Phase behaviour of ester-linked cyanobiphenyl dimers and fluorinated analogues: the direct isotropic to twist-bend nematic phase transition

Abstract

Synthesis of COOnSynthetic procedures of COO3 are representatively described below. Other COOn homologues were synthesised with corresponding α,ω-dibromoalkanes in a manner similar to the synthesis of COO3. Methyl 4'-cyano-[1,1'-biphenyl]-4-carboxylateMethyl 4-bromobenzoate (4.69 g, 21.8 mmol), 4-cyanophenylboronic acid pinacol ester (5.00 g, 21.8 mmol), Cs2CO3 (14.5 g, 44.5 mmol), and Pd(PPh3)4 (0.759 g, 0.657 mmol)were put in a double-necked flask purged with argon gas. THF (20 mL) degassed by bubbling argon gas was added into the prior flask and the mixture was stirred at reflux temperature for 22 h. The mixture was extracted with dichloromethane and washed with water and brine. The organic phase was dried over MgSO4 and the volatiles were evaporated under reduced pressure. The residue was purified via column chromatography on silica gel with a mixed solvent of dichloromethane/hexane (1/1, v/v). Yield: 87.7%. 1 H