Polymorphous one-dimensional tetrapyridylporphyrin coordination polymers which structurally mimic aryl stacking interactions

Two polymorphic structures of rigid one-dimensional (1D) coordination polym ers, [(HgBr2)(2)TPyP]. 2(1,1,2,2-tetrachloroethane, TCE) (1A, 1B), have bee n isolated in which the 1D polymers adopt either stacking or herringbone (o r T-shaped) geometries as observed for simple aromatic hydrocarbons. Polymo rph 1A has a 1D polymeric structure,vith each HgBr2 tetrahedrally coordinat ed to a pyridyl moiety of two TPyP molecules. The 1D polymers in 1A are wea kly cross-linked through long metal-halide bridges forming a 2D steplike sh eet with each sheet stacked to form a continuous open porous structure. The 1D polymers in 1B adopt a T-shaped geometry such that the C-H groups of th e pyrrole rings point toward the porphyrin cavity to maximize C-H ... N or C-H ... C interactions and the crest of the polymer (pyridyl-HgBr2-pyridyl moiety) interdigitates into the supramolecular cavities to form long, but s ignificant Hg ... Br interactions, Indeed, the cause of the stacked versus herringbone structures in 1A and 1B can be traced to the different possible secondary interactions between Br and Hg: edge-on in 1A and side-on in 1B, (This is in contrast to the electrostatic interactions leading to face-to- face versus hydrogen bonding in edge-to-face aromatic packing.) Polymorph 1 A crystallizes in the triclinic space group P-1 with a = 7.3653(9), b = 12. 920(2), and c = 14.320(2) Angstrom, alpha = 72.218(2), beta = 81.858(3), an d gamma = 79.505(3)degrees, V = 1270.5(3) Angstrom(3), D-calc = 2.189 g cm( -3), Z = 1, and R = 0.0672. Polymorph 1B is monoclinic, P2(1)/c with a = 15 .2397(2), b = 30.4642(5), and c = 11.2657(1) Angstrom, beta = 93.212(1)degr ees, V = 5222.06(12) Angstrom(3), D-calc = 2.131 g cm(-3), Z = 4, and R = 0 .0929. (C) 2000 Academic Press.