DISCRETE MACROCYCLES TO INFINITE POLYMERIC FRAMES - CRYSTAL ENGINEERING STUDIES OF AG(I)PYRIMIDINE COMPLEXES

Crystal structures of seven complexes with varying Ag(I):pyrimidine ra tios reveal novel 0D, 1D, 2D, and 3D networks: [Ag(pyrimidine)][NO3] ( 1), [Ag(pyrimidine)][ReO4] (2), [Ag(pyrimidine)(1.5)][BF4]. H2O (3), [ Ag-2.5(pyrimidine)(3)][ClO4](2.5), (4), [Ag(pyrimidine)(1.5)][BF4] (5) , [Ag(pyrimidine)(2)][BF4] (6), and [Ag(pyrimidine)(2)][PF6]. 0.5H(2)O (7). The 1:1 Ag:pyrimidine tetracationic squares observed in complexe s 1 and 2 suggest a simple one-step route to the synthesis of discrete macrocycles. Further, the open channel architecture of the macrocycle s in these complexes facilitates ion exchange. Complex 3 (also 1:1) is solvated with water molecules and has a corrugated molecular brick wa ll architecture with Ag(I) adopting a ''T-shaped'' geometry. The unusu al metal-to-ligand ratio in 4 (2.5:3) leads to the formation of a 1D s taircase polymer comprised of molecular squares linked by dipyrimidine units. Complex 5 (1:1.5) has a 9.5 Angstrom-thick 2D layer structure formed by tetracationic macrocycles that are linked at the corners by pyrimidine units. The 1:2 complexes, 6 and 7, form two different 3D po lymers based on conformational isomerism of Ag(I):pyrimidine tetrahedr a. The structural features of complexes 1-7 suggest that angular ligan ds are far more likely to exhibit supramolecular isomers than linear b ifunctional ligands and that rational design of coordination polymers with multiple metal coordination geometries would result in novel infi nite polymeric frameworks. (C) 1998 Elsevier Scieclce Ltd.