Coordination Complexes of Cd(II), Cu(II), Zn(II), and Substituted Diimide Ligands: Syntheses, Structural Analyses and Gas Sorption Studies

We report the syntheses, structural and thermal analyses of four coordination complexes namely {[Cd(L1)2(NDC)]·4DMF}n·1, {[CuL2]·DMF}n·2, {[Zn(L3)0.5(DDN)]·DMF}n·3 and {[Zn(L4)0.5 (DDN)]·DMF·H2O}n 4. Here, L1 is 2,2′-bis(pyridin-4-ylmethyl)-[5,5′-biisoindoline]-1,1′,3,3′-tetraone; L2 is 2,2′-(1,1′,3,3′-tetraoxo-[5,5′-biisoindoline]-2,2′-diyl)diacetic acid; L3 is 2,7-bis(pyridin-3-ylmethyl)benzo [lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone; L4 is 2,7-bis(pyridin-4-ylmethyl)benzo[lmn][3,8] phenanthroline-1,3,6,8(2H,7H)-tetraone; DMF is N,N-dimethylformamide; H2NDC is 2,6-naphthalene dicarboxylic acid; and H2DDN is 6,6′-dithiodinicotinic acid. Complexes 1, 3, and 4 are three-dimensional, while complex 2 is two-dimensional. Powder X-ray diffraction indicates that complex 1 changes its structure upon desolvation but does not revert to its original form when exposed to DMF. Carbon dioxide (CO2) sorption studies on 1 indicate that the complex adsorbs minimal amounts of CO2 at 273 K.