Guest Inclusion of Butadiyne -Bridged Macrocycles

1. Guest Inclusion of Butadiyne-Bridged Macrocycles Tobe Lab. M1 Hiroshi Takeda

2. Contents ・What is Macrocycles ・Complexation of cyclothiophene with fullerene on a surface ・My work ・Summary

3. Macrocycles: Definition and Utilities • Macrocycles are defined as any molecules having a ring of nine or more atoms. • Macrocyclic natural products ⇒ Superior biochemical functionalities development as drugs clarithromycin

4. Shape-Persistent Macrocycles • In recent years, intense interest have been paid for π-conjugated in shape-persistent macrocycles ⅰ) large, supramolecular building blocks that generate π-stacked structures in solution ⅱ) noncollapsablenanoporous solids In my laboratory syntheses and properties of the shape-persistent macrocycles consisting of aromatic rings and triple bonds have been reported. They showed self-association and binding to large organic substrate.

5. Host-Guest Chemistry Hosts and guests held together in solution in definable structural relationships by electrostatic forces (enthalpic component) Macrocycles (Host): Organic molecule containing convergent binding sites. Synthetic counterparts to receptor sites in enzymes, genes, antibodies and ionophores Guest: Molecules or ions containing divergent binding sites. Counterparts to substrates, inhibitors, cofactors, antigens

6. Complexationof Butadiyne-Bridged Pyridinophanewith ＴropyliumCation in Ｓolution tropylium ion R=C8H17 2 1 R=C8H17 To examine the binding ability of pyridinophanes1 and 2, we choose tropylium ion was chosen as a guest. The chemical shift change of the aromatic protons of 1 and 2 on 1H-NMR titration measurements with tropyliumcation was analyzed and calculate for complex formation constant.

7. Complexationof Butadiyne-Bridged Pyridinophanewith TropyliumCation in Solution > R=C8H17 R=C8H17 2 1 On the basis of 1H-NMR titration measurements, The nonlinear least-squares regression analysis gave K11(1:1) and K21(2:1) →For 1, K11 = 3×103 M-1 and K21 = 3×104M-1 For 2, K11 = 1×102M-1 and K21 = 4×102M-1 The binding constants of 1are larger than those of 2 　→The size of the cavity of 1 is suitable for trapping of tropyliumcation. Kis complex formation constant :錯形成定数

8. Self-Assembly of Butadiyne-Bridged Pyridinophane

9. electron Tunneling current Scanning Tunneling Microscopy (STM) Tip Tunneling current Sample Tip Sample

10. Guest Inclusion Ability of Butadiyne-Bridged Pyridinophaneon Solid Surfaces An empty macrocycle1 ＋ 1 R = COOC8H17 Thebrighter spots within the cavity of 1 are trapped tropyliumcations.

11. Introduction of Paper Bu ≡ 〜 cyclo[12]thiophene fullerene

12. Previous work of Monolayer of C[12]T

13. Previous work of Monolayer of C[12]T ・The individual rings appeared in bright features ・The interior cavity and the insulating alkyl side chains appeared darker in the image

14. Previous work of Monolayer of C[12]T ・The individual rings appeared in bright features ・The interior cavity and the insulating alkyl side chains appeared darker in the image

15. Previous work of Monolayer of C[12]T Top view Side view “spider-like” comformation

16. About Thiophene C[12]T : cyclo[12]thiophene Cyclic π-conjugated cyclothiophene self-assembles at the solid-liquid interface to form well-ordered 2D molecular network. C[12]T p-type (donor)monolayer fullerenes n-type (acceptor)material charge transfer interaction The formation of 1:1 donor–acceptor (D–A) complex

17. Complexationof C[12]T-C60 ・ An isolated C60 molecule (white arrow) adsorbed at the liquid/monolayer interface. ・ The electron-accepting C60 formed a stable 1:1 D–A complex with cyclothiophene. ・ From Semiempirical calculations, the most stable complexation site is at the rim of the macrocycle Providing maximal π–π interaction.

