Synthesis and Characterization of Soluble Conjugated Poly(p-phenylenevinylene) Derivatives Constituted of Alternating Pyrazole and 1,3,4-Oxadiazole Moieties

Abstract

New soluble poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole and pyrazole rings along the main chain were synthesized by Heck coupling. The new conjugated polymers are soluble in common organic solvents as a result of the fully conjugated backbone with dodecyloxy side groups. The polymers show relatively high glass-transition temperatures (up to 160°C) and good satisfactory thermal stability. Solutions of the polymers emit blue-greenish light with photoluminescence (PL) emission maxima around 490–500 nm. The PL spectrum of the polymer’s thin films, with a maximum at 515 nm, shows a red-shift (~20 nm), with respect to the solution spectrum. Cyclic voltammetry reveals that both conjugated polymers have reversible oxidation and irreversible reduction, making them n-type electroluminescent materials. The electron affinity of the new polymers was estimated as 2.73–2.74 eV. The weight-average molecular weights (M w) of the new soluble polymers were in the range of 4790–4950.

Efficient synthesis of 1,3-diaryl-4-halo-1H-pyrazoles from 3-arylsydnones and 2-aryl-1,1-dihalo-1-alkenes

“…These dipolar compounds are readily prepared in two steps from N-functionalized amino acids, and are readily stored and handled. Methods have been disclosed for the [3 + 2] dipolar cycloaddition of sydnones with alkenyl silanes [ 18 ] and stannanes [ 18 ], alkenyl arenes [ 19 ], 1,3-dienes [ 20 – 21 ], α,β-unsaturated esters [ 19 , 22 ] and nitriles [ 23 ], phosphane oxides [ 24 ] or with alkynyl silanes [ 18 ], stannanes [ 18 , 25 – 26 ], arenes [ 27 – 28 ], esters [ 29 – 33 ], boronic esters [ 34 – 35 ]. However, the cycloaddition of sydnones with 1,1-dihaloalkenes is unknown, as is the direct formation of 4-halopyrazoles through the [3 + 2] dipolar cycloaddition of sydnones.…”