Synthesis of an Insulated Oligo(phenylene ethynylene) Dimer Through Cyclodextrin-Based [c2]Daisy Chain Rotaxane

Abstract

Oligo(phenylene ethynylene)s (OPEs) are π-conjugated systems with promising optical, bioactive, and electrical properties, making them valuable candidates for molecular electronics and biosensors. Controlling the arrangement and orientation of π-conjugated systems is crucial in developing molecular devices. Recently, we developed insulated diarylacetylene dimers using a [c2]daisy chain rotaxane strategy, which brings two cores into close proximity without covalent bonding and shields them with permethylated α-cyclodextrins. Here, we synthesized an insulated OPE dimer using a similar rotaxane strategy to investigate its optical properties. The rotaxane structure and optical properties were evaluated using nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization high-resolution mass spectrometry (ESI-HRMS), and absorption and fluorescence spectroscopy. This study is expected to contribute to the development of optical and electronic materials utilizing OPEs.

1. Introduction

Oligo(phenylene ethynylene)s (OPEs) are π-conjugated systems that show considerable potential as building blocks of functional materials, owing to their optical, bioactive, and electrical properties [1,2,3,4,5,6,7,8,9,10,11,12]. For example, their fluorescent properties enable their application as dyes for fluorescence imaging microscopy [3,8,9,12]. Additionally, OPEs exhibit bioactivities that can be regulated by photoexcitation, and selectivity toward specific pathogens and cells can be achieved by modifying their substituents [1]. The rigid and linear π-conjugated systems of OPEs promote their aggregation through π−π interactions, allowing for the formation of self-assembled nanoparticles, which facilitate their cellular delivery [6]. Moreover, OPEs are promising candidates for molecular devices and wiring molecules and are suitable for placement on nanoelectrodes in applications such as molecular electronics and biosensors [2,4,5,7,10,11]. In the development of molecular devices, it is important to control the arrangement and orientation of the π-conjugated systems. Typically, this is achieved by introducing chemical bridges between the π-conjugated systems or by modifying them with suitable substituents [13,14,15,16,17,18,19,20,21,22,23].

Recently, we developed insulated diarylacetylene dimers using a [c2]daisy chain rotaxane strategy [24,25]. In our rotaxane system, two diarylacetylene cores were brought into close proximity without covalent bridging and shielded from the external environments by permethylated α-cyclodextrins (PM α-CDs), which endowed the resultant dimer with unique optical properties [25]. In this study, we investigated the structural and optical properties of an extended π-conjugated molecule and its dimer within a newly prepared rotaxane. Specifically, an insulated OPE dimer was fabricated using our rotaxane strategy, whereby two OPE cores with an extended π-conjugated system were brought into close proximity and encapsulated to investigate the effects of increased overlap between the cores on their optical properties. In particular, we investigated the impact of the PM α-CD positioning along the OPE axle moieties within the rotaxane and the resulting degree of overlap between the OPE cores on the optical properties. The structural and optical properties were evaluated using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy as well as absorption and fluorescence spectroscopy. Overall, this study provides fundamental insights into OPE dimers and contributes to the advancement of optical and electronic materials.

2. Results and Discussion

Monomer 1 was prepared from mono-6-O-(toluenesulfonyl)-permethylated α-cyclodextrin (PM α-CD OTs) [26] over three steps in 77% yield, as shown in Scheme 1. The formation of associated complexes such as face-to-face dimers was investigated using solvent-dependent ¹H NMR measurements (Figure 1). In the aromatic region of the ¹H NMR spectrum in chloroform-d, the signals for the four protons ortho to the alkoxy groups appeared as doublets at 6.87 and 6.94 ppm, while the other eight aromatic proton signals overlapped in the range of 7.45–7.47 ppm. This spectral pattern was in accordance with the structure of non-associated monomer 1 and the absence of associated complexes. In methanol-d₄, the ¹H NMR spectrum contained six new doublet peaks at 6.40, 7.01, 7.40, 7.45, 7.58, and 8.00 ppm, which were attributed to the formation of an associated species, while the monomer peaks became considerably smaller. In a methanol-d₄/deuterium oxide (2/1(v/v)) mixture, the monomer peaks disappeared completely, and only the peaks corresponding to the associated complex were observed. By comparison with the ¹H NMR spectra of previously reported [c2]daisy chain rotaxanes [25], the associated complex was assigned as the face-to-face dimer 2 shown in Scheme 2.

