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Supramolecular Motifs: Concerted Multiple Phenyl Embraces between Ph 4 P + Cations Are Attractive and Ubiquitous
Author(s) -
Dance Ian,
Scudder Marcia
Publication year - 1996
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19960020505
Subject(s) - intermolecular force , supramolecular chemistry , chemistry , van der waals force , crystallography , intermolecular interaction , stereochemistry , crystal structure , molecule , organic chemistry
Examination of the Cambridge Structural Database reveals that Ph 4 P + cations in crystals associate through phenyl‐phenyl nonbonded interactions which are attractive, concerted, and widespread. Intermolecular phenyl‐phenyl conformations, which are offset‐face‐to‐face ( off ), edge‐to‐face ( ef ) or vertex‐to face ( vf ), combine in five classes of supramolecular motifs for {Ph 4 P + } 2 pairs, namely the sextuple phenyl embrace (SPE) with ( ef ) 6 and offset sextuple phenyl embrace (OSPE) containing ( off ) 1 ( ef ) 2 ( ef/vf ) 2 , the translational quadruple phenyl embrace (TQPE) with ( ef ) 4 , the parallel quadruple phenyl embrace (PQPE) with ( off ) 1 ( vf ) 2 , and the double phenyl embrace (DPE) with ( off ) 1 . Typical intermolecular attractive energies (kJ per mol of {Ph 4 P + } 2 ) for these motifs are SPE 85, OSPE 57, TQPE 70, PQPE 41, DPE 34. There is strong interpenetration of the cations in these motifs: 489/770 structures in the CSD have P ⃛P≤7 Å (spherical Ph 4 P + has a van der Waals diameter of 13.6 Å). Of the 812 instances of P ⃛P ≤7 Å, 86% are SPE, 10% are OSPE, 2% are TQPE, and only 2% are unclassified, Average P ⃛P separations in the PQPE and DPE are 8.3 Å. Centrosymmetry is prevalent in all except the TQPE, which has implications for the engineering of noncentric crystals.