Tuning framework formation by flexible ligand elongation and second ligating spacer variation: increasing dimensionality and macrocycle size

Abstract

An investigation on the dependence of the framework formation of coordination polymers is reported based on the self-assembly of copper(I) halide or pseudohalide and two relating nitrogen-containing heterocyclic thioether ligands, L1 and L2 [L1 = bis(2-pyrimidinylthio)methane, L2 = 1,2-bis(2-pyrimidinylthio)ethane]. Four new metal–organic frameworks, namely [Cu2I2(L1)2]n (1), [CuCN(L1)]n (2), [Cu2I2(L2)2]n·nL2 (3) and [CuCN(L2)]n (4) have been synthesized and characterized by X-ray crystallography. Structural diversities of these frameworks can be adjusted by elongation of flexible dithioether ligands and the selection of second ligating spacers, resulting in increasing structural dimensionality from a 1D linear chain (1), 2D layers (2,3) to a 3D diamondoid network (4). There exist fused macrocyclic rings with increasing sizes in these frameworks, ranging from 16-, 22-, 40- to 42- membered rings, respectively. The repeating “square” 40-membered macrocycle [Cu6I2(L2)4] in 3 is so large that two free L2 molecules occupy the voids of the macrocycle, stabilizing the channel-like assembly through intermolecular N⋯S interactions between the pyrimidyl rings of the L2 guest and the macrocycle-based host, whereas large macrocycles lead to two-fold interpenetration of the diamondoid nets of 4. Complexes 1–4 all show yellow photoluminescence in the solid state at room temperature.