Thermally activated and light-induced metal ion complexation of 5′-(hydroxy)spiroindolinonaphthooxazines in polar solvents

Chelation with Al(III), Fe(II) or Cu(II) of the open photomerocyanine form obtained under steady irradiation of spiroindolinonaphthooxazines, with a hydroxyl group at the 5′ position in the naphthooxazine moiety, induces a slight hypsochromic shift of its visible absorption band and increases the lifetime of this form, slowing down its thermal bleaching in the dark (rate constant  10⁻³ s⁻¹). Complexation with Al(III), Fe(II) or Cu(II) allows the spiroindolinonaphthooxazines to isomerize to their open coloured form even under dark conditions giving a complex spectroscopically identical to the photoinduced product. The activation energy of thermal complexation is independent of the metal ion which implies the ring opening as the rate determining step.     

Preparation of Macroporous Acrylamide‐based Hydrogels: Cryogelation under Isothermal Conditions

Macroporous hydrogels based on acrylamide, as well as on 2‐acrylamido‐2‐methylpropane sulfonic acid monomers, were prepared using N,N′‐methylenebis(acrylamide) crosslinker in frozen aqueous solutions. The cryogelation reactions at temperatures as low as ?25°C were carried out isothermally by use of two techniques. First, after addition of the polymerization initiator into the reaction solution, the system was immediately cooled down to ?196°C using liquid nitrogen and then, the system was immersed into a thermostate at the desired subzero temperature T _prep . It was found that the precooling of the reaction system before the onset of the reactions provides formation of superfast responsive hydrogels at temperatures close to the freezing point of water. The precooling step however destroyed the regularity of the pores in the hydrogel networks. As a second technique to achieve isothermal cryogelation, hydroquinone as the polymerization inhibitor was included into the reaction solution. It was shown that, the addition of hydroquinone produces more monodisperse and smaller pores. The hydrogels obtained by both techniques exhibit size‐independent superfast swelling behavior in response to the external stimuli.     

2-Spreads and Transitive and Orthogonal 2-Parallelisms of PG(5, 2)

A 2-spread is a set of two-dimensional subspaces of PG(d, q), which partition the point set. We establish that up to equivalence there exists only one 2-spread of PG(5, 2). The order of the automorphism group preserving it is 10584. A 2-parallelism is a partition of the set of two-dimensional subspaces by 2-spreads. There is a one-to-one correspondence between the 2-parallelisms of PG(5, 2) and the resolutions of the 2-(63,7,15) design of the points and two-dimensional subspaces. Sarmiento (Graphs and Combinatorics 18(3):621–632, 2002) has classified 2-parallelisms of PG(5, 2), which are invariant under a point transitive cyclic group of order 63. We classify 2-parallelisms with automorphisms of order 31. Among them there are 92 2-parallelisms with full automorphism group of order 155, which is transitive on their 2-spreads. Johnson and Montinaro (Results Math 52(1–2):75–89, 2008) point out that no transitive t-parallelisms of PG(d, q) have been constructed for t > 1. The 92 transitive 2-parallelisms of PG(5, 2) are then the first known examples. We also check them for mutual orthogonality and present a set of ten mutually orthogonal resolutions of the geometric 2-(63,7,15) design.     

Application of the Intermolecular α-Amido-alkylation Reaction for the Synthesis of Tertiary Amides and 1-Substituted 2-Acyltetrahydroiso-Quinolines. Synthesis of (±)-Carnegine

Adducts 4 of Schiff bases and 3,4-dihydroisoquinolines with acyl chlorides react with Grignard reagents 5 in an intermolecular α-amidoalkylation reaction to the corresponding tertiary amides or 1-substituted 2-acyltetrahydroisoquinolines.     

