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Tris(ferrocenylmethidene)sumanene: Synthesis, photophysical properties and application for the

efficient caesium cation recognition in water

Artur Kasprzaka*, Agata Kowalczykb, Agata Jagielskac, Barbara Wagnerc, Anna M. Nowickab, Hidehiro Sakuraid

a Faculty of Chemistry, Warsaw University of Technology, Noakowskiego Str. 3, 00-664 Warsaw, Polandb Faculty of Chemistry, University of Warsaw, Pasteura Str. 1, 02-093 Warsaw, Polandc Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Zwirki i Wigury Str. 101, PL-02-093 Warsaw, Polandd Division of Applied Chemistry Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

* corresponding author e-mail: akasprzak@ch.pw.edu.pl

Electronic Supplementary Information (ESI)Table of contents

S1. Experimental section........................................................................................S2S1.1 Materials and methods ..............................................................................S2S1.2 Synthesis of tris(ferrocenylmethidene)sumanene (3) ................................S2S1.3 Estimation of the fluorescence quantum yield (ΦF) of 3 ............................S3S1.4 Electorchemical characterization of 3........................................................S3S1.5 Preparation of the GC/3/nafion® recognition layer and Cs+ binding.........S3S1.6 SEM characterization of GC/3/nafion® recognition layer before and after

Cs+ binding ................................................................................................S4S2. NMR spectra ....................................................................................................S5S3. IR spectrum of 3...............................................................................................S7S4. HRMS data on 3 ..............................................................................................S8S5. UV-Vis data on interactions between 3 and Cs+ ..............................................S9S6. LA-ICP-MS data on interactions between 3 and Cs+, Na+, K+ and Ba2+ ........S11S7. Electrochemical data on 3..............................................................................S11S8. Recognition process of Cs+ with sensor prepared from DCM solution..........S11S9. References.....................................................................................................S16

Electronic Supplementary Material (ESI) for Dalton Transactions.This journal is © The Royal Society of Chemistry 2020

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S1. Experimental section

S1.1 Materials and methods

Chemical reagents were commercially purchased and purified according to the standard methods, if necessary. Air- and moisture-sensitive reactions were carried out using commercially available anhydrous solvents under an inert atmosphere of nitrogen. Following chemical reagents were used for the metal binding experiments: CsNO3, NaNO3, KNO3, Ba(NO3)2, tetrabutylammonium heksafluorophosphate (TBAHFP), tetrabutylammonium tetrafluoroborate (TBAB) and nafion®. The NMR experiments were carried out using a Varian VNMRS 500 MHz spectrometer (1H NMR at 500 MHz or 13C NMR at 125 MHz) equipped with a multinuclear z-gradient inverse probe head. Unless otherwise stated, the spectra were recorded at 25 °C. Standard 5 mm NMR tubes were used. 1H and 13C chemical shifts (δ) were reported in parts per million (ppm) relative to the solvent signal: CDCl3, δH (residual CHCl3) 7.26 ppm, δC 77.2 ppm. NMR spectra were analyzed with the MestReNova v12.0 software (Mestrelab Research S.L). Fourier-transform infrared (FT-IR) spectra were recorded in the Attenuated Total Reflectance (ATR) mode with the Thermo Nicolet Avatar 370 spectrometer with spectral resolution of 2 cm−1 (150 scans). The wavenumbers for the absorption bands ν were reported in cm−1. UV-Vis and PL measurements were performed with a Cytation 3 Cell Multi-Mode Reader (BioTek Instruments, Inc.) with the spectral resolution of 1 nm. For the UV-Vis and PL measurements, the wavelengths for the absorption or emission maxima λmax were reported in nm. TOF-HRMS (ESI) measurements were performed with a Q-Exactive ThermoScientific spectrometer. Melting points were determined on Standford Research Systems MPA 100 and were uncorrected. TLC and PTLC analyses were performed using Merck Silica gel 60 F254 plates.

Sumanene (1)[1] was synthesized according to the literature procedure.

