Emissive Azobenzenes Delivered on a Silver Coordination Polymer

TL;DR

This study demonstrates that aminoazobenzene derivatives form luminescent silver coordination polymers at room temperature, with reversible emission switching upon analyte addition, highlighting potential for sensing applications.

Contribution

It introduces a new class of luminescent silver coordination polymers based on aminoazobenzene derivatives and reveals their reversible emission switching behavior.

Findings

Four aminoazobenzene ligands form luminescent silver polymers.

The polymer's emission can be reversibly switched off and on.

The switching is driven by ligand displacement with analytes.

Abstract

Azobenzene has become a ubiquitous component of functional molecules and polymeric materials because of the light-induced trans-cis isomerization of the diazene group. In contrast, there are very few applications utilizing azobenzene luminescence, since the excitation energy typically dissipates via nonradiative pathways. Inspired by our earlier studies with 2,2'-bis[N,N'-(2-pyridyl)methyl]diaminoazobenzene (AzoAMoP) and related compounds, we investigated a series of five aminoazobenzene derivatives and their corresponding silver complexes. Four of the aminoazobenzene ligands, which exhibit no emission under ambient conditions, form silver coordination polymers that are luminescent at room temperature. AzoAEpP (2,2'-bis[N,N'-(4-pyridyl)ethyl]diaminoazobenzene) assembles into a three-dimensional coordination polymer (AgAAEpP) that undergoes a reversible loss of emission upon the addition of metal-coordinating analytes such as pyridine. The switching behavior is consistent with the disassembly and reassembly of the coordination polymer driven by displacement of the aminoazobenzene ligands by coordinating analytes.