TY - JOUR
T1 - Solution and solid state studies on the binding of isomeric carboranes C2B10H12 by ρ-Bu(t)-calix[5]arene
AU - Clark, Thomas
AU - Makha, Mohamed
AU - Raston, Colin
AU - Sobolev, Alexandre
PY - 2006
Y1 - 2006
N2 - p-Bu-t-calix[5]arene forms crystalline inclusion complexes with o- and m-carboranes in toluene or dichloromethane-hexane, but not with the p-isomer, the extended structures being based on 1:1 host-guest supermolecules, with the p-Bu-t-substituents creating a snug fit for o- and m-carborane; p-carborane forms a highly hexane soluble complex, induced by grinding, which crystallizes as fibres. Solution phase studies showed the presence of a 1:1 host-guest stoichiometry with all three isomeric carboranes as determined from Job plots. The association constants for the o- and m-carborane complexes are 6.4 +/- 0.3 M-1 and 3.8 +/- 0.1 M-1 respectively, whereas the p-isomer is only weakly associated. Competition experiments involving all three isomers show rapid exchange on the NMR time scale, and no selectivity in solution is evident. Selective association involving the o- and m-isomers in the solid state is therefore remarkable, and it is a manifestation of crystal packing forces which embodies the differences in dipole moments of the carboranes.
AB - p-Bu-t-calix[5]arene forms crystalline inclusion complexes with o- and m-carboranes in toluene or dichloromethane-hexane, but not with the p-isomer, the extended structures being based on 1:1 host-guest supermolecules, with the p-Bu-t-substituents creating a snug fit for o- and m-carborane; p-carborane forms a highly hexane soluble complex, induced by grinding, which crystallizes as fibres. Solution phase studies showed the presence of a 1:1 host-guest stoichiometry with all three isomeric carboranes as determined from Job plots. The association constants for the o- and m-carborane complexes are 6.4 +/- 0.3 M-1 and 3.8 +/- 0.1 M-1 respectively, whereas the p-isomer is only weakly associated. Competition experiments involving all three isomers show rapid exchange on the NMR time scale, and no selectivity in solution is evident. Selective association involving the o- and m-isomers in the solid state is therefore remarkable, and it is a manifestation of crystal packing forces which embodies the differences in dipole moments of the carboranes.
U2 - 10.1039/b611399k
DO - 10.1039/b611399k
M3 - Article
C2 - 17117214
SN - 1477-9226
VL - 2006
SP - 5449
EP - 5453
JO - Dalton Transactions: the international journal for inorganic, organometallic and bioinorganic chemistry
JF - Dalton Transactions: the international journal for inorganic, organometallic and bioinorganic chemistry
IS - 46
ER -