(Thia. hia)calix. )calix[4]arene. Section 4b: Molecular Trafficking Based on Latch Circuit

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1 Section 4b: Molecular Trafficking Based on Latch Circuit In the section 4a, we discussed a chemosensor based on thiacalix[4]arene of 1,3-alternate conformation which behaves as a security keypad lock with chemical inputs of Cu 2+ and F - ions in a sequential manner. In continuation of this research work on molecular devices, in the next part of investigation a new chemosensor based on calix[4]arene of paco conformation possessing dansyl moieties in anti orientation has been designed and synthesized. In this chemosensor regulation of Hg 2+ (input 2) and Cl - /Br - /I - (input 3) at variable ph range (input 1) mimics trafficking mechanism (vide infra). The term trafficking denotes the movement or transport of components of a system in an orderly manner either at cellular level 217 in living systems or at road intersections in day to day life. Cellular systems in living beings include number of metal ion trafficking proteins that specifically mobilize or eliminate metal ions and develop homeostatic mechanisms and pathways through which organisms selectively and correctly metallate metalloproteins. 218 This biological system must ensure the transport and delivery of the right metal ion to the right protein. Disturbed metal ion trafficking has been implicated as a cause of range of human diseases such as Wilson and Menkes disease. 219 The transport system of these metal ions involves transporters like voltage gated ion channels, import and export proteins, intracellular metal ion sensors, storage proteins and chaperones which on receiving signals, according to physiological need of cell, transport metal to its specific protein. Similarly, traffic on roads in a day to day life is regulated by traffic signals which play a crucial role in the road safety in same manner as played by transporters in a living cell by directing correct biosynthetic pathway to metal to its specific protein. The electronic circuit of these traffic signals is based on sequential logic circuits i.e. output generated does not only depend upon the combination of inputs but also sequence in which inputs are added. The molecular trafficking represents a phenomenon in which the information is processed and transmitted with signals in a 216 Kumar, M.; Dhir, A.; Bhalla, V. Chem. Commun. 21, 46, Ba, L. A.; Doering, M.; Burkholz, T.; Jacob, C. Metallomics, 29, 1, Atkinson, A.; Winge, D. R. Chem. Rev. 29, 19, Boal, A. K.; Rosenzweig, A. C. Chem. Rev. 29, 19,

2 specific manner at molecular level. The synthetic systems in which the information is processed and transmitted in a specific manner are helpful in rationalizing intricate aspects of inter and intracellular metal trafficking. In addition to this, encoding binary digits of logic conventions, we have proposed a logic circuit for designing molecular traffic signal with incorporation of R-S (Reset-Set) latch 22 circuit i.e. a circuit which responds to sequence of input pulses comprising cross coupled NR logic gates. Such latch circuits are of particular interest to develop Write Read Erase system 221 and random access memory. 222 Nearly all digital electronic devices (microprocessors, digital clocks, mobile phones, cordless telephones, electronic calculators, etc.) are designed on such sequential circuits. Thus, significant role played by trafficking in day to day life and application of latch circuits raised our interest in the development of a molecular system mimicking trafficking mechanism. CH 3 N CH 3 Bu t Bu t Bu t H 2 N S dry THF NEt Bu t Bu t But 3 HN NH 2 2 Bu t Cl S N H 3 C H 3 C NH S Bu t Dansyl Chloride 24 H 3 C Scheme 4.3 N H 3 C 29 Thus, the reaction of diamine with 2.5 mol equiv. of dansyl chloride 24 in the presence of triethyl amine in dry THF afforded compound 29 (44 %), mp. 19 ºC, FAB- 22 Ruiter, G.; Tartavosky, E.; ded, N.; Van der Boom, M. E. Angew. Chem. Int. Ed. 21, 49, Chatterjee, M. N.; Kay, E. R.; Leigh, D. A. J. Am. Chem. Soc. 26, 128, (b) Baron, R.; nopriyenko, A.; Katz, E.; Lioubashevski,.; Willner, I.; Wang, S.; Tian, H. Chem. Commun. 26, (c) Katz, E.; Willner, I. Chem. Commun. 25, (d) Galindo, F.; Lima, J. C.; Luis, S. V.; Parola, A. J.; Pina, F. Adv. Funct. Mater. 25, 15, Reed, M. A.; Chen, J. Appl. Phys. Lett. 21, 78,

