Chiral crystallization and optical properties of three metal complexes based on two non-centrosymmetric tripodal ligands

摘要

Chiral coordination polymers have attracted much attention due to their special properties and significant applications. In this work, we synthesized two non-centrosymmetric ligands, N,N-bis(4-(1H-imidazol-1- yl) phenyl)-4-(pyridin-4-yl) aniline (DIMPPA) and N-(4-(1H-imidazol-1-yl) phenyl)-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl) phenyl) aniline (MIDPPA), via structural modification of two reported centrosymmetric ligands; after that achiral -> chiral induction occurred in the construction of three coordination polymers namely {[Cd(DIMPPA)(5-OH-bdc)](H2O)}(n) (1), {[Co(DIMPPA)(5-OH-bdc)](H2O)}(n) (2) and {[Cd-2(MIDPPA)(2)(D-ca) 2(H2O)(2)](H2O)(5)}(n) (3), when replacing the reported centrosymmetric ligands with non-centrosymmetric ligands (5-OH-H(2)bdc = 5-hydroxyisophthalic acid, D-H(2)ca = D-camphoric acid). Isostructural complexes 1 and 2 exhibit chiral 2D -> 3D frameworks with the coexistence of polyrotaxane and parallel polycatenation features. Complex 3 shows two-fold interpenetrating 3D chiral architecture with cds-type topology. The luminescence emissions of both complexes 1 and 3 are mostly assignable to the internal pi ->pi* electron transition in DIMPPA and MIDPPA, respectively. Complex 3 can satisfy the fundamental requirement of second-order nonlinear optical materials.