S1.2 Synthesis of tris(ferrocenylmethidene)sumanene (3)

Fe

Fe

Fe

3

To a test tube, sumanene (1; 10.0 mg, 0.038 mmol, 100 mol%) and Bu4NBr (12.0 mg, 0,019 mmol, 50 mol%) were added. The reaction flask was purged with argon, and dry THF (0.3 mL) and 30% NaOHaq (2 mL; distilled water used for this reaction was degassed and bubbled with argon) were added. The reaction mixture was stirred for 5 minutes at 27 °C. Solid ferrocenecarboxaldyhyde (Fc-CHO; 41.0 mg, 0.19 mmol, 500

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mol%) was added and the mixture was stirred under atmosphere at 27 °C for 24 hours. Distilled water (6 mL) was added. Water layer was extracted with CH2Cl2 (3x15 mL). The organic layers were combined and washed with saturated NaHCO3 (3 mL), brine (3 mL), dried with MgSO4, filtered, and the solvent was removed in vacuum. The resultant residue was purified by PTLC (40% hex/CH2Cl2) to give tris(ferrocenylmethidene)sumanene (3; 28.5 mg, 88% yield) as the light-purple solid.

Mp: >300 °C; 1H NMR (CDCl3, 500 MHz, ppm), δH 7.68-7.67 (d, J = 7.9 Hz, 1H), 7.57 (s, 2H), 7.30 (s, 2H), 7.17-7.15 (m, 4H), 5.23-5.16 (m, 3H), 4.61-4.45 (m, 9H), 4.31-4.38 (m, 15H); 13C{1H} NMR (CDCl3, 125 MHz, ppm), δC 147.0, 146.9, 146.7, 146.6, 145.5, 145.3, 144.8, 144.7, 144.5, 143.0, 142.9, 127.6, 127.4, 127.0, 124.1 (2C), 123.9 (4C), 123.8, 120.4 (4C), 120.2 (2C), 71.7 (6C), 70.9, 70.7, 70.5, 70.0 (15C), 69.1 (6C); IR (ATR), v 3095, 2910, 2860, 1650, 1620, 1440, 1395, 1235, 1100, 1030, 990, 810, 700 cm-1; UV-Vis, λmax (PhMe) 345, 530 nm; HRMS (TOF): calcd. for C54H36Fe3 [M]+ = 852.0860, found: m/z 852.0850; Rf (40% hex/CH2Cl2) = 0.75.

S1.3 Estimation of the fluorescence quantum yield (ΦF) of 3

ΦF of 3 was given as the relative quantum yield in solution with cresyl violet perchlorate as a standard. The details of this methodology are presented elsewhere.[2] The excitation spectra were measured in PhMe solution (1∙10−6 M) under excitation wavelength of 530 nm. ΦF of 3 was calculated based on the following equation:

ΦF=Φ𝑠

∫𝐼(�̃�)𝑑�̃�

∫𝐼𝑠(�̃�)𝑑�̃�

1 ‒ 𝑒‒ 𝐴𝑠

1 ‒ 𝑒𝐴𝑛2

𝑛2𝑠

where is the fluorescence quantum yield of standard (cresyl violet perchlorate; Φ𝑠 Φ𝑠

= 0.56[3] ); and are the intensities of the sample and standard, respectively; 𝐼(�̃�) 𝐼𝑠(�̃�)A and As are the absorbances of the sample and standard, respectively, at the wavelength at which excitation of the compound has occurred; and n is the refractive index of toluene (1.4968).

S1.4 Electorchemical characterization of 3

Cyclic voltammetric (CV) experiments were carried out in the three electrode system using a an Autolab potentiostat, model PGSTAT 12. The disc glassy carbon electrode ( = 3 mm) was used as a working electrode, whereas the Ag/AgCl/3 M KCl and platinum plate were applied in the role of the reference and counter electrode, respectively. All experiments were carried out in dichloromethane (DCM) or dimethyl sulfoxide (DMSO) with addition of the excess of supporting electrolyte ( = 100): tetrabutylammonium hexafluorophosphate (TBAHFP). The concentration of 3 was 0.77 mM.