3 MS m/z 1282 (M-2) + (Scheme 4.3). The structure of compound 29 was confirmed from its spectroscopic and analytical data. The IR spectrum showed a stretching band at 331 cm -1 due to N-H stretching. The 1 H NMR spectrum of compound 29 showed three singlets (18H, 9H, 9H) at.92, 1.14, 1.28 ppm corresponding to tert-butyl protons, multiplet (6H) at ppm for CH 3, four multiplets (4H, 4H, 8H, 4H) at ppm for CH 2, for NCH 2, for CH 2, for ArCH 2 Ar, a singlet (6H) at 2.86 for NCH 3, two doublets (2H each) at 3.38 and 3.9 for ArCH 2 Ar protons, two doublets (2H each) at 6.49 and 6.63 and two singlets (2H each) at 6.96 and 7.6 for aromatic protons of calix[4]arene, one doublet (4H) and three multiplets (4H, 2H, 2H) at 7.17, , and ppm for aromatic protons of dansyl moiety. This NMR data suggest that compound 29 is in paco conformation. The binding behaviour of compound 29 towards different cations (Cu 2+, Hg 2+, Pb 2+, Zn 2+, Ni 2+, Cd 2+, Fe 3+, Fe 2+, Ba 2+, Co 2+, Ag + K +, Na + and Li + ) was investigated by UV-vis and fluorescence spectroscopy. The absorption spectrum of 29 (1x 1-5 M) is characterized by the presence of a dansyl absorption band at λ = 336 nm in THF/H 2 (9:1) (figure 4.13). The decrease in the absorption band was observed on addition of only Hg 2+ ions with isosbestic points at 268 and 35 nm (figure 4.13). This indicates that Hg 2+ ions are interacting with the receptor 29 and the changes in the absorption spectrum is attributed to the charge transfer interactions between receptor 29 and Hg 2+ ions µm Abs Hg equiv. Intensity µm Hg Wavelength Figure 4.13 UV-visible spectra of 29 (1 1-5 M) in the presence of Hg 2+ ions (8. equiv) in THF/H 2 (9:1, v/v) buffered with universal buffer, ph = Wavelength Figure 4.14 Fluorescence spectra of 29 (1 µm) in response to the presence of Hg 2+ ions (23 µm) in THF:H 2 (9:1,v/v) buffered with universal buffer; ph = 7.; λ = 338 nm. 15

4 In the fluorescence spectrum, compound 29 exhibits a characteristic emission band at 515 nm when excited at 338 nm (figure 4.14). The fluorescence is quenched upon addition of only Hg 2+ ions (23 µm) to the solution of compound 29 which is attributed to a photoinduced charge transfer mechanism (PCT) within 29 and Hg 2+ ions. Under the same conditions as used above for Hg 2+, we also tested the fluorescence response of 29 to other (I -I)I X Cu 2+ Pb 2+ Hg 2+ Zn 2+ Ni 2+ Cd 2+ FeIII 3+ Fe 2+ Ba Co 2+ Ba 2+ Ag + K + Li Na + Li + Metal ions Figure 4.15 Fluorescence intensity changes [(I - I)/I x 1] of 29 (1 µm) in THF:H 2 (9:1, v/v) upon addition of 23 µm of various metal perchlorates. The excitation wavelength was 338 nm. I is the fluorescence intensity at 515 nm of free host and I is the fluorescence intensity after adding metal ions. (I-I)Xconc (I -I)I X1 I/I Conc. of ions Hg Pb I Hg 2+ Pb 2+ Figure 4.16 Titration plot of 29 with Hg 2+, Pb 2+ and I -. Normalized fluorescence intensity of 29 vs ion conc Cu Pb Zn Cd FeII Co Na K 2+ Pb 2+ Zn 2+ Ni 2+ Cd 2+ Fe 3+ Fe 2+ Co 2+ Ba 2+ Ag + K + Na + Li + I - X = mole fraction of metal ion Figure 4.17 Job s plot of 3 toward Hg 2+ ions. Metal ions Figure 4.18 Fluorescence response of 29 (1 µm) to Hg 2+ (23 µm) over other selected metal (1 µm) ions. metal ions such as Cu 2+, Pb 2+, Zn 2+, Ni 2+, Cd 2+, Fe 3+, Fe 2+, Ba 2+, Co 2+, Ag + K +, Na + and Li +, no significant variation was observed with any other metal ion (figure 4.15). The fact that Pb 2+ ions and I - ions (vide infra) do not quench the fluorescence of 29 suggests that 151

