Diversity in Supramolecular Solid-State Architecture Formed by Self-Assembly of 1‑(Diaminomethylene)thiourea and Aliphatic Dicarboxylic Acids

A family of supramolecular complexes of
1-(diaminomethylene)­thiourea
with aliphatic dicarboxylic acids, HOOC­(CH2)nCOOH, with odd and even numbers of methylene groups
in the carbon chain of the acids has been characterized. Using solvent-assisted
and evaporation-based techniques, crystallization of 1-(diaminomethylene)­thiourea
with aliphatic dicarboxylic acids from water solutions yielded ionic
supramolecular complexes with base to acid ratio of 2:1 or 1:1. Malonic,
succinic, adipic, and sebacic acids with 1-(diaminomethylene)­thiourea
form supramolecular complexes of 2:1 ratio (1, 2, 4, and 8), whereas glutaric,
pimelic, azelaic, and suberic acids form supramolecular complexes
of 1:1 ratio (3, 5, 6, and 7). Within all supramolecular complexes only one with adipic
acid crystallizes as a hydrate containing water molecules of crystallization.
In the hydrated crystal with adipic acid, the O–H···O
chains of water molecules interact with adipiate­(2-) anions forming
anionic layers, and the charge is compensated by 1-(diaminomethylene)­thiouron-1-ium
cations. The 2:1 supramolecular complexes further interact each other
via N–H···O hydrogen bonds forming two- or three-dimensional
supramolecular structure. Within 1:1 supramolecular complexes, the
singly deprotonated aliphatic dicarboxylic acids are linked together
via strong symmetrical O···H···O hydrogen
bonds into infinitive chains. The chains are further linked by 1-(diaminomethylene)­thiouron-1-ium
cations to form a two- or three-dimensional hydrogen bonding network.
Interaction between the 1-(diaminomethylene)­thiouron-1-ium and the
singly or doubly deprotonated aliphatic dicarboxylic acid units in
solid of 1–8 supramolecular complexes
were also analyzed by vibrational spectroscopy.