Room temperature Discotic Liquid Crystalline Triphenylene- Pentaalkynylbenzene dyads as an emitter in blue OLEDs and their Charge transfer complexes with ambipolar charge transport behaviour

Note: The originally published ESI document for DOI: 10.1039/c9tc01178a was replaced with this version on 14th February 2020 Room temperature Discotic Liquid Crystalline TriphenylenePentaalkynylbenzene dyads as an emitter in blue OLEDs and their Charge transfer complexes with ambipolar charge transport behaviour Indu Bala, Wan-Yun Yang, Santosh Prasad Gupta, Joydip De, Rohit Ashok Kumar Yadav, Dharmendra Pratap Singh, Deepak Kumar Dubey, Jwo-Huei Jou, Redouane Douali and Santanu Kumar Pal* Indian Institute of Science Education and Research (IISER) Mohali, Sector-81, SAS Nagar, Mohali 140306, India. E-mail: skpal@iisermohali.ac.in Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan Department of Physics, Patna University, Patna800005 Unité de Dynamique et Structure des Matériaux Moléculaires (UDSMM), Université du Littoral Côte d’Opale (ULCO), 50 Rue Ferdinand Buisson, 62228, Calais, France

S3 1.2.2 Polarised Optical Microscopy 1 : "Textural observations of the mesophase were performed with Nikon Eclipse LV100POL polarising microscope provided with a Linkam heating stage (LTS 420). All images were captured using a Q-imaging camera." 1.2.3 DSC Study 1 : "The transition temperatures and associated enthalpy values were determined using a differential scanning calorimeter (Perkin Elmer DSC 8000 coupled to a controlled liquid nitrogen accessory (CLN 2)) which was operated at a scanning rate of 10 °C min -1 both on heating and cooling." 1.2.4 X-ray diffraction studies 1 : "X-ray diffraction (XRD) was carried out using Cu Kα (λ=1.54 Å) radiation from a source (GeniX 3D, Xenocs) operating at 50 kV and 0.6 mA. The diffraction patterns were collected on a two module Pilatus detector." In this formula (ℎ ) are the Miller Indices and , the fractional coordinates in the unit cell.

Photophysical studies
To calculate the electron density, the complex structure factor (ℎ ) has to be written as the product of the phase Φ(ℎ ) and the modulus |F(ℎ )| which is proportional to the square root of the intensity (ℎ ) of the observed reflection F(ℎ ) = |F(ℎ )|e iΦ( ℎ ) = √I(ℎ )e iΦ( ℎ ) While the intensity I(ℎ ) can be easily obtained from the X-ray diffraction experiment, the only information that cannot be obtained directly from experiment is the phase Φ(ℎ ) for each diffraction peak. However, this problem becomes easily tractable when the structure under study is centro-symmetric, that if ρ(x,y)=ρ (-x,-y), F(hk) can only be real hence, Φ(ℎ ) can only be 0 or . For non-centro-symmetric groups, the phase may take every value between 0 and 2. Since the columnar phase observed in these compound assemblies are centro-symmetric and have only limited number of diffraction peaks, it is possible to reconstruct electron density S4 maps of all possible phase combinations. The "correct" map is subsequently chosen on the merit of the reconstructed maps and other physical and chemical knowledge of the system such as, chemical constituents and their sizes etc."

Synthetic details
The compounds 2a-c were prepared according to the procedure as reported in earlier reports. 1,2 2.1 General procedure for the synthesis of the compound 2a-c: In a round bottom flask (R.B), pentabromophenol (1 equiv.), potassium carbonate (5 equiv.) and alkyl bromide (5 equiv.) was refluxed in a 30 ml dry acetone for 12 hours. Potassium iodide was added in a catalytic amount. After completion of the reaction, the acetone was evaporated and then extracted with DCM. The reaction mixture was purified in 100-120 silica gel by using hexane/EtOAc as an eluent.
The compounds 3a-c were prepared according to the procedure as reported in previous reports. 1,2 2.2 General procedure for the synthesis of the compound 3a-c: The sonoghshira of alkylated compound 2 (500 mg) was done by taking 30 ml of dry triethylamine in a round bottom flask which was degassed followed by the addition of Pd(PPh3)2Cl2 (50 mg), CuI (50 mg) & PPh3 (100 mg). The mixture was stirred for 15 minutes followed by the gradual addition of 4-pentylphenylacetylene. The reaction mixture was stirred at 100 °C for 24 h under nitrogen atmosphere & after cooling to room temperature it was poured into 30 ml of 5M HCl. After extracting the reaction mixture with DCM, the compound was purified in 230-400 silica gel by using hexane/EtOAc as an eluent.
The compounds 4a-c were prepared according to the procedure as reported in previous reports. 3 2.3 General procedure for the synthesis of the compound 4a-c: A mixture of compound 2 (1 equiv.) and NaN3 (13 equiv.) in DMF (10 mL) was stirred at room temperature for 12 h.
After addition of water, it was extracted with diethyl ether. The organic layer was dried with Na2SO4, and solvent was removed under reduced pressure. The compound was used without further purification.
The hexahexyloxytriphenylene 5 and monohydroxytriphenylene 6 were prepared as reported in several reports earlier. 4,5 The compound 7 (m=1 & m=2) were prepared as per reference no.
Interestingly, the seventh peak in color green with spacing 3.53 Å attributing the disc to disc separation in column indicating the occurrence of columnar nematic (NC) phase. Å is due to average column-column separation. The second peak in black color is mainly due to background and it is not our concern. The third peak in orange color with spacing 4.78 Å, appearing mainly due to fluid alkyl chain to chain correlation. However, the fourth peak in cyan color with spacing 4.42 Å correlates the average partial chain to chain spacing.
Interestingly, the sixth peak in color green with spacing 3.55 Å attributing the disc to disc separation in column suggesting the formation of columnar nematic (NC) phase. Further, the fifth in color yellow peak with spacing 4.01 Å appearing most possibly due to different kind of arrangement of alky chains. Red color curve represents the combine results of all peaks and well fitted to experimental X-Ray diffraction data. The similar behaviour of diffractogram has been observed in case of 9b.
For 9c at -20.0 °C (Fig. S16c): The first peak at 20.09 Å was observed in a similar manner to its diffractogram at room temperature. The additional peak at 4.43 Å correlates the average partial chain to chain spacing. There was no core to core peak appears in the wide angle region which excludes the possibility of NC phase. The similar behaviour of diffractogram has been observed in case of 8c.

Fluorescence decay measurements
The decay curves were bi-exponential and analysed by using standard method of non-linear least square fitting method. The quality of fits was judged using statistical parameters, reduced χ 2 value and the residual data. d) e) f)  2 = 1.17  2 = 1.05  2 = 1.09  2 = 0.99  2 = 1.09  2 = 1.18