Engineering of co-ordination polymers of trans-4,4′-azobis(pyridine) and trans-1,2-bis(pyridin-4-yl)ethene:: a range of interpenetrated network motifs

Crystallisation experiments involving cobalt(II), copper(I), copper(II) or cadmium(II) and trans-4,4'-azobis(pyridine) (4,4'-azpy) or trans-1,2-bis(pyridin-4-yl)ethene (bpe) yield M-2(NO3)(4)(L)(3)(CH2Cl2)(H2O)(x) (M = Co, L = 4,4'-azpy, x = 0 1; M = Cd, L = 4,4'-azpy, x = 2 2; M = Co, L = bpe, x = 0 6), Cu(BF4)(L)(2) (L = 4,4'-azpy 3; L = bpe 10), Cu(BF4)(2)(L)(2)(H2O)(2) (L = 4,4'-azpy 4; L = bpe 9) and Cd(NO3)(2)(bpe) 8. Crystals suitable for X-ray diffraction analysis were obtained for the 4,4'-azpy complexes 1-3 and Cu(SiF6)(4,4'-azpy)(2)(H2O)(3) 5, prepared during recrystallisation of 4, but not for any of the complexes of bpe. The molecular architectures of the 4,4'-azpy co-ordination polymer networks are metal centre dependent, the preferred co-ordination geometries of Co(NO3)(2)/Cd(NO3)(2) (T-shaped connecting unit), Cu(I) (tetrahedral connecting unit) and Jahn-Teller distorted Cu(II) (square planar connecting unit) dictating the formation of herringbone, adamantoid and square grid constructions for {[M-2(NO3)(4)(mu-4,4'-azpy)(3)]. CH2Cl2. xH(2)O}(infinity) (M = Co, x = 0 1; M = Cd, x = 2 2), {[Cu(mu-4,4'-azpy)(2)][BF4]}(infinity) 3 and {[{Cu(H2O)(2)}(mu-4,4'-azpy)(2)][SiF6]. H2O}(infinity) 5, respectively. All three networks display interpenetration; three-fold parallel interpenetration of novel herringbone sheets in 1 and 2, five-fold interpenetration of adamantoid networks in 3, and inclined perpendicular interpenetration of rhombically distorted sheets in 5. Despite the interpenetration, cavities are present in all three of the architectures and these are filled by anions and/or guest solvent molecules.