5 the quenching of Hg 2+ ions is not associated with heavy atom effect (figure 4.16). The binding log β 1,2 constant of compound 29 with Hg 2+ ions for 1:2 stoichiometry (host: guest) was found to be = The method of continuous variation (Job s plot) 174 was also used to prove the 1:2 stoichiometry (figure 4.17). To test the practical applicability of compound 29 as a Hg 2+ selective fluorescence sensor, competitive experiments were carried out in the presence of Hg 2+ ions at 23 µm mixed with Cu 2+, Pb 2+, Zn 2+, Ni 2+, Cd 2+, Fe 3+, Fe 2+, Ba 2+, Co 2+, Ag + K +, Na + and Li + at 25 µm. No significant variation in the intensity was found by comparison with and without the other metal ions (figure 4.18). In addition to cation binding properties, we also investigated the binding behaviour of 29 toward different anions (F -, Cl -, Br -, I -, HS - 4, CH 3 C -, N - 3, H 2 P - 4 and CN - ) using tetrabutylammonium as counter cation in THF:H 2 (9:1, v/v). No fluorescence change was observed with any anion. To mimic trafficking mechanism, we performed fluorescence experiments of 29 in simultaneous presence of different anions and Hg 2+ ions. It was observed that among all the anions tested, the presence of Cl - /Br - /I - in solution of 29 inhibits the fluorescence quenching with 23 µm of Hg 2+ ions but on addition of 25 µm of Hg 2+ ions, the fluorescence finally gets quenched. This is attributed to the fact that initially Hg 2+ ions complex with Cl - /Br - /I - in solution and after the formation of HgX 2 (X = Cl - /Br - /I - ), the excess Hg 2+ complexes with 29 which results in quenching of fluorescence (figure 4.19). Similarly the addition of any of these three anions (Cl - /Br - /I - ) to the 29.Hg 2+ complex restored the fluorescence of 29 which is ascribed to the formation of HgX 2 (X = Cl - /Br - /I - ) 3 25 a b 2 29 Series1 Intensity c 29 Series2 + Cl Series3 Cl - + Hg Wavelngth Figure 4.19 Fluorescence emission spectra of (a) 29 (b) 29+ Cl - (c) 29+ Cl - + Hg 2+ in THF:H 2 (9:1,v/v) buffered with universal buffer, ph = 7; λ = 338 nm. 152

6 Intensity a b c 29 Series1 29+ Hg 2+ Series2 29+ Hg 2+ + Cl - Series Wavelength Figure 4.2 Fluorescence emission spectra of (a) 29 (b) 29 + Hg 2+ (c) 29 + Hg 2+ + Cl - in THF:H 2 (9:1,v/v) buffered with universal buffer; ph = 7.; λ = 338 nm. Intensity c b a Series1 29 Series2 29+ Hg 2+ Series3 29+ Hg 2+ + Cl - Wavelength Figure 4.21 Fluorescence emission spectra of (a) 29 (b) 29 + Hg 2+ (c) 29 + Hg 2+ + Cl - in THF:H 2 (9:1,v/v) buffered with universal buffer, ph = 1 ; λ = 338 nm ph = 2 Intensity b ph = 4 a Wavelength Figure 4.22 Fluorescence emission spectra of 29 at (a) ph value 2 (b) ph value 4 in THF:H 2 (9:1,v/v) buffered with universal buffer; λ = 338 nm. 153

