Surprisingly Bright Near-Infrared Luminescence and Short Radiative Lifetimes of

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1 Surprisingly Bright Near-Infrared Luminescence and Short Radiative Lifetimes of Ytterbium in Hetero-Binuclear Yb-Na Chelates Nail M. Shavaleev, Rosario Scopelliti, Frédéric Gumy, and Jean-Claude G. Bünzli École Polytechnique Fédérale de Lausanne, Laboratory of Lanthanide Supramolecular Chemistry, BCH 1405, CH-1015 Lausanne, Switzerland Supporting Information 25 pages Contents Part I. Synthesis Part II. 1 H NMR Spectra Part III. X-Ray Crystallography Part IV. Absorption Spectra Part V. Emission and Excitation Spectra

2 2 Part I. Synthesis Syntheses of 4-fluoro-2-aminophenol, 2-carboxaldehyde-8-benzyloxyquinoline, HL, HLCl and HLBr have been described previously (Shavaleev, N. M.; Scopelliti, R.; Gumy, F.; Bünzli, J.-C. G. Inorg. Chem. 2009, 48, 2908). Chemicals obtained from commercial suppliers were used without further purification. Chromatography was performed on a column with an i.d. of 30 mm using silica gel 60 for preparative chromatography (Fluka, catalogue number 60752). The progress of reactions and elution of products was followed on a TLC plate (silica gel 60 F 254 on aluminum sheets, Merck). Synthesis of 5-Fluoro-2-Aminophenol F OH F OH NO 2 NH 2 The reaction was performed under nitrogen. 5-Fluoro-2-nitrophenol (2 g, 12.7 mmol, Aldrich) was dissolved in a mixture of degassed ethanol (20 ml) and water (5 ml) followed by addition of solid Na 2 S 2 O 4 (9 g, 51.7 mmol, excess, Riedel-de-Haen, purified, min. 86%). The resulting suspension was stirred 8 hr at reflux (bath temp. 95 C). At first, reaction mixture attained orange color which disappeared after 1 hr of reflux to give pale yellow solution containing white solid. It was evaporated to remove ethanol; the resulting slurry was diluted with water (ph was adjusted to neutral with aqueous solution of NaHCO 3 and acetic acid) and extracted with ethyl acetate. Organic layer was washed with water and evaporated to yield the product as brown solid. Yield: g (9.77 mmol, 77%, C 6 H 6 FNO; MW ). 1 H NMR (DMSO-d 6 ): 9.40 (s, very br, 1H, OH), 6.52 (dd, J, J 6.0, 1H), 6.46 (dd, J 10.4, J 2.8, 1H), 6.35 (td, J 8.8, J 2.8, 1H), 4.4 (s, very br, 2H, NH 2 ). Synthesis of Ligand Precursors OBn N O HO + H 2 N R' R OBn N N OH DDQ OBn N N O R' R R' R

