Acid/base-regulated reversible electron transfer disproportionation of N–N linked bicarbazole and biacridine derivatives

New acid/base-responsive organic compounds were discovered to undergo electron transfer disproportionation.


Solid State NMR Analysis
In order to confirm the state of solid BC, the solid state NMR spectra of ground crystals of BC were measured.  10 . Spectral analyses were performed using SPARKY3.114 11 . The summary of 1 H-and 13 C-isotropic chemical shifts and the spectra are shown in Table S1, Fig. S1-S4. N N S20

X-ray Crystallographic Analysis
The single crystal of BC was obtained by the slow vaporization from the hexane solution. The single crystal of 8 was obtained by the slow evaporation from the CHCl 3 /hexane solution. The analyses were performed on a Rigaku VariMax RAPID system (Mo-Κα, λ = 0.71073 Å, T = 123 K, 2θmax = 55.0°). The single crystal of TBA was obtained from CH 2 Cl 2 /C 2 H 5 OH. The analysis was performed on a Rigaku Saturn CCD system

S21
A sample solution of BC, TBA, or 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (TEMPOL)(1.00 mM) in in a ESR tube was degassed by the freeze-pump-thaw cycles three times, and the ESR tube was sealed. ESR spectrum at different temperature was recorded in a same setting of parameters. The IT values (I=double integral of ESR signal, T=temperature) of BC and TBA were plotted versus temperature. They were slightly decreased by increasing the temperature (Fig. 8a, S6b). To confirm that this slight decrease comes from the machinery error, the temperature dependence of IT value of ESR signal of TEMPOL (S=1/2) was measured, showing the similar decrease of IT values by increasing the temperature (Fig. S6c). Thus, we concluded that the IT values are constant and the spin state is doublet.

UV-Vis-NIR Spectral Experiments
UV-Vis-NIR measurements were conducted with 1.0 cm quartz cell at 20 °C under air, unless otherwise noted.

UV-Vis-NIR spectral experiment to show the reaction of BC and acid under equilibrium (Fig. S7a)
UV-Vis-NIR spectrum of BC (1.00 mM) with 2000 mol% CF 3 CO 2 H in CH 2 Cl 2 with 1 mm cell was measured (Fig. S7a, orange). The solvent and excess CF 3 CO 2 H of the solution was evaporated in vacuo. The residue was dissolved in CH 2 Cl 2 (1.00 mM) and the spectrum was measured again after 5 h. The comparison of these two spectra indicated the shift of equilibrium reaction under acidic condition depending on the amount of acid. atmosphere. The absorption intensity at 635 nm associated with BC •+ was 0.76 with 150 to 300 mol% NOPF 6

S22
and was decreased according to the increase of oxidant more than 300 mol%. This result indicated that BC •+ was quantitatively generated with 150~300 mol% NOPF 6 and BC •+ was further oxidized to BC 2+ with more than 300 mol% NOPF 6 . The spectrum with 150 mol% NOPF 6 is shown in Fig. 9b. The molar absorption coefficient ε 635 =1.5×10 4 L mol -1 cm -1 of BC •+ at 635 nm was obtained from the spectrum with 150 mol% NOPF 6 . The value was used for the kinetic experiments. The absorption associated with TBA 2+ was not admitted in the spectra with both oxidants. These results demonstrate that TBA •+ was quantitatively generated with 1000 mol% I 2 or 500 mol% DDQ, and TBA •+ was not further oxidized to TBA 2+ with more amount of these oxidants. The absorbance at 821 nm with 1000 mol% I 2 or 500 mol% DDQ was 0.78 in both cases, which is regarded as 100% TBA •+ , since both I 2 and DDQ do not have the absorption at 821 nm. The value was used for the determination of the yield of TBA •+ generated under acidification of TBA. The spectra with 1000 mol% I 2 and 500 mol% DDQ are shown in Fig. 16i. 7.3.4. UV-Vis-NIR spectra of TBA •+ by chemical oxidation of TBA with NOPF 6 (Fig. 16i) To a solution of TBA (1.00 mM) in CH 2 Cl 2 (0.30 mL) under N 2 atmosphere in a glove box was added 100, 200, 500, 1000, or 2000 mol% of NOPF 6 using the 300 mM solution in acetonitrile at ambient temperature, respectively. The solution was diluted by CH 2 Cl 2 to be 3.0 mL with 0.100 mM based on added TBA and left over for 1 day at ambient temperature under N 2 atmosphere in a glove box before the spectral measurement. The sample solution was transferred into a 1 cm quartz cell in a grove box and the measurement was conducted under S23 N 2 atmosphere. The absorption intensity at 824 nm associated with TBA •+ was 0.79 with 100 mol% NOPF 6 and was decreased according to the increase of oxidant more than 200 mol%. The absorption associated with TBA 2+ was clearly admitted with 2000 mol% NOPF 6 . This result indicated that TBA •+ was quantitatively generated with 100~200 mol% NOPF 6 and TBA •+ was further oxidized to TBA 2+ with more than 200 mol% NOPF 6 . The spectrum with 100 mol% NOPF 6 is shown in Fig. 16i. The molar absorption coefficient ε 822 =7.9×10 3 L mol -1 cm -1 of TBA •+ at 822 nm was obtained from the spectrum with 100 mol% NOPF 6 . The value was used for the kinetic experiments.

Determination of the ratio of BC and CF 3 CO 2 H by Job's continuous variation plot (Fig. 13)
The solutions of the mixture of BC and CF 3 CO 2 H were prepared in the ratio of 1:0  (Fig. 17, S8h) The solutions of TBA and CF 3 CO 2 H in the molar ratio of 1:0, 2:1, 1:1, 1:1.  Fig. 17 for clarity.

