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DOI: 10.1055/s-0030-1258578
Colorimetric Fluoride Sensor Based on a Bisthiourea Functionalized Molecular Clip
Publication History
Publication Date:
23 September 2010 (online)
Abstract
A new class of bisthiourea-functionalized molecular clips were designed and synthesized for anion recognition. Clip 1 showed excellent affinity to the biologically relevant fluoride ion in a 1:1 ratio as shown by UV-vis, ¹H and ¹9F NMR studies. Moreover, the binding was accompanied with visually noticeable color changes, enabling the compound to act as a colorimetric fluoride sensor.
Key words
glycoluril - molecular clip - fluoride - sensor - thiourea
Recognizing and sensing of biologically important anion ions via artificial receptors has recently grown into an area of great interest in supramolecular and biological chemistry. [¹] Due to large variation in size, shape, charge distribution, and strong solvation, highly selective recognition for anions is a challenging task. Among various important anionic analytes, the recognition of fluoride ions as biologically and environmentally important anions is attracting a great deal of interest because of its medical applications such as dental heath and possible toxicity. [²] Recently, considerable efforts have been devoted to fluoride ion sensing via UV-vis, fluorescence, or other methods. [³-8] For example, Sessler and co-workers had succeed in developing a series of functionalized calix[4]pyrrole derivatives, and dipyrrolyquinoxalines as new fluorescent chemosensors for fluoride anions. [4] Moreover, bis(thio)urea derivatives, [5] organoboron compounds, [6] amide macrocycles, [7] and other compounds [8] were also applied to the field of recognizing and sensing fluoride ions.
As the essential component of Nolte’s molecular clips, [9] Rebek’s capsules, [¹0] and the cucurbit[n]uril family of macrocycles [¹¹] , glycoluril has become a popular building block for the preparation of new host system. [¹²] Previously, we have developed a series of fluorescent molecular clips based on glycoluril skeleton for sensing metal ions [¹³] and phenols. [¹4] As a part of our contribution to molecular recognition, we have decided to investigate the use of glycoluril molecular clips for sensing anions. It is well known that hydrogen bonding is widely used as the anion-receptor interactions. Typically, molecules employing different combination of amide, thiourea, and pyrrole units can offer one or more H-bonded donor sites for effective binding and sensing of some anions. [¹5] As a result, five molecular clips 1-5 were designed and synthesized by the reaction of the corresponding diamino molecular clip with isothiocyanate or isocyanate (Scheme [¹] ). Because of the special precaved structure of glycoluril molecular clip as a space linker, as well as two cis-thiourea groups as potential H-bonded binding sites to anions, we envisioned that these molecular clips might present suitable binding clefts and sites to capture corresponding anions.
Scheme 1 Reagents and conditions: (i) AcOH, Br2, H2O; (ii) EtOH, HCl (g), 0 ˚C; (iii) PhH, H2NCONH2, TFA, reflux; (iv) 1,2-bis(bromomethyl)-3,6-dibromobenzene, KOt-Bu, DMSO; (v) H2, Pd/C, DMF, r.t.; (vi) isothiocyanate or isocyanate, CH2Cl2, r.t.
