The Impact of C2 Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine‐Cored Donor–Acceptor–Donor Triads

Abstract Novel electron donor–acceptor–donor (D‐A‐D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7‐membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C2 insertion into well‐known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine‐core D‐A‐D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room‐temperature phosphorescence and triplet–triplet annihilation. Furthermore, electrochemical analysis suggested sigma‐dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results.


S1
S9 S10 S10 S11-S12 S13-S18 S19 S2 General Remarks. All reactions were carried out under an atmosphere of nitrogen unless otherwise noted. Products were purified by chromatography on silica gel BW-300 and Chromatorex NH (Fuji Silysia Chemical Ltd.). Analytical thin-layer chromatography (TLC) was performed on pre-coated silica gel glass plates (Wako silica gel 70 FM TLC plate and Fuji Silysia Chromatorex NH, 0.25 mm thickness). Compounds were visualized with a UV lamp. Melting points were determined on a Stanford Research Systems MPA100 OptiMelt Automated Melting Point System. All 1 H and 13 C spectra except were recorded on a JEOL JMTC-400/54/SS Spectrometer ( 1 H NMR, 400 MHz; 13 C NMR, 100 MHz) using tetramethylsilane as an internal standard (for 1 H and 13 C NMR). Infrared spectra were acquired on a SHIMADZU IRAffinity-1 FT-IR Spectrometer. Mass spectra and Highresolution mass spectra were obtained on a JEOL JMS-700 Mass Spectrometer. Steady-state UV-vis spectra were recorded on a Shimadzu UV-2550 spectrophotometer. Steady-state emission spectra were recorded on a HAMAMATSU C11347-01 spectrometer with an integrating sphere. Cyclic voltammetry (CV) was performed with the Biologic SP150 system. UV-Vis-NIR spectroscopy and spectroelectrochemistry were performed using Ocean Optics QE6500 and NIRQuest matrix spectrometers. In situ EPR spectroelectrochemical experiments were undertaken using a JES-FA 200 (JEOL) spectrometer. Thermogravimetric analysis (TGA) was performed with TG/DTA-7200 system (SII Nano Technology Inc.).
Photophysics. Phosphorescence, prompt fluorescence (PF), and delayed fluorescence (DF) spectra and fluorescence decay curves were recorded using nanosecond gated luminescence and lifetime measurements (from 400 ps to 1 s) using either third harmonics of a high energy pulsed DPSS laser emitting at 355 nm (Q-Spark-A50). Emission was focused on a spectrograph and detected on a sensitive gated iCCD camera (Stanford Computer Optics) with sub-nanosecond resolution.
Temperature photophysical measurements were conducted in the Janis CCS-450 closed-cycle helium cytostatic system.

Devices.
OLEDs have been fabricated on pre-cleaned, patterned indium-tin-oxide (ITO) coated glass S3 substrates with a sheet resistance of 20 Ω/sq and ITO thickness of 100 nm. All small molecules and cathode layers were thermally evaporated in Kurt J. Lesker Spectros 150 evaporation system under pressure of 10 -7 mbar without breaking the vacuum. The sizes of the pixels were 4 mm 2 , 8 mm 2 and 16 mm 2 . All organic evaporated compounds were purified by CreaPhys organic sublimation system. All materials were purified by temperature-gradient sublimation in a vacuum. The characteristics of the devices were recorded using a 10-inch integrating sphere (Labsphere) connected to a Source Meter Unit and Ocean Optics USB4000 spectrometer.
Simulations. The computational protocol was consistent with several stages. In the first step, we performed a conformer search using the UFF force field as implemented in the AMS package. S2 From the generated conformers, we selected a set of qualitatively different conformations, which were further optimized at the density functional theory (DFT) PBE0/cc-pVDZ level using the QChem package. S3 The analysis of results revealed three qualitatively different conformers for each compound, differing by the orientation of the IDB or ISB units. Therefore, we selected three conformation, one of the ax-ax, eq-ax, and eq-eq type, for each compound. Simulations of electrochemical properties were done at the PBE0/cc-pVDZ level using the PCM solvent models parametrized for DCM. To this end, we optimized the geometries of charged species and calculated IPs and EAs as total energy differences.
To perform the excited state calculations, we used the optimally tuned range separated functional w*PBE. The w parameter was optimized for the most stable conformers of 1, and 2 and the values were 162 and 166 bohr -1 , respectively. For further, calculations we used the average value w=164 bohr -1 . The time-dependent DFT calculations were done at the ground-state geometries as well as optimized S4 S1 and T1 geometries using a non-equilibrium PCM solvation model parametrized for toluene (e=2.38, e¥=2.24) as implemented in QChem.

Conformation
Relative    Table S6. Excitation energies calculated at the S1 excited state geometry at the w*PBE/cc-pVDZ level, using state-specific PCM solvation model. *The starting eq-eq conformation of 2 relaxed to eq-ax during the excited-state optimization.  Table S7. Energies of different electronic states at the S1 excited state geometry relative to the ax-ax conformer. *The starting eq-eq conformation of 2 relaxed to eq-ax during the excited-state optimization.

Relative energy at the S1 geometry [eV]
1 2 ax-ax eq-ax eq-eq ax-ax eq-ax eq-eq* S0  Table S9. Energies of different electronic states at the S1 excited state geometry relative to the ax-ax conformer. *The starting eq-eq conformation of 1 relaxed to ax-ax during the excited-state optimization.