An anion receptor was synthesized with ferrocene as binding frame. Anion recognition can be monitored by anion complexation-induced changes in UV-vis absorption spectra. Interaction between the receptor and acetate was described on the basis of 1H NMR experiments

Li JW

Lin H

Lin HK

Journal of Coordination Chemistry

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Full Terms & Conditions of access and use can be found athttp://www.tandfonline.com/action/journalInformation?journalCode=gcoo20Download by: [Turku University] Date: 12 January 2018, At: 02:21Journal of Coordination ChemistryISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20Synthesis of an anion receptor for acetate basedon the frame of ferroceneJianwei Li , Hai Lin & Huakuan LinTo cite this article: Jianwei Li , Hai Lin & Huakuan Lin (2009) Synthesis of an anion receptor foracetate based on the frame of ferrocene, Journal of Coordination Chemistry, 62:12, 1921-1927,DOI: 10.1080/00958970802702239To link to this article:  https://doi.org/10.1080/00958970802702239Published online: 13 May 2009.Submit your article to this journal Article views: 34View related articles Citing articles: 6 View citing articles Journal of Coordination ChemistryVol. 62, No. 12, 20 June 2009, 1921–1927Synthesis of an anion receptor for acetate basedon the frame of ferroceneJIANWEI LIy, HAI LINz and HUAKUAN LIN*yyDepartment of Chemistry, Nankai University, Tianjin, ChinazKey Laboratory of Functional Polymer Materials of Ministry of Education,Nankai University, Tianjin, China(Received 24 June 2008; in final form 4 September 2008)An anion receptor was synthesized with ferrocene as binding frame. Anion recognitioncan be monitored by anion complexation-induced changes in UV-vis absorption spectra.Interaction between the receptor and acetate was described on the basis of 1H NMRexperiments.Keywords: Ferrocene; Phenylhydrazone; Receptor; Naked-eye recognition1. IntroductionAnion recognition has attracted attention due to medicinal and environmentalapplications [1–3]. Receptors [4] and sensors [5–7] having strong affinity andselectivity for specific anions are important in supramolecular chemistry [8], butdesign of receptors with high selectivity is challenging [9–11]. Synthetic receptors foranions are usually based on urea/thiourea [12, 13], amides [14, 15], macrocyclicammonium/guanidinium [16, 17], functionalized calixarenes [18, 19], and phenylhy-drazone [20]. Phenylhydrazone, for example, is neutral and synthesis simple; p-nitrophenylhydrazine recognizes anions with a color change. The color ofphenylhydrazone changed so obviously upon addition of anions that naked-eyeddetection could be used. We found recently [21] that the phenylhydrazone-basedindole receptor was effective for acetate in dry DMSO. Cheng et al. [22] showed thatthe pyrrole- and cystine-based cyclopeptido-mimetics bind fluoride and acetate ionsin CH3CN. BF2 complexes of fluorinated dipyrrolyldiketone derivatives were alsoefficient receptors for acetate [23].There are few reports on sensors for acetate based on 1,10-diacetylferrocene;1,10-diacetylferrocene can provide an excellent frame for forming a geometrical cavity*Corresponding author. Email: hklin@nankai.edu.cnJournal of Coordination ChemistryISSN 0095-8972 print/ISSN 1029-0389 online  2009 Taylor & FrancisDOI: 10.1080/00958970802702239Downloaded by [Turku University] at 02:21 12 January 2018 for a specific anion. In the present work, we designed and