Photochromic coenzyme Q derivatives: switching redox potentials with light

A photochromic coenzyme Q derivative could be activated through irradiation with orange light and initiate redox reactions with Hantzsch ester and on isolated mitochondria.


General preliminary remarks
CV measurements and spectroelectrochemical studies were carried out under argon atmosphere. All measurements were performed in MeCN containing 0.1 M tertra n butylammonium tertra fluoroborate using ferrocene/ferrocenium (Fc/Fc+) as an internal reference. A glassy carbon electrode (working electrode), platinum wire counter electrode, and Ag quasi-reference electrode were employed for CV measurements. The scan rate was 50 mV/s, a step potential of 5.0 mV was applied.
Spectroelectrochemical studies were carried out in an optically transparent thin layer electrochemical cell (OTTLE). The scan rate was 2 mV/s, a step potential of 0.02 V was applied. IR spectroscopy was done using an Agilent Cary 630 FTIR. Melting points were recorded on a Stanford Research Systems OptiMelt (MPA100).
Steady state absorption measurements were carried out on a Varian Cary Bio 50 UV/Vis spectrometer.
The combined organic layers were dried over MgSO 4 and the solvent was removed in vacuo. The crude product was purified through MPLC (PE : EtOAc = 0 to 20%). The pure product was isolated as brown solid.  3 (183 mg, 0.16 mmol) was added. The vial was sealed and the reaction mixture was refluxed for 16h. The reaction mixture was cooled to room temperature and the solvent was removed in vacuo. The residue was dissolved in EtOAc (10 mL), a saturated KF solution (aq, 10 mL) was added and the mixture stirred for one hour. The reaction mixture was filtered to remove precipitated Bu 3 SnF and the organic layer was isolated. The aqueous layer was extracted with EtOAc (2 x 20 mL). The organic layers were combined and dried over Na 2 SO 4 . The volatiles were removed in vacuo and the crude product was purified through MPLC (EA (0-55%) in PE) to give a red solid.

Cyclic Voltammery and Spectroelectrochemical Studies (further material)
Molecules included in the study:  Adapting a published strategy, an energy cycle to gain insight into the presence of a non-covalent π stacking between both photoisomers and 13 was calculated according to the following scheme. 7 Then, the energies of the optimized structures (indicated with "min") of both photoisomers, the Hantzsch ester and the respective adduct complexes were compared with single point calculations of mixed structures, revealing the adjustment process (indicated with "ADJ") of the structures upon π stacking. The energy differences are given as follows: 9. X-Ray Structure of 9b Experimental. Single light red block-shaped crystals of (O076) were obtained by recrystallisation from .... A suitable crystal (0.25×0.18×0.10) mm 3 was selected and mounted on ... on a GV1000, TitanS2 diffractometer. The crystal was kept at T = 123.01(10) K during data collection. Using Olex2, the structure was solved with the ShelXT structure solution program, using the Direct Methods solution method. The model was refined with version 2016/6 of ShelXL using Least Squares minimisation. 8

Structure Quality Indicators
Reflections:

Refinement:
A light red block-shaped crystal with dimensions 0.25×0.18×0.10 mm 3 was mounted on ....X-ray diffraction data were collected using a GV1000, TitanS2 diffractometer equipped with a n/a low-temperature device, operating at T = 123.01(10) K.
Data were measured using scans scans of 1.0 ° per frame for 1.0 s using CuK radiation (gradient vaccum rotatinganode X-ray tube, n/a kV, n/a mA). The total number of runs and images was based on the strategy calculation from the program CrysAlisPro (Agilent).The maximum resolution achieved was = 73.474.&nbsp° Cell parameters were retrieved using the CrysAlisPro (Agilent) software and refined using CrysAlisPro (Agilent) on 11290 reflections, 82 % of the observed reflections. Data reduction was performed using the CrysAlisPro (Agilent) software which corrects for Lorentz polarisation. The final completeness is 99.90 out to 73.474 in . The absorption coefficient of this material is 10.606 at this wavelength ( = 1.54184) and the minimum and maximum transmissions are 0.634 and 0.800.
The structure was solved in the space group P2 1 /c (# 14) by Direct Methods using the ShelXT (Sheldrick, 2015) structure solution program and refined by Least Squares using version 2016/6 of ShelXL (Sheldrick, 2015). All nonhydrogen atoms were refined anisotropically. Hydrogen atom positions were calculated geometrically and refined using the riding model. There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1.   19.0(9) 9.2(9) 20.7(9) 0.9(7) 2.9 (7