Optimizing the Electrochemiluminescence of Readily Accessible Pyrido[1,2‐α]pyrimidines through “Green” Substituent Regulation

C─H Activation Enables the Construction of New Bis-Polyaryl Phenylpyridine Ruthenium Complexes: Conjugation and Rigidity Synergistic Effect for Advanced Electrochemiluminescence

The access to bench-stable organometallic compounds unfolds new chemical space for medicinal and material sciences. In particular, stable organoruthenium compounds with constitutional and stereoisomeric forms for subtle regulation of electrochemiluminescence are intriguing and challenging. Here, coordination of polycyclic aromatic hydrocarbons on (2-phenylpyridine)2(CO)2Ru complex allows access to bis-polyaryl phenylpyridine (BPP) Ruthenium complex through C─H activation strategy and coupling reactions for installation of the functionalities with steric and electronic purposes. The photoluminescence and electrochemiluminescence of BPP Ru complexes are affected by the actual polycyclic aromatic hydrocarbons inherent properties. The anthracene derivatized BPP Ru complex (BPP-Ant) shows the best ECL performance and reveals an enormous ECL quantum efficiency of 1.6-fold higher than the golden standard Ru(bpy)3 2+. The unprecedentedly high efficiency is due to the best compromise between the structural conjugation and molecular rigidity from BPP-Ant providing a providential energy gap that facilitated the feasibility of electron transfer and favored the radiative energy release by experimentally and DFT calculations. Moreover, PL and spooling ECL spectroscopies are used to track and link multiple emission peaks of BPP-Ant at 445, 645, and 845 nm to different emissive species. These discoveries will add a new member to the efficient ECL ruthenium complex family and bring more potentials.

Precise Modulation of Intramolecular Aggregation-induced Electrochemiluminescence by Tetraphenylethylene-based Supramolecular Architectures

The precisely modulated synthesis of programmable light-emitting materials remains a challenge. To address this challenge, we construct four tetraphenylethylene-based supramolecular architectures (SA, SB, SC, and SD), revealing that they exhibit higher electrochemiluminescence (ECL) intensities and efficiencies than the tetraphenylethylene monomer and can be classified as highly efficient and precisely modulated intramolecular aggregation-induced electrochemiluminescence (PI-AIECL) systems. The best-performing system (SD) shows a high ECL cathodic efficiency exceeding that of the benchmark tris(2,2'-bipyridyl)ruthenium(II) chloride in aqueous solution by nearly six-fold. The electrochemical characterization of these architectures in an organic solvent provides deeper mechanistic insights, revealing that SD features the lowest electrochemical band gap. Density functional theory calculations indicate that the band gap of the guest ligand in the SD structure is the smallest and most closely matched to that of the host scaffold. Finally, the SD system is used to realize ECL-based cysteine detection (detection limit=14.4 nM) in real samples. Thus, this study not only provides a precisely modulated supramolecular strategy allowing chromophores to be controllably regulated on a molecular scale, but also inspires the programmable synthesis of high-performance aggregation-induced electrochemiluminescence emitters.

Electrochemiluminescence of dimethylaminonaphthalene-oxazaborine donor-acceptor luminophores

Donor-acceptor (D-A) type molecules with a skeleton consisting of a dimethylaminonaphthalene donor and an oxazaborine acceptor were designed as efficient electrochemiluminescence (ECL) luminophores with tunable intramolecular charge transfer (ICT). The D-A ECL luminophores demonstrated that the ICT characteristics play a critical role in the electrochemistry and ECL of luminophores in the presence of tri-n-propylamine, which was rationalised experimentally and computationally. Furthemore, dual-peaked ECL-potential behaviours of the luminophores were rationalised using two competitive pathway ECL mechanisms, elucidated through the use of spooling ECL spectroscopy.

Regulating highly photoelectrochemical activity of Zr-based mixed-linker metal-organic frameworks toward sensitive electrogenerated chemiluminescence sensing of α-glucosidase

The conductivity and emission efficiency of metal-organic frameworks (MOFs) remain challenging factors that limit their electrogenerated chemiluminescence (ECL) sensing applications. Herein, we report a facile approach to address these challenges by integrating an electroactive linker (H2-TCPP) with an ECL active electrogenerated chemiluminescence linker (H4-TBAPy) to construct a highly photoelectrochemical active mixed-linker MOFs (ML-MOFs). ECL results revealed a remarkable 15.4-fold enhancement for the top-performing ML-MOFs (M6-MOFs), surpassing the single linker MOFs. In addition, M6-MOFs also exhibit a remarkable 73-fold enhancement in ECL efficiency compared to commercial Ru (bpy)32+. This improvement should be attributed to the synergistic effects resulting from the combination of two linkers. Furthermore, M6-MOFs are found to be served as a model ECLphore for sensitive and selective detection of α-glucosidase for the first time with good potential practicability in human serum samples. This work represents a promising direction to guide for designing good conductivity and high ECL efficiency MOFs in terms of linker functionalization and thus bandgap modulation for advancing their ECL sensing applications.

Ultrasensitive and Visual Electrochemiluminescence Ratiometry Based on a Constant Resistor-Integrated Bipolar Electrode for MicroRNA Detection

In this work, a new electrochemiluminescence (ECL) platform was constructed for detecting the prostate cancer marker microRNA-141 (miRNA-141) on a constant resistor-integrated closed bipolar electrode (BPE). It consisted of two reservoirs and a constant resistor, and both ends were connected to the anode of the driving electrode and the cathode of BPE. The cathode of BPE was modified with boron nitride quantum dots (BNQDs), and the anode reservoir was the [Ru(bpy)₃](PF₆)₂/TPrA system. After introducing a certain amount of hairpin DNA 3 (H3) and ferrocene-labeled single-stranded DNA (Fc-ssDNA) on the surface of the BNQDs, the ECL emission signal of the BNQDs was difficult to be observed by the naked eye, while [Ru(bpy)₃](PF₆)₂ emitted a strong and visible ECL signal. In the presence of the target, bipedal DNA assembled by catalytic hairpin assembly (CHA) took away the Fc-ssDNA and the ECL intensity of the BNQDs was enlarged, and as the concentration of miRNA-141 increased to the cutoff value, yellow-green light was visible by the naked eye. Meanwhile, the red emission signal of [Ru(bpy)₃](PF₆)₂/TPrA became weakened. Thus, an ultrasensitive "color switch" ECL biosensor for detection of miRNA-141 was constructed and endowed with a wide linear range from 10^-17 to 10^-7 M and a detection limit of 10^-17 M (S/N = 3). This study provides the potential for investigating portable devices in the detection of low-concentration nucleic acids.