Blue-Colored Donor-Acceptor [2]Rotaxane

Taichi Ikeda, Ivan Aprahamian, and J. Fraser Stoddart,Org. Lett. 2007, 9, 1481-1484.

Kazuhiro IKUTATobe Lab.

Contents

□Introduction　・ Structure of Rotaxane　・ Color of the CT complex 　・ Idea of RGB dye　　・ Purpose of this Work

□Results and Discussion　・ Synthesis of Rotaxane　・ UV-vis Spectra　・ Electrochemical Properties

□Summary

Structure of Rotaxane

Ring component

Dumbbell component Stopper unitRotaxane

Shuttling(moving in parallel)

☆ A rotaxane is a mechanically interlocked molecular architecture consisting of a dumbbell-shaped component that is threaded through a ring component.

☆ The ring component can not be pulled out because the bulky substituents called ‘Stoppers’ exist at both edges of axle, then this component is called ‘Dumbbell’.

Color of CT Complex

electron transfer

LUMO of host molecule

HOMO of guest molecule

CT complexation

Stabilization by Coulombic interaction

Idea of RGB dye

・ The color of this three-station catenane changes as a function of the CBPQT4+ ring location which, in principle, can be controlled by the oxidation of each station in turn.

Color change scheme of the RGB dye

Stoddart, J. F. et al. J. Am. Chem. Soc. 2005, 127, 15994.

Purpose of this WorkGreen

Red

≡

Purpose of this Work

・ Synthesis of blue-colored rotaxane・ investigation of its optical and electrochemical properties

Stoddart, J. F. et al. Org. Lett, 2007, 9, 1287.

New guest compound

Synthesis of the Blue-colored [2]Rotaxane

(White powder)

(Orange wax)

(Blue solid)

UV-vis Absorption Spectra

UV-vis absorption spectra (rt, MeCN, 1 mM) of (a) a 1:1 mixture of DFBZ and CBPQT·4PF6, (b) a 1:1 mixture of DFBZ-TEG and CBPQT·4PF6, and (c) the blue-colored [2]rotaxane 1·4PF6. A photograph of the blue-colored [2]rotaxane solution is shown in the inset. 　　

The introduction of tetraethyleneglycol chains

⇒a change of the maximum absorption wavelength (λmax) from 570 to 610 nm.

⇒the HOMO energy level of DFBZ changes as a direct result of the alkylation

Cyclic Voltammetry

The redox potentials of (a) are higherthan those of (b).⇒consistent with UV-vis results.

+0.76+0.95

+0.65+0.83

+0.85

+1.02distorting⇒assuming that the flexible linkerenables the ring to move freelyaround the station.⇒the broadening of the redox CV peak

Cyclic Voltammetry

+0.65+0.83

+0.85

+1.02

Shifting in the same magnitude

⇒ring translocated slightly from the DFBZ station to TEG spacer⇒influence of the CBPQT4+ ring to second redox potential

Cyclic Voltammetry

binding constant

first E1/2 vs SCE (V)

λmax of CT band (nm)

TTF-TEG 416,000 +0.36 835 DFBZ-TEG 300 +0.65 610 DNP-C5DEG 100 +1.16 525

Stoddart, J. F. et al. Org. Lett. 2006, 8, 2205

( ) ( )ⅰ ⅱ 　 ( )ⅲ

Summary

• We have designed, synthesized, and characterized DFBZ-TEG and the [2]rotaxane consisting of DFBZ-TEG and CBPQT4+.

• We confirmed the blue color of the CT absorption band between DFBZ-TEG and CBPQT ・ 4PF6.

• The acquired data on model compounds –absorption spectra, and electrochemical properties – indicates that the design of an RGB dye using the discussed donor –acceptor motif is attainable.

　

補色

610 nm

740 nm

500 nm

Introduction

・ The color of the complex with CBPQT4+ as the host is determined by the wavelength of the CT absorption band.

・ The absorption wavelength depends on the energy gap between the LUMO of CBPQT4+ and the HOMO of the guest molecule.

We can generate a range of different colors by altering the HOMO energy level of the guest molecules.

Guest