Two temperature-induced 1D CuII chain enantiomeric pairs showing different magnetic properties and nonlinear optical responses

At different reaction temperatures, using Cu(NO3)(2)center dot 3H(2)O to react with enantiomerically pure N-donor ligands (L-S/L-R), respectively, two pairs of chiral one-dimensional (1D) Cu-II chain enantiomers formulated as [Cu(mu(2)-NO3)(NO3)(L-S)](n)/[Cu(mu(2)-NO3)(NO3)(L-R)](n) (S-1-Cu/R-1-Cu, formed at 40 degrees C with an NO3- group as a sole bridging ligand) and [Cu(mu(2)-L-S)(NO3)(2)](n)/[Cu(mu(2)-L-R)(NO3)(2)](n) (S-2-Cu/R-2-Cu, formed at 25 degrees C with L-S or L-R as a bridging ligand) were prepared, where L-S/L-R = (+)/(-)-4,5-pinenepyridyl-2-pyrazine. Interestingly, such a disparity in bridging ligands leads not only to their distinct structural features but also to their completely different magnetic couplings together with a large difference in their nonlinear optical responses. S-1-Cu with a 1D helical structure shows weak ferromagnetic coupling between Cu-II ions, while S-2-Cu with a 1D stairway-like structure presents weak antiferromagnetic coupling. In particular, they simultaneously possess both second- and third-harmonic generation (SHG and THG) responses in one molecule with large strength differences. More remarkably, S-1-Cu exhibits a very large THG response (162 x alpha-SiO2), which is 22.5 times that of S-2-Cu, and the SHG strength of S-1-Cu is more than 3 times that of S-2-Cu. This work demonstrates that reaction temperature has a great impact on the self-assembled structures of coordination polymers and subsequently results in their large performance differences.

Automated summary

At different reaction temperatures, two pairs of chiral one-dimensional Cu-II chains with distinct structural features and magnetic couplings were prepared by reacting Cu(NO3)(2)center dot 3H(2)O with enantiomerically pure N-donor ligands. The differences in bridging ligands resulted in significant disparities in their nonlinear optical responses. This work highlights the importance of reaction temperature in controlling the self-assembled structures and performance differences of coordination polymers.