Initially, UV-vis experiments were carried out in MeCN-DMSO (9:1, v/v) solution. [¹6] The absorbance spectrum of compounds 1 and 5 showed peaks at 345 nm and 346 nm, respectively. However, compounds 2-4 with anions did not exhibit any significant absorbance peak. [¹7] A solution of receptor 1 was treated with the representative anions such as tetrabutylammonium (TBA) fluoride, chloride, bromide, iodide, hydrogen sulfate, perchlorate, hexafluorophosphate, acetate, and dihydrogen phosphate. Figure [¹] shows the absorption spectra of receptor 1 in the presence of the various anions. The absorption peak at 345 nm was shifted to 398 nm (Δλmax = 53 nm) when fluoride was added. Significant bathochromic shift of the absorption maximum in the presence of fluoride ion was presumably due to the charge-transfer interaction between the electron-rich thiourea-bound fluoride ion and the electron-deficient p-nitrophenyl moiety. For the externally added Cl-, Br-, I-, HSO4 -, ClO4 -, and PF6 - salts, the UV spectra remained almost unchanged, though a little variation was observed with the AcO- and H2PO4 - salts. These suggested no binding or very weak binding of Cl-/Br-/I-/HSO4 -/ClO4 -/PF6 - and AcO-/H2PO4 - ions to the receptor 1, respectively. For receptor 2, only F-, AcO-, and H2PO4 - ions produced a little change of the absorbance spectra. [¹7]
Figure 1 Absorption spectra of receptor 1 (9.1 µM) upon addition of a particular TBA salt (30 equiv) in MeCN-DMSO (9:1, v/v)
Figure 2 Spectral changes in a UV-vis titration experiment for receptor 1 (10 µM) in MECN-DMSO (9:1, v/v) in the presence of 0.1 to 50.0 equiv of TBAF predissolved in MeCN
To investigate the binding abilities of receptor 1 to fluoride ion, titration studies were performed (Figure [²] ). The binding constant of 1 with fluoride was determined from the titration data to be approximately 5.48 (±0.40)¥104 M-¹. [¹7] The Job plot for receptor 1 at 293 K with fluoride ions as a guest in a MeCN-DMSO (9:1, v/v) solution showed a maximum at a mole fraction of 0.5, which indicated that the host binds to the anionic guest in a 1:1 ratio. [¹8] This also suggested that two cis-thiourea groups act as cooperative binding sites.
As shown in Figure [³] , color changes could be observed easily by mixing the receptor 1 and anions, respectively. Various anions (F-, Cl-, Br-, I-, HSO4 -, ClO4 -, PF6 -, AcO-, and H2PO4 -) were added into 1 in DMSO. Specifically, it was noticeable that a pale yellow receptor solution became dark red when fluoride ions were added to receptor 1. The reason of the color change in the receptor solvent could be ascribed to the charge-transfer interactions between the electron-rich fluoride ions and the electron-deficient p-nitrophenyl moiety, which caused the elongated conjugation of the p-nitrophenyl moieties, resulting in a visible color change. [5d] [i]
Figure 3 Color changes of receptors 1 (1.0˙10-³ M) in DMSO with the addition of TBA anions (4.0˙10-³ M); A = free receptor, B = F-, C = Cl-, D = Br-, E = I-, F = HSO4 -, G = ClO4 -, H = PF6 -, I = AcO-, J = H2PO4 -
To support the result obtained from UV-vis studies for receptor 1, we performed ¹H NMR titration with TBAF. Due to insufficient solubility of 1, NMR studies were performed in DMSO-d 6. However, we could not conduct the ¹H NMR titration of 1 with fluoride ion due to the complete disappearance of the signals of the thiourea-NH upon addition of fluoride ion. As shown in Figure [4] , the signals of N-H protons that resonate at δ = 10.71 and 9.58 ppm broadened gradually, and completely disappeared after adding 1.0 equivalent of fluoride ion. Similar observations were reported before and were attributed to the strong hydrogen bonding with the fluoride ion. [5d] [h] The disappearance of all N-H proton signals also led us to speculate that the proton donor sites make a convergent array of hydrogen bonding for binding fluoride ion by means of a model of (N-H)4˙˙˙F-. Meanwhile, the overlap of two C-H proton signals (Ha and Hb) of aromatic ring suggested the elongated conjugation of the p-nitrophenyl moieties.
