Rhodium paddlewheel dimers containing the π···π stacking, 1,8-naphthalimide supramolecular synthon

The bifunctional ligand 3-(1,8-naphthalimido)propanoate (LC2−), which contains a carboxylate group linked to the robust π···π stacking 1,8-naphthalimide supramolecular synthon, has been used to prepare two new rhodium carboxylate dimer complexes, [Rh2(LC2)4(DMF)2] (1) and [Rh2(LC2)4(py)2]·3DMF (2). Both complexes have been structurally characterized and contain the Rh2(O2CR)4 paddlewheel core, but have different axial ligands. The four naphthalimide side arms in the carboxylate ligands are arranged in the square shape imposed by the SBU in complex 1, but are bent in 2. In both cases, the supramolecular structure is organized into one-dimensional chains by strong π···π stacking interactions between only two of the 1,8-naphthalimide moieties on each dimeric unit. In 1, the other naphthalimide units do not interact strongly and in 2 they intramolecularly π···π stack with the adjacent axial pyridine molecules.

Graphical abstractThe bifunctional ligand 3-(1,8-naphthalimido)propanoate (LC2−) forms two [Rh2(LC2)4(axial ligand)2] complexes, with both supramolecular structures organized only into one-dimensional chains by strong π···π stacking of the naphthalimide rings.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We present an efficient synthetic method for the syntheses of rhodium carboxylate dimers. ► We prepare rhodium carboxylate dimers with robust π···π stacking 1,8-naphthalimide groups. ► These dimers form chain supramolecular metal–organic frameworks (SMOFs).