# Investigation of Mechanochromic and Solvatochromic Luminescence of Cyclometalated Heteroleptic Platinum(II) Complexes with Benzoylthiourea Derivatives

## TL;DR

This paper reports the synthesis and characterization of two new platinum complexes that change their luminescence color under mechanical or thermal stimuli.

## Contribution

The study introduces novel platinum complexes with mechanochromic and solvatochromic properties due to their unique ligand structure.

## Key findings

- The complexes show photoluminescence with quantum yields up to 28.3% in PMMA films.
- They exhibit reversible color changes from green to red-orange under grinding, solvent treatment, or heating.
- Structural and thermal analyses confirm no mesomorphic behavior despite long alkyl chains.

## Abstract

Two novel cyclometalated platinum(II) complexes based on 2-phenylpyridine (ppy) and 2,4-difluorophenylpyridine (dfppy) ligands in combination with a benzoylthiourea (4-(decyloxy)-N-((4-(decyloxy)phenyl)carbamothioyl)benzamide, BTU) functionalized with decyloxy alkyl chains as auxiliary ligands were synthesized and characterized for their mechanochromic and photophysical properties. Structural characterization was achieved through IR and NMR spectroscopy, single-crystal X-ray diffraction, and TD-DFT calculations. Both complexes exhibit significant photoluminescence with quantum yields up to 28.3% in a 1% PMMA film. The transitions in solution-phase spectra were assigned to mixed metal-to-ligand (MLCT) and intraligand (ILCT) charge–transfer characteristics. Temperature-dependent studies and thermal analyses confirm reversible phase transitions without mesomorphic behavior despite the presence of the two long alkyl chains. Both complexes displayed reversible mechanochromic and solvatochromic luminescence, with a change in emission color from green to red-orange emissions upon grinding and solvent treatment or heating at 80 °C.