Influence of Cation Size on the Fluorescent Properties of Bis-Coronand Biphenyl-Derived Complexes Ana M Costero

Influence of cation size on the fluorescent properties of bis-coronand biphenyl-derived complexes Ana M Costero

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Ana M Costero. Influence of cation size on the fluorescent properties of bis-coronand biphenyl-derived complexes. Supramolecular Chemistry, Taylor & Francis: STM, Behavioural Science and Public Health Titles, 2007, 19 (03), pp.151-158. 10.1080/10610270600915300. hal-00513486

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Influence of cation size on the fluorescent properties of bis- coronand biphenyl-derived complexes

Journal: Supramolecular Chemistry

Manuscript ID: GSCH-2006-0041.R1

Manuscript Type: Full Paper

Date Submitted by the 11-Jul-2006 Author:

Complete List of Authors: Costero, Ana; University of Valencia, Organic Chemistry

Keywords: Sensor, Biphenyl, Fluorescence, Conformational chage

Note: The following files were submitted by the author for peer review, but cannot be converted to PDF. You must view these files (e.g. movies) online.

Figure 7.cdx Chart1.cdx Figure 4.cdx

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1 2 3 4 Influence of cation size on the fluorescent properties of bis-coronand 5 biphenyl-derived complexes 6 7 8 Ana M. Costero *, Joaquín Sanchis, Salvador Gil, Vicente Sanz. 9 10 11 Departament de Química Orgánica, Universitat de València, C/ Dr. Moliner 50, 46100 12 Burjassot, Spain. 13 14 15 16 For Peer ReviewAbstract Only 17 18 A new bis-coronand derived from biphenyl has been prepared and its complexing and 19 sensing properties for alkaline, alkaline-earth and transition cations have been studied. 20 Open and clamp complexes are formed depending on the cation size and complex 21 stoichiometry. Both types of geometries can be distinguished due to their different 22 2+ 23 fluorescent behavior. Zn gives rise to 1:1 and 1:2 complexes with a similar geometry. 24 25 Introduction 26 27 28 Molecular systems that combine binding ability and photochemical or 29 1 30 photophysical properties are of great interest for designing chemosensors. It has 31 recently been established that conformational restriction is a viable mechanism for 32 2 33 transducing ion binding into enhanced fluorescence emission in organic fluorophores. 34 35 Thus, biphenyl and bipyridyl derivatives which experiment fluorescence enhancement 36 3 37 after complexation have been described in the literature. However, studies carried out 38 by Benniston et al. have demonstrated that fluorescence quantum yields for byphenyl 39 40 polyethers are dependent on the torsion angle around the biphenyl group. Planar 41 4 42 geometries favour higher yields and longer lifetimes. For all these reasons, we have 43 44 been interested in using the 4,4’-bis(N,N-dimethylamino)biphenyl (TMB, 45 46 tetramethylbenzidine) subunit in the design and synthesis of red-ox and fluorescent 5 47 sensors. TMB-derivatives ligands show very peculiar fluorescent properties. Firstly, the 48 49 presence of additional amino groups in substituents bound to the aromatic rings does not 50 51 give rise to a quenching of the fluorescence whatever the spacer present. Normally, 52 53 amines transfer one electron to the photoproduced vacancy in the HOMO of the 54 fluorophore which quenches fluorescence. In these compounds, however, the 55 56 diaminobiphenyl fluorophore has a rather high energy HOMO (owing to its easy 57 58 oxidabizability), so PET from the amino is not probable. Secondly, an increment in the 59 60 rigidity of these fluorophores makes them less fluorescent.

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1 2 3 We now report the sensing behaviour of a new ligand that contains benzylamino 4 5 coronands as binding units in order to study the influence that the size of different 6 7 cations has in the fluorescent behaviour of the ligand. The most important difference 8 9 would be related to the formation of open-like complexes of clamp-like complexes since 10 the type of complexation is closely related to the dihedral angle between both aromatic 11 12 rings and consequently to the fluorescent properties of the photo physical moiety. 13