As shown in Scheme 3, face-to-face dimer 2 was capped with 4-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}-3,5-dimethylaniline through a condensation reaction facilitated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) in methanol/water (2/1 (v/v)). The desired rotaxane 3 was obtained in 60% yield after purification by silica gel column chromatography, eluting with an ethyl acetate/methanol mixture. The [c2]daisy chain structure of the rotaxane was confirmed by 1D and 2D NMR spectroscopy, as well as electrospray ionization high-resolution mass spectrometry (ESI-HRMS). The peaks in the aromatic region of the ¹H NMR spectrum of 3 were assigned to protons A–G, as shown in Scheme 3 and Figure 2. The nuclear Overhauser effect spectroscopy (NOESY) spectrum of 3 revealed cross-peaks between the OPE protons (D and E) and the inner protons of PM α-CD, as well as between the OPE protons (C, D, and F) and the methyl protons on the rims of PM α-CD, indicating that the PM α-CDs were positioned around the acetylene moiety between the benzene rings, as shown in Scheme 3 and Figure 3. This indicated that the overlap of the OPE cores within 3 was slightly larger compared with that among the previously reported rotaxane-insulating diarylacetylene cores. A similar condensation reaction in dichloromethane afforded the corresponding stoppered monomer 4 in 67% yield. Neither rotaxane 3 nor stoppered monomer 4 formed larger supramolecular complexes in methanol or methanol/water (2/1 (v/v)) (Figure S1).

The absorption spectra of rotaxane 3 and the corresponding stoppered monomer 4 in various solvents are shown in Figure 4, and the absorption maxima (λ_max) and molar absorption coefficients are listed in

Table 1. Maximum absorption wavelengths and the molar absorption coefficients of [c2]daisy chain rotaxane 3 and stoppered monomer 4 in various solvents.

Solvent	Maximum Absorption Wavelengths (nm) 1
	[c2]Daisy Chain Rotaxane 3 2	Stoppered Monomer 4 3
Chloroform	333 (9.87 × 104)	332 (5.51 × 104)
Tatrahydrofuran	333 (9.70 × 104)	332 (5.77 × 104)
Methanol	331 (10.2 × 104)	328 (6.08 × 104)
Acetonitrile	331 (9.97 × 104)	329 (5.98 × 104)
Dimethylsulfoxide	334 (9.64 × 104)	335 (5.28 × 104)

¹ The values in parentheses represent the molar absorption coefficients ((mol/L)⁻¹ · cm⁻¹). ² [3] = 1.5 × 10⁻⁵ mol/L. ³ [4] = 3.1 × 10⁻⁵ mol/L.

. The absorption spectra of 3 differed minimally in various solvents, and the λ_max shifted by only 3 nm, which is smaller than that observed for stoppered monomer 4 (7 nm). This indicated that the influence of the solvent on the OPE axle moieties in rotaxane 3 was minimal, that is, that they were effectively isolated from the external environment by PM α-CD. The molar absorption coefficients of rotaxane 3 in various solvents were approximately twice those of stoppered monomer 4. In addition, no significant differences were observed in the spectral shapes of compounds 3 and 4, suggesting that the two OPE moieties in [c2]daisy chain rotaxane 3 exist independently.

The fluorescence spectra of rotaxane 3 and the corresponding stoppered monomer 4 in various solvents are shown in Figure 5, and the emission maxima (λ_max) are listed in

Table 2. Maximum emission wavelengths of [c2]daisy chain rotaxane 3 and stoppered monomer 4 in various solvents.

Solvent	Maximum Emission Wavelengths (nm) 1
	[c2]Daisy Chain Rotaxane 3 2	Stoppered Monomer 4 3
Chloroform	369, 387	366, 383
Tatrahydrofuran	368, 386	366, 383
Methanol	369, 385	364, 380
Acetonitrile	370, 385	369, 382
Dimethylsulfoxide	372, 388	376, 388

¹ Excitation at the maximum absorption wavelength. ² [3] = 6.8 × 10⁻⁷ mol/L, ³ [4] = 1.7 × 10⁻⁶ mol/L.

