Temperature-induced chiral Ag(i) coordination polymers with structural variation from 1D to 2D: synthesis, luminescence and SHG response

Abstract

Three new chiral Ag(I) coordination polymers with dual chiral components, {{Ag₃[(1R,2R,N¹S,N²S)-2,3-pcd]₂(H₂O)}·3BF₄·3H₂O}_n (1), {{Ag₅[(1R,2R,N¹S,N²S)-2,3-pcd]₄(BF₄)}·3BF₄·NO₃·2H₂O·CH₃OH}_n (2) and {{Ag_2.5[(1R,2R,N¹S,N²S)-2,3-pcd]₂}·2.5BF₄}_n (3) (where (1R,2R)-2,3-pcd = (1R,2R)-N¹-(pyridin-2-ylmethyl)-N²-(pyridin-3-ylmethyl)cyclohexane-1,2-diamine) have been synthesized with the same materials at 15, 25 and 40 °C, respectively, in which 1 is a one-dimensional (1D) linear chain, 2 displays a branched zigzag chain, while 3 has a two-dimensional (2D) (4,4) topology. 1 can be transformed to 3 by heating at 40 °C in methanol. The conformations and coordination ability of the ligand, as well as coordination numbers of metal centers are altered with the increasing of temperature. Circular dichroism spectra and second-harmonic generation efficiency measurements of these three compounds confirmed that they were of structural chirality in the bulk samples. Luminescent properties indicated that they may have potential applications as optical materials. The present result demonstrates that temperature is a crucial factor for the construction of coordination polymers.