Reversibly modulating a conformation-adaptive fluorophore in [2]catenane

•A conformation-adaptive fluorophore is reversibly modulated in [2]catenanes•The mechanically interlocked structure enables a robust fluorescent molecular switch•Two modulation modes, including wavelength and intensity, can be programmed Developing systems with tunability plays an important role many practical applications such as sensors, photo-electric devices, imaging, display devices. Learning from naturally occurring green proteins that embed fluorophores the noncovalent environments of peptide assemblies, here, we report properties supramolecular environment [2]catenanes. By comparing switching ability different environments, are found to enable unique capability most remarkable signal change excellent reversibility. This work provides distinctive strategy for designing switches by combining machines. Tuning emission chemical means has long been fundamental topic, because emerging methodologies mechanisms this topic usually bring lot opportunities multi-disciplinary applications. Here, demonstrate reversible fluorophore, 9,14-diphenyl-9,14-dihydrodibenzo[a,c]phenazine (DPAC), incorporating unit into [2]catenane. Taking advantage mechanical bond [2]catenane, conformational freedom DPAC-macrocycle co-conformational state thus enabling DPAC. Owing structure, system switched dual-mode (wavelength or intensity), visually recognizable, highly manner. distinct mechanism modulating structures. switchability aroused large amount research interest,1Callan J.F. de Silva A.P. Magri D.C. Luminescent sensors early 21st century.Tetrahedron. 2005; 61: 8551-8588Crossref Scopus (1053) Google Scholar, 2Van Linde S. Sauer M. How switch fluorophore: undesired blinking controlled photoswitching.Chem. Soc. Rev. 2014; 43: 1076-1087Crossref PubMed 3Sedgwick A.C. Wu L. Han H.H. Bull S.D. He X.P. James T.D. 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X-ray single-crystal obtained 2A; Table S1). distance oxygen atoms 7.464 Å (O1···O5, Figure S1), supporting adequate space benzene (? 5.0 Å) pass cavity. were investigated S2). acetonitrile, maximum absorption/emission 350/490 nm, respectively 2B). dichloromethane, absorption spectra showed slight red-shift (353/491 nm), which consistent results reported previous literature.25Chen ScholarScheme 1Synthesis routes [2]catenanesShow full caption(A) Synthesis DPAC-ring. dihedral angle describing planes 1 (C1, N1, N2) 2 (N1, N2, C2) denoted ?d all titled compounds, larger indicates planarization. characteristic angles (?S1: ?C3-N2-N1; ?S2: ?C4-N1-N2) marked well.(B) [2]catenane 6-H 7-H. hydrogens labeled.View Large Image ViewerDownload Hi-res image Download (PPT)Figure 2Host-guest combination pseudorotaxane DPAC-ring·1-HShow Design DPAC-ring·1-H (Plane C1-N1-N2; Plane 2: C2-N2-N1).(B) Normalized CH3CN CH2Cl2.(C) Job plot curve 1-H complex CH3CN.(D) upon titration CH3CN.(E) Fluorescence DPAC-ring: (1:12) DBU (?ex = 350 nm).View (PPT) (A) well. (B) labeled. C2-N2-N1). CH2Cl2. (C) CH3CN. (D) (E) nm). Then studied. Dibenzylammonium (DBA) (1-H) selected due binding affinity crown-ether-based hosts.41Zhang NMR dibenzylammonium compared stoichiometric mixture CD3CN S3), confirming 1:1 proton shift. association constants (Ka) calculated 52.49 M?1 25°C via titration44Hibbert D.B. Thordarson death plot, transparency, open science online tools, uncertainty estimation methods other developments data analysis.Chem. Comm. 2016; 52: 12792-12805Crossref (Figures 2C S4). approximately accordance corresponding Ka value 360 DB24C8·1-H CH3CN.45Ashton P.R. Campbell Glink Philp Spencer Chrystal E.J.T. Menzer Williams D.J. Tasker P.A. Dialkylammonium ion/crown ether complexes: forerunners molecules.Angew. 1995; 34: 1865-1869Crossref (386) Moreover, displayed main peak m/z 850.4218 ESI-MS, assigned [DPAC-ring·1-H]+ S5). pseudo[2]rotaxane S2 showing mediated hydrogen bonds. (?C1-N1-N2-C2, ?d) (136.98°/140.16°) distances benzyl (7.464 6.938 Å, Figures S1 S6), ground-state twisted presence 1-H. observations suggested enhanced tension after combination, leading deplanarization backbone unit. recognition-induced revealed both blue-shifted (350?347 S7) (490?477 S4; 2D). nature, could dissociated adding excess base (1,8-diazabicyclo[5,4,0]-undec-7-ene, DBU), recovering back original 2E). blank experiment absence non-responsive property acid/base stimuli S8; Density functional theory (DFT) understand solution. geometries ground optimized obtain global minimum S9; Data conformer sampling GFN-FF level46Spicher Grimme Robust atomistic modeling materials, organometallic, biochemical systems.Angew. 15665-15673Crossref (98) (see Conformer followed DFT optimization allowed geometry stable state. computed TD(10 states)-PBE0/def2-SVP 1) TD(5 states)-?B97X-D/def2-SVP levels information), qualitatively comparable inspection transitions involved processes. extended (vide infra). cases examined, subject TD-DFT computational analysis populate excited partial charge-transfer state, where aniline nitrogen N1 N2 (and aryls) donate phenanthrene moiety part folded S9A), indicating higher mobility free flexible unfolded S9B). structural observation substantial difference before guest. (141.16°) (137.28°), feature one single crystals (Table 1; 2A). S0?S1 S0 geometry, following Franck-Condon excitation vertical S1?S0 transition S6).21Zhang Scholar,25Chen maxima comparable, experimental data. Analogously, peaks blue-shift respect (446?441 1), experimentally observed trend 2D).Table 1Experimental wavelengths acetonitrile (S0?S1 compounds), (S1?S0 relevant oscillator strengthsAbsorptionEmissionCompound?exp (nm)?calcbValues either ?B97X-D/def2-SVP using SMD(CH3CN) implicit solvent method. (nm)f?exp (nm)?em (%)?calc[b] (nm)fDPAC-ring3503630.12749019.64460.177DPAC-ring·1-HaThe solution 1-H, DPAC-ring·1-H.3473690.111477_4410.232[2]Catenane 6-H3473620.14044724.34340.226[2]Catenane 63623760.14846722.44370.214[2]Catenane 7-H3483740.15044721.24360.226[2]Catenane 73553590.1524456.94240.238a DPAC-ring·1-H.b Values