Figure 4 Partial ¹H NMR (600 MHz) spectra of 1 (40 mM in DMSO-d 6 at 293 K) upon successive addition of 0-1.0 equiv of [(n-Bu)4N]F
Figure 5 ¹9F NMR (376 MHz) spectrum of 1 (20 mM in DMSO-d 6 at 293 K) upon successive addition of 1.0-10.0 equiv of (n-Bu)4N+F- in DMSO-d 6
Due to the application of ¹9F NMR as a very effective probe for examining the interaction of the highly electronegative F- with hosts in solution, [4e-4j] [7c] the ion-binding properties of receptor 1 were probed by ¹9F NMR spectroscopy by addition of 1.0-10.0 equivalents of TBAF in DMSO-d 6 (Figure [5] ). When one equivalent of fluoride ion was added to 1, the fluoride signal shifted from δ = -107.7 to -152.4 ppm indicating that the fluoride ion was encapsulated by four N-H hydrogen bonds, which would shield the fluoride and cause an upfield shift of the signal. Further addition of fluoride in excess (5.0 equiv) shifted the fluoride signal to δ = -144.3 ppm which could be assigned to the formation of hydrogen-bonded fluoride (HF) species [8g] and the signal of free fluoride appeared firstly. We speculated that four H atoms of thiourea groups bound with fluoride ions after adding four equivalents of TBAF, without more H atoms for bonding with more fluoride ions. In addition, the septet of double peak (J HF = 106.0 Hz) would be the result of bonding between H and F. We also noted that the signal was at the highest upfield region when only 1.0 equivalent of TBAF was added, which provide further confirmation that F- is the best bonding as 1:1 inclusion complex in solution.
Based on the above-described UV-vis, ¹H and ¹9F NMR studies, we proposed that the process of recognition as follow: when the receptor binds to 1.0 equivalent of fluoride ions, four hydrogen bonds are constructed with F- to form stable complexes. The RHF/6-31G*-optimized geometry of 1˙F- complex showed the possibility. [¹7] Then, addition of fluoride ions beyond one equivalent causes the deprotonation of four NH of thiourea and forms hydrogen-bonded fluoride (HF) species (Figure [6] ). The deprotonated clip 1 could be stablilized by the delocalization of negative charge on the nitrogen atoms of the thiourea over the nitrophenyl moieties. Interestingly, addition of a few drops of water triggered the disappearance of the dark red color of the 1-fluoride complex, which suggested the whole procession of recognition and deprotonation was reversible in nature. [8g] [¹7]
Figure 6 A proposed binding mode and deprotonation of 1 with fluoride ions
In conclusion, we have synthesized five new molecular clips 1-5 with two thiourea groups, of which 1 exhibits an excellent affinity to fluoride ions. When 1 was treated with fluoride ion, a distinct color change was observed by extending the conjugated system, which is caused by the formation of a fluoride-receptor complex. The skeleton of glycoluril molecular clip acts as an effective template with an appropriate distance of separation between the thiourea groups for selective binding of fluoride ion. Studies aimed at investigating the mechanism, scope of the recognition, the synthesis, and application of the chemosensor based on glycoluril molecular clips are under way and will be reported in due course.
Supporting Information for this article is available online at http://www.thieme-connect.com.accesdistant.sorbonne-universite.fr/ejournals/toc/synlett.
- Supporting Information for this article is available online:
- Supporting Information
Acknowledgment
We thank the National Natural Science Foundation of China (Grant No. 20872042 and 21032001) for funding and the research was supported in part by the PCSIRT (No. IRT0953). We also gratefully thank Prof. L. Isaacs for helpful discussions and Prof. Y. J. Pan for HRMS.
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Bianchi A.Bowman-James K.Garcia España E. Supramolecular Chemistry of Anions Wiley-VCH; New York: 1997. - 1b
Gale PA. Coord. Chem. Res. 2003, 240: 191 - 1c
Beer PD.Gale PA. Angew. Chem. Int. Ed. 2001, 40: 486 - 1d
Sessler JL.Gale PA.Cho W.-S. Anion Receptor Chemistry RSC Publishing; Cambridge / UK: 2006. - 1e
Schmidtchen FP.Berger M. Chem. Rev. 1997, 97: 1609 - 1f
Caltagitone C.Gale PA. Chem. Soc. Rev. 2009, 38: 520 - 1g
Gale PA.Garcia-Garrido SE.Garric J. Chem. Soc. Rev. 2008, 37: 151 - 2a
Krik KL. Biochemistry of Halogens and Inorganic Halides Plenum Press; New York: 1991. 591: - 2b
Kleerekoper M. Endocrinol. Metab. Clin. North Am. 1998, 27: 441 - 3
Cametti M.Rissanen K. Chem. Commun. 2009, 2809 - 4a
Miyaji H.Sato W.Sessler JL. Angew. Chem. Int. Ed. 2000, 39: 1777 - 4b
Miyaji H.Anzenbacher P.Sessler JL.Bleasdale ER.Gale PA. Chem. Commun. 1999, 1723 - 4c
Anzenbacher P.Jursíková K.Sessler JL.