14 NMe2 NMe2 15 O O 16 For Peer Review Only 17 N O O O N 18 X 19 X O O O N 20 N 21 1 X=CO 3 22 O O NMe 2 X=CH2 23 2 NMe2 24 Chart 1 25 26 27 28 Photophysical characteristics of 2 and effect of protonation. Photophysical 29 30 properties of 2 in CH 3CN were studied (table 1). As expected, they are not so different 31 6b 32 from those observed for the related compounds previously described. Emission of 33 fluorescence in 2 is remarkably blue-shifted in comparison to TMB , and is even more 34 35 so when compared with its carbonylic counterpart 1 (Figure 1). By contrast, 2 shows a 36 37 similar behaviour to that observed for control compound 3. 38 39 40 Table 1: Data for absorption in the UV and emission of fluorescence for the ligands in CH 3CN 41 Ligand Absortion λλλ (nm) Emission λλλ (nm) Quantum Yield ( φφφ) 42 max max (εεε cm -1M-1) 43 TMB 310 (34668) 401 0.13 44 1 295 (29600) 474 0.08 45 2 270 (42135) 363 0.057 46 3 269 (27781) 360 0.061 47 48 49 50 51 52 53 54 55 56 57 58 59 60

* Fax: 34 963543152; Tel: 34 96 354 4410; [email protected]

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1 2 3 4 2 5 80E+05 TMB 6 1 7 3 8 60E+05 9 10

11 40E+05 12 13 cps 14 20E+05 15 16 For Peer Review Only 17 0 18

19 350 400 450 500 550 600 650 700 20 wavelenght (nm) 21 22 Figure 1. TMB 1 2 3 λ λ 23 Fluorescence Spectra for , , and in CH 3CN at 20ºC. exc = 310 nm, exc = 300 nm, 24 λexc = 300 nm and λexc = 340 nm respectively. 25 26 This behaviour is in agreement with the hypothesis of an excited state, in which both 27 28 biphenyls rings are coplanar and destabilised by the presence of substituents. Thus, S 1 is 29 30 unfavoured by sterical repulsions and then, the energetic difference S 1→S0 is enhanced 31 in comparison with TMB . On the other hand, in the presence of a weak acid such as 32 33 citric acid, a quenching of fluorescence was obtained (Figure 2). Protonation of the 34 35 azacrown nitrogen by the citric acid would induce the formation of an intramolecular 36 37 hydrogen bond with the nitrogen in the opposite crown, forcing the dihedral angle in the 38 39 biphenyl far from the coplanarity, which induces a quenching of the fluorescence. After 40 addition of TFAA, the arylic nitrogens are also protonated, and then emission of 41 42 fluorescence in 2 is strongly blue-shifted just as TMB is in the same acidic conditions. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4 5 80E+05 6 7 2 8 60E+05 9 10

11 cps 40E+05 12 13 2+ Cítric acid 14 15 20E+05 16 For Peer Review Only 17 2 + TFAA 18 0

19 320 340 360 380 400 420 440 460 480 500 20 wavelenght (nm) 21

22 23 Figure 2. Fluorescence spectrum of 2 under different acid-base conditions in CH 3CN at 20 ºC, λ exc = -6 24 300 nm and initial concentration of ligand of 2.30 x 10 M in CH 3CN. 2: ligand in CH 3CN or in 2.63 x -5 -6 25 10 M of tetramethylamonnium hydroxide in CH 3CN. 2+Cítric acid : ligand in 9.54 x 10 M of citric 26 acid in CH 3CN. 2 + TFAA: ligand in a great excess of trifluoroacetic acid in CH 3CN. 27 28 29 Complexation studies with alkaline cations. 30 + + + + 31 Titrations of 2 with perchlorates of Na , K , Cs and Li were performed in CH 3CN. 32 + 7 33 Data of the titration with Na were fitted by SPECFIT to a 1:1 + 1:2 (L:M) 34 35 stoichiometry model, where the complexation constants were log K 1 = 5.2 ± 0.7 and log 36 K2 = 11.5 ± 0.2. The theoretical spectra modelisation of the complexes (see 37 38 suplementary material Fig. 9 and 10) suggested that the 1:1 complex would exhibit a 39 40 lower quantum yield than 2, while it should be higher for LM 2 than for the free ligand 41 42 which was the experimentally observed behaviour (Figure 3a). According to our 43 previously reported results, 6 a 1:1 clamp-type complex was proposed in which a more 44 45 constrained angle in the biphenyl moiety would be translated in a quenching of the 46 47 fluorescence. Evolution from the 1:1 clamp-complex to an open 1:2 complex will make 48 49 both rings more coplanar, aided by the presence of charge repulsions between both 50 cations. This modification in the dihedral angle would explain the enhancement of 51 52 fluorescence observed. 53 54 55 56 57 58 59 60

