Two versatile N,N′-bipyridine-type ligands for preparing organic-inorganic coordination polymers:: New cobalt- and nickel-containing framework materials

The Schiff base ligands 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (L1, monoclinic, P2(1)/c, a = 3.856(1) Angstrom, b = 11.032(2) Angstrom, 12.738(3) Angstrom, beta 92.21(3)degrees, Z = 2) and 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (L2, monoclinic, P2(1)/c, a = 10.885(2) Angstrom, b = 4.613(1) Angstrom, 14.978(3) Angstrom, beta = 92.827(4) degrees, Z = 2) were used in the synthesis of four new organic-inorganic coordination polymers, each of them adopting a different structural motif. Synthesis, X-ray structural determinations, and spectroscopic and thermogravimetric analyses are presented. The reaction between Co(NO3)(2 .)6H(2)O and L1 afforded a two-dimensional noninterpenetrating brick-wall structure, [CO(C12N4H10)(l.5)(NO3)(2)(H2O)(CH2Cl2)(2)](n) (1, triclinic, P (1) over bar; a=10.242(7) Angstrom, b=10.802(7) Angstrom, c=15.100(1) Angstrom, alpha = 70.031(1), beta = 75.168(11), gamma = 76.155(11), Z = 2), while Ni(NO3)(2 .)6H(2)O combined with L1 yielded an interpenetrating three-dimensional rhombus-grid polymer, [Ni(C12N4H10)(2)(NO3)(2)(OC4H8)(1.66)(H2O)(0.33)](n) (2, monoclinic, C2/c; a =20.815(8) Angstrom, b = 23.427(8) Angstrom, c = 17.291(6) Angstrom, beta = 116.148(6), Z = 8). The reaction of Co(NO3)(2). 6H(2)O and L2 was found to be solvent-sensitive and resulted in the formation of two different noninterpenetrating compounds: [Co(C14N4H14)(2)(NO3)(C6H6)(1.5)](n) (3, monoclinic, C2/c; a = 22,760(2) Angstrom, b = 21.010(3) Angstrom, c= 25.521(2) Angstrom, beta = 97.151(2), Z = 8), which adopts a two-dimensional square-grid motif formed by propeller-type modules, and [Co(C14N4H14)(1.5)(NO3)(2)(CH2Cl2)(2)](n) (4, monoclinic, P2(1)/n; a = 14.432(2) Angstrom, b = 14.543(8) Angstrom, 15.448(4) Angstrom, beta = 96.968(0), Z = 4), consisting of T-shaped building blocks assembled into a one-dimensional ladder-type structure. These four coordination polymers all exhibit impressive thermal stability. Thermogravimetric studies showed that after complete removal of the solvents, the frameworks are stable to temperatures between 234 degreesC and 260 degreesC.