Unique homoleptic cyclic tetranuclear Ln4(Salen)4 complexes [Ln4(L)2(HL)2(μ3-OH) 2Cl2]·2Cl (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3; Ln = Gd, 4) or Ln4(Salen)2 complexes [Ln4(L) 2(μ3-OH)2(OAc)6] (Ln = Nd, 5; Ln = Yb, 6; Ln = Er, 7; Ln = Gd, 8) have been self-assembled from the reaction of the hexadentate Salen-type Schiff-base ligand H2L with LnCl 3·6H2O or Ln(OAc)6·6H 2O (Ln = Nd, Yb, Er, or Gd), respectively (H2L: N,N′-bis(salicylidene)cyclohexane-1,2-diamine). The result of their photophysical properties shows that the strong and characteristic NIR luminescence for complexes 1-2 and 5-6 with emissive lifetimes in microsecond ranges are observed, and the sensitization arises from the excited state (both 1LC and 3LC) of the hexadentate Salen-type Schiff-base ligand with the flexible linker. Temperature dependence (1.8-300 K) magnetic susceptibility studies of the eight complexes suggest the presence of an antiferromagnetic interaction between the Ln3+ ions. © 2012 American Chemical Society.
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