. For both compounds, only monomer emissions were observed. Similar to the absorption spectra, a difference between the shifts in the emission wavelength (λ_max) was observed for the fluorescence spectra of 3 and 4, indicating a shielding effect of the PM α-CDs on the OPE moieties. Additionally, for stoppered monomer 4, the emission intensity increased significantly at longer wavelengths compared to that at shorter wavelengths in solvents with higher dielectric constants. In contrast, although the spectra of rotaxane 3 showed a similar trend, the change was smaller, owing to the shielding effect of PM α-CD. In our previous study, prominent excimer emissions were observed for the insulated diarylacetylene dimer [25]; in contrast, no excimer emissions was observed for the present insulated OPE dimer, suggesting that the overlap between the two OPE moieties may be unsuitable for excimer emissions.

3. Materials and Methods

3.1. General Procedures

Mono-6-O-(toluenesulfonyl)-permethylated α-cyclodextrin (PM α-CD OTs), ethyl 4-(4-iodophenoxy)butyrate, and 4-{2-[2-(2-hydroxyethoxy)ethoxy)]ethoxy}-3,5-dimethylaniline were prepared according to previously reported procedures [25]. Other reagents were purchased from commercial sources and used without further purification. Commercially available dehydrated N,N-dimethylformamid (DMF) was used as received without further distillation. Melting points were measured using a MP-500 micro (Yanaco, Tokyo, Japan) melting point apparatus. ¹H NMR (400 MHz), ¹³C NMR (100 MHz), and NOESY spectra were recorded on a JNM-Alice 400 spectrometer (JEOL, Tokyo, Japan) at ambient temperature. ¹H NMR chemical shifts are reported relative to tetramethylsilane (TMS, 0.00 ppm) or residual solvent peaks (7.26 ppm for CDCl₃ or 3.31 ppm for CD₃OD). ¹³C NMR Chemical shifts are reported relative to CDCl₃ (77.0 ppm). The electrospray ionization high-resolution mass spectrometry (ESI-HRMS) spectra were recorded on a micrOTOF II-KE02 instrument (Bruker, Billerica, MA, USA) using sodium trifluoroacetate as the cationization reagent. Absorption spectra were recorded using a U-1900 UV-Vis absorption spectrometer (HITACHI, Hitachi, Japan). Fluorescence spectra were recorded using a FL-7000 fluorescence spectrophotometer (HITACHI, Hitachi, Japan).