3 3 This is a two-step, one-pot reaction. In Step 1, a Schiff base was prepared from aldehyde and o-aminophenol in quantitative yield and was used without purification. In Step 2, a Schiff base was oxidized to benzoxazole using DDQ. Both reactions were performed under nitrogen using degassed (but not dried) solvents. Step 1. 2-Carboxaldehyde-8- benzyloxyquinoline was dissolved in hot ethanol (70-80 C, 30 ml) and o-aminophenol was added to this solution. The resulting dark yellow solution was stirred for 30 min at C and was rotor-evaporated. In order to drive the reaction to completion, the yellow solid (Schiff base) was re-suspended with sonication in ethanol (20 ml) and suspension was rotor-evaporated again. Step 2. Schiff base was dried under vacuum and dissolved in CH 2 Cl 2 (its volume depended on the solubility of Schiff base). Solid DDQ (small excess, Aldrich) was added in one portion to this solution. A dark colored suspension formed instantly which upon sonication for 1 hr at room temp.-40 C (strict temperature control was not required) turned into brown suspension. It was diluted with saturated aqueous NaHCO 3, evaporated to remove CH 2 Cl 2 and extracted with aqueous NaHCO 3 /water/ethyl acetate. Organic layer was washed with water, evaporated and passed through a column (6-8 g of silica, CH 2 Cl 2 ) to give crude product. The main point of chromatography was to remove dark red impurities which followed the target fraction (thorough purification at that stage was not required). Crude fraction was reduced in volume, diluted with ethanol (details are provided below) and CH 2 Cl 2 was rotorevaporated to give a suspension of the product in ethanol. It was allowed to settle at rt and was filtered; the solid was washed with small amount of ice-cold ethanol. The product was checked by TLC and 1 H NMR and, if required, was recrystallized again from CH 2 Cl 2 /ethanol. All products display bright blue luminescence in solution and in solid state. Further synthetic details are provided below. BnLMe. The reaction was performed with 2-carboxaldehyde-8- benzyloxyquinoline (600 mg, 2.28 mmol), 4-methyl-2- O N aminophenol (281 mg, 2.28 mmol, Aldrich) and DDQ (530 mg, OBn N 2.33 mmol). In Step 2, the volume of CH 2 Cl 2 was 40 ml. The product was recrystallized from 30 ml of ethanol. White solid: 447 mg (1.22 mmol, 54%; C 24 H 18 N 2 O 2 ; MW ). 1 H NMR (400 MHz, CDCl 3 ): 0

4 4 (d, J 8.8, 1H), 8.31 (d, J, 1H), 7-6 (m, 4H), 1-4 (m, 2H), 1 (t, J, 2H), 7.33 (t, J, 1H), 7.13 (dd, J 6.4, J 2.4, 1H), 5.52 (s, 2H), 2.52 (s, 3H), 1H (arom.) obscured by solvent peak. BnLMe*. The reaction was performed with 2- carboxaldehyde-8-benzyloxyquinoline (600 mg, 2.28 mmol), O N 5-methyl-2-aminophenol (281 mg, 2.28 mmol, Aldrich) and OBn N DDQ (530 mg, 2.33 mmol). In Step 1, Schiff base precipitates from hot ethanol solution upon stirring of reagents. In Step 2, the volume of CH 2 Cl 2 was 30 ml. The product was recrystallized twice each time using 20 ml of ethanol. Pale brown solid: 170 mg (0.46 mmol, 20%; C 24 H 18 N 2 O 2 ; MW ). 1 H NMR (400 MHz, CDCl 3 ): 9 (d, J 8.8, 1H), 8.31 (d, J, 1H), 7.72 (d, J, 1H), 1 (d, J, 2H), 1 (s, 1H), 9-3 (m, 2H), 1 (t, J, 2H), 7.33 (t, J, 1H), 2 (d, J, 1H), 7.14 (dd, J 6.4, J 2.4, 1H), 5.52 (s, 2H), 2.54 (s, 3H). BnLF. The reaction was performed with 2-carboxaldehyde-8- O benzyloxyquinoline (491 mg, 1.86 mmol), 4-fluoro-2- N OBn N aminophenol (237 mg, 1.86 mmol) and DDQ (435 mg, 1.92 mmol). In Step 2, the volume of CH 2 Cl 2 was 50 ml. The F product was recrystallized from 15 ml of ethanol. Pale pink solid: 486 mg (1.31 mmol, 71%; C 23 H 15 FN 2 O 2 ; MW ). 1 H NMR (400 MHz, CDCl 3 ): 8 (d, J 8.8, 1H), 8.33 (d, J 8.8, 1H), 5 (dd, J 8.8, J 4.0, 1H), 0 (d, J, 2H), 3 (dd, J, J 2.4, 1H), 1-3 (m, 2H), 1 (t, J, 2H), 7.33 (t, J, 1H), (m, 2H), 5.52 (s, 2H). N O BnLF*. The reaction was performed with 2-carboxaldehyde- 8-benzyloxyquinoline (800 mg, 3.04 mmol), 5-fluoro-2- OBn N F aminophenol (386 mg, 3.04 mmol) and DDQ (705 mg, 3.11 mmol). In Step 2, the volume of CH 2 Cl 2 was 35 ml. The product was recrystallized from 25 ml of ethanol. Pale pink solid: 891 mg (2.41 mmol, 79%; C 23 H 15 FN 2 O 2 ; MW ). 1 H NMR (400 MHz, CDCl 3 ): 6 (d, J, 1H), 8.32