synthesized the receptor 1,which senses acetate.2. Results and discussion2.1. UV-vis spectroscopic measurementThe UV-vis experiments of 1 with anions such as fluoride, chloride, bromide, iodide,dihydrogen phosphate, and acetate (tetrabutylammonium salts (TBA)) were carried outin DMSO at 298.2 0.1K. The anions were titrated into solution of 1, which exhibitedselective recognition for AcO as shown in figure 1. The UV-vis curves of 1 withdifferent concentrations of acetate were studied (figure 2). The intensity of theabsorption at 426 nm markedly decreased with simultaneous growth of a new peak at585 nm as the anion concentration increased. The spectral changes of AcO are moreobvious than F and H2PO4 , but similar to OH. The presence of isobestic points at475 nm during titration with acetate reveal formation of 1 : 1 complexes. No significantchange in absorption was observed for Cl, Br, and I.Continuous variation method was used to determine the stoichiometric ratios ofthe receptor to the fluoride guest. Figure 3 shows the receptor-AcO Job plot of the585 nm band absorption versus the molar fraction of guest {[G]/([H]þ [G])} for a seriesof solutions in which the total concentration of the host and fluoride was constant(4.0 105mol dm3), with the molar fraction of the guest continuously varying [24].The result illustrates that the receptor-anion complex concentration approaches amaximum when the molar fraction of the host {[H]/([H]þ [G])} is about 0.50, meaningthat the receptor forms a 1 : 1 complex with fluoride.300 450 600 7500.000.250.50Host, Cl−, Br−, I−H2PO−4F−AcO−AbsorbanceWavelength (nm)Figure 1. UV-vis changes of 1 operated in DMSO (1.0 105M) after addition of two equivalent of anion.1922 J. Li et al.Downloaded by [Turku University] at 02:21 12 January 2018 For a complex of 1 : 1 stoichiometry, the relation in equation (1) could be derivedeasily, where X is the absorption intensity and CH or CG is the concentration of thehost or the anion guest correspondingly [25].X ¼ X0 þ ðXlim  X0ÞfCH þ CG þ 1=Kass ½ðCH þ CG þ 1=KassÞ2 4CHCG1=2g=2CHð1ÞDetailed data are given in table 1. The association constant Kass was calculated bynonlinear least square regression [21]. The association constant for AcO was largerthan that of OH, F, or H2PO4 . The reason was probably that recognition of acetateis related to the configuration of acetate matching with the receptor (figure 1) and thebasicity of acetate, as well as the acidity of the binding sites of receptor. The O–C–Oangle is about 120, with the distance of two oxygens fitting to the hydrogens onrecognition points of receptor. Although the basicity of AcO is weaker than OH, itssize matches the cavity better. Basicity of acetate is stronger than the other anions.Therefore, the association constant Kass for acetate was maximal. The O–P–O angle isabout 108 for H2PO4 ; the distance of two oxygen atoms of AcO is longer than that ofH2PO4 such that oxygens of H2PO4 could not match well with two hydrogens onrecognition sites. F has the smallest radius, but the better basicity gives a higherassociation constant Kass than H2PO4 . Table 1 shows the receptor binds anions in theorder AcO4OH4F4H2PO4 4ClBr I.2.2. 