3.2. Synthesis

Monomer 1

PM α-CD OTs (1.1 g, 0.81 mmol) and 4-iodophenol (0.26 g, 1.2 mmol) were dissolved in dry DMF (15 mL). Anhydrous K₂CO₃ (0.28 g, 2.0 mmol) was added to the solution, and the mixture was stirred under nitrogen at 100 °C for 22 h and cooled to ambient temperature. The mixture was diluted with ethyl acetate (EtOAc) and washed with saturated aqueous solution of sodium bicarbonate (sat. NaHCO₃ (aq)) and brine. The organic layer was separated and dried over anhydrous sodium sulfate (Na₂SO₄). The solvent was removed in vacuo, and the residue was purified via column chromatography on silica gel (eluent: EtOAc/methanol(MeOH) = 95/5 (v/v)) to yield PM a-CD iodide as a white, formed solid (1.2 g, quantitative). PM α-CD iodide (0.92 g, 0.65 mmol), ethyl 4-{4-[(4-ethynylphenyl)ethynyl]phenoxy}butyrate (0.65 g, 2.0 mmol), tetrakis(triphenylphosphine)palladium(0) (37 mg, 0.032 mmol), and copper(I) iodide (7.4 mg, 0.039 mmol) were dissolved in degassed diisopropylamine (i-Pr₂NH)/tetrahydrofuran (THF) (3/1 (v/v)) (20 mL). The mixture was stirred at ambient temperature for 16 h under a nitrogen atmosphere. The mixture was diluted with EtOAc and washed with a saturated aqueous solution of ammonium chloride aqueous solution (sat. NH₄Cl (aq)) and brine. The organic layer was separated and dried over anhydrous magnesium sulfate (MgSO₄). The solvent was removed in vacuo, and the residue was purified by column chromatography on silica gel (eluent: EtOAc/toluene = 1/1 (v/v) then EtOAc/MeOH = 9/1(v/v)), and gel permeation chromatography (GPC) using JAIGEL-1H (eluent: CHCl₃) to yield PM a-CD ethyl ester as a white, formed solid (0.89 g, 84%). PM α-CD ethyl ester (0.89 g, 0.56 mmol) was dissolved in mixture solvent of MeOH (20 mL) and 0.56 M KOH (10 mL). The resulting mixture was stirred at 60 °C for 2 h under a nitrogen atmosphere. The reaction mixture was cooled to ambient temperature, diluted with EtOAc, and washed with dilute hydrochloric acid (HCl (aq)) and brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo to yield monomer 1 as a pale-yellow, formed solid (0.81 g, 92%). m.p. 107–108 °C. ¹H NMR (400 MHz, CDCl₃, 25.1 °C) d: 7.47–7.45 (m, 8H), 6. 94 (d, J = 7.8 Hz, 2H), 6.87 (d, J = 7.8 Hz, 2H), 5.10–5.01 (m, 6H), 4.44–4.34 (m, 2H), 4.09–4.03 (m, 4H), 3.83–3.14 (m, 83H), 2.59 (t, J = 7.2 Hz, 2H), 2.14 (m, 2H), (The carboxylic acid proton was not observed.). ¹³C NMR (100 MHz, CDCl₃, 25.0 °C) d: 176.96, 158.87, 158.82, 132.98, 132.91, 131.22, 131.18, 123.05, 122.81, 115.45, 115.10, 114.63, 114.42, 100.12–99.91 (several peaks overlapped), 99.75, 91.13, 90.87, 88.01, 87.82, 82.85, 82.44, 82.37, 82.27, 82.19, 82.06-81.97 (several peaks overlapped), 81.88, 81.18, 77.20, 71.45, 71.27–71.10 (several peaks overlapped), 70.57, 67.84, 66.52, 61.73–61.64 (several peaks overlapped), 58.94–58.79 (several peaks overlapped), 57.89, 57.80–57.70 (several peaks overlapped), 30.15, 24.24. ESI-HRMS m/z: 1611.6958 ([M · Na]⁺ calculated for C₇₉H₁₁₂O₃₃Na: 1611.6978).

[c2]Daisy chain rotaxane 3

Monomer 1 (110 mg, 0.069 mmol) and 4-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}-3,5-dimethylaniline (83 mg, 0.31 mmol) were dissolved in MeOH/H₂O (2/1 (v/v)) (3 mL) to obtain face-to-face dimer 2 quantitatively. After cooling the solution to 2 °C, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) (56 mg, 0.29 mmol) was added to the solution to cap the two ends of face-to-face dimer 2. The mixture was stirred at 2 °C for 2 h and then at ambient temperature for an additional 3 h. The reaction mixture was acidified with dilute HCl (aq), diluted with EtOAc, and washed with brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo, and the residue was purified by column chromatography on silica gel (eluent: EtOAc/MeOH = 9/1 (v/v) then EtOAc/MeOH = 4/1 (v/v)) and GPC using JAIGEL-1H (eluent: CHCl₃) to yield [c2]daisy chain rotaxane 3 as a white, formed solid (76 mg, 60%). m.p. decomposition > 300 °C. ¹H NMR (400 MHz, CDCl₃, 24.9 °C) d: 8.02 (d, J = 8.1 Hz, 4H), 7.50–7.45 (m, 8H), 7.39 (d, J = 7.4 Hz, 4H), 7.14 (s, 4H), 7.05–7.02 (m, 6H), 6.39 (d, J = 7.6 Hz, 4H), 5.04–4.96 (m, 12H), 4.32–3.09 (m, 202 H), 7.45 (t, J = 7.4 Hz, 4H), 2.37 (brs, 2H), 2.27 (s, 12H), 2.20–2.13 (m, 4H). ¹³C NMR (100 MHz, CDCl₃, 20.6 °C) d: 169.88, 159.61, 158.79, 152.18, 134.35, 133.28, 132.85, 131.57, 131.40, 131.30, 123.83, 122.03, 120.25, 114.55–114.51 (two peaks overlapped), 114.03–113.98 (two peaks overlapped), 100.67, 100.23–100.15 (two peaks overlapped), 99.88, 99.66, 92.36, 91.84, 87.78, 87.17, 82.93, 82.60–81.95 (several peaks overlapped), 81.80, 81.36, 81.16–80.80 (several peaks overlapped), 77.20, 72.46, 72.00, 71.85, 71.75, 71.48–71.41 (several peaks overlapped), 71.25, 70.97, 70.75, 70.43, 70.33, 70.13, 67.49, 66.80, 61.72–61.50 (several peaks overlapped), 59.21, 59.04, 58.82, 57.83–57.61 (several peaks overlapped), 33.31, 24.78, 16.28. ESI-HRMS m/z: 1250.2437 ([M · 3Na]⁺³ calculated for C₁₈₆H₂₆₆N₂O₇₂Na₃: 1250.2320).