5 5 (d, J 8.8, 1H), 7.79 (d, J 8.8, J 4.8, 1H), 0 (d, J, 2H), (m, 5H), 7.34 (t, J, 1H), (m, 2H), 5.52 (s, 2H). BnLCl*. The reaction was performed with 2- O carboxaldehyde-8-benzyloxyquinoline (600 mg, 2.28 N OBn N mmol), 2-amino-5-chlorophenol (327 mg, 2.28 mmol, Cl Acros) and DDQ (530 mg, 2.33 mmol). In Step 2, the volume of CH 2 Cl 2 was 30 ml. The product was recrystallized from 25 ml of ethanol. Pale pink solid: 621 mg (1.61 mmol, 70%; C 23 H 15 ClN 2 O 2 ; MW ). 1 H NMR (400 MHz, CDCl 3 ): 7 (d, J 8.8, 1H), 8.33 (d, J, 1H), 7.77 (d, J, 1H), 7.72 (d, J 1.6, 1H), 0 (d, J, 2H), (m, 5H), 7.34 (t, J, 1H), 7.15 (dd, J, J 1.6, 1H), 5.52 (s, 2H). Synthesis of Lutetium Complexes General procedure for the synthesis of the complexes can be found in the main text. Na[Lu(LMe) 4 ]. Orange solid: 53 mg (0.041 mmol, 76%) from HLMe (60 mg, mmol), NaOH (8.69 mg, mmol) and LuCl 3 6H 2 O (21.14 mg, mmol). Anal. Calcd for C 68 H 44 LuN 8 NaO 8 (MW ): C, 62.87; H, 3.41; N, Found: C, 63.04; H, 3.43; N, 5. Na[Lu(LF*) 4 ] 2H 2 O. Dark red solid: 57 mg (0.042 mmol, 81%) from HLF* (60 mg, mmol), NaOH (6 mg, mmol) and LuCl 3 6H 2 O (20.4 mg, mmol). Anal. Calcd for C 64 H 32 F 4 LuN 8 NaO 8 2H 2 O (MW ): C, 56.90; H, 2.69; N, 9. Found: C, 56.43; H, 2.46; N, H NMR (400 MHz, CD 2 Cl 2 ): ( M) 4 (d, J 8.8, 2H), 3 (d, J 8.8, 2H), 1 (dd, J 8.8, J 5.2, 2H), 9 (d, J, 2H), 0 (t, J, 2H), 6 (d, J, 2H), 6.98 (d, J, 2H), 6.90 (dd, J, J 2.0, 2H), (m, 6H), (m, 4H), 6.57 (d, J, 2H), 6.05 (td, J 9.6, J 1.6, 2H), 5.77 (d, J, 2H). Na[Lu(LMe*) 4 ]. Orange solid: 27 mg (0.021 mmol, 77%) from HLMe* (30 mg, mmol), NaOH (4.34 mg, mmol) and LuCl 3 6H 2 O (10.5 mg, mmol). Anal. Calcd for C 68 H 44 LuN 8 NaO 8 (MW ): C, 62.87; H, 3.41; N, Found: C, 63.23; H, 3.30; N, 7. 1 H NMR (400 MHz, CD 2 Cl 2 ): ( M) 2 (d, J 8.8, 2H), 0