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1 2 3 4 9.6E+06 9.9E+06 5 9.5E+06 (a) 9.8E+06 9.4E+06 (b) 9.7E+06 6 9.3E+06 7 9.2E+06 9.6E+06 cps 8 9.1E+06 cps 9.5E+06 9.0E+06 9 9.4E+06 10 8.9E+06 8.8E+06 9.3E+06 11 8.7E+06 9.2E+06 12 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 13 [L]/[M] [L]/[M] 14

15 16 For Peer Review Only Figure 3. Fluorescence emission of 2 at λem = 361 nm in CH 3CN at 20 ºC,  λexc = 300 nm in presence 17 of increasing amounts of (a) sodium perchlorate and (b) potassium perchlorate. 18 19 20 + 21 A good correlation was observed for K with the model 1:1 + 1:2 (L:M), being the 22 complexation constants of log K = 7.3 ± 0.5 and log K = 12.0 ± 0.6. In this case, the 23 1 2 24 fluorescence of 1:1 complex is quite similar to the observed for the ligand which was 25 26 also observed by the experimental data reflected in figure 3b. For this reason therefore, 27 28 an open structure was proposed. LM 2 has much higher φ, which is in agreement with 29 + 30 the coplanarity of the rings forced by the electrostatic repulsions of both cations. K 31 (1.33 Å) has a suitable size to fit in the crown cavity and interacts properly with the 6 32 33 oxygen atoms. By contrast, Na + (0.95 Å) is too small and does not interact with all of 34 35 them, thus, the lack of coordination with the oxygen atoms of one crown would be 36 37 compensated for the interaction with the oxygen atoms in the other crown forming the 38 39 clamp-type complex and inducing the quenching of fluorescence (Figure 4). 40 41 42 43 44 45 46 47 48 49 50 51 52 53 =Na+ 54

55 + 56 = K 57 58 59 Figure 4 . Complex 1:1 and 1:2 for 2 with Na + and K + 60

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1 2 3 Titration with Cs + was fitted to the model, and the best results were obtained with 4 + 5 the 1:1 model, with a constant value of log K 1= 7.3 ± 0.9. The quantum yield for 2· Cs 6 + 7 was slightly lower than that for the free ligand. Cs is too big to fit in a crown and 8 + 9 might not interact with only one crown, but with both crowns. The size of Cs would 10 mean that the crowns might not approach so much as in the case of Na +, and the 11 12 complex would probably be formed with a small modification of dihedral angle; it is for 13 14 this reason that the fluorescences of 2 and 2·Cs + are so similar. 15 16 Table 2. : ForStoichiometry, Peer topology of the complexReview and constant of complexation Only for the complexes with 2 with alkaline and earth-alkaline cations in CH 3CN, 298 K. 17 18 19 Cation Stoich. (L:M) log K 1 geometry log K 2 geometry 20 Na + 1:1 + 1:2 5.2 ± 0.7 clamp 11.5 ± 0.2 open 21 + 22 K 1:1 + 1:2 7.3 ± 0.5 open 12.0 ± 0.6 open 23 Cs + 1:1 7.3 ± 0.9 clamp - - 24 25 26 + 27 In the case of Li , data did not fit well to any complexation model. Slight quenching 28 + 29 was observed after addition of Li over 2, probably owing to 1:1 (or higher) 30 stoichiometries. In these complexes Li + would be surrounded by 4 oxygen atoms in the 31 32 same crown. Li + is a hard cation and is compatible with oxygen atoms, but it is too 33 34 small to be surrounded by lot of them. 35 36 Finally, some tests of selectivity towards a cation in the presence of others were 37 carried out. Titrations of 2 with mixtures of Na +/Cs + and K +/Cs + showed that, 38 39 enhancements of fluorescence were obtained in all cases. This was expected, regarding 40 + + 41 the constants of complexation, and indicates that the LM 2 with Na and K complex are 42 43 preferred by the ligand (figure 5). 44 45 46 47 48 49 50 51 52 53 54 55 56 Figure 5. Experiments of competence between K + / Cs + (left) and Na + / Cs + (right). Experiments were -6 57 performed in CH 3CN, at 298 K and λexc = 300 nm. Initial concentration of 2 was circa 2.5 x 10 M in all cases. 58 Amounts of an equimolecular mixture of K +/Cs + or Na +/Cs + were added over the ligand, depending on the 59 experiment. Represented relative intensity refers to the intensity at each point divided by the intensity at the 60 beginning of the titration.

