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The Diiodine Basicity Scale: Toward a General Halogen‐Bond Basicity Scale
Author(s) -
Laurence Christian,
Graton Jérôme,
Berthelot Michel,
El Ghomari Mohamed J.
Publication year - 2011
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.201101071
Subject(s) - chemistry , halogen , halogen bond , hydrogen bond , lewis acids and bases , substituent , acceptor , pyridine , medicinal chemistry , inorganic chemistry , crystallography , stereochemistry , organic chemistry , molecule , alkyl , catalysis , physics , condensed matter physics
The new diiodine basicity scale p K BI2 is quasi‐orthogonal to most known Lewis basicity scales (hydrogen‐bond, dative‐bond and cation basicity scales). The diiodine basicity falls in the sequence N>P≈Se>S>I≈O>Br>Cl>F for the iodine‐bond acceptor atomic site and SbO≈NO≈AsO>SeO>PO>SO>CO>O>SO 2 or PS≫S>CS≫NCS for the functionality of oxygen or sulfur bases. Substituent effects are quantified through linear free energy relationships, which allow the calculation of individual complexation constants for each site of polybases and thus the classification of aromatic ethers as carbon π bases and of aromatic amines, thioethers and selenoethers as N, S and Se bases, respectively. The p K BI2 values of n Bu 3 N + ‐N − C≡N, 2‐aminopyridine and 1,10‐phenanthroline reveal a superbasic nitrile, a hydrogen‐bond‐assisted iodine bond and a two‐centre iodine bond, respectively. The diiodine basicity scale is a general inorganic but family‐dependent organic halogen‐bond basicity scale because organic halogen‐bond donors such as IC≡N and ICF 3 have a stronger electrostatic character than I 2 . The family independence can be restored by the addition of an electrostatic parameter, either the experimental p K BHX hydrogen‐bond basicity scale or the computed minimum electrostatic potential.