White Light Emissive Eu(III) Complexes through Ligand Engineering and their Applications in Cool Near Ultraviolet White Light Emitting Diodes and Thermometer

Swetha Maredi; Sibani Mund; Sandhya Rani Nayak; Samatha Devineni; Subrahmanyam C; Vaidyanathan Sivakumar

doi:10.1002/cphc.202400320

White Light Emissive Eu(III) Complexes through Ligand Engineering and their Applications in Cool Near Ultraviolet White Light Emitting Diodes and Thermometer

Chemphyschem. 2024 May 9:e202400320. doi: 10.1002/cphc.202400320. Online ahead of print.

Authors

Swetha Maredi¹, Sibani Mund², Sandhya Rani Nayak³, Samatha Devineni², Subrahmanyam C⁴, Vaidyanathan Sivakumar⁵

Affiliations

¹ Department of Chemistry, IIT Hyderabad, chemistry, INDIA.
² IIT Hyderabad, chemistry, INDIA.
³ Department of Chemistry, IIT Hyderabad, Chemistry, INDIA.
⁴ IIT Hyderabad, Chemistry, INDIA.
⁵ Indian Institute of Technology Hyderabad, Chemistry, 5th Floor F-17, Department of Chemistry, Indian Institute of Technology, Hyderabad Kandi Sangareddy 502285 Telangana Indi, 502285, Sangareddy, INDIA.

PMID: 38725280
DOI: 10.1002/cphc.202400320

Abstract

In pursuit of enhancing white light quality for SSL applications, an attempt has been made to design novel imidazo-bipyridyl ligands as an ancillary ligand to obtain multiple emissions (mimic sunlight) in the Eu-complex. By strategically modifying the phenanthroline core with imidazo-bipyridyl incorporation with 1 or 2-Napthyl groups at the C1 position, the excitation spectral line is successfully shifted from Ultraviolet (UV) to near UV/visible spectrum (where the LED emission occurs). The ligands showed greenish blue emission in solid and solution. The analysis revealed that the energy transfer is incomplete, primarily attributed to the proximity of triplet state energy levels to the resonance level of Eu(III) ions as reflected in solvatochromism. These complexes exhibit a unique dual emissive behavior (emitting multi-color) including white light across various solvents. The fabricated white LED showed an excellent color rendering index (CRI ~93 %). Beyond lighting, this distinctive property opens avenues for temperature sensing ([Eu(DBM)31-Naph] shows the highest sensitivity of Sr = 10.97 %, and [Eu(DBM)32-Naph] shows the highest sensitivity of Sr = 5.5 % at 333K) and vapoluminescent studies. This research pioneers the development of these complexes as potential single-component materials for white LEDs, underlining their multifaceted utility in cutting-edge lighting and sensing technologies.

Keywords: Energy transfer; Eu(III) ion; LED; Sensors; vapoluminescence.