UV-Vis-NIR spectrum of TBA with CF 3 CO 2 H under N 2 atmosphere. (Fig. S8a)
CH 2 Cl 2 with CaH 2 was degassed by the freeze-pump-thaw cycles three times and distilled by the valve-to-valve method. NEt 3 and CF 3 CO 2 H were degassed by the freeze-pump-thaw cycles three times. Preparation of a solution of TBA (0.100 mM) in CH 2 Cl 2 with 2000 mol% of CF 3 CO 2 H was performed in a grove box with 2-5 ppm O 2 level during experiment. The sample solution was transferred into a 1 cm quartz cell in a grove box and the measurement was conducted under N 2 atmosphere. (Fig.   18a, Table S2) S24 Sample solution of TBA (0.100 mM, CH 2 Cl 2 , 3.0 mL) was transferred into a 1 cm quartz cell equipped with magnetic stirrer bar and the spectrum under neutral condition was measured. CF 3 CO 2 H (0.5 µL, 6 µmol, 2000 mol%) was then added to the neutral TBA solution at ambient temperature. After stirring for 30 min at that temperature, the spectrum under acidic condition was measured to confirm the conversion. Then, the acidic solution was neutralized by addition of NEt 3 (1.3 µL, 9 µmol, 3000 mol%) at ambient temperature, and the spectrum was measured after 10 min. Same experiments were conducted 5 times. The recovery yield of TBA was calculated from the absorption intensities at 412 nm (Table S2), and the average was determined to be 98.6% yield with the five experiments.

UV-Vis-NIR spectral study on the reversibility of the reaction of TBA by repeating the addition of
acid/base treatment (Fig. 18b, c, d) Sample solution of TBA (0.100 mM, CH 2 Cl 2 , 3.0 mL) with 1000 mol% NEt 3 was transferred into a 1 cm quartz cell equipped with magnetic stirrer bar and the spectrum was measured. In each cycle, the spectra were measured at 10-60 min after addition of CF 3  The spectra were shown in Fig. 18b and the absorbance at 412 and 822 nm were plotted in Fig. 18c, d.

Determination of quantum yield of BC
Quantum yield of the solution of BC (4.50×10 -5 M) in CH 2 Cl 2 was determined to be 0.6875 by the absolute S25 method using a JASCO FP6500 spectrometer equipped with integrating sphere JASCO ILF-533 using 1 mm cell.
For reference, quantum yield of quinine sulfate (5.00×10 -3 M) in 1 M aq. H 2 SO 4 was determined by the same method to be 0.5644, which was comparable to the reported value 0.546. 12

Determination of quantum yield of TBA
The quantum yield of TBA was determined by the compared method [equation (1) (Table S3). For the fluorescence spectral measurements, these solutions were diluted by 1% to be 1.00 µM solutions in order to prevent reabsorption of fluorescence. The fluorescence spectra were measured under air with 1 cm quartz cell at 20 °C, giving F TBA =8.2 × 10 and F DPA =1.7 × 10 3 , respectively (Table S3). From these values and equation (2), the quantum yield of TBA is determined to be 17% yield.

Determination of the kinetic constant and activation barrier energy of disproportionation of BC
From the experiments on determination of reaction order, the reaction rate equation is expressed to be equation In the condition using excess amount of BC or CF 3 CO 2 H, a-3/2x or b-3/2x is regarded to be the initial concentrations a or b. Thus, the equation (3) becomes (4) or (5).
The definite integral of the equations give the equation (6) and (7).

Determination of reaction orders of the disproportionation of TBA
9.4.1. Reaction order in TBA (Fig. 20a, b of TBA •+ and the absorption change (cm -1 s -1 ) between 290~510 s after well-mixing of the solution, the generation rate (mol L -1 s -1 ) of TBA •+ at each concentration was determined (Table S6). In the condition using constant excess amount of CF 3 CO 2 H, lnk + ln[TFA] 0 is regarded to be constant in the equation (2). Thus, the reaction order n of TBA was determined from the slope of the plot of lnv 0 against ln[TBA] 0 to be 1.2, which means 1st order to TBA.  for more than 600 s at -60 °C. Using the molar absorption coefficient ε 822 =7.9×10 3 L mol -1 cm -1 of TBA •+ and the absorption change (cm -1 s -1 ) between 290~510 s after well-mixing of the solution, the generation rate (mol L -1 s -1 ) of TBA •+ at each concentration was determined (Table S7). In the condition using constant excess amount of CF 3 CO 2 H, lnk + ln[TBA] 0 is regarded to be constant in the equation (2). Thus, the reaction order m of TFA was determined from the slope of the plot of lnv 0 against ln[TFA] 0 to be 2.0, which means 2nd order to TFA.
The definite integral of equation (9) gives equation (10); where a, b, and C are the initial concentrations of TBA and CF 3 CO 2 H, and intercept, respectively.  Table S8).
The Eyring plot in equation (11) gave the enthalpy of activation ΔH ‡ and the entropy of activation ΔS ‡ (Table   S8).

Theoretical Calculation
All the theoretical calculations were performed at UωB97XD    LGCPMAS was set to 60 µs to correlate 13 C and attached 1 H. Isotropic chemical shifts of 1 H attached to 13 C were obtained for individual sites as summarized in Table S1. Asterisks indicate spinning side bands of aromatic backbone signals.       (Fig. S7d) and that of BC •+ (Fig. 9b) and the spectrum (red) of BCH 3 + (Fig. S7e). The subtracted spectrum was obtained from the equation [ (Fig. S7d) - (Fig. 9b)

No. 1
The absorption after 20 sec were adjusted to zero.