Fluorescent and Electroactive Low Viscosity Tetrazines based Organic Liquids

Transcription

1 Supporting information Fluorescent and Electroactive Low Viscosity Tetrazines based Organic Liquids Clémence Allain, a Jonathan Piard, b Arnaud Brosseau, a Madeleine Han, b Julien Paquier, b Thomas Marchandier, b Médéric Lequeux, b Cédric Boissière, c and Pierre Audebert a * a. PPSM, ENS Cachan, CNRS, Université Paris-Saclay, 9423 Cachan, France. b. Département de Chimie, ENS Cachan, Université Paris-Saclay, 9423 Cachan, France c. Laboratoire Chimie de la Matière Condensée, Collège de France, UPMC, CNRS, 7 Paris, France Corresponding author: Pierre Audebert audebert@ppsm.ens-cachan.fr S-1

2 1. General procedures Synthesis All chemical reagents and solvents were purchased from commercial sources (Aldrich, Acros, SDS) and used as received. Spectroscopic grade solvents purchased from Aldrich were used for spectroscopic measurements. Analytical TLC was performed on Kieselgel F-24 precoated plates. Visualization was done with UV lamp. Flash chromatography was carried out with silica gel 6 (23-4 mesh) from SDS. 1 H and 13 C NMR spectra were recorded on a JEOL 4 MHz spectrometer, and chemical shifts (δ) were reported in ppm relative to TMS and referenced to the residual solvent. Coupling constants (J) are reported in Hz and refer to apparent peak multiplicities. Multiplicities are reported using the following abbreviations: s, singlet; d, doublet; t, triplet; q, quadruplet; m, multiplet. High-resolution mass spectra were performed at ICSN (Imagif platform, CNRS, Gif-sur- Yvette, France). 3,6-dichloro-s-tetrazine was prepared according to literature procedure 1. Electrochemical studies Electrochemical studies were performed using dichloromethane (SDS, anhydrous for analysis) as a solvent, with N-tetrabutylammonium hexafluorophosphate (Fluka, puriss.) as the supporting electrolyte. The substrate concentration was ca. 1 mm. A 2 mm platinum electrode was used as the working electrode, along with a Ag wire pseudo reference electrode and a Pt wire counter electrode. The cell was connected to a PAR 273A potentiostat. The reference electrode was checked vs. ferrocene as recommended by IUPAC. All solutions were degassed by argon bubbling prior to each experiment. Photophysical studies Thin films for photophysical measurements were prepared by casting a drop of neat liquid 1 or 2 between a microscope glass side and a cover glass. UV-Visible absorption spectra were recorded on an Agilent CARY spectrophotometer. Excitation and emission spectra were recorded on a Fluorolog-3 (Horiba Jobin-Yvon). A right-angle configuration was used for measurement in cuvettes. Optical density of the samples was checked to be less than.1 to avoid reabsorption artifacts. A front-face configuration was used for measurements on thin films. Quantum yields were measured using Rhodamine 6G in ethanol as a reference (φ=.9) for relative measurements in solution and using an integrating sphere (F-318 from Horiba Jobin-Yvon, internal diameter 12mm) for absolute measurements on neat films. Measurements on neat films were corrected from reabsorption as recommended in the literature. 2 We have performed absorption coefficient measurement on neat tetrazine 1, infiltrating the neat liquid by capillarity within a home-made 1 µm thick cell, realized by squeezing one aluminum commercial 1 µm thick foil between two glass slides. The thin layer cell was then used like a standard cell, measuring for tetrazine 1 an optical density of 4.1. For compound 1 in solution (long fluorescence lifetime), fluorescence decay curve was obtained using an Edinburgh instrument LP92 laser flash photolysis spectrometer, with an NdYAG laser (Surelite II-1 from Continuum) and a tripling crystal used to reach 3 nm excitation. The repetition rate is 1 Hz, and the pulse width is 4-6 ns (fwhm) at 3 nm. The Levenberg-Marquardt algorithm was used for non-linear least square fit (tail fit) as implemented in the L9 software (Edinburgh S-2