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1 2 3 Studies of the ability towards transition and post-transition cations by 2. 4 5 The complexation ability of ligand 2 was tested towards Zn 2+ , Cd 2+ and Cu 2+ in 6 2+ 7 CH 3CN (see supplementary material Fig. 11 and 12). Results with Zn revealed that 8 9 data fitted to a 1:1 + 1:2 (L:M) model where the calculated constants were log K1= 9.8 ± 10 0.1 and log K = 17.8 ± 0.2 (table 3). The emission tendency in the presence of this 11 2 12 cation is different to this observed with the alkaline cations. Whereas the 1:1 complex 13 14 showed a φ similar to that observed for 2·Na + or 2·Cs +, what suggest a clamp complex 15 2+ 16 between 2 andFor Zn , thePeer 1:2 (L:M 2)Review complex showed a Only significant quenching of the 17 18 fluorescence. 19 20 1.0E+07 9.0E+06 21 8.0E+06 22 7.0E+06 6.0E+06 23 5.0E+06 cps 24 4.0E+06 25 3.0E+06 2.0E+06 26 1.0E+06 27 0.0E+00 28 0 1 2 3 [L]/[M] 29 30 31 Figure 6 . Fluorescence emission of 2 at λem = 361 nm in CH 3CN at 20 ºC,  λexc = 300 nm in presence 32 of increasing amounts of zinc triflate. 33 34 This behaviour was clearly different to that shown by the studied alkaline cations 35 36 and suggests that both L:M and L:M 2 complexes have a clamp geometry. This type of 37 geometry has been widely observed in binuclear zinc (II) complexes with different type 38 39 of ligands. 8 In some of these complexes a decrease in the Zn····Zn separation via 40 9 41 bridging contraions or solvent molecules has been described. 42 43 44 k 45 46 N f g h N 47 a e O 48 b O O O O 2+ O 49 j Zn c d O O O 50 N O i N 51 2+ Zn O 52 N 2+ O Zn 53 O N O O O O O 54 O O N N 55 L:M L:M 56 2 57 Figure 7. Structure proposed for the 2·Zn 2+ and 2·2Zn 2+ complexes. 58 59 60

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1 2 3 Table 3. Stoichiometry, topology of the complex and constant of complexation for the complexes with 2 2+ 2+ 4 with Zn and Cd in CH 3CN, 298 K. 5 6 Cation Stoich. (L:M) log k geometry log k geometry 7 1 2 8 Zn 2+ 1:1 + 1:2 9.8 ± 0.1 clamp 17.8 ± 0.2 clamp 9 2+ Cd 1:1 + 1:2 7.4 ± 0.2 clamp 14.2 ± 0.2 clamp 10 11 12 2+ 13 In order to obtain more information about the way ligand 2 interacts with Zn , 14 1 13 15 several NMR experiments were carried out. H NMR and C NMR spectra were 16 For Peer Review Only 17 registered for solutions in CD 3CN of free ligand and free ligand in the presence of 1 and 18 2 equiv of Zn(tfl) 2. Chemical shifts are shown for the most interesting signals in Table 19 20 4. 21 22 23 2+ Table 4. Chemical shifts for 2 and 2 with 1 equiv. and 2 equiv. of Zn in CD CN at 298 K. 24 3 25 1H H H H H H H H H H H H 26 a b c d e f g h i j k 27 2 7.01 6.62 6.84 3.24 2.56 3.38 3.47-3.55 2.93 28 29 2·Zn 2+ 7.12 6.92 7.15 4.43/3.90 3.02-3.05 3.54-3.61 3.04 30 31 2·Zn 4+ 7.23 6.92 7.13 4.43/3.70 2.72-3.01 3.37-3.73 3.02 32 2