7 with simultaneous decomplexation of 29.Hg 2+ complex, resulting in restoration of fluorescence of 29 (figure 4.2). These set of experiments with Hg 2+ and Cl - /Br - /I - were performed at variable ph values. At high ph values (ph > 4) results were similar (figure I p H Figure 4.23 Fluorescence Intensity plot of 29 at different ph in THF: H 2 (9:1). Dansyl aromatics protons B C Dansyl aromatics protons Dansyl aromatics protons A Figure H NMR of (A) 29 (B) equiv Hg 2+ ions (C) equiv Hg 2+ ions + 4. equiv. Cl - ions in CDCl 3 :CD 3 CN (8:2) shows the results at ph 1). At low ph values (ph < 4) the fluorescence intensity of the 29 remained quenched irrespective of any cation or anion in the system (figure 4.22) (variation of fluorescence intensity of 29 with ph is shown in figure 4.23). All these 154

8 results demonstrate that interaction between Hg 2+ ions and Cl - / Br - /I - is stronger than between Hg 2+ ions and 29. This was further confirmed from 1 H NMR spectrum. n addition of Cl - ions to the 29.Hg 2+ complex, original 1 H NMR spectrum of 29 was recovered after the changes caused by the addition of Hg 2+ ions (figure 4.24). To acquire molecular trafficking based on Boolean arithmetic, we envisaged Hg 2+, Cl - /Br - /I - and ph as inputs (ph values greater than 4 and less than 4 are taken as and 1 respectively), the table 4.1 is constructed based on binary logic. The input 1 (ph) is designated red signal, input 2 (Hg 2+ ) is designated yellow signal, input 3 (Cl - /Br - /I - ) is designated green signal (figure 4.25) and fluorescence output at 515 nm in on and off state substantiates with movement of traffic on and movement of traffic off respectively. At high ph values (ph values > 4), in the absence of any chemical input, 29 shows a characteristic band of dansyl at 515 nm, i.e. output is 1 (table 4.1). By operation of input 3 (Cl - /Br - /I - ions) Table 4.1- Boolean arithmetic operation on molecular system 29. Sr No. Input-1 ph Input-2 Hg 2+ Input-3 Fluorescence utput Cl - / Br - / I nm ph Hg 2+ Cl - /Br-/I - Figure 4.25 Assignment of traffic signal colour to different inputs B (added second ) 5 1A (added first ) 1A (added first) 1B (added second)

9 I Traffic Moves Input 1 Input 2 Input 3 INPUTS Figure 4.26 n addition of input 3 [Cl - /Br - /I - (green color)] to the solution of 29 the fluorescence emission remains N (traffic movement on); I is the fluorescence emission after addition of input 3 Cl - /Br - /I -. (I -I)/I X Traffic Stops Input 1 Input 2 Input 3 INPUTS Figure 4.28 n addition of input 2 [Hg 2+ ions (yellow color)] to the solution of 29 containing input 3 (Cl - /Br - /I - ), fluorescence emission gets quenched (traffic movement off); I is the fluorescence intensity at 515 nm of free host and I is the fluorescence emission after adding Hg 2+ ions. (I -I)/I X Input 1 Input 2 Input 3 Traffic Stops INPUTS Figure 4.27 n addition of input 2 [Hg 2+ ions (yellow color)] the fluorescence emission of 29 gets quenched (traffic movement off); I is the fluorescence emission at 515 nm of free host and I is the fluorescence emission after adding Hg 2+ ions. I Traffic Moves Input 1 Input 2 Input 3 INPUTS Figure 4.29 n addition of input 3 [Cl - /Br - /I - (green color)] to 29.Hg 2+ complex the fluorescence emission is restored and gets N (traffic movement on); I is the fluorescence emission after addition of input 3 Cl - /Br - /I -. (I-I)/I X Input 1 ph 4 Input 1 ph 3 Input 1 ph 2 Traffic Stops INPUTS Figure 4.3 n ph (red signal) the fluorescence intensity is quenched (traffic movement off); I is the fluorescence intensity at 515 nm of free host and I is the fluorescence emission after adding Hg 2+ ions. 156