J. Am. Chem. Soc. 2000, 122: 9350 - 4d
Anzenbacher P.Try AC.Miyaji H.Jursíková K.Lynch VM.Marquez M.Sessler JL. J. Am. Chem. Soc. 2000, 122: 10268 - 4e
Woods CJ.Camiolo S.Light ME.Coles SJ.Hursthouse MB.King MA.Gale PA.Essex JW. J. Am. Chem. Soc. 2002, 124: 8644 - 4f
Camiolo S.Gale PA. Chem. Commun. 2000, 1129 - 4g
Gale PA.Sessler JL.Král V. Chem. Commun. 1998, 1 - 4h
Black CB.Andrioletti B.Try AC.Ruiperez C.Sessler JL. J. Am. Chem. Soc. 1999, 121: 10438 - 4i
Scherer M.Sessler JL.Gebauer A.Lynch V. Chem. Commun. 1998, 85 - 4j
Gale PA.Twyman LJ.Handlin CI.Sessler JL. Chem. Commun. 1999, 1851 - For selected examples, see:
- 5a
Kim SK.Yoon J. Chem. Commun. 2002, 770 - 5b
Xu G.Tarr MA. Chem. Commun. 2004, 1050 - 5c
Cho EJ.Moon JW.Ko SW.Lee JY.Kim SK.Yoon J.Nam KC. J. Am. Chem. Soc. 2003, 125: 12376 - 5d
Lee JY.Cho EJ.Mukamel S.Nam KC. J. Org. Chem. 2004, 69: 943 - 5e
Jiménez D.Martínez-Máñez R.Sancenón F.Soto J. Tetrahedron Lett. 2002, 43: 2823 - 5f
Thangadurai TD.Singh NJ.Hwang I.-C.Lee JW.Chandran RP.Kim KS. J. Org. Chem. 2007, 72: 5461 - 5g
Kwon Y.Jang YJ.Kim SK.Lee K.-H.Kim JS.Yoon J. J. Org. Chem. 2004, 69: 5155 - 5h
Jose DA.Kumar DK.Ganguly B.Das A. Org. Lett. 2004, 6: 3445 - 5i
Cho EJ.Ryu BJ.Lee YJ.Nam KC. Org. Lett. 2005, 7: 2607 - 5j
Boiocchi M.Boca LD.Gómez DE.Fabbrizzi L.Licchelli M.Monzan E. J. Am. Chem. Soc. 2004, 126: 16507 - 6a
Solé S.Gabbaï FP. Chem. Commun. 2004, 1284 - 6b
Nicolas M.Fabre B.Simonet J. Chem. Commun. 1999, 1881 - 6c
Cooper CR.Spencer N.James TD. Chem. Commun. 1998, 1365 - 6d
Yamamoto H.Ori A.Ueda K.Dusemund C.Shinkai S. Chem. Commun. 1996, 407 - 6e
Dusemund C.Sandanayake KRAS.Shinkai S. J. Chem. Soc., Chem. Commun. 1995, 333 - 6f
Hudnall TW.Gabbaï FP. Chem. Commun. 2008, 4596 - 6g
Agou T.Sekine M.Kobayashi J.Kawashima T. Chem. Commun. 2009, 1894 - 6h
Bozdemir OA.Sozmen FS.Buyukcakir O.Guliyev R.Cakmak Y.Akkaya EU. Org. Lett. 2010, 12: 1400 - 6i
Liu XY.Bai DR.Wang S. Angew. Chem. Int. Ed. 2006, 45: 5475 - 6j
Hudnall TW.Gabbaï FP. J. Am. Chem. Soc. 2007, 129: 11978 - 6k
Melaimi M.Gabbaï FP. J. Am. Chem. Soc. 2005, 127: 9680 - 6l
Xu Z.Kim SK.Han SJ.Lee C.Kociok-Kohn G.James TD.Yoon J. Eur. J. Org. Chem. 2009, 3058 - 7a
Piatek P.Jurczak J. Chem. Commun. 2002, 2450 - 7b
