Radical Cyclic [3]Daisy Chains

•Supramolecular [c3]DCs form on account of radical and anion templations•Molecular with 18 positive charges are synthesized in near quantitative yields•The air stability is enhanced because aggregation•The undergo “co-conformational” switching upon a redox stimulus Mechanically interlocked molecules (MIMs), which controllable motions between their component parts more than one dimension, interest controlling nanoconfinement three-dimensional space. Cyclic [n]daisy chains ([cn]DCs) class garland-like rotaxanes composed self-complementary monomers cross-threaded architectures. They represent promising new range mechanically interlocked, multi-dimensional artificial molecular switches. Although [c2]DCs have been widely investigated as prototypes muscles, selectively efficiently producing high-order [cn]DCs n > 2 remains an alluring goal. In this paper, we present efficient strategy for the synthesis >90% yields by employing geometry restraints along templations. These display some attractive properties, including states well redox-switchable 2D coming-and-going expansions contractions. This research paves way development switchable cross-linked polymers frameworks future applications shape adjustable nets breathable membranes. (MIMs) that internal dimension rare entities world. [2]daisy ([c2]DCs) MIMs identified muscles. It remains, however, challenge to synthesize efficiently. Herein, report design anionic templates. Two were obtained yields. One [c3]DC displayed good its cationic form, while other underwent reversible open macrocyclic closed trisarm-shaped forms under electrochemical control. findings provide not only two-dimensional electronic but also starting point extended arrays, could become forerunners The stimuli-responsive molecules1Bruns C.J. Stoddart J.F. Nature Mechanical Bond: From Molecules Machines. Wiley, 2016Crossref Scopus (369) Google Scholar (MIMs)—such bistable rotaxanes2Tian H. Wang Q.C. Recent progress rotaxanes.Chem. 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Advances receptor chemistry.Chem. 6: 61-141Abstract (90) templation. preorganized conformation plus additional templation PF6− counterions, unprecedentedly formation [c3]DC12·18PF6 With structure self-aggregation, nonaradical nonacationic [c3]DC129(⋅+) shows dramatically stability. Moreover, macrocycle, [c3]DC1218+ solution, switched conveniently reversibly oxidized reduced stimulus. demonstrate potential [c3]DCn18+ act linking units uses nanotechnology. At outset, employed 2A ) radical-based recognition61Cai Vemuri Cui al.Tuning interactions trisradical tricationic complexes varying host-cavity sizes.Chem. 11: 107-112Crossref Scholar,62Cai Mao W.G. al.Highly stable organic bisradicals protected bonds.J. 7190-7197Crossref mCBPQT2(⋅+) BIPY⋅+ [c3]DC29(⋅+) [c3]DC129(⋅+). mCBPQT2(⋅+), binding BIPY⋅+, had smaller association constant (Ka 8.9 × 103 M‒1 MeCN) 3.9 104 para analog, CBPQT2(⋅+), it several advantages when approaching [c3]DCs. First all, m-xylylene linker functionalized 5-position easily retaining local C2v symmetry.63Low symmetric monomers—i.e., CBPQT4+ derivative substituted p-xylylene units—will result highly complicated NMR spectra [cn]DCs, will make difficult grow crystals obtain ordered crystal superstructures structures. Second, derivatives straightforward often satisfactory.50Coutrot Third, BIPY⋅+⊂mCBPQT2(⋅+) pairs positively polycations them candidates construction electrochemically Finally, both host (mCBPQT2(⋅+)) guest (BIPY⋅+) species—an important property comes preorganizing conformations monomers—and consequence, selectivity achieved during [c3]DCs.Figure 3ESI MS TWIM Spectra [c3]DC12·18PF6Show full caption(A) ESI (top) (bottom) [c3]DC2·18PF6. insets show comparison theoretical experimental isotope patterns 5+ peaks [c3]DC2·18PF6.(B) [c3]DC12·18PF6. [c3]DC12·18PF6.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Low (A) (B) Another crucial choice made favoring production bridge unit covalently links ring unit. described article, single methylene group was chosen 2A) linker, convenient synthetically introduces necessary rigidity. structural features corresponding monomer makes unwanted unfavorable. Instead, preferential favored occurs expected. alkyne tail, M2-CC·6PF6, straightforward. See Supplemental Sections B Starting (3,5-bis(bromomethyl)phenyl)methanol, M2-CC·6PF6 prepared five steps involving sequence SN2 substitutions overall ~30%. scaled up gram scale quite easily, tail altered will—for M2-N3·6PF6 M12-N3·6PF6 Scheme 1—so enable modification structure. visible/NIR (Vis/NIR) absorption spectroscopy reducing conditions. reduction colorless MeCN excess Zn dust followed filtration, giving deep-purple-colored solution. Vis/NIR spectrum 2B) exhibited intense NIR band centered 1,060 nm, observation characteristic61Cai complex formation. tells us assemblies—cyclic acyclic—must We recorded 0.10 mM state temperatures. temperature-dependent intensity decreased gradually heating 351 Meanwhile, absorbance peak 600 nm increased heating, clear isosbestic points observed 766 536 nm. observations indicate dissociated temperature, involved optically states—the daisy-chain assemblies monomers. order deeper insight process, performed thermodynamic analyses spectroscopic data M2-CC3(⋅+) MeCN. Section Based van 't Hoff analysis S27), apparent64For 1:1 Ka calculated applying ’t data. For linked, same data, apparent Kapp. enthalpy (ΔHa −13.8 ± 0.3 kcal·mol−1) entropy (ΔS −24.4 0.9 cal·mol−1·K−1) determined pair Hence, associated 298 K approximately 4.9 M−1, value significantly larger (8.9 M−1) host–guest complex, MV⋅+⊂mCBPQT2(⋅+). Accordingly, leading strongly cooperative65Hunter Anderson H.L. What cooperativity?.Angew. 48: 7488-7499Crossref (576) implying these very like