6 6 (d, J, 2H), 8 (d, J, 2H), 7 (d, J, 2H), 9 (t, J, 2H), 5 (d, J 8.8, 2H), 6.96 (d, J, 2H), (m, 6H), 6.77 (d, br, J, 2H), 6.63 (t, J, 2H), 6.59 (d, J, 2H), 6.54 (br, 2H), 6.03 (d, J, 2H), 5.75 (d, J, 2H), 2.23 (s, 6H), 1.85 (s, 6H). The complex appears to be slightly hygroscopic; elemental analysis re-measured after 7 months of storage in closed vial under air in the dark matches the composition Na[Lu(LMe*) 4 ] H 2 O. Anal. Calcd for C 68 H 44 LuN 8 NaO 8 H 2 O (MW ): C, 62.01; H, 3.52; N, 1. Found: C, 62.24; H, 3.25; N, Synthesis of NaLF* The reaction was performed under air. Ligand HLF* (20 O N mg, mmol) was suspended in ethanol (10 ml), ONa N F followed by addition of NaOH (2.86 mg, 0.72 mmol) dissolved in 0.5 ml of water. The color of suspension immediately changed to red and it turned into a solution which was rotor-evaporated to dryness. In order to drive the reaction to completion, the solid was re-suspended in ethanol (10 ml) and rotor-evaporated again and finally dried under vacuum to give dark red solid which is insoluble in CH 2 Cl 2, slightly soluble in ethanol, and soluble in DMSO. No further purification was attempted; the yield was assumed to be quantitative. Anal. Calcd. for C 16 H 8 FN 2 NaO 2 (MW ): C, 63.58; H, 2.67; N, Found: C, 63.65; H, 2.93; N, H NMR (DMSO-d 6 ): 8.11 (d, J, 1H), 7.98 (d, J 8.8, 1H), 1 (dd, J 8.8, J 5.2, 1H), 6 (dd, J, J 2.0, 1H), 7.30 (td, J 10.0, J 2.4, 1H), 3 (t, J, 1H), 6.49 (d, J 6.8, 1H), 6.43 (d, J, 1H). Absorption spectrum of the salt could not be recorded because it was unstable in dilute DMSO solution ( M).

7 7 Part II. 1 H NMR Spectra Figure S1. 1 H NMR spectrum of 5-fluoro-2-aminophenol in DMSO-d 6.

8 Figure S2. 1 H NMR spectrum of precursor BnLMe in CDCl 3.

9 Figure S3. 1 H NMR spectrum of precursor BnLMe* in CDCl 3.

10 Figure S4. 1 H NMR spectrum of precursor BnLF in CDCl 3.

11 Figure S5. 1 H NMR spectrum of precursor BnLF* in CDCl 3.

12 Figure S6. 1 H NMR spectrum of precursor BnLCl* in CDCl 3.

13 Figure S7. 1 H NMR spectrum of ligand HLMe in DMSO-d 6.

14 Figure S8. 1 H NMR spectrum of ligand HLMe* in DMSO-d 6.

15 Figure S9. 1 H NMR spectrum of ligand HLF in DMSO-d 6.

16 Figure S10. 1 H NMR spectrum of ligand HLF* in DMSO-d 6.

17 Figure S11. 1 H NMR spectrum of ligand HLCl* in DMSO-d 6.

18 Figure S12. 1 H NMR spectrum of salt NaLF* in DMSO-d 6, 1 hr after preparation of solution; the spectrum recorded 23 hr later (not shown) indicated partial decomposition of the sample.

19 19 Part III. X-Ray Crystallography Table S1. Coordination Environment Around Sodium a bond lengths (Å) complex Na-µ-O Na-N(q) b Na-N(b) b Na-O(b) b Na[Yb(L) 4 ] 2.402(4) 2.548(4) (6) 2.458(6) (4) 2.521(4) Na[Yb(LCl) 4 ] 2.364(12) 2.387(12) 2.444(13) 2.473(14) 2.801(15) c 2.801(15) c 2.684(13) Na[Yb(LF*) 4 ] 2.336(4) 2.319(4) 2.599(4) 2.410(4) (4) (5) Na[Yb(LCl*) 4 ] 2.399(7) 2.509(7) (8) 2.400(8) (9) 2.590(9) Na[Yb(LMe*) 4 ] 2.432(5) 2.489(6) (6) 2.392(6) (6) 2.600(7) a Each line in the table corresponds to one and the same ligand in the complex (where appropriate). Numbers in bold are averaged data. b N(q), N(b) and O(b) are nitrogen or oxygen atoms of quinoline (q) or benzoxazole (b). c The benzoxazole ring is disordered; Na is coordinated either to N(b) or O(b) atoms.

