# Acetylenic Substituent: Influence on the Structure, Electrochemical, Photophysical, and Thermal Properties of Rhenium(I) and Platinum(II) Complexes

## TL;DR

This paper studies how adding an acetylenic group to a ligand affects the properties of rhenium and platinum complexes, including their light emission and electron transfer abilities.

## Contribution

The first use of a 4-phenylacetylene-functionalized ligand in Re(I) and Pt(II) complexes to explore its impact on photophysical and electrochemical properties.

## Key findings

- The acetylenic substituent enables room-temperature emission in Re(I) and Pt(II) complexes.
- The Pt(II) complex shows microsecond photoluminescence lifetime, while the Re(I) complex has a nanosecond lifetime.
- DFT and TD-DFT calculations support the experimental photophysical results.

## Abstract

The ‘wire-like’ acetylenic moiety is an important building block in organic and coordination chemistry that can facilitate electron transfer in donor–acceptor compounds, contributing to the enhancement of their photophysical properties. 2,6-Bis-(thiazol-2-yl)pyridine (dtpy) functionalized with a 4-phenylacetylene group (Ph-C≡C-dtpy) was, for the first time, used for the preparation of [ReCl(CO)3(Ph-C≡C-dtpy)] and [Pt(Ph-C≡C-dtpy)Cl]CF3SO3 in order to understand the properties derived from the use of the acetylenic substituent. The coordination ability of Ph-C≡C-dtpy toward Pt(II) and Re(I) centers was determined. All the studied compounds were characterized using FT-IR, 1H NMR, and 13C NMR spectroscopies, elemental analysis and, in the case of the free ligand and rhenium(I) complex, single-crystal X-ray analysis was also used. Their electrochemical, photophysical, and thermal properties were compared with the previously described similar systems. The photoluminescence spectra of Ph-C≡C-dtpy, [ReCl(CO)3(Ph-C≡C-dtpy)] and [Pt(Ph-C≡C-dtpy)Cl]CF3SO3 were investigated in solution and in the solid state at 298 K and 77 K. The experimental results were supported by the DFT and TD-DFT calculations. As a result of the introduction of the -C≡C- moiety into the organic ligand skeleton, the Re(I) and Pt(II) complexes display room-temperature emission. In the case of [Pt(Ph-C≡C-dtpy)Cl]CF3SO3, photoluminescence lifetime in a microsecond regime was observed, whereas nanosecond lifetime for [ReCl(CO)3(Ph-C≡C-dtpy)] in solution is comparable to lifetimes previously observed for rhenium(I) compounds with 4-substituted dtpys.