U. Olsher et al., Structural and conformational studies of alcohol, diol and methyl ether derivatives of dibenzo-14-crown-4. Implications for ligand and tecton design, J CHEM S P2, (11), 1999, pp. 2557-2564
Citations number
32
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
Molecular structures are determined for six dibenzo-14-crown-4 derivatives
that have one or two substituents on the central carbon(s) of the three-car
bon bridge(s). The series of compounds includes three crown ether alcohols,
one crown ether trans-diol, and two methoxy crown ether compounds, The cry
stal structures for these six crown ethers reveal that due to hydrogen-bond
ing and steric interactions, a hydroxy substituent;is directed, at least pa
rtially, toward the crown ether cavity and an unusual intra- and intermolec
ular hydrogen bond network is formed between the hydroxy group protons and
the ether oxygens of the crown ether ring. On the other hand, an ether grou
p or a substituent with carbon as the first atom is oriented away from the
polyether ring. The structure of sym-(methoxy)(methyl)dibenzo-14-crown-4 is
markedly different from that of sym-(hydroxy)(methyl)dibenzo-14-crown-4 bo
th in terms of the Substituent orientation and. very significant distortion
from planarity of the four crown ether oxygens in the former. Support for
an unusual conformation for sym-(methoxy)(methyl)dibenzo-14-crown-4 in solu
tion is derived from C-13 NMR measurements. Crown ether alcohols are hydrog
en-bonding "tectons" that participate in strong, specific and directional i
ntermolecular interactions.