Luminescent zinc aliphatic dicarboxylate coordination polymers with bis(4-pyridylmethyl)piperazine: Effect of chain length and steric bulk on topology and water molecule aggregation

Abstract

Hydrothermal reaction of zinc nitrate, aliphatic dicarboxylic acids, and the long-spanning hydrogen-bonding capable tethering ligand bis(4-pyridylmethyl)piperazine (4-bpmp) has produced seven coordination polymer solids that were characterized via single-crystal X-ray crystallography. [Zn(suc)(4-bpmp)(H2O)2]n (1, suc=succinate) shows 2D+2D→3D mutually inclined interpenetrated parallel coordination polymer layers with (4,4) grid topology. {[Zn2(dms)2(4-bpmp)]·2H2O}n (2, dms=2,2-dimethylsuccinate) exhibits 1-D [Zn2(dms)2]n ribbons featuring {Zn2(OCO)2} dimeric units pillared into 2-D by 4-bpmp ligands. {[Zn(glu)(4-bpmp)]·6H2O}n (3, glu=glutarate) manifests a 3-fold interpenetrated 3-D 66 diamondoid topology with embedded C(10)A(4) water chains. [Zn(22dmg)(4-bpmp)]n (4, 22dmg=2,2-dimethylglutarate) and [Zn(33dmg)(4-bpmp)]n (5, 33dmg=3,3-dimethylglutarate) both display stacked zig–zag (4,4) grid layered topologies, and do not entrain any co-crystallized water molecules. Reduction of the steric hindrance by using 3-methylglutarate (3mg) afforded {[Zn(3mg)(4-bpmp)]·3H2O}n (6), which also displays a (4,4) grid topology, but with embedded R(4)A(2) water molecule hexamers connecting to three different layer motifs. [Zn(adp)(4-bpmp)]n (7, adp=adipate) possesses a system of 5-fold interpenetrated diamondoid nets. Thermal and luminescent properties of these materials are discussed herein.