Supramolecular Assembly of Isocyanorhodium(I) Complexes: An Interplay of Rhodium(I)···Rhodium(I) Interactions, Hydrophobic–Hydrophobic Interactions, and Host–Guest Chemistry

A series
of tetrakis­(isocyano)­rhodium­(I) complexes with different
chain lengths of alkyl substituents has been found to exhibit a strong
tendency toward solution state aggregation upon altering the concentration,
temperature and solvent composition. Temperature- and solvent-dependent
UV–vis absorption studies have been performed, and the data
have been analyzed using the aggregation model to elucidate the growth
mechanism. The aggregation is found to involve extensive Rh­(I)···Rh­(I)
interactions that are synergistically assisted by hydrophobic–hydrophobic
interactions to give a rainbow array of solution aggregate colors.
It is noted that the presence of three long alkyl substituents is
crucial for the observed cooperativity in the aggregation. Molecular
assemblies in the form of nanoplates and nanovesicles have been observed
in the hexane–dichloromethane solvent mixtures, arising from
the different formation mechanisms based on the alkyl chain length
of the complexes. Benzo-15-crown-5 moieties have been incorporated
for selective potassium ion binding to induce dimer formation and
drastic color changes, rendering the system as potential colorimetric
and luminescent cation sensors and as building blocks for ion-controlled
supramolecular assembly.