10 to 29 at high ph values (ph values > 4), no change in fluorescence emission was observed i.e. output remains 1 (table 4.1). The input 3 corresponds to the green colour which directs the traffic to move and defines on state of fluorescence (figure 4.26). By operation of input 2 (Hg 2+ ) ions to 29 at high ph values (ph values > 4) the fluorescence emission at 515 nm is quenched i.e. output is (table 4.1). The input 2 corresponds to the yellow colour which directs the traffic to get prepared to stop and defines off state of fluorescence (figure 4.27). n sequential addition of both the inputs, i.e. when input 2 (Hg 2+ ions) follows input 3 (Cl - /Br - /I - ions) at high ph values (ph values > 4) the fluorescence of 29 gets quenched i.e. output is (table 4.1). Hence, input 2 is added afterwards which means finally yellow signal glows which directs the traffic to get prepared to stop and defines off state of fluorescence (figure 4.28). n the other hand, when addition of input 3 (Cl - /Br - /I - ) follows input 2, the fluorescence of 29 is restored i.e. INPUT 1 ph R-S Latch utput nm NR S-INPUT 3 Cl - /Br - /I - R- NPUT 2 Hg 2+ Figure 4.31 Integrated logic gate comprising R-S latch and NR gate with three inputs and one output combinations. output is 1 (table 4.1). Thus, input 3 is added afterwards which means that finally green signal glows which directs the traffic to move and defines on state of fluorescence (figure 4.29). At low ph value (ph value < 4), the fluorescence of 29 is in quenched state in absence or presence of any of the chemical input i.e. at low ph value (ph value < 4) output is (table 4.1). Thus, the ph value which corresponds to the red signal, directs that traffic must stop and defines the off state of fluorescence (figure 4.3). The combination of these intrinsic properties with selectivity of actions by different chemical inputs allows its implementation to design a complex integrated logic circuit with Q 157

11 incorporation of a R-S latch circuit and NR logic gate for traffic signal as shown in figure In electronics a latch is a kind of multivibrator an electronic circuit which can store one bit of information. In R-S latch, where S stands for set and R stands for reset is constructed from pair of cross coupled NR gates. The stored bit is present on the output marked Q. To conclude we have synthesized a chemosensor 29 which is a unique platform to mimic functions of a traffic signal. It represents a molecular device in which information is processed and transmitted at molecular level. Such systems are also helpful in understanding homeostatic mechanisms which exist to regulate the bio-available pools of metal ions within various compartments of cells. A R-S latch based circuit for the traffic signal is constructed which is an important component of memory devices. Conclusions To sum up, we have designed and synthesized chemosensors based on (thias of 1,3-alternate and paco conformation which behave as molecular devices. This type of work has been inspired in part by role played by metal ions in the transduction of nerve signals. Such artificial systems will help to understand these complexities of living systems in a better way. Moreover, the extension of this paradigm to artificial systems is a promising alternative to the problematic miniaturization of conventional electronic devices down to the nanoscale. The working principles of future information storage and elaboration devices might be similar to those governing neurotransmission rather than being surrogates of those ruling present computers. 158

