Abstract
Tris{4-[(1,3-diphenyl-1H-pyrazol-4-yl)methylene]-41-aminobiphenyl}amine was synthesized from N-(4-bromophenyl)-N-[(1,3-diphenyl-1H-pyrazol-4-yl)methylene]amine and tris(4-bromophenyl)amine based on Ullmann coupling reaction. The synthesized compound was characterized by NMR, IR, MS and elemental analysis.
As part of a study towards the preparation of highly conjugated polyaromatcs incorporating a pyrazole motif with potential application in photovoltaic devices, the title compound tris{4-[(1,3-diphenyl-1H-pyrazol-4-yl)methylene]-41-aminobiphenyl}amine is prepared. The triarylamine moiety fulfills the requirement of easy and reversible oxidation and therefore constitutes the building block of many of the hole-transporting materials [1].
Electrolytic copper (100 mg, 1.6 mmol), KOH (10 mg, 0.178 mmol ) and 1,10-phenanthroline (1.0 mg, 0.006 mmol) were added to a stirred solution of N-(4-bromophenyl)-N-[(1,3-diphenyl-1H-pyrazol-4-yl)methylene]amine [2,3,4] (121 mg, 0.3 mmol) and tris(4-bromophenyl)amine (48 mg, 0.1 mmol) in anhydrous DMF. The resultant mixture was heated at 130 °C for 18 h and then filtered hot to remove the copper compounds and the base [5,6]. The solvent DMF was evaporated under vacuum and the dark brown solid was triturated with ethyl acetate, filtered and further purified by chromatography on silica gel, using ethyl acetate-hexane (1:4) as eluent. The product is most probably the E isomer, given the high degree of symmetry deduced from the 13C NMR data and the 1H NMR data which indicate there is only one product formed.
Yield: 65%
M.p.: 128 °C
IR (KBr) cm−1: 2998 (Ar C-Hstr), 1603 (C=Nstr), 1452 (Ar C=Cstr), 1337 (Ph-Nstr), 1023 (Ar C-Hdef).
1H NMR (500 MHz, CDCl3) δ ppm: 10.23 (s, 3H, pyrazole 5-H), 8.72 (s, 3H, HC=N), 7.93–6.69 (m, 54H, Ar).
13C NMR (75 MHz, DMSO-d6): 158.0, 140.5, 139.0, 136.0, 129.1, 128.3, 127.0, 123.0, 118.0, 112.5, 106.0, 103.7.
MS: m/z (ES), 1209 [(MH)+].
Elemental analysis calculated for C84H60N10 (1208.5): C, 83.42%; H, 5.00%; N, 11.58%. Found: C, 84.32%; H, 5.25%; N, 11.43%.
Supplementary materials
Supplementary File 1Supplementary File 2Supplementary File 3Acknowledgement
We are thankful to NIIST, Thiruvanathapuram for recording NMR spectra.
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