33 13 34 C Cd Ce Cf Cg Ch Ci Cj Ck 35 36 2 58.49 55.10 70.66 71.02 71.17 71.21 71.30 40.97

37 2+ 38 2·Zn 55.10 53.84/53.59 63.65/63.44 69.76 69.85 69.95 70.19 39.62

39 4+ 40 2·Zn 2 54.42 54.10/54.18 69.58/63.40 69.66/69.61 69-86/69.76 70.20 70.24 39.96 41 42 43 These data indicate that complexation with 1 equiv of Zn 2+ gives rise to clear 44 45 modifications in the area of the crown cavity close to the nitrogen atom (H d, He, H f and 46 47 Cd, C e and C f). This fact is in accordance with the structural proposal for the 1:1 48 49 complex that involves both cavities in the cation complexation (see figure 7). The 50 NMR spectra registered in the presence of a second equivalent of Zn 2+ showed two 51 52 important data. Firstly, no modification in the N(CH 3)2 was observed, which indicates 53 54 that these groups were not involved in complexation, and secondly the number of 55 56 carbons of the cavity modified in this new complex extended from H d to H h which was 57 in accordance with the complexation of one cation in each cavity. However these 58 59 experiments were not conclusive about the open or clamp geometry of the complex. 60

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1 2 3 The same pattern is observed for Cd 2+ (0.97 Å), i.e., a 1:1 clamp complex with a 4 5 constant of complexation value of log K 1 = 7.4 ± 0.2 and an open nearly-quenched 1:2 6 7 complex (log K2 = 14.2 ± 0.2) 8 2+ 9 A monotonic quenching throughout the addition of Cu to 2 was observed. 10 However, the same situation was observed in the titration of TMB with Cu 2+ , so these 11 12 results are not relevant. Cu 2+ can quench both, by binding the N in the TMB subunit or 13 14 by mere collision with the compound (Figure 8). 15 16 For Peer Review Only 17 18 225 19

20 175 21 22 23 125

24 Absorbance

25 75 26 27 28 25

29 325 375 425 475 525 30 Wavelength (nm) 31 32 2+ Figure 8. Emission of fluorescence spectra in the titration of 2 with Cu in CH 3CN, 298 K. Initial concentration 33 of 2 was 2.15 x 10 -6 M. 0 to 5.46 equivalents of Cu 2+ were added. It was no possible to fit any model from SPECFIT 34 to these data. 35 36 37 38 Experimental Section 39 40 General Methods. All commercially available reagents were used without further 41 42 purification. Benzene was dried over sodium. Water sensitive reactions were performed 43 44 under argon. Column chromatography was carried out on SDS activated neutral 45 46 aluminium oxide (0.05-0.2 mm; activity degree 1). Melting points were measured with a 47 48 Cambridge Instrument and are uncorrected. IR spectra were recorded on a Perkin-Elmer 49 1750 FT-IR and a Bruker Equinox 55 FT-IR. NMR spectra were recorded with Bruker 50 51 Avance 300/500 and Varian Unity-300/400 spectrometers. Chemical shifts are reported 52 53 in parts per million downfield from TMS. Spectra were referenced to residual 54 55 undeuterated solvent. High resolution mass spectra were taken with a Fisons VG- 56 AUTOSPEC and those using the eletrospray ionizing technique were recorded on an 57 58 HPLC-MS with ion trap Bruker 3000-Esquire Plus. UV spectra were run at 20ºC 59 60 (thermostatted) either on a Shimadzu UV-2102 PC or on a Biotech Instruments XL spectrometer. Steady-state fluorescence measurements were carried out using an

