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Phase behaviour and crystal structures of 2′,3′‐difluorinated p ‐terphenyl derivatives
Author(s) -
Gupta Sakuntala,
Das Partha Pratim,
Kula Przemysław,
Parisi Emmanuele,
Centore Roberto
Publication year - 2021
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229621006367
Subject(s) - monoclinic crystal system , triclinic crystal system , crystallography , terphenyl , crystal structure , molecule , moiety , chemistry , crystal (programming language) , stereochemistry , differential scanning calorimetry , mesogen , phase (matter) , organic chemistry , physics , liquid crystalline , computer science , programming language , thermodynamics
The crystal structures of difluorine derivatives of p ‐terphenyls ( n T m ) have been determined by single‐crystal X‐ray diffraction. For the unsymmetrical substituted compounds 2′,3′‐difluoro‐4‐methyl‐ p ‐terphenyl (1T0, C 19 H 14 F 2 ) and 4‐ethyl‐2′,3′‐difluoro‐4′′‐methyl‐ p ‐terphenyl (1T2, C 21 H 18 F 2 ), the crystal structure is disordered, with molecules statistically entering the crystal in up and down orientations, with full superposition of all the atoms, except for those of the terminal groups (H/methyl for 1T0 and methyl/ethyl for 1T2). For triclinic 2′,3′‐difluoro‐4,4′′‐dimethyl‐ p ‐terphenyl (1T1, C 20 H 16 F 2 ), with the space group P , the two crystallographically independent molecules have the same conformation, which is different from monoclinic 1T0 (space group C 2) and 1T2 (space group C 2/ c ). A common feature of the conformation of the three compounds is the noncoplanar twisted arrangement of the three rings of the p ‐terphenyl moiety. Two‐dimensional (2D) Hirshfeld fingerprint plots are consistent with H…H and C…H contacts in the crystal packing. For the three compounds, the phase behaviour has been investigated by POM (Petra/Osiris/Molinspiration) and differential scanning calorimetry (DSC) analysis. 1T2 is mesogenic, with enantiotropic nematic behaviour.