Self-assembly of luminescent platinum-salen Schiff-base complexes

Treatment of K2PtCI4 with the MeO-salen Schiff base H2L [H2L = N,N'-bis(3-methoxysalicylidene)ethylene-1,2-diamine] gave the precursor complex PtL, which, upon recrystallization from two different solvent mixtures, afforded different solvate forms of PtL center dot H2O (1) and PtL center dot DMF (2) with different solid-state colors. The self-assembly of the PtL precursor with K2Pt(CN)(4) or K2Pd(CN)(4) leads to the isolation of isostructural compound [K-2(PtL)(2)Pt(CN)(4)]center dot 1.5H(2)O (3) or [K-2(PtL)(2)Pd(CN)(4)]center dot 1.5H(2)O (4), respectively. The solid-state structures of 1-4 were established by X-ray crystallography. It is interesting that the helix of the PtL units, along with the other two homochiral helical arrangements of K+ and M2+ (M = Pt or Pd) ions, can generate a unique fake example of a triple-stranded helix in a 1-D helical polymeric chain. Two such triple-stranded helical chains intertwining one another can give rise to a double-stranded helix formed by intermolecular weak C-H center dot center dot center dot N hydrogen-bonding interactions with a long helical pitch of ca. 56 angstrom. The optical absorption and photoluminescence properties of 1-4 were also examined. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).