12 Experimental General experimental procedures-: All the fluorescence spectra were recorded on SHIMADZU RF-531 PC spectrofluorometer. UV Spectra were recorded on SHIMADZU UV-245 PC spectrophotometer with a quartz cuvette (path length: 1 cm). IR spectra were recorded with SP3-3 IR spectrophotometer PYE UNICAM by using KBr as medium. Elemental analysis was done using Flash EA 1112 CHNS- analyzer of Thermo Electron Corporation. 1 H and 13 C NMR spectra were recorded on JEL-FT NMR-AL 3 MHz spectrophotometer using CDCl 3 as solvent and TMS as internal standards. Data are reported as follows: chemical shifts in ppm (δ), multiplicity (s = singlet, d = doublet, br = broad singlet, m = multiplet), coupling constants (Hz), integration, and interpretation. All spectrophotometric titration curves were fitted with SPECFIT\32 software. Synthesis Synthesis of Compound 27: To a solution of diamine 3 (.1 g,.79 mmol) in Bu t Bu t S S S S N Bu t Bu t N H 2 N H 27 N 2 1:1 mixture of chloroform and methanol (1 ml) was added solution of 2-hydroxy-5-nitrobenzaldehyde (.26 g,.158 mmol) 26 in methanol (5 ml). The mixture was stirred at room temperature for 24h. The solid compound precipitated which was recrystallized from CHCl 3 :MeH to give compound 27 in 84% yield (.11g); mp. 26 C; ν max (KBr pellet, cm -1 ) 163 cm -1 ; 1 H NMR (CDCl 3, 3 MHz); δ(ppm) = 1.28 [s, 18H, C(CH 3 ) 3 ], 1.34 [s, 18H, C(CH 3 ) 3 ], 3. [t, J = 7.5 Hz, 4H, NCH 2 ], 3.14 [t, J = 7.5 Hz, 4H, CH 2 ], 3.39 [br, 4H, CH 2 ], 3.59 [br, 4H, CH 2 ], 3.94 [t, J = 7.5 Hz, 4H, CH 2 ], δ 4.12 [t, J = 7.5 Hz, 4H, CH 2 ], 6.99 [d, J = 9 Hz, 2H, Ar-H], 7.36 [s, 4H, Ar-H], 7.39 [s, 4H, Ar-H], δ 8.17 [s, 2H, Ar-H], δ 8.2 [d, J=3., 2H, Ar-H], 8.26 [s, 2H, HC=N], [br, 2H, Ar-H]; 13 C NMR (CDCl 3, 75 MHz); δ(ppm) [C], 159

13 31.4 [(CH 3 ) 3 ], [(CH 3 ) 3 ], [C], [NCH 2 ], [CH 2 ], [CH 2 ], 7.12 [CH 2 ], 71.4 [CH 2 ], [CH 2 ], 1.55 [Ar-C], [Ar-C], [Ar- C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C]; FAB-MS m/z 1264 (M+ 1) + ; Anal. Calcd for C 66 H 78 N 4 S 4 13 : C, %; H, 6.17 %; N, 4.43 %; S, % Found: C, %; H, 6.47 %; N, 4.13 %; S, 1.2 %. Synthesis of Compound 28: To a solution of diamine 12 (.1 g,.84 mmol) in 1:1 Bu t Bu t S S S S N Bu t Bu t N H H 28 2 N N 2 mixture of chloroform and methanol (15 ml) was added solution of 2-hydroxy-5-nitrobenzaldehyde (.29 g,.168 mmol) 26 in methanol (5 ml). The mixture was stirred at room temperature for 24 h. The solid compound precipitated which was recrystallized from CHCl 3 :MeH to give compound 28 in 81 % yield (.11 g); mp. 24 C; ν max (KBr pellet, cm -1 ) 1625 cm -1 ; 1 H NMR (CDCl 3, 3 MHz); δ(ppm) = 1.28 [s, 18H, C(CH 3 ) 3 ], 1.32 [s, 18H, C(CH 3 ) 3 ],.64 [t, J = 7.5, 6H, CH 3 ], [m, 4H, CH 2 ], 3.45 [t, J = 7.5 Hz, 4H, NCH 2 ], 3.83 [t, J = 7.5 Hz, 4H, CH 2 ], 4.19 [t, J = 6 Hz, 4H, CH 2 ], 6.98 [d, J = 9. 2H, Ar-H], 7.41 [s, 4H, Ar-H], 7.35 [s, 4H, Ar-H], 8.18 [s, 2H, Ar-H], 8.2 [d, J = 3 Hz, 2H, Ar-H], 8.29 [s, 2H, HC=N], [br, 2H, Ar-H]; 13 C NMR (CDCl 3, 75 MHz); 1.7 [CH 2 ], [CH 3 ], [(CH 3 ) 3 ], [(CH 3 ) 3 ], [C], [C], [NCH 2 ], [CH 2 ], 7.39 [CH 2 ], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar-C], [Ar- C], [Ar-C], [Ar-C] ; FAB-MS m/z 1189 (M+ 1) + ; Anal. Calcd for C 64 H 76 N 4 S 4 1 : C, %; H, 6.39 %; N, 4.71 %; S, 1.77 %. Found: C, %; H, 6.42 %; N, 4.73 %; S, 1.52 %. 16

