Novel single-crystal-to-single-crystal anion exchange and self-assembly of luminescent d10 metal (CdII, ZnII, and CuI) complexes containing C3-symmetrical ligands

Ligands L1 and L2' (L1= N,N',N ''-tris(4-pyridyl)trimesic amide, L2'= N,N,N ''-tris(3-pyridinyl)-1,3,5-benzenetricarboxamide) belonging to an interesting family of tripyridyltriamides with C-3-symmetry have been utilized to construct 3D porous or hydrogen-bonded frameworks. Through a novel single-crystal-to-single-crystal anion-exchange process, [Cd(L1)(2)-(CIO4)(2)](n) (1c) can be obtained from [Cd(L1)(2)Cl-2](n) (1b) in the presence of ClO4- anions. This anion-exchange process is highly selective and only the substitution of Cl- by ClO4- or PF6- could be realized; Cl- was found not to be substituted by BPh4-. This demonstrates that the exchange process depends on the size of the anions in relation to the size of the cavities in the host material (ca. 7.5 angstrom). In addition, the anion-exchange properties of 1b have also been investigated by means of powder X-ray diffraction (PXRD), elemental analysis (EA), and infrared absorption spectroscopy (IR). Structurally, [Zn(L1)(NO3)(2)](n) (2) consists of a 2D coordination network with five-coordinate Zn-II ions. Surprisingly, different trigonal-bipyramidal Zn-II ions propagate to form distinct respective sheet structures, A and B, which are packed in an A-B-A-B manner in the crystal lattice, and these are hydrogen-bonded to give a 3D extended framework. The molecular structure of [CuI(L2')](n) (3) shows that the Cu-I ion adopts a distorted tetrahedral geometry and 3 also forms a 2D coordination network. Significantly, this 2D coordination network is further assembled into a remarkable 3D homochiral framework through triple hydrogen bonding and pi center dot center dot center dot pi interactions. All of these 3D coordination polymers and/or hydrogen-bonded frameworks are luminescent in the solid state, and their solid-state luminescent properties have been investigated at room temperature and/or at 77 K.