Blue-Emitting 2D-and 3D-Zinc Coordination Polymers Based on Schiff-Base Amino Acid Ligands

The solvothermal reaction of Zn(NO3)(2)center dot 4H(2)O, 1-OH-2-naphthaldehyde, and 2-methylalanine (mAla) in MeOH leads to the formation of complex {[ZnL1]}(2n) (1) (H2L1 = the Schiff-base resulting from the reaction of 1-OH-2-naphthaldehyde and mAla) in good yields. The structure of the neutral species, as determined by single-crystal crystallography, describes a two-dimensional coordination polymer, with repeating {Zn-2} units bridged by syn, anti-carboxylate groups of the Schiff-base ligands. Repeating the same reaction using glycine (gly) instead of mAla leads to the formation of complex {[ZnL2]center dot 0.33MeOH}(3n) (2.0.33MeOH) (H2L2 = the Schiff-base resulting from the reaction of 1-OH-2-naphthaldehyde and gly), again in good yields. Complex 2 describes a three-dimensional coordination polymer based on {Zn-2} building blocks, arranged by anti, anti-carboxylate groups in a 3D motif. Complexes 1 and 2 were found to strongly emit at similar to 435 nm (lambda(exc) = 317 nm) both in solution and solid state, with complex 2 displaying a slightly longer lifetime of tau(av) = 2.45 ns vs. tau(av) = 2.02 ns for 1.

Automated summary

In this study, two complexes were synthesized through a solvothermal reaction in methanol, forming two-dimensional and three-dimensional coordination polymers connected by Schiff base ligands. Both complexes exhibit similar strong emission properties in solution and solid state, with complex 2 displaying a slightly longer lifetime.