Metal-Directed Assembly of Coordination Polymers with a Multifunctional Semirigid Ligand Containing Pyridyl and Benzimidazolyl Donor Groups

A new multifunctional semirigid Schiff-base ligand comprising two pyridyl (Py) and two benzimidazolyl (Bim) donor groups, 1,2-bis(1-(1-(pyridine-3-ylmethyl)benzimidazol-2-yl)ethylidene)hydrazine (L), has been synthesized, with which 10 coordination polymers of different transition metal ions, namely, {[AgL]CF3SO3 center dot CH3OH}(n) (1), {[Ag2L](p-CH3C6H4SO3)(2)center dot 2CH(3)OH}(n) (2), {[Hg3LCl6]center dot CHCl3}(n) (3), [HgLBr2](n) (4), {[CdL(CH3CO2)(2)H2O]center dot 1.5H(2)O}(n) (5), [CdLI2](n) (6), ([MnL(H2O)(4)](ClO4)(2)center dot H2O}(n) (7), [MnL(p-CH3C6H4SO3)(2)](n) (8), {[ZnL2(CH3CN)(2)(H2O)(2)](CF3SO3)(2)}(n) (9), and {[ZnL2(CH3CH2OH)(2)(H2O)(2)](p-CH3C6H4SO3)(2)}(n) (10) have been prepared and characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction, and single-crystal X-ray diffraction. In complexes 1, 2, and 3, L acts as a tetradentate ligand to connect four metal ions that show the same coordination environment in 1 or different coordination environments in 2 and 3, generating two-dimensional (2D) networks of the (4, 4) net topology. In complexes 4-8, 1, acts as a bidentate ligand to bridge two metal ions that display diversified coordination environments depending on coordination of the anions and/or water molecules. Complexes 4-7 have similar one-dimensional (1D) chain structures, while 8 is a three-dimensional (3D) framework with dia topology. In complexes 9 and 10, L acts as a monodentate ligand to form mononuclear coordination motifs. Besides versatile coordination modes, ligand 1, takes oil different conformations responsive to donor affinity of different metal ions. In the case that the ligand L is bidentate or monodentate, there are Py and/or Bim groups free of coordination, thus being able to form hydrogen bonds through their noncoordinating N-py or N-Bim atoms. Therefore, the assembly processes are directed by synergistic effects involving metal-ligand coordination, hydrgoen-bonding, pi center dot center dot center dot pi stacking, and other influencing factors Such as solvents and counteranions.