Utilizing proton transfer to produce molecular salts in bromanilic acid substituted-pyridine molecular complexes - predictable synthons?

作者：Thomas Lynne H^*; Adam Martin S; O' Neill Andrew; Wilson Chick C

来源：Acta Crystallographica Section C-Crystal Structure Communications, 2013, 69: 1279-U1349.

DOI：10.1107/S0108270113029533

• crystal structure
• crystal engineering
• hydrogen bonding
• proton transfer
• lutidine salts
• picoline salts
• bromanilic acid

Controlled introduction of proton transfer into the design of a series of molecular complexes is described, delivering the systematic production of ionic molecular complexes (molecular salts). The controlled production of molecular salts has relevance as a potential strategy in the design of pharmaceutical materials. In nine molecular complexes consisting of bromanilic acid with the N-heterocyclic compounds 2-, 3- and 4-picoline [bis(2/3/4-methylpyridinium) 2,5-dibromo-3,6-dioxocyclohexa-1,4-diene-1,4-diolate, 2C(6)H(8)N(+)center dot C6Br2O42-], 2,3-, 2,4-, 2,5- and 3,5-lutidine [2,3/2,4/2,5/3,5-dimethylpyridinium 2,5-dibromo-4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-olate, C7H10N+center dot C6HBr2O4-], and 3-bromo-4-methylpyridine [3-bromo-4-methylpyridinium 2,5-dibromo-4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-olate, C6H7BrN+center dot C6HBr2O4-] and 2-bromo-3-methylpyridine [2-bromo-3-methylpyridine-2,5-dibromo-3,6-dihydroxycyclohexa-2,5-diene-1,4-dione (1/1), C6H6BrN center dot C6H2Br2O4], proton transfer occurs readily between the bromanilic acid molecule and the N heteroatom of the pyridine ring, in all cases producing a charge-assisted bifurcated N-H center dot center dot center dot O hydrogen bond. This reinforces the value of this motif as a design tool in the crystal engineering of such complexes. The protonation state (and stoichiometry) significantly affect the supramolecular synthons obtained, but 1:2 stoichiometries reliably give rise to PBP synthons and 1:1 stoichiometries to PBBP synthons (where P indicates a methylpyridine co-molecule and B a bromanilic acid molecule). The influence of halogen interactions on the wider crystal packing is also discussed, with C-H center dot center dot center dot Br and Br center dot center dot center dot O interactions the most prevalent; only one Br center dot center dot center dot Br interaction is found.

• 出版日期2013-11