Korendovych IV.Cho M.Makhlynets OV.Butler PL.Staples RJ.Rybak-Akimova EV. J. Org. Chem. 2008, 73: 4771 - 7c
Kang SO.Day VW.Bowman-James K. J. Org. Chem. 2010, 75: 277 - 8a
Miyaji H.Sessler JL. Angew. Chem. Int. Ed. 2001, 40: 154 - 8b
Bhosale SV.Bhosale SV.Kalyankar MB.Langford SJ. Org. Lett. 2009, 11: 5418 - 8c
Mizuno T.Wei W.-H.Eller LR.Sessler JL. J. Am. Chem. Soc. 2002, 124: 1134 - 8d
Sun Y.Wang S. Inorg. Chem. 2009, 48: 3755 - 8e
Dydio P.Zieliński T.Jurczak J. J. Org. Chem. 2009, 74: 1525 - 8f
Lin Y.-C.Chen C.-T. Org. Lett. 2009, 11: 4858 - 8g
Chawla HM.Shrivastava R.Sahu SN. New J. Chem. 2008, 32: 1999 - 8h
Kim HJ.Kim SK.Lee JY.Kim JS. J. Org. Chem. 2006, 71: 6611 - 8i
Zhao P.Jiang J.Leng B.Tian H. Macromol. Rapid Commun. 2009, 30: 1715 - 8j
Peng X.Wu Y.Fan J.Tian M.Han K. J. Org. Chem. 2005, 70: 10524 - 8k
Bates GW.Gale PA.Light ME. Chem. Commun. 2007, 2121 - 8l
Wang Q.Xie Y.Ding Y.Li X.Zhu W. Chem. Commun. 2010, 46: 3669 - 9
Rowan AE.Elemans JAAW.Nolte RJM. Acc. Chem. Res. 1999, 32: 995 - 10
Rebek J. Angew. Chem. Int. Ed. 2005, 44: 2068 - 11a
Lagona J.Mukhopadhyay P.Chakrabarti S.Isaacs L. Angew. Chem. Int. Ed. 2005, 44: 4844 - 11b
Lee JW.Samal S.Selvapalam N.Kim H.-J.Kim K. Acc. Chem. Res. 2003, 36: 621 - 12a
Chiang PT.Cheng PN.Lin CF.Liu YH.Lai CC.Peng SM.Chiu SH. Chem. Eur. J. 2006, 12: 865 - 12b
Chiang PT.Chen NC.Lai CC.Chiu SH. Chem. Eur. J. 2008, 14: 6546 - 12c
Kang J.Jo J.In S. Tetrahedron Lett. 2004, 45: 5225 - 12d
In S.Kang J. Tetrahedron Lett. 2005, 46: 7165 - 13
Hu SL.She NF.Yin GD.Guo HZ.Wu AX.Yang CL. Tetrahedron Lett. 2007, 48: 1591 - 14
She NF.Gao M.Cao LP.Wu AX.Isaacs L. Org. Lett. 2009, 11: 2603 - For recent reviews, see:
- 15a
Galf PA. Amide- and Urea-Based Anion Receptors, In Encyclopedia of Supramolecular Chemistry Marcel Dekker; New York: 2004. p.31-41 - 15b
Amendola V.Esteban-Gómez D.Fabbrizzi L.Licchelli M. Acc. Chem. Res. 2006, 39: 343 - 15c
Galf PA. Acc. Chem. Res. 2006, 39: 465 - 15d
Li X.Wu Y.-D.Yang D. Acc. Chem. Res. 2008, 41: 1428 - 16 Due to the dimerization of molecular
clips, we perform these experiments in MeCN-DMSO solvent
system. The stabilities of hydrogen-bonded aggregates destroyed
by DMSO, see:
Mammen M.Simanek EE.Whitesides GM. J. Am. Chem. Soc. 1996, 118: 12614 - 18
Job P. Ann. Chim. 1928, 9: 113
References and Notes
See Supporting Information.