18. Complexation of C[12]T-C60 ・ Four individual C60fullerenes, labeled “C” (cavity) or “R” (rim), are adsorbed on top of a C[12]T monolayer . ・ A R-type fullerene is imaged brighter, the three C-type fullerenes can be observed as rather diffuse spots.

19. Complexation of C[12]T-C60 • During scanning, the C-type fullerenes were desorbed • There are two types of fullerenes (R diameter ∼ 1 nm versus C diameter ∼ 1.6 nm) • The C-type is not immobilized, but rather rotates around an axis perpendicular to the substrate. a complexationsite on top of the conjugated “rim”is stable position

20. Complexation of C[12]T-C60 Complexes with more than one fullerene per macrocyclewere never seen The fullerenes interact with the cyclothiophenes at the same position and form perfectly ordered domains. The complexation ratio is exclusively 1:1. The C[12]T monolayer acts as a veritable template

21. The 1:1 D–A complex ・ The electron density of macrocycle’s HOMO is drastically shifted by the complexation of C60. ・ It becomes unfavorable when C60 occupy the electron-deficient part of the C[12]T macrocycle. The macrocyclecan form complex with fullerenes.

22. Scanning tunneling Spectroscopy (STS) STS provides a useful tool in the study of the electrical properties of molecular monolayer. On the sample, it can detect the tunneling current by changing of the bias voltages, which probe the local density of electronic states (LDOS) and the band gap of surfaces and materials on surfaces at the atomic scale. The I(V) and dI/dV data refrectthe conductivity of organic molecules may be changed in a variety of ways. dI/dV ∝ LDOS

23. The electrical properties of C[12]T C[12]T The asymmetric I–V curve was observed. The asymmetry is clearly seen in the differential curve (dI/dV–V) The frontier orbitals of the system were localized at -0.7 and 0.95 V, below and above the Fermi level, respectively. The general p-doping character of electron-rich thiophene compounds. Relate to the local density of states (LDOS) of the molecule. HOMO–LUMO gap is 1.65 V. C[12]T–C60complex C[12]T

24. The electrical properties of C[12]T–C60 complex C[12]T–C60 complex The shape of the I–V curve at positive bias is very similar to the non-complexedmacrocycle. However at negative bias the current behavior is quite different. From the differential (dI/dV–V) curve, a bigger gap between the frontier orbitals (1.85 V) The shift of the HOMO to higher voltages (–0.9 V) The typical exponential behavior of the tunneling current in semiconductors is blocked starting at a value of –1.06 V. The saturation of the current at negative bias is a special spectroscopic characteristic of the D–A complex. C[12]T–C60complex C[12]T

25. Summary • self-assembled and highly ordered monolayers of macrocyclicthiophenesC[12]T can be used as template to epitaxially grow 3D nanoarchitectures with C60-fullerenes. • Submolecularly resolved STM images allow the investigation of unique 1:1 complexes comprising a ring-shaped p-type and a spherical n-type semiconductor. • The dynamics of C60 adsorption and the complexationsite on the macrocycle have been analyzed by STM • The electronic properties of the complexes have been elucidated by means of STS showing interesting saturation behavior in the I–V curves.

26. Purpose of My Work host ・Formation of 2D molecular networks on the solid surface. ・Guest inclusion ability toward larger guest molecule -My purpose- guest ・Synthesis of butadiyne-bridged pyridinophane which possesses a larger cavity ・Evaluation of its guest inclusion ability

27. Purpose of My Work <STM image & model of macrocycle> ・Synthesis of butadiyne-bridged pyridinophane which possesses a larger cavity ・Evaluation of its guest inclusionin solution and on surface.

28. Synthesis of Butadiyne-Bridged Pyridinophane

29. Synthesis of Butadiyne-Bridged Pyridinophane Route 1 Route 2

30. Summary • The molecular network of macrocycles would serve as an appropriate template layer for guest adsorption • A purpose of my work is to synthesize butadiyne-bridged pyridinophane which possesses a larger cavity and evaluate its guest inclusion.