Peter Baran

Interplay between Vacuum-Grown Monolayers of Alkylphosphonic Acids and the Performance of Organic Transistors Based on Dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene.

Monolayers of six alkylphosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2,3-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum-deposited monolayers improved with increasing length of the aliphatic tail. At the same time, Fourier transform infrared (FTIR) measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by density functional theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ∼17.5 mJ/m(2) with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in transistor performance was observed with increasing length of the aliphatic tail. Upon going from C8 to C18, the mean threshold voltage decreased from -1.37 to -1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm(2)/(V·s), the off-current decreased from ∼8 × 10(-13) to ∼3 × 10(-13) A, and for transistors with L = 30 μm the on-current increased from ∼3 × 10(-8) to ∼2 × 10(-6) A, and the on/off-current ratio increased from ∼3 × 10(4) to ∼4 × 10(6). Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely dry fabrication route for ultrathin dielectrics and low-voltage organic transistors.

Synthesis of novel chiral 1,4-dihydropyridinyl Schiff-base ligands, with characterization and evaluation of calcium channel blocker activity

Treatment of 2-formyl-1,4-dihydropyridines with primary diamines gave rise to different products depending on the molar ratio of reactants. In the case of stoichiometric amounts of substrate and reactant, only tricyclic cis-diastereoisomer was obtained in yields ranging from 53 % up to 54xa0%. In addition, reaction of the above carboxaldehyde with primary diamines in a molar ratio of 2/1 resulted in the formation of bis-iminoderivatives in high yields of 80–97xa0%. All these compounds were examined as ligands for synthesis of complexes with metal salts. Ultimately, the selected compounds, in enantiopure and racemic form, were tested for their effect on both basal and agonist (or vanadate)-induced 45Ca2+ influx.Graphical Abstract

6-(4-Hydroxy­benzyl­amino)purin-3-ium chloride: a protonated form of para-topoline

The structure of the title compound, C12H12N5O+·Cl−, comprises a 6-(4-hydroxyxadbenzylxadamino)purinium cation and a chloride anion. The cation exists as the N3-H tautomer. Interxadmolecular N—H⋯N hydrogen bonds connect cations into centrosymmetric dimers, with an N⋯N distance of 2.821u2005(2)u2005A. Furthermore, the secondary structure is stabilized by O—H⋯Cl and N—H⋯Cl hydrogen bonds, weak nonbonding interxadatomic contacts of the types C—H⋯Cl [3.1652u2005(4)u2005A] and C—H⋯C [2.897u2005(2)u2005A], and π–π stacking interxadactions [3.357u2005(4)u2005A].