# Roles of Water Molecules in the Structures and Magnetic Properties of Coordination Polymers with a Dicarboxylate Ligand

## TL;DR

This paper explores how water molecules influence the structure and magnetic properties of coordination polymers made with a specific dicarboxylate ligand.

## Contribution

The study reveals distinct structural roles of water molecules in coordination polymers and their impact on magnetic behavior.

## Key findings

- Water molecules mediate antiferromagnetic superexchange in Co(II) and Ni(II) compounds.
- Water molecules form hydrogen-bonded ladder motifs in Zn(II) compounds, creating a 3D supramolecular architecture.
- Spin-canting structures emerge in Co(II) compounds at low temperatures due to water-mediated interactions.

## Abstract

Three new coordination polymers, {[M(nbpdc)(DMF)(H2O)2]·H2O}∞ (M = Co and Ni) and [Zn(nbpdc)(DMF)(H2O)]∞, were synthesized from 2-nitrobiphenyl-4,4′-dicarboxylate (nbpdc2−). The isomorphous Co(II) and Ni(II) compounds exhibited a two-dimensional coordination network in which the chains with single-water bridges and the chains with single-nbpdc2− bridges intersected each other by sharing the metal ions. The coordination networks were connected with uncoordinated water molecules through hydrogen bonds. The rarely identified single-water-bridged coordination chain was reinforced by water-based intrachain hydrogen bonds. The single-water bridges mediated modest antiferromagnetic superexchange in both Co(II) and Ni(II) compounds and afforded a spin-canting structure for the Co(II) compound at low temperatures. Water molecules played a distinct structural role in the Zn(II) compound, which was a one-dimensional coordination polymer with single-nbpdc2− bridges. Instead of bridging metal ions, each water molecule was coordinated to one metal ion and hydrogen-bonded to the coordination spheres of other two metal ions, resulting to an infinite ladderlike hydrogen-bonding motif. The ladders interlinked the nbpdc-bridged chains into a three-dimensional supramolecular architecture featuring the 5-conneted {44.64} net.