1H NMR titrationsFurther support that formation of a hydrogen bond of N–H with anion came from 1HNMR spectroscopic analyses. These were carried out in DMSO-d6 under conditions of200 400 6000.000.250.50−0.0002 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 0.0012 0.0014 0.00160.000.020.040.060.080.100.120.14Wavelength (nm)AbsorbanceFigure 2. UV-vis spectra of 1 at 2 105M in DMSO solution during titration with TBA acetate; theinset figure shows the nonline fitting profile of the receptor at 585 nm upon addition of TBA acetate.Anion receptor 1923Downloaded by [Turku University] at 02:21 12 January 2018 NMR titration, with the spectra of the receptors being recorded in the presence ofincreasing concentrations of anions (figure 4). Resonances corresponding to C–H ofphenyl shift upfield during the titration, indicating increase of electron density on thephenyl ring from through-bond effects. Simultaneously, signals from the binding sitesbroadened with a downfield shift of 0.52 ppm upon addition of 0.3 equivalent of AcO,0.0 0.2 0.4 0.6 0.8 1.00.100.150.200.250.300.35AbsorbanceAnion molar fractionFigure 3. Job plot of 1 with AcO; total concentration is 4.0 105M.Figure 4. N–H 1H NMR (400MHz) spectra of 1 in DMSO-d6 in the absence (a) and (b) the presence of 0.3equivalent of AcO or 0.6 equivalent of AcO (c).Table 1. Association constants, Kass, of 1 with anions in DMSO at 298.2 0.1K.Anion AcO OH F H2PO4 Cl Br IKass (M1) 3.91 104 9.8 103 4.3 103 1.6 103 ND ND NDNote: The anions were added as their tetrabutylammonium salts. All errors are 10%; ND: the spectra have too small changewith adding anion to determine the affinity constant.1924 J. Li et al.Downloaded by [Turku University] at 02:21 12 January 2018 and disappear when 0.6 equivalent of AcO was added, indicating completedeprotonation of 1. The results indicate that there are two steps in anion recognition:(1) in the first step, acetate hydrogen bonds with 1, and (2) deprotonation of 1 takesplace. The proposed binding process between 1 and acetate is given in scheme 1.3. ConclusionCompound 1 has been developed as a colorimetric receptor for anions (scheme 2).The synthesis of this receptor is simple and high yielding. The receptor binds anionsin 1 : 1 stoichiometry with obvious colorimetric changes; deprotonation is proved by 1HNMR titration. The receptor has a selectivity for acetate and may have promisingpractical applications.4. Experimental4.1. ReagentsThe tetrabutylammonium salts with different anions were purchased from Sigma-Aldrich Chemical Co., stored in a desiccator containing dry silica gel under vacuum,and used without purification. Solvents were purified and stored under nitrogen prior touse. DMSO was dried with calcium hydride and distilled at reduced pressure. Unlessstated otherwise, commercial grade chemicals were used without purification.FeOO+NHH2NNO2FeNNHNHN NO2NO2ethanolrefluxScheme 2. The synthetic procedure for 1.FeNNNN NO2NO2HHFeNNNN NO2NO2HHFeNNNN NO2NO2AcO− OO−AcO−Scheme 1. The proposed binding between 1 and acetate.Anion receptor 1925Downloaded by [Turku University] at 02:21 12 January 2018 4.2. Synthesis of receptor 1, 1,10-diacetylferrocene di-p-nitrophenylhydrazoneA solution of 1,10-diacetylferrocene (0.625 g, 2.5mmol) in ethanol (20mL) wasadded dropwise to a solution of p-nitrophenylhydrazine (0.765, 5mmol) in ethanol(60mL) with stirring at reflux. After stirring for 6 h, the solution was concentratedby evaporation. Recrystallization from ethanol yielded brown crystals. 