14 Synthesis of Compound 29: CH 3 N CH 3 S HN NH S H 3 C N H 3 C 29 Dansyl chloride 24 (82.2 mg,.31 mmol) was added drop wise to the stirred solution of diamine 2 (1 mg,.12 mmol) and Et 3 N (61 mg,.6 mmol) in 5ml dry dichloromethane. The reaction was stirred at room temperature for 6h. After the completion of reaction, the reaction mixture was washed with water. The organic layer was separated, dried over anhydrous sodium sulphate and distilled under reduced pressure to give a crude residue. The pure compound was obtained in 44% yield after column Chromatography on silica gel (ethyl acetate); mp. 19 ºC; IRν max (KBr pellet, cm -1 ) 331 cm -1 (N-H stretching); 1 H NMR (3 MHz, CDCl 3 ): δ (ppm) = (m, 6H, CH 3 ),.92 (s, 18H, C(CH 3 ) 3, 1.14 (s, 9H, C(CH 3 ) 3 ), 1.28 (s, 9H, C(CH 3 ) 3 ), (m, 4H, CH 2 ), 2.86 (s, 6H, NCH 3 ), 3.38 (d, J=18, 2H, Ar-CH 2 -Ar), (4H, m, NCH 2 ), (4H, m, Ar-CH 2 - Ar), (8H, m, CH 2 ), 3.9 (d, J=18, 2H, Ar-CH 2 -Ar ), 6.49 (2H, d, J = 2.4 Hz, Ar-H), 6.63 (2H, d, J = 2.1 Hz, Ar-H), 6.96 (2H, s, Ar-H), 7.6 (2H, s, Ar-H), 7.17 (d, J = 9 Hz, 4H, Ar-H), (m, 4H, Ar-H), (m, 2H, Ar-H), (m, 2H, ArH); 13 C NMR (75 MHz, CDCl 3 ): δ (ppm) = 1.75 [CH 3 ], δ 24.6 [CH 2 ], δ 3.95 [CH 3 ], δ [CH 3 ], δ [C], δ 32. [C], δ [CH 2 ], δ [CH 2 ], δ [CH 2 ], [Ar-C], δ 125. [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ 13.2 [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C], δ [Ar-C]; FAB-MS: m/z 1282 (M-2) + ; Anal cal. for C 78 H 1 N 4 S 2 8 ; C, %; H, 7.78 %; N, 4.35%, Found: C, 72.2%; H, 7.75 %; N, 4.57 %. Experimental procedure for analytical studies performed for compound 29. UV-vis titrations were performed on 1 x 1-5 M solution of ligand 29 in THF:H 2 (9:1) buffered with N-2-hydroxyethylpiperazine-N -2-ethane sulphonic acid (HEPES) buffer. Fluorescence titrations were performed on 1 x 1-6 M solution of ligand 25 in THF:H 2 161

15 (9:1). Typically, aliquots of freshly prepared M(Cl 4 ) 2 (M= Cu 2+, Hg 2+, Pb 2+, Zn 2+, Ni 2+, Cd 2+, Ag +, K +, Na +, Li + ) standard solutions (1-1 to 1-4 M) in THF:H 2 (9:1) were added and spectra of the samples were recorded. 162