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S1.5 Preparation of the GC/3/nafion® recognition layer and Cs+ binding

The recognition layer (GC/3/nafion®) was formed at the glassy carbon (GC) electrode surface by applying the 10-L droplet of 0.77 mM solution of 3 in DMSO with the addition of 100 mM tetrabutylammonium hexafluorophosphate (TBAHFP) and 5% nafion® and allowing it to dry in desiccator.

The studies related to the highly specific interaction of 3 with the caesium cation (Cs+) were carried out in the aqueous solution. Caesium nitrate was used for this studies.

S1.6 SEM characterization of GC/3/nafion® recognition layer before and after Cs+ binding

The morphologies of the recognition layer before and after interaction with Cs+ were characterized by using field emission scanning electron microscopy (Merlin; Carl Zeiss Germany). In order to enhance the material contrast, the images obtained using InLens secondary electron detector and Energy Filtered Back Scattered electron (also in-lens) were mixed. All images were taken at low EHT (3 kV).

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S2. NMR spectra

Fig. S1. 1H NMR (CDCl3, 500 MHz) spectrum of 3.

Fig. S2. 13C NMR (CDCl3, 125 MHz) spectrum of 3.

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Fig. S3. Comparison of the 1H NMR (CDCl3, 500 MHz) spectrum of 3 (top) and 1H NMR spectrum measured after keeping this solution in air for 3 weeks (bottom).

Fig. S4. Comparison of the 1H NMR (CDCl3, 500 MHz) spectrum of 3 just after preparation of this compound (top) and 1H NMR spectrum measured after keeping keeping the solid 3 in air for 3 weeks (bottom).

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S3. IR spectrum of 3

100015002000250030003500

Tra

nsm

ittan

ce (a

rb. u

.)

Wavenumber (cm-1)

3095

2910 28

60 1650

1620

1440 1395

1235

810

700

1030

1100 99

0

Fig. S5. FT-IR (ATR) spectrum 3.

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S4. HRMS data on 3

Fig. S6. HRMS (TOF) spectrum of 3 (top: measured, bottom: calculated).

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S5. UV-Vis data on interactions between 3 and Cs+

350 400 450 500 550 600 650

x(3) = 1.00

Abso

rban

ce (a

rb. u

.)

wavelenght (nm)

x(3) = 0.25

x(3) = 0.50 x(3) = 0.67 x(3) = 0.75

x(Cs+) x(3)

x(3) = 0.86

Fig. S7. UV-Vis spectrum (DMF : H2O = 1:1 v/v) of 3 in the presence of the increasing amounts of Cs+, x(3) stands for the molar fraction of compound 3 in the sample, x(Cs+) stands for the molar fraction of Cs+ in the sample.

0,0 0,2 0,4 0,6 0,8 1,0

0,00

0,05

0,10

0,15

0,20

0,25

0,30

x(3)

(I-I

0)

x (3)

.

complex stoichometry (3:Cs+) = 2:1x(3) = 0.67

Fig. S8. Job’s plot constructed on the basis UV-Vis analyses data (Fig. S7).

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350 400 450 500 550 600 650

x([cation]) = 0.00

Abso

rban

ce (a

rb. u

.)

wavelenght (nm)

x(K+) = 0.75

x(Ba2+) = 0.75 x(Na+) = 0.75

Fig. S9. UV-Vis spectrum (DMF : H2O = 1:1 v/v) of 3 in the presence of the excess of Na+, K+ or Ba2+ ([cation]), x([cation]) stands for the molar fraction of [cation] in the sample.

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S6. LA-ICP-MS data on interactions between 3 and Cs+, Na+, K+ and Ba2+

An Inductively Coupled Plasma Mass Spectrometer (Perkin Elmer NexION 300) was used with a laser ablation system (LSX-200+, CETAC, USA) that combines a stable, environmentally sealed 213 nm UV laser (Nd-YAG, solid state). The LA set-up was operated at the constant 20 Hz repetition rate, energy of 5 mJ·puls-1 and spot size equal to 50 µm. The signal intensities were registered for 9 selected isotopes, using peak hopping mode: 13C, 23Na, 39K, 57Fe, 85Rb, 133Cs and 137Ba.

