Effects of End-Groups on Photophysical Properties of Poly(9,9-di-n-octylfluorene-2,7-vinylene)s Linked with Metalloporphyrins: Synthesis and Time-Resolved Fluorescence Spectroscopy

Abstract

A series of poly­(9,9-di-n-octyl-fluorene-2,7-vinylene)­s (PFVs) containing metalloporphyrins at the chain ends with different conjugation lengths (ca. average 8 or 24 FV repeat units), PFV-[Por­(M)]2, have been prepared by olefin metathesis of the vinyl chain ends in PFVs (prepared by acyclic diene metathesis polymerization by ruthenium–carbene catalysts) using molybdenum–alkylidene catalyst (reagent) followed by Wittig-type cleavage with formyl porphyrin containing different metal ions [Zn­(II), Cu­(II), Ni­(II), and Pt­(II)]. Effects of the metalloporphyrins on photophysical properties of PFVs were studied by means of time-resolved fluorescence spectroscopy. The fluorescence spectral profile from PFV moiety in all the polymers with end-porphyrins was almost identical to that of the reference PFV. However, fluorescence quantum yields were remarkably lower, depending upon the central metal ion and the chain length. The observed reduction of the quantum yields is ascribed to intramolecular energy transfer to the end-groups as well as enhancement of intersystem crossing within the PFV unit. In the zinc derivative, PFV(High)-[Por­(Zn)]2, fluorescence from zinc porphyrin was also observed with a higher fluorescence quantum yield. It was found that radiative rate constant in zinc porphyrin moiety was enhanced about 3 times, suggesting specific interaction between the PFV and the porphyrin. On the other hand, time-resolved fluorescence signals of PFV moiety in all the PFV end-modified by metalloporphyrins decay with two or more components without any change of spectral profile. A model in which the excitation is localized in several pieces of FV units is proposed.

The effect of estrogen on craniofacial dimensions: a systematic review

“…The authors followed different protocols to evaluate the effect of estrogen levels or ERs in the maxilla and mandible growth. Only one study used zebrafish as animal model (13). The others 4 studies used mammals, 2 female rats (10,11) and 2 female mice (9,12).…”

Well‐Defined End‐Functionalized Conjugated Polymers/Oligomers Exhibiting Unique Emission Properties through the End Groups: The Exclusive Synthesis by Combined Olefin Metathesis with Wittig‐type Coupling

“…As described above, the fluorescence spectra in PFV‐Ar 2 were affected by the end groups . Placing ferrocene (Fc) moiety into the PFV chain ends (expressed as PFV‐Fc 2) caused a drastic quenching of photoluminescence ( Figure ), probably due to an exciton transfer to the Fc units.…”

“…to the vinyl group for completion of olefin metathesis), and the subsequent addition of various aldehydes (ArCHO, excess for completion of Wittig‐type coupling) afforded PFVs containing functionalities at the both polymer chain ends (expressed as PFV‐Ar 2 , Scheme ). The procedure thus enables the exclusive end‐modification of PFV, as demonstrated syntheses of PFVs containing oligo(thiophene)s moieties, F‐BODIPY, and so forth. (Scheme ) …”

“…are highly affected by called defect (such as halogen [and/or palladium] contaminated, regio‐/stereo‐irregularity, cross‐linking [through coupling reactions], sulfur remained in the main chain, etc.). It has also been revealed recently that the properties are influenced by the end groups, as demonstrated in poly(fluorene)s and poly(9,9‐dialkyl‐fluorene‐2,7‐vinylene)s (PFVs) . Moreover, it has been widely recognized that their fundamental properties are affected by the interchain interactions (such as supramolecular, nano/meso scale organization) .…”

“…prepared in the presence of Ru catalysts possess vinyl end groups exclusively (described below), in addition to that the resultant polymers/oligomers possess all trans olefinic double bonds due to a steric bulk in the metallacycle intermediate . As introduced in this article, quantitative end‐modification by adopting olefin metathesis of the vinyl chain ends (using molybdenum catalyst/reagent) followed by addition of aldehyde (Wittig‐type coupling) can be thus possible, as introduced below …”