Stable isotopes determination in some Romanian wines

This paper presents a study concerning the isotopic fingerprint ((18)O and (13)C) of some wines prepared from relevant Romanian grape varieties (e.g. Feteasca Alba (FA), Feteasca Regala (FR) and Cabernet Sauvignon (CS)) obtained in different vintage years (2002, 2003, 2004, 2007 and 2008). These wines were obtained from different vineyards having a significant role in the wine market: Cotesti, Tohani, Stefanesti, Aiud, Cotnari, Bucium, Murfatlar, Bujoru, Dragasani and Valea Calugareasca. Several observations related to the dependence of isotope ratios on geographical origin and climatic conditions were drawn. The authentic wines obtained from the FA grape variety from six different vineyards showed δ(18)O values in the range of+3.28 (Cotesti region - 45?°38'N/27?°04'E) to-2.60 ‰ (Aiud region - 46?°19'N/23?°45'E). The δ(13)C values were very similar for all the samples with an average of about-26 ‰. The difference between the δ(18)O values was due to the different climatic zones, which have an influence on the δ(18)O values of wine water. For the wine variety CS obtained from the Dealu Mare-Tohani vineyard, production years 2003 and 2004, a greater difference in the δ(18)O values of wine water ranging from 1.89 (in 2004) to 5.35 ‰ (in 2003) was noted. This difference is explained by the different mean annual temperatures in 2003 and 2004.     

Novel Multifunctional Graphene Sheets with Encased Au/Ag Nanoparticles for Advanced Electrochemical Analysis of Organic Compounds

This work is the first presentation of the synthesis of few‐layer graphene decorated with gold and silver nanoparticles (Gr–Au–Ag) by chemical vapor deposition over a catalytic system formed of bimetallic Au–Ag nanoclusters supported on MgO and with methane used as the source of carbon. The sheetlike morphology of the graphene nanostructures, with mean sizes in the range of hundreds of nanometers, was observed by high‐resolution electron microscopy. The distinctive feature found in all the samples was the regular rectangular or square shapes. This multi‐component organic–inorganic nanomaterial was used to modify a platinum substrate and subsequently employed for the detection of carbamazepine, an anti‐convulsion drug. UV/Vis spectroscopy revealed that a strong hypochromism occurred over time, after mixing solutions of graphene–Au–Ag with carbamazepine. This can be attributed to π–π stacking between the aromatic groups of the two compounds. Linear sweep voltammetry (LCV) provided evidence that the modified platinum substrate presented a significant electrocatalytic reaction toward the oxidation of carbamazepine. The intensity of the current was found to increase by up to 2.5 times, and the oxidation potential shifted from +1.5 to +1.35 V(Ag/AgCl) in comparison with the unmodified electrode. Electrochemical impedance spectroscopy (EIS) was further used to thoroughly assess the activity of the platinum electrode that was modified by the deposition of the Gr‐Au‐Ag composites in the presence of various concentrations of carbamazepine. The experimental EIS records were used for the generation of an equivalent electrical circuit, based on the charge‐transfer resistance (R_ct), Warburg impedance (Z_D), solution resistance (R_s), and a constant phase element (CPE) that characterizes the non‐ideal interface capacitive responses.     

Polyelectrolyte complexes. VII. Complex nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) tailored by the titrant addition rate

Nonstoichiometric interpolyelectrolyte complexes (IPECs) as colloidal dispersions have been widely used for the past decade as reactive materials for flocculation and surface modification. In this context, some new aspects of the preparation and properties of IPEC nanoparticles based on NaPAMPS, in salt‐free aqueous solutions, are reported in this article. IPEC dispersions with different characteristics, z‐averaged particle sizes, polydispersity indices, and colloidal stabilities were tailored by the addition rate of the titrant, a less investigated factor in the synthesis of IPECs as nanoparticles. Poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) (NaPAMPS) and two polycations bearing positive charges in the backbone, poly(diallyldimethylammonium chloride) and a polycation containing 95 mol % N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride units, were used for this purpose. The complex nanoparticle characteristics and storage stability were monitored via the optical density at 500 nm and dynamic light scattering. IPEC nanoparticles with z‐averaged particle sizes of 100–250 nm resulted from the same polyion pair and the same polyion concentrations when the addition rate of the titrant, either the polyanion or polycation, varied within the range of 0.1–1.5 mL/mL of the starting polyion × h. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5244–5252, 2004