Crystal Engineering of Molecular Networks: Tailoring Hydrogen-Bonding Self-Assembly of Tin-Tetrapyridylporphyrins with Multidentate Carboxylic Acids As Axial Ligands

This study reveals the self-assembly patterns of six-coordinate
complexes of the tetra­(4-pyridyl)- and tetra­(3-pyriyl)-tin-porphyrin
moieties (SnT4PyP and SnT3PyP, respectively)
with multidentate carboxylic acids as axial ligands. Detailed structural
characterization of the supramolecular organization in the resulting
ordered solids by X-ray diffraction is reported. Crystals of the five
new Sn­(acid)2-TPyP complexes consist of multiporphyrin
polymeric chains and networks that are sustained by extensive hydrogen
bonding, involving the functional substituents on the axial ligands
as proton donors and the peripheral N-sites of the porphyrin as proton
acceptors. The use of different ligands leads to different connectivity
features of the supramolecular assemblies that form. Structures with
the 5-hydroxy-isophthalic acid and trimesic acid ligands (1 and 2)
reveal the formation of one-dimensional hydrogen-bonded chains only,
as solvation effects prevent interporphyrin interaction in other directions.
Reaction of the tin-porphyrin with 5-amino-isophthalic acid yielded
a two-dimensional hydrogen-bonding network (3), while the reaction
products with cis-1,3,5-cyclohexane-tricarboxylic
acid (4) and 5-bromo-isophthalic acid (5) are characterized by three-dimensionally
interlinked assemblies. The above examples highlight the pronounced
effect of the axial ligands (A) on the hydrogen-bonding-driven supramolecular
aggregation of the Sn­(A)2-TPyP building blocks in crystals.