Synthesis and properties of compounds related to stilbazole

Abstract

We report attempts to create conjugated polymers consisting of alternating phenylene and heterocyclic rings separated by double bonds by means of condensations between terephthdaldehyde and dimethyl nitrogen bases. Because the products precipitated during their formation even at 180 "C in N-methyl-2-pyrrolidinone (NMP), only oligomers of up to ca. 30 rings (DP = 15) could be obtained; most of the adequately soluble products had DP between 4 and 8, and from these oligomers films on glass or quartz could be made. When the films were exposed to Iz, N q , or SbF,, most of them, initially very good insulators, showed an increase in electrical conductivity of up to 6 powers of 10; but the rapid reversal of this change when the reagent evaporated and the lack of any clear changes in the UV-vis spectrum of the films showed that most likely true "doping" had not occurred.Extensive syntheses with a variety of quaternised bases also failed to yield oligomers oxidisable by electron-acceptors.For reference purposes, especially for their spectra, a large number of pure "model" compounds of the distyrylpyridine and distyrylpyrazine type, and quaternised analogues of the former, were synthesised, many of them new compounds. These were also used as calibrants for a GPC column operating with NMP solutions.Several improvements were made in the synthetic techniques.ZUSAMMENFASSUNG: Diese Arbeit beschreibt Versuche, durch Kondensation von Terephthalaldehyd mit Dimethylstickstoffbasen konjugierte Polymere zu synthetisieren, die aus alternieren-* Present address: Institute of Polymer Technology, Loughborough University of

New Liquid Crystalline Conjugated Derivatives of 3,3‘-Bipyridine as Components for Optoelectronic Materials

“…An example of a molecule meeting these requirements is 2,5-dimethylpyrazine, whose condensation products with aromatic aldehydes have been reported earlier …”

Synthesis of Vinylene-Linked Covalent Organic Frameworks by Monomer Self-Catalyzed Activation of Knoevenagel Condensation

“…The absorptions in the higher-energy regions might mainly arise from the conjugated segments linked at the ortho-or para-position of pyridine rings, while the moieties crossing the 2-and 6-positions of pyridine rings possess longer π-conjugation lengths, likely offering the absorptions at longer wavelengths. 31 Accordingly, the optical band gaps of the COFs were determined from Kubelka−Munk function 32 associated with an indirect transition as 2.30 and 2.10 eV for COF-DFB and COF-BPDA, respectively (Figure 4a, inset). In addition, we performed density-functional-theory (DFT) calculations to theoretically study the electronic properties of COF-DFB and COF-BPDA.…”

“…Additionally, both COF-DFB and COF-BPDA exhibit relatively broad absorption bands with shoulders or tails in the low-energy regions, which could be attributed to the segments with different π-conjugated lengths involved in the in-plane backbones of these COFs. The absorptions in the higher-energy regions might mainly arise from the conjugated segments linked at the ortho - or para -position of pyridine rings, while the moieties crossing the 2- and 6-positions of pyridine rings possess longer π-conjugation lengths, likely offering the absorptions at longer wavelengths . Accordingly, the optical band gaps of the COFs were determined from Kubelka–Munk function associated with an indirect transition as 2.30 and 2.10 eV for COF-DFB and COF-BPDA, respectively (Figure a, inset).…”

Hexatopic Vertex-Directed Approach to Vinylene-Linked Covalent Organic Frameworks with Heteroporous Topologies

“…As a consequence, the D−π–A segment consisting of para -linked phenylene, vinylene, and 2,6-linked pyridine units was repeatedly aligned in a head-to-tail fashion around the larger hexagonal pores, depicted as the independent π-conjugated motifs within the topological patterns of such kinds of COFs (Figure S48b). − Upon excitation at 470 nm, steady-state photoluminescence (PL) spectra exhibit emission maxima at λ em = 584 and 570 nm for g-TPYP-COF and g-TPYBP-COF, respectively (Figure S16). The amplitude-weighted average lifetimes of g-TPYP-COF and g-TPYBP-COF were estimated to be 2.76 and 4.49 ns, respectively (Figure S17 and Table S5).…”