Intramolecular Halogen Bonding
Supported by an Aryldiyne
Linker
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Abstract
Intramolecular
halogen bonds between aryl halide donors and suitable
acceptors, such as carbonyl or quinolinyl groups, held in proximity
by 1,2-aryldiyne linkers, provide triangular structures in the solid
state. Aryldiyne linkers provide a nearly ideal template for intramolecular
halogen bonding as minor deviations from alkyne linearity can accommodate
a variety of halogen bonding interactions, including O···Cl,
O···Br, O···I, N···Br,
and N···I. Halogen bond lengths for these units, observed
by single crystal X-ray crystallography, range from 2.75 to 2.97 Å.
Internal bond angles of the semirigid bridge between halogen bond
donor and acceptor are responsive to changes in the identity of the
halogen, the identity of the acceptor, and the electronic environment
around the halogen, with the triangles retaining almost perfect co-planarity
in even the most strained systems. Consistency between experimental
results and structures predicted by M06-2X/6-31G* calculations demonstrates
the efficacy of this computational method for modeling halogen-bonded
structures of this type