# Design of a Triple Emissive Cu4I4 Coordination Polymer through Ligand Engineering

## TL;DR

Scientists designed a new copper-based material that emits three different colors of light when cooled, using smart chemical design and advanced simulations.

## Contribution

A triple emissive coordination polymer was created through ligand engineering, showing three distinct emissions from different electronic transitions.

## Key findings

- CP1 emits three long-lived emissions at 573, 732, and 785 nm at liquid nitrogen temperatures.
- Emissions are attributed to triplet metal/ligand-to-ligand charge transfer, ligand-centered, and excimer transitions.
- Quantum simulations using DFT and TD-DFT accurately predicted the emission maxima.

## Abstract

Through rational ligand design, the coordination polymer
1D-[Cu4(μ3-I)4(μ2-L1)2]
n
(CP1; L1 = 1,1-(1′-naphthylthio)­methane)
has been
predictably prepared from CuI and L1 in acetonitrile
where both the node, closed cubane Cu4(μ3-I)4 cluster, and the assembling ligand containing naphthyl
aromatic pendants are known to be emissive. At liquid nitrogen temperature, CP1 exhibits simultaneously three long-lived emissions centered
at 573, 732, and 785 nm, decaying in the ms time scale (∼7.1
ms), which are readily assigned to triplet metal/ligand-to-ligand
charge transfer (3 M/XLCT), ligand-centered (3LC; i.e., 3ππ*), and excimer (3excimer), respectively. These assignments, which strikingly diverge
from the classical low-energy cluster-centered (3CC) emission
emerging from the Cu4(μ3-I)4 cluster, were based on in-depth photophysical studies and advanced
quantum simulations by density functional theory (DFT) and time-dependent
DFT (TD-DFT), which also calculated the emission maxima with high
precision and degree of agreement.