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1 2 3 Instruments SA (Jobin-Yvon) Fluoromax-2, equipped with a red sensitive Hamamatsu 4 5 R928 photomultiplier tube and a Varian Cary Eclipse Fluorimeter. Spectra were 6 7 corrected for the wavelength dependence of the detector using a calibration curve 8 9 generated with a standard lamp. 10 11 12 Synthesis of 2,2’-bis(1-aza-18-crown-6-methylen)-4,4’-bis(dimethylamino) biphenyl 13 (2). Compound 15a (193 mg, 0.23 mmol) was dissolved in dry THF (20 ml) in a round 14 15 bottom flask provided with a stirrer and under an argon atmosphere. BH 3-THF (ca. 1.0 16 For Peer Review Only 17 M in THF) (10 ml, 10 mmol) was dropped to the stirred solution at room temperature. 18 19 After 24 hours, more BH 3-THF (10 ml, 10 mmol) was added and the reaction was 20 stirred for a further 24 hours. H O was cautiously dropped until effervescence was over. 21 2 22 HCl (6M) (2 ml) was added afterwards and the solution was stirred for 4 hours at room 23 24 temperature. NaOH in pellets was added then until pH was ca . 9 and the latter solution 25 26 was extracted in a continuous mode with CHCl 3 for 48 hours. After drying over sodium 27 28 sulphate and the distillation of solvent the product (98 mg, 54 %) was obtained. IR 29 (KBr) ν (cm -1): 2940 (CH), 2870, 1607 (Ar), 1495 (CN), 1352 (CN), 1113 (CO), 807 30 max 31 1 32 H NMR (400 MHz, CDCl 3) δ (ppm): 7.09 (2H, d, J = 2.8 Hz, Ar-H), 6.91 (2H, d, 33 J = 8.4 Hz, Ar-H), 6.62 (2H, dd, J = 8.4 Hz, J = 2.8 Hz, Ar-H), 3.69-3.64 (24H, m, 34 35 OCH 2), 3.60 (8H, m, OCH 2), 3.51 (8H, m, NCH 2CH 2O), 3.33 (4H, d, J = 8.0 Hz, 36 13 37 ArCH 2N), 2.99 (12H, s, N(CH 3)2), 2.69 (8H, t, J=5.9 Hz, NCH 2CH 2O). C NMR (100 38 39 MHz, CDCl 3) δ (ppm): 147.9 (s), 137.7 (s), 129.9 (d), 128.4 (s), 111.8 (d), 109.5 (d), 40 + 41 69.8-69.1 (t), 56.7 (t), 53.1 (t), 39.7 (q), 29.3 (t). HRMS (EI): M found 790.5064. 42 C H O N requires 790.5092. UV (CH CN) λ = 270 nm, ε = 42135; shoulder at 43 42 70 10 4 3 max 44 λ=310 nm. Emission of fluorescence (CH 3CN ): λem = 362 nm at λexc = 300 nm. Quantum 45 46 yield (CH 3CN): 0.057 (quinine sulphate in 1M H 2SO 4). 47 48 General procedure for fluorometric studies. Fluorimetric titrations were carried 49 50 out in 1 cm pathlength quartz fluorescence cells at 20ºC (thermostatted). The 51 52 concentration of ligand was ca. 5·10 -6 M in acetonitrile (Spectroscopic grade). An 53 54 approximately constant ionic strength was maintained by adding the inert salt 55 56 N(Bu) 4PF 6 ( ca . 30 mol per mol of ligand). Measurements were recorded in the presence 57 of the corresponding metal triflates (metal-to-ligand ratio between 0.25 to 12 58 59 equivalents). Quantum yields were measured using quinine sulphate monohydrate in 60 H2SO 4 (1 M, aq) as the standard ( Φ=0.546). Complexation constants were determined

