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The search for formal electrostatic effects on molecular conformation and crystal packing: crystal structure of 2,2′′‐disubstituted (H versus PPh 2 ) 1,1′‐(1,2‐phenylene)bis(3‐methyl‐1 H ‐imidazol‐3‐ium) bis(trifluoromethanesulfonate)
Author(s) -
Duhayon Carine,
Canac Yves,
Dubrulle Laurent,
Maaliki Carine,
Chauvin Remi
Publication year - 2016
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/s2053229616002576
Subject(s) - delocalized electron , electrostatics , chemistry , crystallography , trifluoromethanesulfonate , hydrogen bond , crystal (programming language) , crystal structure , phenylene , steric effects , charge (physics) , chemical physics , molecule , stereochemistry , polymer , physics , organic chemistry , quantum mechanics , computer science , programming language , catalysis
Electrostatic interactions between localized integral charges make the stability and structure of highly charged small and rigid organics intriguing. Can σ/π‐electron delocalization compensate reduced conformational freedom by lowering the repulsion between identical charges? The crystal structure of the title salt, C 14 H 16 N 4 2+ ·2CF 3 SO 3 − , (2), is described and compared with that of the 2,2′′‐bis(diphenylphosphanyl) derivative, (4). The conformations of the dications and their interactions with neighbouring trifluoromethanesulfonate anions are first analyzed from the standpoint of formal electrostatic effects. Neither cation exhibits any geometrical strain induced by the intrinsic repulsion between the positive charges. In contrast, the relative orientation of the imidazolium rings [ i.e. anti for (2) and syn for (4)] is controlled by different configurations of the interactions with the closest trifluoromethanesulfonate anions. The long‐range arrangement is also found to be specific: beyond the formal electrostatic packing, C—H…O and C—H…F contacts have no definite `hydrogen‐bond' character but allow the delineation of layers, which are either pleated or flat in the packing of (2) or (4), respectively.