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1 Redox-Driven Switching in Pseudorotaxanes Ali Trabolsi, a Mohamad Hmadeh, b Niveen M. Khashab, a Douglas C. Friedman, a Matthew E. Belowich, a Nicolas Humbert, b Mourad Elhabiri, b Hussam A. Khatib, a Anne-Marie Albrecht-Gary* b and J. Fraser Stoddart* a a Department of Chemistry, Northwestern University, 45 Sheridan Road, Evanston, Il, 6008, USA. Fax : (+) , Tel : (+) stoddart@northwestern.edu b Laboratoire de Physico Chimie Bioinorganique, ULP-CNRS (UMR 777), Institut de Chimie, ECPM, 5 rue Becquerel, 6700 Strasbourg, France. Fax: (+33) , Tel: (+33) amalbre@chimie.u-strasbg.fr Revised Version Supplementary Information * To whom correspondence should be addressed S

2 Introduction In this Supplement, we describe the spectroscopic characterization of the inclusion complexes of the two threads 4Cl and Cl with cucurbit[8]uril (designated CB[8]). This extensive physicochemical study requires, first of all, the examination of model compounds namely, a monotopic dicationic system V Cl acting as a π-electron accepting unit and two π-electron donating counterparts N- or N-. Their host-guest complexes (V + CB[8], V + N- CB[8] and V + N- CB[8]) with CB[8] were characterized using spectroscopic techniques (absorption and emission) which are described herein. Figure S shows the absence of dilution effects on the charge transfer (CT) absorption bands of 4Cl and Cl, exemplifying the lack of intermolecular dimer formation in 4Cl or Cl and providing evidence for the self-folding processes for these compounds at 460 nm [.4Cl] (x 0-4 M) at 475 nm [.Cl] (x 0-4 M) λ (nm) λ (nm) (a) (b) Figure S. Absorption Spectrophotometric spectra of (a) 4Cl and (b) Cl showing the effect of dilution on the CT absorption bands. Solvent: H O, ph 7.0 (phosphate buffer 0. M), T = 5.0() C. (a) : [ 4Cl] = M; : [ 4Cl] = M. (b) : [ Cl] = M; : [ Cl] = M. Insets show that the CT absorptions obey the Beer-Lambert law. S

3 Figure S displays the spectral variation recorded on an equimolar mixture of V Cl and N-. It clearly shows the absence of a CT complex between V Cl and N- in the absence of CB[8] λ (nm) λ (nm) (a) (b) Figure S. Absorption Spectrophotometric spectra of equimolar mixtures of V Cl and N- at a variety of concentrations. Solvent: H O, ph 7.0 (phosphate buffer 0. M), T = 5.0() C, () M, () M, (3) M, (4) M, (5) M, (6) M, (7) M. a) full spectral window, b) zoom-in of the visible region. Spectroscopic Characterization of V + CB[8] Complex The Job plot presented in Figure S3 clearly confirms that a : complex is formed exclusively between V Cl and CB[8]. Figure S3: Job plot (ΔA/ΔA max at 300 nm) obtained upon mixing V Cl and CB[8]. Solvent: H O; T = 5.0(0.) C; ph = 7.0 (phosphate buffer 0. M); [V Cl] tot + [CB[8]] tot = M; l = 0.5 cm. Figure S4 shows the electronic spectra of V Cl S3

4 and of its host-guest complex with CB[8]. The corresponding absorption spectrophotometric titration is given in Figure in the manuscript. Inclusion of the dicationic viologen derivative within the macrocycle cavity results in a significant hypochromic shift of the main V Cl absorption band centered at 63 nm. A weak bathochromic shift of these π-π* electronic transitions is also observed. Figure S4: Absorption electronic spectra of V Cl and the V + CB[8] complex. Solvent: H O; ph = 7.00 (phosphate buffer 0. M); T = 5.0() C. S4

5 Absorption Spectrophotometric Titration of V Cl and N- by CB[8]. Figure S5 portrays the spectrophotometric titration of an equimolar mixture of N- and V Cl by CB[8]. Figure S5: A UV-Visible absorption spectrophotometric titration of an equimolar mixture of N- and V Cl with CB[8]. Solvent: H O; ph = 7.0 (phosphate buffer 0. M); T = 5.0() C; [V Cl] tot = M; [N-] = M () [CB[8]] tot = 0; () [CB[8]] tot = M; l = cm. Spectroscopic Characterization of V + N- CB[8] Ternary Complex Figure S6 presents the electronic spectra of V Cl, N- and of the V + N- CB[8] ternary hostguest complex with CB[8]. The V + N- CB[8] ternary complex is characterized by the formation of a broad and weak CT absorption band at about 445 nm along with a significant hypochromic shift of the V Cl-centred absorption band with respect to the sum of V Cl and N- electronic spectra. A weak bathochromic shift of the V + π-π* transitions with respect to those of V Cl and V + CB[8] is also observed. Figure S6: Absorption electronic spectra of V Cl and N- and of V + CB[8] and V + N- CB[8] complexes. Solvent: H O; ph = 7.0 (phosphate buffer 0. M); T = 5.0() C. Absorption Spectrophotometric Titration S5