Stoppered monomer 4

Monomer 1 (193 mg, 0.12 mmol) and 4-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}-3,5-dimethylaniline (136 mg, 0.50 mmol) were dissolved in dichloromethane (3 mL). EDC·HCl (95 mg, 0.50 mmol) was added to the solution. The mixture was stirred at ambient temperature for 20 h. The reaction mixture was acidified with dilute HCl (aq), diluted with EtOAc, and washed with brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo, and the residue was purified by GPC using JAIGEL-1H (eluent: CHCl₃) to yield stoppered monomer 4 as a white, formed solid (151 mg, 67%). m.p. 148–151 °C. ¹H NMR (400 MHz, CDCl₃, 24.8 °C) d: 7.47–7.45 (m, 8H), 7.11 (s, 2H), 7.08 (s, 1H), 6.94 (d, J = 8.8 Hz, 2H), 6.88 (d, J = 8.7 Hz, 2H), 5.11–5.00 (m, 6H), 4.44–4.34 (m, 2H), 4.10–4.04 (m, 4H), 3.92–3.13 (m, 95H), 2.55 (t, J = 7.0 Hz, 2H), 2.40 (brs, 1H), 2.26–2.18 (m, 8H). ¹³C NMR (100 MHz, CDCl₃, 25.0 °C) d: 170.42, 158.86–158.80 (two peaks overlapped), 152.08, 133.29, 132.98, 132.89, 131.25–131.16 (several peaks overlapped), 122.99, 122.81, 120.42, 115.40, 115.10, 114.61, 114.44, 100.07–99.85 (several peaks overlapped), 99.72, 91.07, 90.87, 87.97, 87.84, 82.83, 82.43-81.86 (several peaks overlapped), 81.11, 77.20, 72.42, 71.45, 71.34, 71.18–71.03 (several peaks overlapped), 70.65, 70.52, 70.36, 70.24, 67.82, 66.80, 61.69–61.54 (several peaks overlapped), 58.92–58.76 (several peaks overlapped), 57.87, 57.78–57.68 (several peaks overlapped), 33.46, 24.87, 16.18. ESI-HRMS m/z: 943.4198 ([M · 2Na]⁺² calculated for C₉₃H₁₃₃NO₃₆Na₂: 943.4213).