3 instrument). In order to estimate the quality of the fit, the weighted residuals were calculated. A fit was said appropriate for reduced χ 2 values between.8 and 1.2. For compound 2 in solution and compounds 1 and 2 in thin neat films, the fluorescence decay curves were obtained with the time-correlated single-photon-counting method using a Spectra-Physics titanium-sapphire Tsunami laser pumped by a Millennia Xs laser (82 MHz, repetition rate lowered to 4 MHz thanks to a pulse-picker, around fs pulse width, a doubling crystal is used to reach 49 nm excitation). Fluorescence photons are detected at 9, through a monochromator, with a Hamamatsu MCP photomultiplier R389U. The data were acquired using a SPC-63 TCSPC system (Becker & Hickl GmbH). The analysis is performed with the Globals software from Laboratory for Fluorescence Dynamics (LFD). DSC was performed on a Perkin Elmer Diamond instrument in alumina caps under a nitrogen flow at a scan rate of 2 C.min -1 from 3 C to -6 C. TGA were performed on a Perkin Elmer instrument in alumina caps under a nitrogen flow at a scan rate of 1 C.min -1 from 3 C to 3 C. 2. Synthetic procedures Compound 1 (3-chloro-6-((2-ethylhexyl)oxy)-1,2,4,-tetrazine) 2,4,6-collidine (29µL, 48mg, 4.mmol, 1. eq.) is added to a solution of 3,6-dichlorotetrazine (64mg, 4.mmol, 1.eq.) and 2-ethyl-1-hexanol (62µL, 21mg, 4.mmol, 1.eq) in dry dichloromethane (8mL). The resulting solution is stirred for 4 hours then concentrated and purified by column chromatography (eluent petroleum ether/dichloromethane 7/3) to yield 1 as a pink fluorescent liquid (742mg, 76% yield). 1 H NMR (4MHz, CDCl 3 ):.91 (t, J = 6.8Hz, 3H),.97 (t, J = 7.4 Hz, 3H), (m, 4H), (m, 4H), 1.89 (m, 1H), 4.6 (dd, J = 6. Hz, J = 2.4Hz, 2H) 13 C NMR (1MHz, CDCl 3 ): 167., 164.3, 73., 39., 3.3, 29., 23.7, 23.1, 14.2, 11.1 ESI-MS: 24.1 ([M+H + ], 1%), ([M+CH 3 CN+H + ], 7%), HRMS: calc. for C 1 H 18 N 4 OCl found (1.6 ppm) Compound 2 (3,6-bis((2-ethylhexyl)oxy)-1,2,4,-tetrazine) 2,4,6-collidine (29µL, 48mg, 4.mmol, 1. eq.) is added to a solution of 3,6-dichlorotetrazine (64mg, 4.mmol, 1.eq.) and 2-ethyl-1-hexanol (1.38mL, 1.1g, 8.8mmol, 2.2eq) in dichloromethane (8mL). The resulting solution is stirred for hours then 4-dimethylaminopyridine S-3

4 (1.74g, 8.8mmol, 2.2eq) is added in one portion. The reaction mixture is stirred overnight then concentrated and purified by column chromatography (eluent petroleum ether/dichloromethane from 8/2 to 7/3) to yield 422mg of 2 as a pink fluorescent liquid (422mg, 31% yield), contaminated by traces of monosubstituted 1 as revealed by TLC. To obtain a compound suitable for spectroscopic analyses, crude 2 is dissolved in dry acetonitrile (2mL), 7mg imidazole is added and the mixture is stirred at rt for 24h then concentrated. Column chromatography (eluent petroleum ether/ dichloromethane 1/1) allows an easy separation of pure 2 (378mg, 28% yield) from 6-((2- ethylhexyl)oxy)-3-(1-imidazolyl)-s-tetrazine derived from compound 1. 1 H NMR (4MHz, CDCl 3 ):.91 (t, J = 6.8Hz, 6H),.96 (t, J = 7.4 Hz, 6H), (m, 8H), (m, 8H), 1.86 (m, 2H), 4.4 (dd, J = 6. Hz, J = 2.4Hz, 4H) 13 C NMR (1MHz, CDCl 3 ): 166.4, 72.4, 39.1, 3.3, 29.1, 23.7, 23.1, 14.2, 11.1 ESI-MS: ([M+H + ], 1%), HRMS: calc. for C 18 H 3 N 4 O found (2.4 ppm) S-4

5 3. NMR spectra Figure S1: 1 H NMR spectrum of compound 1 Figure S2: 13 C NMR spectrum of compound 1 S-

6 Figure S3: 1 H NMR spectrum of compound 2 Figure S4: 13 C NMR spectrum of compound 2 S-6

7 4. Viscosity measurements 7 6 compound 2 y =.84x R² =.996 Pa 4 compound 1 3 y =.282x R² = Shear rate (1/s) Figure S: shear stress as a function of shear rate for compound 1 (blue) and 2 (red). S-7

8 . TGA analysis Figure S6: TGA analysis for compounds 1 (in blue) and 2 (in red). Boiling points of 167 C for compound 1 and 246 C for compound 2 are estimated by taking the intersection of the two tangent lines to the TGA curve. S-8

9 6. Fluorescence decays Volts/ Residuals Time/ns Figure S7: fluorescence lifetime of compound 1 in DCM (τ=18ns χ²=1.3). For compound 1 in neat film: a1=.27 τ1= 1.7ns ; a2=3.626 τ2=4.72ns ; χ²=1.8 Average lifetime is defined as <τ>= (a1τ1²+a2τ2²)/(a1τ1+a2τ2) Residues emission lamp time (ns) Figure S8: fluorescence lifetime of compound 1 in neat film. S-9

10 Residues emission lamp time (ns) Figure S9: fluorescence lifetime of compound 2 in DCM (τ=33.1ns χ²=1.9). Residues emission lamp time (ns) file 1 Figure S1: fluorescence lifetime of compound 2 in neat film (τ=29.7ns χ²=1.7). S-1

11 References 1 Gong, Y. H. ; Miomandre F.; Meallet-Renault R. ; Badre S. ; Galmiche L. ; Tang J. ; Audebert P. ; Clavier, G. Synthesis and Physical Chemistry of s-tetrazines: Which Ones are Fluorescent and Why?, Eur. J. Org. Chem., 29, Wurth C.; Lochmann C.; Spieles M.; Pauli J.; Hoffmann K.; Schuttrigkeit T.; Franzl T.; Resch-Genger U.; Evaluation of a Commercial Integrating Sphere Setup for the Determination of Absolute Photoluminescence Quantum Yields of Dilute Dye Solutions, Appl. Spectrosc., 21, 64, S-11