- For recent books and reviews for anion receptors, see:
- 1a
Bianchi A.Bowman-James K.Garcia España E. Supramolecular Chemistry of Anions Wiley-VCH; New York: 1997. - 1b
Gale PA. Coord. Chem. Res. 2003, 240: 191 - 1c
Beer PD.Gale PA. Angew. Chem. Int. Ed. 2001, 40: 486 - 1d
Sessler JL.Gale PA.Cho W.-S. Anion Receptor Chemistry RSC Publishing; Cambridge / UK: 2006. - 1e
Schmidtchen FP.Berger M. Chem. Rev. 1997, 97: 1609 - 1f
Caltagitone C.Gale PA. Chem. Soc. Rev. 2009, 38: 520 - 1g
Gale PA.Garcia-Garrido SE.Garric J. Chem. Soc. Rev. 2008, 37: 151 - 2a
Krik KL. Biochemistry of Halogens and Inorganic Halides Plenum Press; New York: 1991. 591: - 2b
Kleerekoper M. Endocrinol. Metab. Clin. North Am. 1998, 27: 441 - 3
Cametti M.Rissanen K. Chem. Commun. 2009, 2809 - 4a
Miyaji H.Sato W.Sessler JL. Angew. Chem. Int. Ed. 2000, 39: 1777 - 4b
Miyaji H.Anzenbacher P.Sessler JL.Bleasdale ER.Gale PA. Chem. Commun. 1999, 1723 - 4c
Anzenbacher P.Jursíková K.Sessler JL.
J. Am. Chem. Soc. 2000, 122: 9350 - 4d
Anzenbacher P.Try AC.Miyaji H.Jursíková K.Lynch VM.Marquez M.Sessler JL. J. Am. Chem. Soc. 2000, 122: 10268 - 4e
Woods CJ.Camiolo S.Light ME.Coles SJ.Hursthouse MB.King MA.Gale PA.Essex JW. J. Am. Chem. Soc. 2002, 124: 8644 - 4f
Camiolo S.Gale PA. Chem. Commun. 2000, 1129 - 4g
Gale PA.Sessler JL.Král V. Chem. Commun. 1998, 1 - 4h
Black CB.Andrioletti B.Try AC.Ruiperez C.Sessler JL. J. Am. Chem. Soc. 1999, 121: 10438 - 4i
Scherer M.Sessler JL.Gebauer A.Lynch V. Chem. Commun. 1998, 85 - 4j
Gale PA.Twyman LJ.Handlin CI.Sessler JL. Chem. Commun. 1999, 1851 - For selected examples, see:
- 5a
Kim SK.Yoon J. Chem. Commun. 2002, 770 - 5b
Xu G.Tarr MA. Chem. Commun. 2004, 1050 - 5c
Cho EJ.Moon JW.Ko SW.Lee JY.Kim SK.Yoon J.Nam KC. J. Am. Chem. Soc. 2003, 125: 12376 - 5d
Lee JY.Cho EJ.Mukamel S.Nam KC. J. Org. Chem. 2004, 69: 943 - 5e
Jiménez D.Martínez-Máñez R.Sancenón F.Soto J. Tetrahedron Lett. 2002, 43: 2823 - 5f
Thangadurai TD.Singh NJ.Hwang I.-C.Lee JW.Chandran RP.Kim KS. J. Org. Chem. 2007, 72: 5461 - 5g
Kwon Y.Jang YJ.Kim SK.Lee K.-H.Kim JS.Yoon J. J. Org. Chem. 2004, 69: 5155 - 5h
Jose DA.Kumar DK.Ganguly B.Das A. Org. Lett. 2004, 6: 3445 - 5i
Cho EJ.Ryu BJ.Lee YJ.Nam KC. Org. Lett. 2005, 7: 2607 - 5j