20 20 Part IV. Absorption Spectra ε 10-3 / M -1 cm Wavelength / nm L LCl LBr Figure S13. Absorption spectra of complexes Na[Yb(L) 4 ] H2O ( M), Na[Yb(LCl) 4 ] (H 2 O) 0.5 ( M), and Na[Yb(LBr) 4 ] (H 2 O) 0.5 ( M) in CH 2 Cl 2. ε 10-3 / M -1 cm Wavelength / nm HLMe Yb Lu Figure S14. Absorption spectra of ligand HLMe ( M), and its complexes Na[Yb(LMe) 4 ] ( M), and Na[Lu(LMe) 4 ] ( M) in CH 2 Cl 2.

21 21 ε 10-3 / M -1 cm HLMe* Yb Lu Wavelength / nm Figure S15. Absorption spectra of ligand HLMe* ( M), and its complexes Na[Yb(LMe*) 4 ] ( M), and Na[Lu(LMe*) 4 ] ( M) in CH 2 Cl HLF Yb ε 10-3 / M -1 cm Wavelength / nm Figure S16. Absorption spectra of ligand HLF ( M), and its complex Na[Yb(LF) 4 ] ( M) in CH 2 Cl 2.

22 22 ε 10-3 / M -1 cm HLF* NaLF*, 0.5 hr NaLF*, 22 hr Wavelength / nm Figure S17. Absorption spectra in DMSO of ligand HLF* ( M), and its salt NaLF* ( M, at 0.5 hr and 22 hr after preparation of solution). The main maxima for HLF*, λ/nm (ε 10-3 /M -1 cm -1 ): 342 (1), 329 (16.8), 302 (3). The ILCT transition of NaLF* is at λ max = 523 nm; ε could not be calculated because the salt was unstable in dilute DMSO solution (see spectra at 0.5 hr and 22 hr); the decomposition was obvious within 0.5 hr of the preparation of solution. ε 10-3 / M -1 cm Wavelength / nm HLF* Yb Lu Figure S18. Absorption spectra of ligand HLF* ( M), and its complex Na[Yb(LF*) 4 ] H 2 O ( M), and Na[Lu(LF*) 4 ] 2H 2 O ( M) in CH 2 Cl 2.

23 23 ε 10-3 / M -1 cm Wavelength / nm Na[Yb(LCl*) 4 ] Figure S19. Absorption spectrum of complex Na[Yb(LCl*) 4 ] ( M) in CH 2 Cl LF* LMe* ε / M -1 cm Wavelength / nm Figure S20. Near-infrared spectra of f-f absorption transition for the complexes Na[Yb(LF*) 4 ] H 2 O ( M), and Na[Yb(LMe*) 4 ] ( M) in CH 2 Cl 2.

24 24 Part V. Emission and Excitation Spectra LCl* LF* Intensity / a.u. LMe LBr LCl LF L Wavelength / nm Figure S21. Luminescence spectra (correct, normalized) of Na[Yb(ligand) 4 ] nh 2 O in solid state (blue trace, emission slit nm) and in CH 2 Cl 2 solution (red trace, M, emission slit 1 nm) at room temperature under air.

25 25 Na[Yb(LMe*) 4 ] Intensity / a.u Time / µs Figure S22. Luminescence decay of complex Na[Yb(LMe*) 4 ] in solid state at room temperature (λ exc = 355 nm). Red trace is a fit to a single exponential decay function. solid solution Intensity / a.u Wavelength / nm Figure S23. Excitation spectra (corrected and normalized) of Na[Yb(LMe*) 4 ] in solid state and in solution in CH 2 Cl 2 ( M). The samples were optically thick (saturated signal) at wavelengths < nm.