Dendrimeric Oligo(phenylenevinylene)‐Extended Dithieno[3,2‐b:2′,3′‐d]phospholes—Synthesis, Self‐Organization, and Optical Properties

Abstract

A boost from the branches: Incorporation of the dithieno[3,2-b:2',3'-d]phosphole system as a core in oligo(phenylenevinylene) dendrimers (an example is shown here) provides materials that exhibit energy-transfer features relaying incoming photons from the dendrons towards the core, which in turn shows enhanced emission intensity. The optical properties and self-assembly features of the dendrimers can be impacted by the terminal groups (-H, -CF(3), or -NPh(2)) employed.To establish this system as a fluorescent core in pi-conjugated dendrimers, a series of oligo(phenylenevinylene) (OPV)-extended dithieno[3,2-b:2',3'-d]phospholes has been prepared by means of a Wittig-Horner protocol with a dithienophosphole dialdehyde and appropriately functionalized phosphonates. The "zero-generation" model compounds have provided the general accessibility of OPV-functionalized dithienophospholes, and show varying emission colors covering the optical spectrum from green to red. Expansion of the synthetic strategy towards the corresponding first-generation dendrimers has provided materials that show intriguing self-organization features in case of the phenyl-terminated dendrimer, forming large one-dimensional microfibres, as well as desirable energy-transfer processes from the dendrons to the dithienophoshole core resulting in an enhanced emission intensity for the latter. The present study has revealed that the terminal end-groups of the OPV branches have significant impact on the optical features of the OPV dendrimers as a whole.

Structure–property relationships of acylated asymmetric dithienophospholes

“…Photoluminescence quantum yields (f PL ) were obtained for dichloromethane solutions of 1, 2, and 3; however, most values range between f PL = 11-31%, which is significantly lower than usually observed for dithienophospholes (f PL = 35-90%) [3,4]. The lower values can be attributed to the quenching character of the incorporated ketone functionalities, opening up significant non-radiative relaxation pathways, and are in line with earlier observations for a diformyl-functionalized dithienophosphole [7]. Surprisingly, after bromination of compounds 2 and 3, the quantum yield was found to increase.…”

“…Both compounds also exhibit similar orientations of the carbonyl moieties, lying in the same plane as the thiophene S atoms, similar to a diformyl-functionalized phosphole reported earlier [7]. The thiophene carbonyl bond lengths and twisting are similar to those found in a related di-2-thienyl ketone [8].…”

Anorganische Chemie 2009

“…Das Einbetten eines Dithieno[3,2‐b:2',3'‐d]phospholbausteins als Kern in p‐konjugierte Oligo(m‐phenylenvinylen)‐Dendrimere liefert Materialien mit gesteigerter Lumineszenzintensität. Der Grund ist der Energietransfer von den Seitenarmen zum zentralen Phospholchromophor 1_75. Die Kombination mehrerer Dithienophospholbausteine mit unterschiedlichen Fluoreszenz‐Emissionsfarben erlaubt es, weiße Lumineszenz zu generieren, die für Beleuchtungsanwendungen wichtig ist 1_76…”

Synthesis and Properties of an Electropolymer Obtained from a Dimeric Donor/Acceptor System with a 4,4′-Spirobi[cyclopenta[2,1-b:3,4-b′]dithiophene] Core

“…This procedure avoided the massive formation of deformylation byproducts which is known to occur in Wittig−Horner reactions with thienyl carbaldehydes. 44 The subsequent selective formylation of 3 in the 6,6′-position of the SCPDT core was readily achieved under Vilsmeier reaction conditions, giving dicarbaldehyde 4 in good yield (76%). The targeted compound SO1 was finally obtained in 71% yield by Knoevenagel condensation of 4 with malononitrile in the presence of piperidine.…”