Ethyl 4-{4-[(4-ethynylphenyl)ethynyl]phenoxy}butyrate

An overview of the synthesis of ethyl 4-{4-[(4-ethynylphenyl)ethynyl]phenoxy}butyrate is shown in Scheme S1. 1-Bromo-4-iodobenzene (3.60 g, 16 mmol), bis(triphenylphosphine)palladium(II) dichloride (567 mg, 0.81 mmol), and copper(I) iodide (91 mg, 0.48 mmol) were dissolved in degassed i-Pr₂NH/THF (4/1 (v/v))(50 mL) under nitrogen atmosphere. tert-Butyldimethylsilyl acetylene (2.44 g, 17 mmol) was added, and the resultant mixture was stirred at ambient temperature for 2 h. 2-Hydroxy-2-methyl-3-butyne (2.05 g, 24 mmol) was added, and the resulting mixture was stirred at ambient temperature for 16 h. The mixture was diluted with EtOAc and washed with sat. NH₄Cl (aq) and brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo, and the residue was purified by column chromatography on silica gel (eluent: hexane/EtOAc = 5/1 (v/v)) to yield 2-hydroxy-2-methyl-4-{4-[(tert-butyldimethylsilyl)ethynyl]phenyl}-3-butyne (5) as a pale brown solid (3.8 g, 79%). Compound 5 (3.8 g, 13 mmol) was dissolved in toluene (60 mL). Crushed sodium hydroxide (NaOH) (1.1 g, 27 mmol) was added to the solution, and the mixture was stirred at 120 °C for 6 h under nitrogen atmosphere. The reaction mixture was cooled to ambient temperature, diluted with EtOAc, and washed with sat. NH₄Cl (aq) and brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo to yield 4-[(tert-butyldimethylsilyl)ethynyl]phenylacetylene (6) as a black solid (2.5 g, 80%). Compound 6 was used in the next step without purification. Ethyl 4-(4-iodophenoxy)butyrate (1.1 g, 3.4 mmol), compound 6 (2.4 g, 10 mmol), tetrakis(triphenylphosphine)palladium(0) (103 mg, 0.15 mmol), and copper(I) iodide (22 mg, 0.12 mmol) were dissolved in degassed i-Pr₂NH/THF (3/1 (v/v)) (35 mL). The mixture was stirred at ambient temperature for 20 h under a nitrogen atmosphere. The mixture was diluted with EtOAc and washed with sat. NH₄Cl (aq) and brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo, and the residue was purified via column chromatography on silica gel (eluent: hexane/EtOAc = 9/1 (v/v)) to yield ethyl 4-{4-[(4-tert-bulyldimethylsilylethynylphenyl)ethynyl]phenoxy}butyrate (7) as a pale, brown solid (1.4 g, 90%). Compound 7 (1.4 g, 3.1 mmol) was dissolved in THF (40 mL), followed by the addition of tetrabuthylammonium fluoride (TBAF) solution in THF (1.0 M, 3.1 mL), and the mixture was stirred at ambient temperature for 1 h. The reaction mixture was diluted with chloroform and washed with sat. NH₄Cl (aq) and brine. The organic layer was separated and dried over MgSO₄. The solvent was removed in vacuo, and the residue was purified by column chromatography on silica gel (eluent: hexane/EtOAc = 6/1 (v/v)) to yield ethyl 4-{4-[(4-ethynylphenyl)ethynyl]phenoxy}butyrate as a white solid (0.90 g, 88%). m.p. 78-80 °C. ¹H NMR (400 MHz, CDCl₃, 17.2 °C) d: 7.46–7.44 (m, 6H), 6.86 (d, J = 8.8 Hz, 2H), 4.15 (q. J = 7.2 Hz, 2H), 4.03 (t, J = 6.1 Hz, 2H), 3.17 (s, 1H), 2.52 (t, J = 7.3 Hz, 2H), 2.12 (m, 2H), 1.27 (t, J = 7.2 Hz, 3H). ¹³C NMR (100 MHz, CDCl₃, 17.9 °C) d: 173.06, 159.00, 133.04, 131.96, 131.20, 124.03, 121.36, 114.90, 114.45, 91.44, 87.56, 83.27, 78.74, 66.67, 60.41, 30.62, 24.43, 14.15. ESI-HRMS m/z: 355.1405 ([M · Na]⁺¹ calculated for C₂₂H₂₀O₃Na: 355.1305).

4. Conclusions

An insulated OPE dimer was synthesized using our previously developed [c2]daisy chain rotaxane strategy, and its structure and optical properties were evaluated using NMR, absorption, and fluorescence spectroscopy. The results of the NMR measurements indicated that the overlap of the expanded π-conjugated OPE cores within the newly prepared rotaxane was slightly increased compared to that of the diarylacetylene cores in the previously reported rotaxane. Additionally, optical analyses indicated that PM α-CDs efficiently insulated the OPE dimer. However, no excimer emission was observed for the insulated OPE dimer. This study provides fundamental insights into the properties of encapsulated OPE dimers, contributing to advancements of optical and electronic materials.