Electronic Supplementary Information 1. Reagents All the L-amino acids and L-glutathione (reduced form) were purchased from Sangon Biotch. o. (Shanghai, hina); Methyl orange, potassium tetrachloropalladate(ii), 3-aminopropionic acid, tris(hydroxymethyl)aminomethane, 3,3 -dimethylglutaric acid, and the derivatives of anilines used, were purchased from Acros Organics o., they were used without any further purification. All other reagents were of analytical grade or better and used without further purification. MOP was prepared by a modified method of the literature [8]. In a typical preparation, methyl orange ( mmol) and the stoichiometric amounts of potassium tetrachloropalladate(ii) ( mmol) were dissolved in a 30 ml dioxan/water (1:1) mixture and stirred at room temperature for a week. After the blue reaction mixture was concentrated to about 2 ml by rotary evaporation, the blue precipitate was collected and washed with ethanol and diethyl ether. The black solid was dried under vacuum to give 95 mg of MOP-2K (74% in yield). L-glutathione was received as reduced form as illustrated below. OH SH O O H 2 H H 2 H 2 H 2 H H O H H 2 OOH Structure of Glutathione 2. haracterization of MOP (1) Mass spectrum (Figure 4) of MOP The high-resolution mass spectrum of MOP (solvent: H 2 O) was measured on a Reflex III MALDI-TOF mass spectrometer (Bruker Dalton o., US; made in Germany). The main peak appearing at m/z 661 (1/2MOP+H 2 O) clearly confirmed the formation of MOP. MOP molecules were ruptured at the high-energy chloro-bridged Pd--Pd bonds during vaporization. (2) FT-IR (Figure 5) of MOP 1
The υ - band of aromatic rings at 1608 cm -1 of methyl orange was weakened and shifted to 1595 cm -1 in the IR spectrum of MOP. Besides, the dense and strong absorbance usually appearing at 1000-1200 cm -1,which is characteristic of azo bond, was greatly weakened in the IR spectrum of MOP. Both confirmed the formation of cyclometalated metal-azo complex. H 2 O H 3 H 3 2 K + - SO 3 Pd b a Pd Pd a OH 2 b Pd - SO 3 MOP-2K H H 3 3 H 3 H 3 H 2 O K + Pd b a Pd OH 2 H 2 O - SO 3 1/2 MOP-K + H 2 O vaporized (FW: 661.21) Figure 4. TOF-MS spectrum of MOP and its chemical illustration. (3) MR spectra of MOP ( 13 -MR, Figure 6; 1 H-MR, Figure 7) The MR spectra showed that the carbon and hydrogen atoms on the aromatic rings of methyl orange were placed in asymmetry after the palladium-azo cyclometallization. The 1 H-MR spectrum provided a more convicting proof for the formation of MOP-2K. 1 H-MR [(D 3 ) 2 SO](500 MHz): δ 3.17 (s, 6H, -H 3 ); 6.62(d, 1H, Ph-H); 7.20 (s, 1H, 2
Ph-H); 7.29 (d, 1H, Ph-H); 7.91 (s, 1H, Ph-H); 8.20 (d, 1H, Ph-H); 8.50 (d, 1H, Ph-H); 2.5 (DMSO); 3.5 (H 2 O); 3.39 (s, 2H, Pd-OH 2 ). 72 Methyl Orange 70 % transmittance 68 66 64 62 60 58 2345.74 1368.24 816.30 2926.50 574.26 1608.35 624.09 1200 1039.04 697.71 1120.74 3448.26 4000 3000 2000 1000 0 Wavenumbers (cm -1 ) 23 MOP 22 % Transmittance 21 20 19 18 17 1635.62 1595.17 1384.31 1174.66 628.78 1032.66 1121.40 16 15 3446.28 4000 3000 2000 1000 0 W avenumbers (cm -1 ) Figure 5. FT-IR spectra of methyl orange and MOP solids in KBr. 159.747 150.748 149.368 144.683 142.052 139.457 132.713 1351 122.319 121.347 119.428 1161 62.784 415 400 300 200 100 0 ppm (f1) 150 100 50 3
