Supramolecular hybrids based on Ru(ii) porphyrin and octahedral Mo(ii) iodide cluster

Abstract

The coordination-driven design and synthesis of new stable supramolecular cluster–porphyrin (CP) hybrids based on an A₂-type ruthenium porphyrin 5,15-bis[(p-tolyl)porphyrinato(2-)]ruthenium(carbonyl)(aqua) [RuDTolP(CO)H₂O] and an octahedral molybdenum(II) iodide cluster with six terminal isonicotinate ligands (Bu₄N)₂[{Mo₆I₈}(OOC-C₅H₄N)₆] (PyMoC) are reported. The stepwise supramolecular assembly of the PyMoC “superoctahedron” with RuDTolP(CO)H₂O has been studied by ¹H NMR and 2D ¹H–¹H COSY, ¹H–¹⁵N HMBC and DOSY techniques, as well as by UV-vis spectroscopy and HR-ESI mass spectrometry. The formation of discrete cluster–porphyrin CP_n adducts with different numbers of coordinated porphyrins (n = 1–6), including the geometrical isomers of CP₂, CP₃ and CP₄, has been observed. Using a double equivalent amount of RuDTolP(CO)H₂O relative to the cluster (C : P ratio 1 : 12) affords a mixture of CP₅ and CP₆ species in solution, while only the CP₆ complex is crystallized from this system. Fine tuning of crystallization conditions leads to the formation of a more complex architecture CP₆₊₂, where the CP₆ assembly incorporates two additional porphyrin molecules bound to the cluster core by hydrogen bonds. Thus, the coordination-based supramolecular approach provides new stable cluster–multiporphyrin 3D arrays based on two types of photosensitizers, which can be promising for the design of photoactive materials.