conversion of epoxide in presence of TBAI under the reaction temperature and time, respectively, 90°C and 6 hr, respectively. The ring opening polymerization of ε-caprolactone is also appraised subjecting the Al derivatives, 1 – 3 , as catalysts in presence of benzyl alcohol and all the conversions of ε-caprolactone reach over 95% at the reaction condition of 100°C and 1 hr.