Luminescence and nonlinear optics of 1D N,N′-bis(salicylidene)-1,2-cyclohexanediamine lanthanide coordination polymers

A series of five new N,N′-bis(salicylidene)-1,2-cyclohexanediamine (H2L) lanthanide coordination polymers, namely, [Nd(H2L)(NO3)3MeOH]n (1), {[Sm(H2L)Cl2(MeOH)3]Cl·3MeOH}n (2), {[Ln(H2L)Cl2(MeOH)3]Cl·2MeOH}n [Ln = Gd (3) and Er (4)] and {[Lu(H2L)Cl3(MeOH)]·H2O}n (5) have been isolated by reactions of H2L with LnCl3·6H2O and Ln(NO3)3·6H2O, respectively. X-ray crystallographical analysis revealed that H2L effectively functions as a bridging ligand forming a series of 1D linear polymers 1 and 5 as well as 1D spiral polymers 2–4. The luminescence of complexes 1 and 2 has been investigated. Complex 1 exhibits the NIR luminescence of Nd(III) ion and complex 2 exhibits co-luminescence of the ligand and the Sm(III) ions. The lowest triplet level of ligand H2L was calculated on the basis of the phosphorescence spectrum of complex 3. The energy transfer mechanism in the 2 were described and discussed. Strikingly, coordination polymer 5 is SHG active, and the SHG efficiency is 0.4 times as much as that of urea.