Guest Exchange Reactions in Isostructural 3D Porous Coordination Polymers of Ni(II), Co(II), and Mn(II)

Abstract

A series of isostructural compounds, {[Ni2(DBIBA)3]·(BF4)·6H2O}n (1), {[Ni2(DBIBA)3]·(ClO4)·3H2O}n (2), {[Ni2(DBIBA)3]·(NO3)·3H2O}n (3), {[Ni2(DBIBA)3]·Cl·C2H5OH}n (4) {[Co2(DBIBA)3]·(ClO4)·3H2O}n (5), {[Co2(DBIBA)3]·Cl·3C2H5OH}n (7), {[Co2(DBIBA)3]·Cl·3DMF}n (8), {[Co2(DBIBA)3]·Cl·3CH3COCH3·7H2O}n (9), and {[Mn2(DBIBA)3]·Cl·3DMF·3H2O}n (10), have been afforded via anion and solvent exchanges of previously reported coordination polymers {[Ni2(DBIBA)3]·Cl·18H2O}n, {[Co2(DBIBA)3]·Cl·9H2O}n, and {[Mn2(DBIBA)3]·Cl·3H2O}n (DBIBA = 5-di(1H-benzo[d]imidazol-1-yl)benzoate). Anion-exchanged compounds including {[Co2(DBIBA)3]·(NO3)·3H2O}n (6) have also been synthesized under solvothermal conditions by employing metal salts and the corresponding acid hydrolysis of the cyanide functional group of 5-di(1H-benzo[d]imidazol-1-yl) benzonitrile (DBIBN). These structures are obtained with retaining crystallinity, and only insignificant changes are observed in bond lengths and bond angles involving the metal ion. However, noncovalent supramolecular interactions (anion−π, π–π, and hydrogen bonding) are utterly affected or changed. Interestingly, in complex 9, the chloride ion moves from the node of the parent complex to the center of the cavity, where it is surrounded by a hexameric water cluster revealing strong H-bonding, which is very rare to be seen. Exchange of solvent molecules leaves the size of the voids unaltered, but anion exchanges are accompanied by shrinking of the voids, except in the case of NO3– exchange, where there is no change in volume. All are isoreticular structures with a binodal 4,6-connected stp net topology. These compounds have been characterized by single-crystal X-ray crystallography, IR spectroscopy, TGA, PXRD, and elemental analysis.