Rapidly sequence-controlled electrosynthesis of organometallic polymers

Single rich-stimuli-responsive organometallic polymers are considered to be the candidate for ultrahigh information storage and anti-counterfeiting security. However, their controllable synthesis has been an unsolved challenge. Here, we report the rapidly sequence-controlled electrosynthesis of organometallic polymers with exquisite insertion of multiple and distinct monomers. Electrosynthesis relies on the use of oxidative and reductive C–C couplings with the respective reaction time of 1 min. Single-monomer-precision propagation does not need protecting and deprotecting steps used in solid-phase synthesis, while enabling the uniform synthesis and sequence-defined possibilities monitored by both UV–vis spectra and cyclic voltammetry. Highly efficient electrosynthesis possessing potentially automated production can incorporate an amount of available metal and ligand species into a single organometallic polymer with complex architectures and functional versatility, which is proposed to have ultrahigh information storage and anti-counterfeiting security with low-cost coding and decoding processes at the single organometallic polymer level.


Supplementary Fig. 5 Electrosynthesis of self-assembled Ru II organometallic polymers. a, b
Illustrations of UV-vis absorbance and intensities as function of switching times during iterative synthesis. c, d Illustrations of CV and its intensities of redox peaks as function of switching times during iterative synthesis. Supplementary Fig. 6 Surface coverage. a Surface coverage of Os II organometallic polymers. b Surface coverage of Ru II organometallic polymers. These values were calculated by Γ = A(λ peak )/ε(λ peak )/1000 as function of switching times of oxidative and reductive reactions. Supplementary Fig. 7 Calculations of molecular lengths. Theoretical length of Ru II organometallic polymer with 10 units and the thicknesses of assembled films in SEM images. There is 4.4 nm between thicknesses of 10-mer and 12-mer, in good agreements with iterative synthesis in single monomer precise. Supplementary Fig. 8 AFM observations. AFM images of self-assembled Ru II organometallic polymers with different lengths, and height differences of organometallic polymers as solid film in AFM images. All images have similar roughness of morphology, and the height differences in all images are less than 2.0 nm, which is similar to the length of single monomer, in good agreement with iterative synthesis in single monomer precise. Supplementary Fig. 17 Photos for observations. a, b Photos of Ru II XY solutions before and after iterative synthesis. c Photo of bare ITO electrode without pre-assmebled molecule after electrolysis of Ru II XY at 1.0 V for 1h. The precipitation can be found after interative synthesis, indicating the oligomers become insoluble, and also implying that the single organometallic polymer with 10 units will be hard to be soluble. After electrolysis of Ru II XY at 1.0 V for 1h, the dark red film was found on ITO surface (c) and directly dissolved for measurements of NMR and Mass spectra as shown in Supplementary Fig. 18,19, demonstrating that this film was mainly composed of dimer with bad solubility. We have tried to get the isolated products from excess supporting electrolytes mostly via silica gel chromatography. This experiment failed because the dimer with counterion is eluted out along with Bu 4 NH 4 ClO 4 .
Supplementary Fig. 18 Structural characterization. 1 H NMR spectra of Ru Ⅱ XY and its dimer in CD 3 CN obtained by electrolysis in Supplementary Fig. 17c without any purification. Regarding the impurity feature, the unreactive monomer could possibly and S12 physically co-deposite into film during continuously electrolysis of 1h. We did not find the clear evidence that the carbazole coupling at 1.0 V is forming regioisomers for these monomers or other monomers, which we were and are studying on. Herein, this possibility should be limited in iterative electrosynthesis because of steric hindrance within organometallic polymers. Additionally, it is well-known that the purity will decrease in case of large scale synthesis. Compared to synthesis on 1.0 cm 2 substrate (10 -10 mol and 10 -7 g for each step in Supplementary Fig. 4), the experiment in Supplementary Fig. 18 (c.a. 2 mg) was enlarged in over 10000 times. Iterative synthesis in manuscript took place at a distance of 20 nm from electrode surface, while this electrodeposition fabricated the film with probable thickness of >10 μm. Therefore, the coupling ratio in Supplementary Fig. 18 and the coupling ratio of each step for iterative synthesis of organometallic polymers could not be simply compared. The relationship should be an clear curve even if there was significant decrease in total conversion (c.a. 10% after 10th coupling). The relationship between units and steps in Fig. 2 and Supplementary Fig. 6 shows excellent linear, demonstrating that there is no significant change in conversion yield. Fig. 19 Structural characterization. MALDI-TOF mass spectrum of Ru II XY dimer directly obtained by electrolysis in Supplementary Fig. 17c without any purification. S13 Supplementary Fig. 20 Photo of sample for Mass spectra. Organometallic polymers of Os and Ru at ITO coated glass (2.5 cm × 7.5 cm) for measurements of MALDI-TOF mass spectra. In the experiment, DCTB (20 mg/mL) was used as matrix and spotted on the polymers coated ITO (2.5 cm × 2.0 cm). The calibration was carried out using PMMA (polymethyl methacrylate). Both reflection and linear modes were used to obtain signals. Fe core was not incorporated into organometallic polymers because its weak coordination 5 is unstable compared to Os and Ru cores. Herein, we have prepared 3 types of Ru and Os organometallic polymers (1111122222, 1122112212, 1212121212, 1 = Ru, 2 = Os). Ru coordination is more stable than Os coordination in Supplementary Fig.  21-23. Mass does not reach the theoretical value probably due to weak coordination, which could lead to more small fragments and also result in deviation in Ru and Os alternative organometallic polymers, while there is extremely tiny polymers on ITO substrate. Therefore, the alternative Ru and Os organometallic polymers are not well-recognized in main peaks of their mass spectra ( Supplementary Fig. 24-28). and 18% changes for surface confined organometallic polymers and random polymerization film, respectively, implying that this strategy has superior advantage for fabrication of ultrathin and uniform film in contrast to conventional electropolymerization. Generally, the potential drop on different positions on surface of electrode usually leads to thickness difference for conventional electropolymerization. In this paper, single-monomer-precise is not really affected by potential drop. Additionally, we want to note that the intensity changes in both absorption spectra should be tinily affected by quality of ITO glasses.

