Self‐Assembly of Luminescent Platinum‐Salen Schiff‐Base Complexes

Treatment of K 2 PtCl 4 with the MeO‐salen Schiff base H 2 L [ H 2 L = 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· H 2 O ( 1 ) and PtL· DMF ( 2 ) with different solid‐state colors. The self‐assembly of the PtL precursor with K 2 Pt(CN) 4 or K 2 Pd(CN) 4 leads to the isolation of isostructural compound [K 2 (PtL) 2 Pt(CN) 4 ]· 1.5H 2 O ( 3 ) or [K 2 (PtL) 2 Pd(CN) 4 ]· 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 M 2+ (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 ··· N hydrogen‐bonding interactions with a long helical pitch of ca. 56 Å. The optical absorption and photoluminescence properties of 1 – 4 were also examined.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)