A Supramolecular Approach to the Preparation of Nanographene Adlayers Using Water‐Soluble Molecular Capsules

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are excellent building blocks for the creation of two-dimensional (2D) nanosheets.However,large PAHs tend to exhibit poor or no solubility in organic solvents and water.T oo vercome this issue,w ee mployed water-soluble micellar capsules consisting of V-shaped amphiphilic molecules.C haracteristic electrochemical behavior was observed in 0.1m H 2 SO 4 in the presence of the water-soluble capsules containing PAHs,s uch as ovalene,c ircobiphenyl, and dicoronylene.F urthermore, under these conditions,P AHs were released from the capsules, resulting in the formation of a2 Da dlayer of PAHs at the electrochemical interface.F inally,u sing electrochemical scanning tunneling microscopy, we demonstrate that our molecular containers based on water-soluble molecular capsules allowthe facile preparation of 2D PAHa dlayers in addition to structurally controlling nanostructure formation on Au surfaces.Carbon materials,s uch as graphene,h ave been extensively studied for their application in electronic devices, [1][2][3] photodetectors, [4][5][6] capacitors, [7] electrocatalysis, [8][9][10] and sensors. [11] Similarly,p olycyclic aromatic hydrocarbons (PAHs) with planar structures exhibit excellent donor abilities owing to their p-conjugated structures.A ss uch, PA Hs are promising materials for use as two-dimensional (2D) nanoarchitectures, such as "nanographene", which should create novel functionalities for electronic devices,i ncluding electrochromic devices [1,12] and quantum dots. [13] Fore xample,f unctionalized graphene quantum dots that allow the control of band gaps indicate the structural dependence of photocatalysts in water splitting and carbon dioxide reduction under visible-light irradiation. [13] Indeed, to date,anumber of attractive PA Hs have been synthesized by the Müllen group. [1, 12,14] Thedesign and synthesis of structurally defined PA Hs are essential for the creation of functional graphenes based on elemental doping and periodical defects (or vacancies) as the building blocks.However,large PA Hs without peripheral substituents are insoluble in both water and organic solvents.T he formation of adlayers on electrode surfaces is challenging because PA Hs without peripheral substituents are used as 2D molecular templates, [15] have applications in conductance enhancement between nanographene and Au junctions, [16] and are used in organic field-effect transistors (OFETs). [17] In contrast, the V-shaped amphiphilic molecule 1 (Scheme 1) forms micellar capsules (1) n in water and solubilizes various water-insoluble compounds.I np articular, p-conjugated planar molecules,s uch as metalloporphyrins,p hthalocyanines,p entacenes,a nd coronenes,h ave been applied for this purpose. [18,19] We report herein water-soluble molecular capsules consisting of V-shaped amphiphilic molecules for the uptake of large PA Hs (i.e., ovalene,c ircobiphenyl, and dicoronylene; Scheme 1). In this study,w ea lso examined the electrochemical behavior of the PA H-containing molecular capsules an...

Syntheses of Organic Semiconductors in Water. Recent Advancement in the Surfactants Enhanced Green Access to Polyconjugated Molecules

“…By combination of self-assembly in water solution and clever designing of coordinative bonding around palladium atoms, the group developed association colloids featuring remarkable applications in host guest chemistry, selective recognition, modulation of guest reactivity, water solubilization of organic dyes and nanocarbons. [64][65][66][67][68][69][70][71] Figure 4. Anthracene dimers-based aromatic nanocaspules.…”

A Polyaromatic Gemini Amphiphile That Assembles into a Well‐Defined Aromatic Micelle with Higher Stability and Host Functions

“…To compare the host capability between aromatic micelles 3 and 4,N ile red (NR)a nd methyl-capped resorufin were initially employed as at ypical solvatochromic dye [15] and its reference compound with the same core structure,r espectively.R ed solid NR was manually ground with amphiphile 1 or 2 in a1:1 molar ratio for 5min using asmall-sized agate mortar and pestle,a nd the resultant solids were mixed with H 2 Oa tr oom temperature (Figure 5a). [10,16] Removal of suspended, hydrophobic NR by centrifugation and filtration afforded clear aqueous solutions of host-guest composites 3·(NR) n (n % 5) and 4·(NR) n (n % 2). Theh ost-guest ratios and the product sizes (that is,2 .7 nm for 3·(NR) n and 2.1 nm for 4·(NR) n in core diameter) were estimated by 1 HNMR (in CD 3 OD) and DLS analyses (Figure 5c), respectively.T he UV/Vis spectrum of the resultant, pale red purple solution of 4·(NR) n contained new broadened absorption bands at 410-740 nm, derived from the encapsulated NR guests (Figure 5a, left and 5d).…”

Polyaromatic nanocapsules as photoresponsive hosts in water

“…The light-inactive amphiphiles assemble into spherical micellar capsules through π-stacking interactions and the hydrophobic effect 24 . The capsule displays wide-ranging host abilities in water toward various hydrophobic guests, due to the flexible polyaromatic frameworks adaptable to the guest size and shape 25–27 . Thus we envisioned that incorporation of the ortho -derivative, capable of undergoing the intramolecular [4+4] photocyclization of the anthracene panels 28–30 , into the water-soluble capsule systems could generate a photoresponsive host with both guest uptake and release functions in water.…”