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 {[Zn3(η9-LI)(η2-H2O)1(η1-H2O)7]·(H2O)5}3n (1), {[Co3(η9-LI)(η2-H2O)1(η1-H2O)7]·(H2O)5}3n (2), {[Cu5(η8-HLI)2·10H2O]·(H2O)4}3n (3), {[Ni3(η12-LII)(η1-H2O)6]·1.5H2O}3n (4), to ternary {[Zn(η3-H4LI)(4,4′-bipy)(η1-H2O)]·(H2O)2}2n (5), {[Zn2(η4-H3LI)(1,10-phen)3·(η1-NO3)]·H2O}1n (6), {[Cd2(η4-H4LI)2(2,2′-bipy)2(η1-H2O)2]·(2,2′-bipy)·(H2O)3}1n (7), {[Co1.5(η3-H3LI)(η1-4,4′-bipy)3(η1-H2O)3]·6H2O}1n (8), [Mn(1,10-phen)2(H2O)2]·(H4LI)·(H2O)5 (9) (LI = all-cis (a,e,a,e,a,e) conformation L6−, LII = 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 {32;4}{3;63;86} network in the Schlafli notation. Complex 3 is a 3,6-connected {43}{45;67;83} network. Complex 4 is a 3,9-connected 9-noted with {42;6}3{46;621;89} 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 LII, while in all the other room temperature complexes, L adopts an LI 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 °C.