6 of V Cl and N- by CB[8] Figure S7 illustrates the spectrophotometric titration of an equimolar mixture of N- and V Cl by CB[8]. Figure S7: UV-Visible absorption spectrophotometric titration of an equimolar mixture of N- and V Cl with CB[8]. Solvent: H O; ph = 7.0 (phosphate buffer 0. M); T = 5.0() C; [V Cl] tot = M; [N-] tot = M; () [CB[8]] tot = 0; () [CB[8]] tot = M; l = cm. Spectroscopic Characterization of V + N- CB[8] Ternary Complex Figure S8 illustrates the electronic spectra of the V Cl and N- systems and of the V + N- CB[8] ternary host-guest complex. The ternary complex is characterized by the formation of a broad and a weak CT absorption band at about 570 nm along with significant hypochromic and bathochromic shifts of the V Cl-centred absorption band. Figure S8: Absorption electronic spectra of V Cl and N- and of V + CB[8] and V + N- CB[8] complexes. Solvent: H O; ph = 7.0 (phosphate buffer 0. M) T = 5.0() C. S6

7 Emission Spectrophotometric Titration of V Cl and N- by CB[8] Figure S9 describes the spectrofluorimetric titration of an equimolar mixture of N- and V Cl by CB[8]. These excited state data have been analyzed according to Stern-Volmer approach (see figure in the inset). Figure S9: Spectrofluorimetric titration of an equimolar mixture of N- and V Cl with CB[8]. Solvent: water; ph = 7.00 (phosphate buffer 0. M); T = 5.0() C; [V Cl] tot = [N-] = M; () [CB[8]] tot = 0; () [CB[8]] tot = M; λ exc = 35 nm; l = cm; emission and excitation slit widths = 5 nm. Inset: Stern- Volmer analysis (F 0 /F = + K V +.N- CB[8] [CB[8]]) at λ = 340 nm. Absorption Spectrophotometric Titration of 4Cl by CB[8] Figure S0 describes the spectrophotometric titration of the thread 4Cl with CB[8]. Statistical processing of these data allowed us to calculate the electronic spectra of 4+ CB[8] and 4+ (CB[8]). They are available in Figure 7b. Figure S0: UV-Visible absorption spectrophotometric titration of 4Cl with CB[8]. Solvent: H O; ph = 7.0 (phosphate buffer 0. M); T = 5.0() C; [ 4Cl] tot = M; () [CB[8]] tot / [ 4Cl] tot = 0; () [CB[8]] tot / [ 4Cl] tot = 8.6; l = cm. Absorption Spectrophotometric Titration S7

8 of Cl by CB[8] Figure S describes the spectrophotometric titration of thread Cl by CB[8]. Statistical processing of these data allowed us to calculate the electronic spectrum of + CB[8], which is available in Figure 7a λ(nm) λ(nm) Figure S: UV-Vis absorption spectrophotometric titration of Cl with CB[8]. Solvent: H O; ph = 7.0 (phosphate buffer 0. M); T = 5.0() C; [ Cl] tot = M; () [CB[8]] tot / [ Cl] tot = 0; () [CB[8]] tot / [ Cl] tot = 6.7; l = cm. Switching Properties of the []Pseudorotaxanes A cyclic voltammogram of + CB[8] recorded at 50 mv s shows further evidence of a peak at.0 V characteristic of the dimerization of viologen units in the cavity of CB[8]. Figure S: Cyclic voltammograms of 3 Cl (mm) with a scan rate = 50 mv.s in H O, ph = 7.0 (phosphate buffer 0. M). S8

9 NMR Spectroscopic Investigations Complexes 4+ CB[8] and + CB[8] were also examined by H NMR spectroscopy (Figures S3 and S4). Assignments of the peaks in the NMR spectrum for their respective compounds, 4Cl and Cl, were aided by D NMR techniques. The D H NMR spectra supports the formation of : complexation for 4Cl and Cl with CB[8]. Examining the resonances for compound 4Cl confirms the C symmetry around the central naphthalene unit. Upon addition of CB[8] the C axis is nullified and provides for structurally different viologen units as well as a doubling of the naphthalene resonances in the formation of 4+ CB[8]. Additionally, the naphthalene resonances are all shifted upfield ~0.6 ppm, consistent with naphthalene as a guest for CB[8]. Splitting of the four viologen units indicates, not only two structurally different viologens, but also an additional loss of symmetry for the encircled viologens (Figure S3). Upon addition of extra equivalents of CB[8], significant broadening of the viologen signals is observed; a phenomenon which supports the UV/Vis spectroscopic data, indicating an additional binding site (albeit much weaker) for CB[8]. Similar information is gleaned from the NMR spectrum of + CB[8] (Figure S4). Again, the C axis of the thread ( Cl) is destroyed upon addition of CB[8]. In response to this loss of symmetry, the single (formerly symmetric) viologen unit is split into four broad singlets and the naphthalene units split into encircled and unencircled resonances. Encircled naphthalene manifests an upfield shift of ~ ppm. Figure S3: H NMR Spectrum of 4+ CB[8] in D O at 75K Figure S4: H NMR Spectrum of + CB[8] in D O at 80K S9