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Anion Recognition with Hydrogen‐Bonding Cyclodiphosphazanes
Author(s) -
Klare Helge,
Hanft Sebastian,
Neudörfl Jörg M.,
Schlörer Nils E.,
Griesbeck Axel,
Goldfuss Bernd
Publication year - 2014
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.201403013
Subject(s) - chemistry , denticity , hydrogen bond , urea , medicinal chemistry , chloride , derivative (finance) , crystallography , nuclear magnetic resonance spectroscopy , crystal structure , stereochemistry , molecule , organic chemistry , financial economics , economics
Abstract Modular cyclodiphosph(V)azanes are synthesised and their affinity for chloride and actetate anions were compared to those of a bisaryl urea derivative ( 1 ). The diamidocyclodiphosph(V)azanes cis ‐[{ArNHP(O)(μ‐ t Bu)} 2 ] [Ar=Ph ( 2 ) and Ar= m ‐(CF 3 ) 2 Ph ( 3 )] were synthesised by reaction of [{ClP(μ‐N t Bu)} 2 ] ( 4 ) with the respective anilines and subsequent oxidation with H 2 O 2 . Phosphazanes 2 and 3 were obtained as the cis isomers and were characterised by multinuclear NMR spectroscopy, FTIR spectroscopy, HRMS and single‐crystal X‐ray diffraction. The cyclodiphosphazanes 2 and 3 readily co‐crystallise with donor solvents such as MeOH, EtOH and DMSO through bidentate hydrogen bonding, as shown in the X‐ray analyses. Cyclodiphosphazane 3 showed a remarkably high affinity (log[ K ]=5.42) for chloride compared with the bisaryl urea derivative 1 (log[ K ]=4.25). The affinities for acetate (AcO − ) are in the same range ( 3 : log[ K ]=6.72, 1 : log[ K ]=6.91). Cyclodiphosphazane 2 , which does not contain CF 3 groups, exhibits weaker binding to chloride (log[ K ]=3.95) and acetate (log[ K ]=4.49). DFT computations and X‐ray analyses indicate that a squaramide‐like hydrogen‐bond directionality and C α H interactions account for the efficiency of 3 as an anion receptor. The C α H groups stabilise the Z , Z ‐ 3 conformation, which is necessary for bidentate hydrogen bonding, as well as coordinating with the anion.