Spectroscopic and Electrochemical Insights into Strategies Tuning Red-Green-Blue (RGB) Electrochemiluminescence from a Single Ruthenium Complex

Understanding the relationship between emissive centers and molecular structure is crucial for designing single-molecule complexes capable of generating white light. Herein, we present a systematic spectroscopic study of a ruthenium-based complex (S3) that emits green and blue light in chemiluminescence (CL) and photoluminescence (PL) processes while enabling tunable white light emission through potential modulation in electrochemiluminescence (ECL). The S3 complex consists of a Ru(pipy)2(CO)2 (pipy = 2-phenylpyridine) core structure with two anthracene units ligated to the phenylpyridine moieties of the ruthenium center. During the CL process, the S3 complex exhibited a time-dependent emission shift from green to blue. The blue emissions at 405 and 445 nm primarily originate from the phenyl anthracene moiety, while the green emission at 525 nm is attributed to the Ru center. Interestingly, the red emission at 640 nm was not observed in PL or CL, suggesting that this red-shifted emission arises from exciplex formed uniquely during the ECL process. By adjusting the applied potential to −2.3 V vs SCE, white light emission was achieved with CIE coordinates of (0.31, 0.31). The absolute ECL and CL quantum efficiencies were determined to be 0.00018% ± 0.00004% and 0.18% ± 0.03%, respectively. The ability to generate multicolor emissions, including tunable white light, from a single complex simplifies the ECL process and underscores its potential for applications in multicolor biosensing, advanced lighting, and display technologies. This work paves the way for the future development of single-component ECL systems with tunable optical properties.