Poly(p-phenylene)s. Synthesis, Optical Properties, and Quantitative Analysis with HPLC and MALDI−TOF Mass Spectrometry

Abstract

A series of soluble low molecular weight poly(p-phenylene)s (PPP) has been synthesized by an excess polycondensation with the Suzuki coupling method. The reaction mixture therefore only contains oligomers of an odd number of phenylene units which are terminated by bromine atoms. The mixture has been preparatively separated into monodisperse fractions of the respective oligomers of up to 17 phenylene units. The absorption and emission spectra as well as the extinction coefficient of each fraction have been measured. On the basis of these data, the effective conjugation length can be estimated to be around 11 phenylene units. The fraction x i of each oligomer in the reaction mixture has been calculated and quantified by analytical HPLC and MALDI−TOF mass spectrometry. The theoretically expected exponential decay of the fraction sizes with increasing length is found in the HPLC analysis; however, significant deviations are found if analyzed by MALDI−TOF mass spectrometry. Possible reasons for this deviation will be discussed.

The cationization mechanism study of novel oligo (p-phenyleneethynylene)s

“…The oligomers demonstrated very strong tendency on its radical cationization. In fact, radical cationization has been reported before, e.g., McCarley and Limbach's study on metallocenes, Räder and coworkers on poly(pphenylene)sä [30],äJanssenäetäal.äonäpoly(3-alkylthiophene)säandäpoly(thienylene-phenylene)sä [31,ä32].äIn McCarley and Limbach's study, terthiophene and anthracene were used as matrices, which are known as good electron-transfer matrices for their large extinction coefficient at 337 nm, the wavelength of the laser in MALDI. These matrices can absorb laser radiation and become radical cations by photoionization.…”

Small molecule analysis by MALDI mass spectrometry

“…Matrix interferences and UV absorption of the polymer oligomers themselves were attributed as probable causes of inaccuracy. [49] Some of the variability in molecular weight accuracy may be attributed to the type of polymer and matrix utilized. For example, using a solvent-free sample preparation Skelton et al examined polyamides mixed with 3-aminoquinoline or dithranol as the matrix and pressed into a pellet.…”

Synthesis and Electronic Properties of Monodisperse Oligophenothiazines

“…[9] Likewise, well defined conjugated oligomers are key elements in molecular electronics. [10] Among numerous p systems suitable for repetitive syntheses of well defined oligomers, [11] electron-rich entities are of peculiar interest due to their ease of oxidation. In particular, reversibly oxidizable heterocyclic redox systems can be very promising not only for the design of suitable hole-transport materials for molecule-based OLED and OFET (organic field effect transistor) devices but also for switchable molecular wires for future molecular electronics.…”