Transient signals were registered during the 4-line ablation over the area selected across the surface of the sample with blank registration for 20 s. For each selected isotope the registered blank values were subtracted from the signals recorded during the ablation of the samples. All experiments were performed using Ar as the carrier gas and standard ablation cell.

Table S1. Instrumental settings and data acquisition parameters used during LA-ICPMS measurements:

Laser ablation characteristics and settingsWavelength, nmPulse durationEnergy output, mJBeam diameter, µmRepetition rate, HzScan Rate, µm s-1

2136 ns

5502025

ICP-MS characteristics and settingsRF Power, WNeb. gas flow rate, L min-1

Plasma gas flow rate, L min-1

Auxiliary gas flow rate, L min-1

Carrier gas

13500.9

18.01.2Ar

ICP-MS data acquisition parametersScanning modeDwell time, msSweepsReadingsReplicatesPre-integration time, sIntegration time, s

Peak hopping101

36501

2060

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S7. Electrochemical data on 3

The regression equation describing the dependence Ip = f(v0.5) has the form: Ip = (114.021.20) v0.5 + (2.450.53); R2 = 0.9981. In the case of diffusion-controlled reversible or quasi-reversible electrochemical reaction, the peak current is described by Randles–Sevcik equation[4] :

(1)𝐼𝑝= 2.69 ∙ 105 ∙ 𝑛

32 ∙ 𝐷

12 ∙ 𝐴 ∙ 𝐶 ∗0 ∙ 𝑣

where: Ip is the peak current, n stands for the number of electrons exchanged during the electrode process, A is the surface area of the working electrode, D stands for the

diffusion coefficient of the electroactive species, is the concentration of the 𝐶 ∗0electroactive species and v is the scan rate of voltammograms. Thus, the diffusion coefficients for the studied 3 can be calculated from the slope of the plot of anodic peak current versus square root of the scan rate.

Experimental condition: DCM: potential window -0.5 1.1 V; potential step 0.0024 V; scan rate: 5, 10, 25,

50, 75, 100, 200, 300, 400, 500, 750 and 1000 mV·s-1; DMSO: potential window -0.6 1.15 V; potential step 0.0024 V; scan rate: 5, 10,

25, 50, 75, 100, 200, 300, 400, 500, 750 and 1000 mV·s-1.

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Fig. S10. Plots of 3 oxidation currents versus scan rate and square root of the scan rate in DCM (A) and DMSO (B). Experimental conditions: C3 = 0.77 mM, CTBAHFP = 100 mM, T = 21 °C.

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S8. Recognition process of Cs+ with sensor prepared from DCM solution

Fig. S11. (a) DPV voltammograms of GC/3-TBAHFP/nafion® in the presence of Cs+ ions in water with addition 100 mM TBAB. Layer components: DCM; C3 = 0.77 mM; CTBAHFP = 100 mM; T = 21 °C. (b) Plots of oxidation current and position of the oxidation peak of GC/3-TBAHFP/nafion® versus concentration of Cs+. Experimental conditions: modulation time: 0.002 s; interval time: 0.1 s; modulation amplitude: 0.04995 V; step potential: 0.00495 V.

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Fig. S12. DPV voltammograms of GC/3-TBAHFP/nafion® in the absence (dashed line) and presence of different interferent cations (solid line). Experimental conditions: modulation time: 0.002 s; interval time: 0.1 s; modulation amplitude: 0.04995 V; step potential: 0.00495 V. Recognition layer was formed form DCM solution.

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S9. References

[1] H. Sakurai, T. Daiko, T. Hirao. Science, 2003, 301, 1878.[2] M. Urban, K. Durka, P. Jankowski, J. Serwatowski, S. Lulinski. J. Org. Chem.,

2017, 82, 8234−8241.[3] IUPAC data, see: A. M. Brouwer, A. M. Pure Appl. Chem., 2011, 83, 2213[4] A. J. Bard, L. R. Faulkner, Electrochemical methods: Fundamentals and

Applications, 1980, Wiley, New York.