Isolierte molekulare Drähte

Abstract

In den erstaunlich unterschiedlichen Strukturen, die bisher als “isolierte molekulare Drähte” (insulated molecular wires, IMWs) beschrieben wurden, zeigt sich, wie vielfältig die Ansätze zur elektrisch‐chemischen Isolierung auf molekularer Ebene sind. Gemeinsam verdeutlichen diese Systeme die Bedeutung von Einkapselungsstrategien bei der Entwicklung optoelektronischer Materialien und organischer Halbleiter. Dieser Aufsatz beleuchtet die Synthese und die strukturelle Charakterisierung von IMWs. Struktur‐Eigenschafts‐Beziehungen sollen zudem erklären, wie eine Isolierung die Leistungsmerkmale eines molekularen Drahtes verbessern kann. Wir konzentrieren uns auf drei IMW‐Arten: Polyrotaxane, polymerumhüllte π‐Systeme und dendronisierte Polymere. Die Eigenschaften dieser Systeme werden mit denjenigen von konjugierten Polymeren verglichen, die in mesoporöse Netzwerke und Zeolithe eingefädelt sind. Der Einschluss molekularer Drähte verstärkt so unterschiedliche Eigenschaften wie Lumineszenz, elektrische Transportgrößen und die chemische Beständigkeit, sodass Anwendungen in Elektrolumineszenzdisplays, Sensoren und der photochemischen Wasserstofferzeugung denkbar werden.

Creation of Circularly Polarized Luminescence from an Achiral Polyfluorene Derivative through Complexation with Helix‐Forming Polysaccharides: Importance of the meta‐Linkage Chain for Helix Formation

“…[14c-e, 15] In addition, we previously reported that SPG complexes can show a high thermal stability; for example, the ICD signal of the SPG/PT1 complex at 90 8C still kept 80 % intensity relative to that at 20 8C.…”

Solid‐Phase Synthesis of Oligo(phenylene ethynylene) Rotaxanes

“…[17] At first sight it seems surprising that the two cyclodextrin units in the [3]rotaxane 3(a-CD) 2 are localized on the end alkyne units without visiting the central alkyne, whereas in the [2]rotaxane 2a-CD the cyclodextrin hops between both alkynes. The explanation is simply that the length of an OPE repeat unit (6.9 ) is less than the length of a cyclodextrin (8.2 ), [8] so that if the two a-CDs were to sit over adjacent alkynes, one of them would be pushed over a 2 , TPPTS, CuI, Na 2 CO 3 , H 2 O; solid phase: 6 a, a-CD, Pd(OAc) 2 , TPPTS, CuI, Na 2 CO 3 , H 2 O, then LiOH. [15] bulky phenylene residue.…”

“…[8] The challenge in translating this chemistry onto a solid support is to find a support that is compatible with the aqueous cyclodextrin-threading process. We chose controlled-pore glass because it has large rigid pores which should provide a suitable environment for aqueous host-guest chemistry, in contrast to solvent-swollen gels, which tend to exclude high-molecular-weight solutes, such as cyclodextrins.…”

“…[1] This strategy has been exploited to synthesize p-conjugated oligomers for optoelectronic applications, such as oligo(phenylene ethynylene)s (OPEs), [2][3][4] oligothiophenes, [5,6] and oligo(phenylene triacetylene)s. [7] Solid-phase synthesis is also a promising strategy for the synthesis of monodisperse oligomeric "insulated molecular wires". [8] Recently we have developed the synthesis of polyrotaxane-type insulated molecular wires by threading cyclodextrin (CD) macrocycles onto a conjugated polymer chain to achieve supramolecular control of the chemical stability, photoluminescence, and electroluminescence efficiency. [8,9] Herein we report the first solid-phase synthesis of rotaxanes of this type.…”

“…[8] Recently we have developed the synthesis of polyrotaxane-type insulated molecular wires by threading cyclodextrin (CD) macrocycles onto a conjugated polymer chain to achieve supramolecular control of the chemical stability, photoluminescence, and electroluminescence efficiency. [8,9] Herein we report the first solid-phase synthesis of rotaxanes of this type. We have investigated the solid-phase synthesis of two [2]rotaxanes, 1a-CD and 2a-CD, and a [3]rotaxane, 3(a-CD) 2 .…”