Charge density studies on 2,3,5,6-tetrafluoro- and pentafluoropyridine

Solving the enigma of weak fluorine contacts in the solid state: a periodic DFT study of fluorinated organic crystals

“…(i) Peruorinated compounds with only C-F/F-C contacts: tetrauoromethane (CF 4 ), 54 hexa-uorobenzene (C 6 F 6 ) 55 and pentauoropyridine (C 5 NF 5 ). 56 (Fluorine and nitrogen atoms are considered to be isolobal with respect to the supramolecular architecture in the crystalline phase 57 ). (ii) Molecular crystals with prevalent C-F/F-C/C-H/ F-C contacts: 1,1,2,4,4-pentauorobuta-1,3-diene (C 4 HF 5 ), 58 1,2,3,5-tetrauorobenzene (m-C 6 H 2 F 4 ), 23 1,2,3,4-tetra-uorobenzene (o-C 6 H 2 F 4 ) 59 and 2,3,5,6-tetrauoropyridine (C 5 NHF 4 ).…”

“…(ii) Molecular crystals with prevalent C-F/F-C/C-H/ F-C contacts: 1,1,2,4,4-pentauorobuta-1,3-diene (C 4 HF 5 ), 58 1,2,3,5-tetrauorobenzene (m-C 6 H 2 F 4 ), 23 1,2,3,4-tetra-uorobenzene (o-C 6 H 2 F 4 ) 59 and 2,3,5,6-tetrauoropyridine (C 5 NHF 4 ). 56 (iii) Crystals where a competition occurs between intermolecular C-F/F-C, C-H/F-C and C-H/O contacts: 2,3-diuoro-1,4-naphthoquinone (DFNAPQ), 60 3-(3,5-diuorophenyl)-1-phenylprop-2-en-1-one (YICBES) 61 and 3,4-diuoro-6-phenyl-2H-pyran-2-one (KEGWEZ) 62 . The designations of the crystals given in bold; they will be used below.…”

“…The shrinking factor of the reciprocal space net was set to 4. The space groups and the unit cell parameters of the considered crystals obtained in the experimental studies [54][55][56][58][59][60][61][62][63] were xed for the calculations. This is a common approximation for calculating molecular crystals with Hal/Hal contacts 27,72,73 as the change in the volume of a cell of molecular crystals appears to be insignicant aer full optimization.…”

Analysis of charge density in nonaaquagadolinium(III) trifluoromethanesulfonate – insight into GdIII—OH2 bonding

“…There is a paucity of data concerning the experimental charges in the trifluoromethyl group; therefore other systems must be invoked for comparison purposes. In tetra-and pentafluoropyridine (Stammler et al, 2013) the F experimental atom charges were between À0.65 and À0.45; the theoretical ones ranged between À0.68 and À0.54. Thus the present experimental charges of F are smaller than those in the fluorinated pyridines, while the theoretical values are similar.…”

Competition between hydrogen and halogen bonding in the structures of 5,10-dihydroxy-5,10-dihydroboranthrenes

“…The FÁ Á ÁF contacts are shorter than 2.95 Å (twice the van der Waals radius for F) and can formally be considered as halogen-bond interactions. The role of F interactions in crystal engineering and the ability of so-called 'organic F atoms' to participate in intermolecular interactions have been a matter of recent discussions (Berger et al, 2011;Chopra, 2012;Chopra et al, 2005;Collas et al, 2010;Feyereisen et al, 1996;Hathwar, Gonnade et al, 2011;, Mariaca et al, 2006Metrangolo et al, 2011;Murray et al, 2009;Politzer et al, 2008;Reichenbä cher et al, 2004;Schwarzer et al, 2004;Schwarzer & Weber, 2008;Stammler et al, 2013). The F atom has a relatively small size, high electronegativity and very low polarizability, and hence does not exhibit a strong tendency to form halogen-bond interactions.…”