Novel complexes constructed by flexible 1,2,3,4,5,6-cyclohexanehexacarboxylate and transition metal ions - From 0D mononuclear to 3D porous coordination polymers

Nine novel coordination polymers were prepared from flexible 1,2,3,4,5,6-cyclohexanehexacarboxylate (H6L) and corresponding metal ions at room temperature and/or hydrothermal conditions, namely from binary {[Zn-3(eta(9)-L-I)(eta(2)-H2O) (1)(eta(1)-H2O)(7)]center dot(H2O)(5)}(n)(3) (1), {[Co-3(eta(9)-L-I)(eta(2)-H2O)(1)(eta(1)-H2O)(7)]center dot(H2O)(5)}(n)(3) (2), {[Cu-5(eta(8)-HLI)(2)center dot 10H(2)O]center dot(H2O)(4)}(n)(3) (3), {[Ni-3(eta(12)-L-II)(eta(1)-H2O)(6)]center dot 1.5H(2)O}(n)(3)(4), to ternary {[Zn(eta(3)-H4LI)(4,4'-bipy)(eta(1)-H2O)]center dot(H2O)(2)}(n)(2) (5), {[Zn-2(eta(4)-H3LI)(1,10-phen)(3)center dot(eta(1)-NO3)]center dot H2O}(n)(1) (6), {[Cd-2(eta(4)-H4LI)(2)(2,2'-bipy)(2)(eta(1)-H2O)(2)]center dot(2,2'-bipy)center dot(H2O)(3)}(n)(1) (7), {[Co-1.5(eta(3)-H3LI)(eta(1)-4,4'-bipy)(3)(eta(1)-H2O)(3)]center dot 6H(2)O}(n)(1) (8), [Mn(1,10-phen)(2)(H2O)(2)]center dot(H4LI)center dot(H2O)(5) (9) (L-I = all-cis (a,e,a,e,a,e) conformation L6-, L-II = all-trans (e,e,e,e,e,e) conformation L6-, where a and e represent the carboxylate that is almost perpendicular/parallel to the least square of the cyclohexane moiety. 2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine, 1,10-phen = 1,10-phenanthroline). Complexes 1, 2, 3 and 4 have 3D coordination frameworks, in which H6L are fully deprotonated or only mono-protonated, their coordination numbers are 8, 9 and 12. Complexes 1 and 2 are isomorphous with each other and exhibit 3,5-connected with {3(2);4}{3;6(3);8(6)} network in the Schlafli notation. Complex 3 is a 3,6-connected {4(3)}{4(5);6(7);8(3)} network. Complex 4 is a 3,9-connected 9-noted with {4(2);6}(3){4(6);6(21);8(9)} network. 5-8 are ternary complexes with secondary building blocks where L binds 2 to 4 protons, respectively. The coordination number of L decreased to 3-4 in complexes 5-8. Complex 9 is a mononuclear complex where H4L2- acts as a counter ion to balance the charge of the metal ion. The ligand in hydrothermal synthesized 4 adopts the all-trans configuration L-II, while in all the other room temperature complexes, L adopts an L-I configuration. As a role, it is always the e-position carboxylate that prefers to coordinate to the metal ion. The solid state photoluminescence studied indicates that there are ligand-centered emissions in 1, 5, 6, and 7. Complex 2 is a breathable porous coordination polymer, X-ray powder diffraction patterns (PXRD) studies have shown that the dehydration/rehydration of 2 can be fully reversible under 100 degrees C.