1H NMR (400MHz, DMSO-d6, Me4Si): 9.9 (s, 2H, N–H), 8.1 (dd, 4H, Ar–H), 7.2 (dd, 4H,Ar–H), 4.7 (m, 4H, Fc), 4.4 (m, 4H, Fc), 1.0 (S, 6H, CH3–H);13C NMR (DMSO): 151.2, 147.1, 137.8, 125.8, 111.5, 85.6, 70.5, 68.2, 67.7, 65.9, 64.1, 63.8, 39.6 ppm.Calcd for C26H26FeN6O4: C, 57.56; H, 4.79; N, 15.50. Found: C, 57.77; H, 4.68;N, 15.23. ESI-MS (m/z): 542.41(MþH)þ.4.3. General methodsUnless otherwise specified, all UV-vis titration experiments were carried out at298.2 0.1K. The 1H NMR spectra were recorded on a Varian UNITY-plus 400MHzspectrometer using tetramethylsilane (TMS) as an internal standard. UV-vis spectrawere recorded on a Shimadzu UV-2450 PC spectrophotometer.4.4. Absorption titration studiesBinding ability of the receptor for CH3CO2 , H2PO4 , and halide anions(as tetrabutylammonium salts) was investigated by UV-vis spectrometry in DMSOusing a constant host concentration (2.0 105M) and increasing concentrations of theanions (0–12 equivalence). The change in absorbance at 584 nm for the receptor wasplotted against anion concentration and fitted by the equation described byConnors [24].4.5. 1H NMR titrationsThe receptor (5.0 103M in DMSO-d6) was titrated against acetate (tetrabutylam-monium salts) by addition of excess anion in DMSO-d6.AcknowledgmentThis work was supported by a project 20371028, 20671052 from the National NaturalScience Foundation of China.References[1] P.D. Beer, P.A. Gale. Angew. Chem., Int. Ed., 40, 486 (2001).[2] P.A. Gale. Coord. Chem. Rev., 199, 181 (2000).[3] A. Bianchi, K. Bowman-James, E. Garcia-Espana. Supramolecular Chemistry of Anions, Wiley-VCH,New York (1997).[4] F.P. Schmidtchen, M. Berger. Chem. Rev., 97, 1609 (1997).1926 J. Li et al.Downloaded by [Turku University] at 02:21 12 January 2018 [5] R.M. Martinez, F. Sancenon. Chem. Rev., 103, 4419 (2003).[6] C. Suksai, T. Tuntulani. Chem. Soc. Rev., 32, 192 (2003).[7] P.D. Beer. Acc. Chem. Res., 31, 71 (1998).[8] J.L. Atwood, J.E. Davies, D.D. MacNicol, F. Vogtle, K.S. Suslick. Comprehensive SupramolecularChemistry, Pergamon, Oxford (1996).[9] Y. Kubo, M. Tsukahara, S. Ishihara, S. Tokita. Chem. Commun., 653 (2000).[10] M.J. Deetz, M. Shang, B.D. Smith. J. Am. Chem. Soc., 122, 6201 (2000).[11] K. Choi, A.D. Hamilton. J. Am. Chem. Soc., 123, 2456 (2001).[12] B.H.M. Snellink-Ruel, M.G.M. Antonisse, J.F.J. Engbersen, P. Timmerman, D.N. Reinhoudt. Eur. J.Org. Chem., 2000, 165 (2000).[13] E. Fan, S.A. Van Arman, S. Kincaid, A.D. Hamilton. J. Am. Chem. Soc., 115, 369 (1993).[14] P.B. Beer. Chem. Commun., 689 (1996).[15] S. Valiyaveettil, J.F.J. Engbersen, W. Verboom, D.D. Reinhoudt. Angew. Chem., 105, 942 (1993).[16] E. Kimura, S. Aoki, T. Koike, M. Shiro. J. Am. Chem. Soc., 119, 3068 (1997).[17] K. Niikura, A. Metzger, E.V. Anslyn. J. Am. Chem. Soc., 120, 8533 (1998).[18] Y. Morzherin, D.M. Rudkevich, W. Verboom, D.N. Reinhoudt. J. Org. Chem., 58, 7602 (1993).[19] J. Schreeder, J.F.J. Engbersen, A. Casnati, R. Ungaro, D.N. Reinhoudt. J. Org. Chem., 60, 6448 (1995).[20] Z.H. Lin, S.J. Ou, C.Y. Duan, BG. Zhang, Z.P. Bai. Chem. Commun., 624 (2006).[21] Y.H. Wang, H. Lin, J. Shao, Z.Sh. Cai, H.K. Lin. Talanta, 74, 1122 (2008).[22] Y.H. Zhang, Zh.M. Yin, J.Q. He, J.P. Cheng. Tetrahedron Lett., 48, 6039 (2007).[23] H. Maeda, Y. Ito. Inorg. Chem., 45, 8205 (2006).[24] K.A. Connors. Binding Constants. 1st Edn, John Wiley & Sons, New York (1987).[25] J.S. Kim, O.J. Shon, S.H. Yang, J.Y. Kim, M.J. Kim. J. Org. Chem., 67, 6514 (2002).Anion receptor 1927Downloaded by [Turku University] at 02:21 12 January 2018 

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Synthesis of an anion receptor for acetate based on the frame of ferrocene

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