Boiocchi M.Boca LD.Gómez DE.Fabbrizzi L.Licchelli M.Monzan E. J. Am. Chem. Soc. 2004, 126: 16507 - 6a
Solé S.Gabbaï FP. Chem. Commun. 2004, 1284 - 6b
Nicolas M.Fabre B.Simonet J. Chem. Commun. 1999, 1881 - 6c
Cooper CR.Spencer N.James TD. Chem. Commun. 1998, 1365 - 6d
Yamamoto H.Ori A.Ueda K.Dusemund C.Shinkai S. Chem. Commun. 1996, 407 - 6e
Dusemund C.Sandanayake KRAS.Shinkai S. J. Chem. Soc., Chem. Commun. 1995, 333 - 6f
Hudnall TW.Gabbaï FP. Chem. Commun. 2008, 4596 - 6g
Agou T.Sekine M.Kobayashi J.Kawashima T. Chem. Commun. 2009, 1894 - 6h
Bozdemir OA.Sozmen FS.Buyukcakir O.Guliyev R.Cakmak Y.Akkaya EU. Org. Lett. 2010, 12: 1400 - 6i
Liu XY.Bai DR.Wang S. Angew. Chem. Int. Ed. 2006, 45: 5475 - 6j
Hudnall TW.Gabbaï FP. J. Am. Chem. Soc. 2007, 129: 11978 - 6k
Melaimi M.Gabbaï FP. J. Am. Chem. Soc. 2005, 127: 9680 - 6l
Xu Z.Kim SK.Han SJ.Lee C.Kociok-Kohn G.James TD.Yoon J. Eur. J. Org. Chem. 2009, 3058 - 7a
Piatek P.Jurczak J. Chem. Commun. 2002, 2450 - 7b
Korendovych IV.Cho M.Makhlynets OV.Butler PL.Staples RJ.Rybak-Akimova EV. J. Org. Chem. 2008, 73: 4771 - 7c
Kang SO.Day VW.Bowman-James K. J. Org. Chem. 2010, 75: 277 - 8a
Miyaji H.Sessler JL. Angew. Chem. Int. Ed. 2001, 40: 154 - 8b
Bhosale SV.Bhosale SV.Kalyankar MB.Langford SJ. Org. Lett. 2009, 11: 5418 - 8c
Mizuno T.Wei W.-H.Eller LR.Sessler JL. J. Am. Chem. Soc. 2002, 124: 1134 - 8d
Sun Y.Wang S. Inorg. Chem. 2009, 48: 3755 - 8e
Dydio P.Zieliński T.Jurczak J. J. Org. Chem. 2009, 74: 1525 - 8f
Lin Y.-C.Chen C.-T. Org. Lett. 2009, 11: 4858 - 8g
Chawla HM.Shrivastava R.Sahu SN. New J. Chem. 2008, 32: 1999 - 8h
Kim HJ.Kim SK.Lee JY.Kim JS. J. Org. Chem. 2006, 71: 6611 - 8i
Zhao P.Jiang J.Leng B.Tian H. Macromol. Rapid Commun. 2009, 30: 1715 - 8j
Peng X.Wu Y.Fan J.Tian M.Han K. J. Org. Chem. 2005, 70: 10524 - 8k
Bates GW.Gale PA.Light ME. Chem. Commun. 2007, 2121 - 8l
Wang Q.Xie Y.Ding Y.Li X.Zhu W. Chem. Commun. 2010, 46: 3669 - 9
Rowan AE.Elemans JAAW.Nolte RJM. Acc. Chem. Res. 1999, 32: 995 - 10
Rebek J. Angew. Chem. Int. Ed. 2005, 44: 2068 - 11a
Lagona J.Mukhopadhyay P.Chakrabarti S.Isaacs L. Angew. Chem. Int. Ed. 2005, 44: 4844 - 11b
Lee JW.Samal S.Selvapalam N.Kim H.-J.Kim K. Acc. Chem. Res. 2003, 36: 621 - 12a