Figure 6. 13 -MR spectrum of MOP. 8.510 8.492 8.210 8.194 7.913 7.297 7.281 7.203 6.626 6.621 6.607 6.602 3.389 3.174 2.500 15000 10000 5000 0 6.00 2.00 2 0.96 6 1 0.99 0.94 9.0 ppm (f1) 8.0 7.0 6.0 5.0 4.0 3.0 2.0 2500 8.510 8.492 8.210 8.194 7.913 7.297 7.281 7.203 6.626 6.621 6.607 6.602 2000 1500 1000 500 0 2 0.96 6 1 0.99 0.94 ppm (t1) 8.50 8.00 7.50 7.00 6.50 Figure 7. 1 H-MR spectrum of MOP. (4) XPS spectra of MOP (Figure 8: a-total; b, Pd 3d ; c- 2d) The relative atom concentrations of,, O, S, and Pd was calculated from the XPS spectra of MOP: n : n : n O : n S : n : n Pd = 13:3:4:1:2:2 (Figure 9a). Only Pd(II), no Pd(III) 4
or Pd(IV) was found in MOP (Figure 9b). The valence number of all the atoms of MOP was 1 as displayed by the XPS spectrum (Figure 9c). (a) 30000 Pd 3d O 1s Relative Intensity 20000 10000 2p S 2p 1s 1s Pd 3p Pd MV K LMM Pd 4d 0 0 500 1000 Binding Energy (ev) (b) 3d 5/2 Pd 3d 5/2 = 336.8 ev; D = 5.26 ev. 3d 3/2 332 334 336 338 340 342 344 346 Binding Energy (ev) (c) 2d 3/2 2d 3/2 = 197.5 ev; D = 1.54 ev. 2d 1/2 194 195 196 197 198 199 200 201 202 203 Dinding Energy (ev) Figure 8. Total (a) and Pd 3d (b) and 2d (c) XPS spectra of dried MOP solid. 5
3. Effect of ph on the sensing response (Figure 9) 5 0 0.35 0.30 (a) ys ph 3.0 1 0.50 5 0 0.35 0.30 (b) Ala ph 6.0-9.0 5 0 0.15 ABS 5 0 0.15 0.10 5 0-5 300 400 500 600 700 800 0.10 5 0 ph 4.0-5.6-5 300 400 500 600 700 800 0.34 0.32 0.30 8 6 4 2 0 0.18 0.16 0.14 0.12 0.10 8 6 4 2 0 (c) Lys ph 3.0 5.6 6.0 1 0.55 0.50 5 0 0.35 0.30 5 0 0.15 0.10 5 0-5 (d) Tyr ph 3.0 1 300 400 500 600 700 800 300 400 500 600 700 800 Figure 9. Effect of ph on the sensing responses of MOP (0 10-5 M) towards different amino acids (2.00 10-4 M). Buffer: ph 3.0-5.8, 2 M potassium biphthalates; ph 6.0-8.0, 2 M sodium phosphates; ph 9.2-1, 2 M sodium carbonates. 4. Differential UV-vis spectral responses of MOP to L-α-amino acids with different tyes of side chain grous in aqueous solution (Figure 10). 6
1.4 1.2 (a) L-Glu 0.7 (b) L-Lys L-Asp 0.5 L-Arg 0.3 1.1 (c) 0.9 L-Hcy L-ys L-Met 0.9 0.7 (d) L-Ser L-Thr 0.7 0.5 0.3 0.5 0.3 0.1-0.1 0.1 1.4 1.2 (e) L-Trp L-Pro L-His 1.5 1.4 1.3 1.2 1.1 0.9 0.7 0.5 0.3 0.1 (f) L-Ala L-Val L-Leu -0.1 Figure 10. orption spectra of MOP sensing solutions (2.50 10-5 M; buffered at ph 7.4 with 2 M phosphate buffer) in the presence of L-amino acids (4.00 10-4 M) with different side chain groups: a) carboxyl-containing groups; b) basic groups; c) S-donor-containing groups; d) hydroxy-containing groups; e) heterocyclic rings; f) alkyl groups. orption spectra were recorded after 2-hour incubation in 50 o water bath. 5. Effect of coexisting ions on the speed of sensing reactions (Figure 11) 7
1.2 A B Asp His Met Tyr ys Lys Ala L-amino acids Figure 11. orbance values of MOP sensing solutions (2.00 10-5 M, buffered at ph 7.4 with 2 M phosphate) reacted with different amino acids (8.00 10-5 M ) in the absence (A) and presence (B) of the mixed coexisting anions (0.10 M a, 20 M a 2 SO 4, 30 M aho 3 and 2.0 10-3 M ao 3 ) after 1-hour incubation in a 50 o water. Wavelengths at which absorbance were measured: Asp, 607nm; His, 559nm, Met, 577nm; tyr, 600nm; ys, 550nm; Lys, 585nm; Ala, 603nm. 8