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1 2 3 from the analysis of the spectral assembly, regarding LM 2, LM and L 2M as possible 4 5 stoichiometries by fitting the data to one of the general models (specified in each case). 6 7 8 9 Acknowledgments 10 11 12 We acknowledge the support from the Dirección General de Ciencia y Tecnología, 13 project CTQ 2005-07562-C04-01, and Generalitat Valenciana, project GVACOMP2006- 14 112. J.S. thanks the University of Valencia for a predoctoral fellowship. Finally, SCSIE 15 (Universitat de València) is gratefully acknowledged for all the equipment employed. 16 For Peer Review Only 17 18 References 19 20 21 22 1. a) De Silva, A.P.; Gunaratne, H.Q.G.; Huxley, C.P.; McCoy, C.P.; Radamacher, 23 24 J.T.; Rice T.E. Chem. Rev . 1997 , 97, 1515. b) Valeur, B.; Leray, I. Coord. 25 Chem. Rev . 2000, 205 3. c) Luca Prodi, L.; Bolletta, F.; Montalti, M.; 26 27 Zaccheroni, N. Coord. Chem. Rev . 2000, 205 59. c) Martínez-Máñez, R.; 28 29 Sancenón, F. Chem. Rev . 2003 , 103, 4419. 30 31 2. a) McFarland S.A.; Finney N.S. J. Am. Chem. Soc . 2001 , 123, 1260. b) 32 33 McFarland S.A.; Finney N.S. Chem. Comm . 2003 288. (c) Mello J. S.; Finney N. 34 S. Angew. Chem., Int. Ed . 2001 , 40, 1536. 35 36 3. (a) Fang A. G.; Mello J. S.; Finney N. S. Tetrahedron , 2004 , 60, 11075; (b) 37 38 Cody J. C.; Fahrni C. J. Tetrahedron , 2004 , 60, 11099. 39 40 4. Benniston A.C.; Harriman A.; Patel P.V.; Sams C.A. Eur. J. Org. Chem . 2005 , 41 4680. 42 43 5. a)Costero, A.M.; Sanchis, J.; Peransi S.; Gil, S.; Sanz V.; Domenech A. 44 45 Tetrahedron 2004 , 60, 4683. b) Costero, A.M., Sanchis, J.; Gil, S.; Sanz, V.; 46 47 Ramirez de Arellano, C.; Williams, J.A.G. Supramolecular Chemistry 2004 , 48 49 435. 50 6. a) Costero, A.M., Gil, S.; Sanchis, J.; Peransí, S.; Sanz, V.; Williams, J.A.G., 51 52 Tetrahedron 2004 , 60, 6327. b)Costero, A.M., Sanchis, J.; Gil, S.; Sanz, V.; 53 54 Williams, J.A.G., J. Mat. Chem. 2005 , 15, 2848. 55 56 7. SPECFIT/32 2 GLOBAL ANALYSIS SYSTEM, v.3.0, Spectrum Associates, 57 Marlborough, MA, USA, www.bio-logic.info/rapid-kinetics/specfit.html. 58 59 8. (a) Pariya, C.; Chi, T-Y.; Mishra, T.K.; Chung. C-S. Inorg. Chem. Commun . 60 2002 , 5, 119. (b) Fry, F.H.; Fallon, G.D. Spiccia, L. Inog. Chim Acta , 2003 , 346,

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1 2 3 57. (c) Brudenell, S.J.; Spiccia, L.; Hockless, D.C.R.; Tiekink, E.R.T. J. Chem. 4 5 Soc. Dalton Trans. 1999 , 1475. 6 7 9. a) Koike, T.; Inoue, M.; Kimura, E.; Shiro, M. J. Am. Chem. Soc. 1996 , 118, 8 9 3091. b) Atkins, A.J.; Black, D.; Finn, R.L.; Marin-Becerra, A.; Blake, A.J.; 10 Ruiz-Ramirez, L.; Li, W-S.; Schröder, M. J. Chem. Soc. Dalton Trans. 2003 , 11 12 1730. 13 14 15 16 For Peer Review Only 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4

5 1.1E+8 6 7 1 0 0 8 9.0E+7 9 10 11 7.0E+7 12 1 1 0

13 5.0E+7

14 Epsilon(/M/cm) 15 16 For3.0E+7 Peer Review Only

17 1 2 0 18 19 1.0E+7 20 21 320 340 360 380 400 420 440 460 480 22 Wavelength (nm) 23 + 24 Figure 9. Model of SPECFIT for the titration of 2 with Na . Fitting to LM + LM 2 stoichiometries. Simulated 25 emission spectra for the formed complexes. 26 27 28 1.4E+8 29 30 1 0 0 31

32 1.0E+8 33 34 35 1 1 0 36 37 6.0E+7 38 Epsilon(/M/cm) 39 40 1 2 0 41 2.0E+7 42 43

44 320 340 360 380 400 420 440 460 480 45 Wavelength (nm) 46 47 + 48 Figure 10. Model of SPECFIT for the titration of 2 with K . Fitting to LM + LM 2 stoichiometries. 49 Simulated emission spectra for the formed complexes. 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4 5 1.1E+8 6 7 1 0 0 9.0E+7 8 9