Chiang PT.Cheng PN.Lin CF.Liu YH.Lai CC.Peng SM.Chiu SH. Chem. Eur. J. 2006, 12: 865 - 12b
Chiang PT.Chen NC.Lai CC.Chiu SH. Chem. Eur. J. 2008, 14: 6546 - 12c
Kang J.Jo J.In S. Tetrahedron Lett. 2004, 45: 5225 - 12d
In S.Kang J. Tetrahedron Lett. 2005, 46: 7165 - 13
Hu SL.She NF.Yin GD.Guo HZ.Wu AX.Yang CL. Tetrahedron Lett. 2007, 48: 1591 - 14
She NF.Gao M.Cao LP.Wu AX.Isaacs L. Org. Lett. 2009, 11: 2603 - For recent reviews, see:
- 15a
Galf PA. Amide- and Urea-Based Anion Receptors, In Encyclopedia of Supramolecular Chemistry Marcel Dekker; New York: 2004. p.31-41 - 15b
Amendola V.Esteban-Gómez D.Fabbrizzi L.Licchelli M. Acc. Chem. Res. 2006, 39: 343 - 15c
Galf PA. Acc. Chem. Res. 2006, 39: 465 - 15d
Li X.Wu Y.-D.Yang D. Acc. Chem. Res. 2008, 41: 1428 - 16 Due to the dimerization of molecular
clips, we perform these experiments in MeCN-DMSO solvent
system. The stabilities of hydrogen-bonded aggregates destroyed
by DMSO, see:
Mammen M.Simanek EE.Whitesides GM. J. Am. Chem. Soc. 1996, 118: 12614 - 18
Job P. Ann. Chim. 1928, 9: 113
References and Notes
See Supporting Information.
Scheme 1 Reagents and conditions: (i) AcOH, Br2, H2O; (ii) EtOH, HCl (g), 0 ˚C; (iii) PhH, H2NCONH2, TFA, reflux; (iv) 1,2-bis(bromomethyl)-3,6-dibromobenzene, KOt-Bu, DMSO; (v) H2, Pd/C, DMF, r.t.; (vi) isothiocyanate or isocyanate, CH2Cl2, r.t.
Figure 1 Absorption spectra of receptor 1 (9.1 µM) upon addition of a particular TBA salt (30 equiv) in MeCN-DMSO (9:1, v/v)
Figure 2 Spectral changes in a UV-vis titration experiment for receptor 1 (10 µM) in MECN-DMSO (9:1, v/v) in the presence of 0.1 to 50.0 equiv of TBAF predissolved in MeCN
Figure 3 Color changes of receptors 1 (1.0˙10-³ M) in DMSO with the addition of TBA anions (4.0˙10-³ M); A = free receptor, B = F-, C = Cl-, D = Br-, E = I-, F = HSO4 -, G = ClO4 -, H = PF6 -, I = AcO-, J = H2PO4 -
Figure 4 Partial ¹H NMR (600 MHz) spectra of 1 (40 mM in DMSO-d 6 at 293 K) upon successive addition of 0-1.0 equiv of [(n-Bu)4N]F
Figure 5 ¹9F NMR (376 MHz) spectrum of 1 (20 mM in DMSO-d 6 at 293 K) upon successive addition of 1.0-10.0 equiv of (n-Bu)4N+F- in DMSO-d 6
Figure 6 A proposed binding mode and deprotonation of 1 with fluoride ions