New Triphenylamine-Based Oligomeric Schiff Bases Containing Tetraphenylsilane Moieties in the Backbone

Abstract

Three new triphenylamine-based oligomeric Schiff bases (polySB1, polySB2 and polySB3) containing tetraphenylsilane core (TPS-core) in the main chain were obtained from TPS-core-based diamines and bis(4-formylphenyl)phenylamine by a high-temperature polycondensation reaction. These new oligomers were structurally characterized by FT-IR, NMR and elemental analysis. All polySBs were highly soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene. Samples showed moderate molecular average molecular weight (Mw) and a high thermal stability above 410 °C. Likewise, polySBs showed absorption near 400 nm in the UV-vis range and photoluminescence. The HOMO levels and band-gap values were found in the ranges of −6.06 to −6.18 eV and 2.65–2.72 eV, respectively. The lowest band-gap value was observed for polySB2, which could be attributed to a more effective π-conjugation across the main chain. The results suggest that silicon-containing polySBs are promising wide-band-gap semiconductors materials for optoelectronic applications.

New cardo silylated poly(azomethine)s containing 9,9′‐diphenylfluorene units as materials with Brønsted acid‐dependent fluorescence

“…). The first bands were attributed to the π – π * transitions on the benzene rings of the biphenyl and diphenylfluorene moieties . The second bands are partially overlapped with the first bands and look like small shoulders centered at 342 nm.…”

“…According to previous reports of diphenylfluorene‐based PAzMs, it is possible to establish a correlation between the absorption maxima and the chemical structure of the PAzMCs. Thus, in both samples, a marked hypsochromic displacement attributed to the disruption of the π ‐conjugation by the tetrahedral C9 of the fluorene moiety was added to the effect of the silane fractions already mentioned.…”

“…The second bands are partially overlapped with the first bands and look like small shoulders centered at 342 nm. These signals were assigned to n– π * transitions of the nitrogen lone pair on the imine unit . Both PAzMCs showed a solvatochromism effect with a red shift of approximately 13 nm (bathochromic shift) for the π – π * transition bands when DMSO was used as a solvent instead of THF.…”

“…In Table are summarized the optical and electrochemical properties of the PAzMCs. The optical bandgaps ( E g opt ) were calculated from the Tauc approximation ( E g opt = 1240/ λ edge , where λ edge corresponds to the absorption edge wavelength of the lower electronic transition band) . For DMSO or THF PAzMCs solutions, the estimated bandgaps were ca 3.12 eV.…”

“…The similar HOMO and LUMO levels observed for the samples indicates that no substantial impact on their electrochemical properties was exerted by the modification of the silane unit (PhSiR 2 Ph with R = Me or Ph). The incorporation of central silane‐based moieties in wide‐bandgap materials plays a key role due to interruption of π ‐conjugation along the polymer chains and tends to decrease their LUMO energy level values …”