10 7.0E+7 11 12 1 1 0 13 5.0E+7

14 Epsilon(/M/cm) 15 16 For3.0E+7 Peer Review Only

17 1 2 0 18 19 1.0E+7 20 21 320 340 360 380 400 420 440 460 480 22 Wavelength (nm) 23 24 2+ Figure 11. Model of SPECFIT for the titration of 2 with Zn . Fitting to LM + LM 2 stoichiometries. 25 26 Simulated emission spectra for the formed complexes. 27 28 1.6E+8 29 30 1 0 0 31 32 1.2E+8 33 34 1 1 0 35 8.0E+7 36 Epsilon(/M/cm) 37 38 4.0E+7

39 1 2 0 40

41 0.0 42 325 375 425 475 43 Wavelength (nm) 44 45 46 2+ 47 Figure 12. Model of SPECFIT for the titration of 2 with Cd . Fitting to LM + LM 2 stoichiometries. 48 Simulated emission spectra for the formed complexes. 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4 5 225 6 7 8 175 9

10 125 11 12 Absorbance 13 75 14

15 25 16 For Peer Review Only 17 325 375 425 475 525 Wavelength (nm) 18

19 2+ 20 Figure 8. Emission of fluorescence spectra in the titration of 2 with Cu in CH 3CN, 298 K. Initial concentration -6 2+ 21 of 2 was 2.15 x 10 M. 0 to 5.46 equivalents of Cu were added. It was no possible to fit any model from SPECFIT 22 to these data.

23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4 2 5 80E+05 TMB 6 1 7 3 8 60E+05 9 10

11 40E+05 12 13 cps 14 20E+05 15 16 For Peer Review Only 17 0 18

19 350 400 450 500 550 600 650 700 20 wavelenght (nm) 21 22 Figure 1. TMB 1 2 3 23 Fluorescence Spectra for , , and in CH 3CN at 20ºC. λexc = 310 nm, λexc = 300 nm, 24 λexc = 300 nm and λexc = 340 nm respectively. 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4

5 80E+05 6 7 2 8 60E+05 9 10

11 cps 40E+05 12 13 2+ Cítric acid 14 15 20E+05 16 For Peer Review Only 17 2 + TFAA 18 0

19 320 340 360 380 400 420 440 460 480 500 20 wavelenght (nm) 21 22 23 Figure 2. Fluorescence spectrum of 2 under different acid-base conditions in CH 3CN at 20 ºC, λ exc = -6 24 300 nm and initial concentration of ligand of 2.30 x 10 M in CH 3CN. 2: ligand in CH 3CN or in 2.63 x -5 -6 25 10 M of tetramethylamonnium hydroxide in CH 3CN. 2+Cítric acid : ligand in 9.54 x 10 M of citric 26 acid in CH 3CN. 2 + TFAA : ligand in a great excess of trifluoroacetic acid in CH 3CN. 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 4 9.6E+06 9.9E+06 5 9.5E+06 9.8E+06 9.4E+06 (a) (b) 9.7E+06 6 9.3E+06 7 9.2E+06 9.6E+06 cps 8 9.1E+06 cps 9.5E+06 9.0E+06 9 9.4E+06 8.9E+06 10 8.8E+06 9.3E+06 11 8.7E+06 9.2E+06 12 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 13 [L]/[M] [L]/[M] 14

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Figure 5. Experiments of competence between K + / Cs + (left) and Na + / Cs + (right). Experiments were circa -6 16 performed in CHFor3CN, at 298 PeerK and λexc = 300 nm.Review Initial concentration of 2Only was 2.5 x 10 M in all cases. + + + + 17 Amounts of an equimolecular mixture of K /Cs or Na /Cs were added over the ligand, depending on the 18 experiment. Represented relative intensity refers to the intensity at each point divided by the intensity at the 19 beginning of the titration. 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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1 2 3 1.0E+07 4 9.0E+06 5 8.0E+06 6 7.0E+06 6.0E+06 7 5.0E+06 8 cps 4.0E+06 3.0E+06 9 2.0E+06 10 1.0E+06 0.0E+00 11 0 1 2 3 12 [L]/[M] 13 14 15 Figure 6 . Fluorescence emission of 2 at λem = 361 nm in CH 3CN at 20 ºC,  λexc = 300 nm in presence 16 of increasing amountsFor of zincPeer triflate. Review Only 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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