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) A, b = 11.032(2) A, c = 12.738(3) A, 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) A, b = 4.613(1) A, c = 14.978(3) A, 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(NO(3))(2).6H(2)O and L1 afforded a two-dimensional noninterpenetrating brick-wall structure, [Co(C(12)N(4)H(10))(1.5)(NO(3))(2)(H(2)O)(CH(2)Cl(2))(2)](n)() (1, triclinic, P1; a = 10.242(7) A, b = 10.802(7) A, c = 15.100(1) A, alpha = 70.031(1), beta = 75.168(11), gamma = 76.155(11), Z = 2), while Ni(NO(3))(2).6H(2)O combined with L1 yielded an interpenetrating three-dimensional rhombus-grid polymer, [Ni(C(12)N(4)H(10))(2)(NO(3))(2)(OC(4)H(8))(1.66)(H(2)O)(0.33)](n) (2, monoclinic, C2/c; a = 20.815(8) A, b = 23.427(8) A, c = 17.291(6) A, beta = 116.148(6), Z = 8). The reaction of Co(NO(3))(2).6H(2)O and L2 was found to be solvent-sensitive and resulted in the formation of two different noninterpenetrating compounds: [Co(C(14)N(4)H(14))(2)(NO(3))(2)(C(6)H(6))(1.5)](n)() (3, monoclinic, C2/c; a = 22.760(2) A, b = 21.010(3) A, c = 25.521(2) A, beta = 97.151(2), Z = 8), which adopts a two-dimensional square-grid motif formed by propeller-type modules, and [Co(C(14)N(4)H(14))(1.5)(NO(3))(2)(CH(2)Cl(2))(2)](n)() (4, monoclinic, P2(1)/n; a = 14.432(2) A, b = 14.543(8) A, c = 15.448(4) A, 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 degrees C and 260 degrees C.