General Characterizations
1 H NMR spectra were obtained at room temperature using a Bruker Avance 300 NMR spectrometer. Electronic absorption spectra were recorded on a JASCO V-770 spectrophotometer at room temperature. Photoluminescence spectra were recorded using Perkin Elmer LS50B Luminescence Spectrometer. AFM study was carried out using a commercial AFM unit (SPA 300HV with a SPI 3800N Probe Station, Seiko Instruments Inc., Japan). All AFM images were taken in dynamic force mode (DFM, i.e., tapping mode) at optimal force. SEM images were obtained using a FEL XL30ESEM-FEG scanning electron microscope with acceleration voltage of 10-20 keV. The atomic structure of the Os II and Ru II alternative organometallic polymers was characterized using

Synthesis of Ru II XY
A two-step coordination protocol was applied to synthesize asymmetric Ru II XY type of

Synthesis of Os II XY
Os II XY was synthesized by stepwise coordinaiton of (NH 4 ) 2 OsCl 6 (43.9 mg, 0.  Then saturated NH 4 PF 6 aq. was added to complete the counterion exchange, the precipitation was filtered, washed and dried to yield Fe II XY as purple powder (48.6 mg, 45.0%). Then saturated NH 4 PF 6 aq. was added to complete the counterion exchange, and the precipitation was filtered, washed and dried to yield Co II XY as pale orange powder (77.0 mg, 30.2%).

Synthesis of Os Ⅱ XP
(NH 4 ) 2 OsCl 6 (43.9 mg, 0.100 mM) and L2 (47.4 mg, 0.100 mM) dissolving in 10 mL ethylene glycol were loaded into a round bottom flask equipped with a condenser, the mixture was heated up to reflux and allowed to react at that temperature for 12 h under argon atmosphere. After cooling down, L3 (36.9 mg, 0.100 mM) dissolving in 5.0 mL ethylene glycol was added, and the mixture was left to react in reflux for another 12 h under argon atmosphere. Complex Os II L2L3 was isolated by adding saturated NH 4 PF 6 S43 aq., and resultant precipitation was collected by filtering, washing and drying steps.
Complex Os II L2L3 (127.0 mg, 0.0958 mM) dissolving in 10.0 mL anhydrous CH 3 CN was loaded into a dried three-neck round bottom flask, which was equipped with a condenser. The system was then sealed, and trimethylbromosilane (0.100 mL, 0.758 mM) was introduced via a syringe under argon atmosphere. This mixture was left to react at 70 o C for 48 h. After cooling down, 1.0 mL methanol was injected into the mixture via a syringe, stirred for another 1 h to complete the alcoholysis. The solvent was evaporated under reduced pressure, then the crude product was purified by silica gel chromatography with an eluent of CH 3 CN/CH 3 OH/saturated KNO 3 aq. (50:50:1, volume ratio). The product was further purified by adding saturated NH 4 PF 6 aq. into its methanol solution, the resultant precipitation was filtered, washed with diethyl ether and dried to yield Os II XP as a dark brown powder (60.8 mg, 50.1%). 1

Synthesis of Os Ⅱ X 2
(NH 4 ) 2 OsCl 6 (43.9 mg, 0.100 mM) and L2 (94.8 mg, 0.200 mM) dissolving in 10 mL ethylene glycol were loaded into a round bottom flask equipped with a condenser, and the mixture was heated up to reflux and allowed to react at that temperature for 12 h under argon atmosphere. The solvent was evaporated under reduced pressure. The crude product was purified by silica gel chromatography with an eluent of CH 3 CN/toluene (1:1, volume ratio). The product was further purified by adding saturated NH 4 PF 6 aq. into its methanol solution. The resultant precipitation was filtered, washed with diethyl ether and dried to yield Os II X 2 as a dark brown powder (45.1 mg, 63.1%). 1