Three potential ligand molecules have been investigated.
6,6'-o-Phenylenedioxybis(2,2-dimethyl-4-oxahexanoic
acid), C20H3008 (I), has twofold crystallographic symmetry
and adopts a conformation in which the two pendant
carboxylic arms minimize any potential molecular
cavity between them; zigzag polymeric chains
are formed as a result of C==O .. .H--O hydrogen
bonding about inversion centers. 2,2,9,9-Tetramethyl-
4,7-dioxadecanedioic acid, C12H2206 (II), also forms
polymeric hydrogen-bonded chains involving the carboxylic acid moieties but differs from (I) in its
molecular conformation. 2,2,6,6,10,10-Hexamethyl-4,8-
dioxaundecanedioic acid, Ci5H2806 (III), forms discrete
rectangular-shaped centrosymmetric dimers in which
any potential molecular cavity is minimized as a result
of the close proximity of two of the pendant etheral
arms.
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