Multivalent Hydrogen-Bonded Cu-Complexes as a Template for Topochemical Reactivity of Intercalated Pyridyl Derivatives

The crystal engineering of eight H-bonded metal assemblies based on a combination of Cu2+/(2,3-pyridyl)dicarboxylate moieties and N-heterocyclic derivatives is described. Single-crystal X-ray diffraction characterization revealed that all arrays were built from the self-assembly of their components via supramolecular heterodimeric synthons between carboxylic acid and pyridine groups. Compounds 1–3 form 2D arrays based on the self-assembly of metal–organic chains [Cu(2,3-Hpdc)]n or {[Cu(2,3-pdc)]2–}n with pyridyl compounds through hydrogen bonding interactions. Compounds 4–6 consist of 2D H-bonded double ribbons/layers, enabling the intercalation of stilbazole molecules head-to-tail fashion between metallic dimers [Cu2(2,3-pdc)4]4–. Compounds 7–8 were built from a mononuclear Cu2+ complex self-assembled via H-bonding interactions. As [Cu(2,3-Hpdc)2(4,4′-bpe)2] (7) displays a 3-fold parallel interpenetrated 2D H-bonded network, [Cu(2,3-pdc)(2,3-Hpdc)(OH2)]− (8) forms H-bonded bilayers between the Cu2+ complexes and water crystallization molecules. Adjacent bilayers are linked by a photoproduct generated in situ via a single-crystal-to-single-crystal transformation. These arrays 4, 7 and 8 are photoactive in the solid state upon UV irradiation, leading to the regioselective synthesis of rctt-cyclobutane derivatives in high-to-moderate yields. The structure-templating features of these arrays are described in terms of the concomitance of multiple supramolecular interactions. They encoded self-complementary donor–acceptor site information through a recurrent pattern of H-bonding preferences. These assemblies resulted from the concurrence of heterosynthons between the carboxylic and pyridyl groups and the presence of short contacts between the double bonds of the N-heterocycle derivatives, assisted by cation−π interactions and metal-building units with a modulable multivalency capacity.