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

Abstract

Bright and low‐cost emitting organic molecules are very desirable for electrochemiluminescence (ECL). Here, we report a facile one‐step, three‐component reaction of readily available precursors to synthesize pyrido[1,2‐α]pyrimidine derivatives (1–4), all which give off green photoluminescence (PL). In contrast, the electrochemistry and ECL properties of these luminophores are affected by the extent of the conjugation and the nature of the peripheral substituents. Density functional theory (DFT) calculations identified the aromatic chain substitution could extend the conjugation of pyrido[1,2‐α]pyrimidine core and stabilize the electrogenerated radicals required for generation of an excited state, affording pyrido[1,2‐α]pyrimidine 3 the highest ECL activity among the studied samples. ECL in annihilation route confirmed weak emission, but great improvement was made using oxidizing co‐reactant species (benzoate radical from benzoyl peroxide, BPO) with an efficiency of 43 % relative to that of Ru(bpy)3(PF6)2. The pyrido[1,2‐α]pyrimidine 3/BPO system is more robust than those of reducing co‐reactant species [tri‐n‐propylamine radical or 2‐(dibutylamino) ethanol radical] and is one of the highest among the reported organic electrochemiluminophores. ECL spectroscopy revealed that the monomeric excited states were the main species to emit light. Their straightforward, one‐step, green synthesis, and their structure tunability represent significant advantages in the development of readily accessible dyes for PL and especially ECL applications.

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

“…The annihilation reaction produces ground and excited states, and the excited species emit light and return to the ground state. Hence, in ECL annihilation systems, the emitter is the only source of excited states [23] . In fact, the ECL signals of TPE and its supramolecular architectures are weak because of the free rotation of the AIE‐active architectures in the solution state, causing a certain nonradiative energy loss [24] …”

High‐Efficiency Electrogenerated Chemiluminescence of Novel Zr‐Based Metal–Organic Frameworks through Organic Linkers Regulation

“…As summarized in Table S2 (Supporting Information), the enthalpy of the radical ion reaction for cationic and anionic NU-1000 radical was calculated to be 2.34 eV by using the equation ΔH ann = E Ox1 À E Red1 À 0.16 while those values for NU-1000/K 2 S 2 O 8 and NU-1000/TPrA are 4.69 eV and 1.89 eV, respectively, by following equations of ΔH K2S2O8 = E(SO 4 *À /SO 4 2À )À E Red1 À 0.16 and ΔH TPrA = E Ox1 À E(P/TPrA * )À 0.16, in which the E(SO 4 *À /SO 4 2À ) = 3.15 V and E(P/TPrA * ) = 1.70 V. [1a] Meanwhile, the energy required to generate the lowest excited singlet state (E s ) of NU-1000 was estimated to be 2.64 eV by adopting the equation E s = 1239.81/λ max (nm, PL). [33] It is known that if the enthalpy of the radical ion reaction is smaller than its E s , the system is typically energy-sufficient and the reaction follows the S-route, alternatively, it is the energy-deficient system and follows the Troute. For the T-route, a triplet species is first produced upon the reaction of the radical ions and then obtain a singlet species by triplet-triplet annihilation, which usually accounts for a low ECL efficiency.…”

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

“…The red light emitted by this material is in strong contrast with the yellow-green light emitted by BNQDs, making the detection results colorful and easy to observe. Therefore, [Ru­(bpy) 3 ]­(PF 6 ) 2 can be chosen as the anode luminescent material. , …”

“…Therefore, [Ru(bpy) 3 ]-(PF 6 ) 2 can be chosen as the anode luminescent material. 25,26 An efficient signal amplification strategy was also a prerequisite for ultrasensitive detection of miRNAs. Traditional signal amplification techniques, including hybridization chain reaction, 27,28 rolling circle amplification, 29 strand displacement amplification, 30,31 and other amplification reactions, 32 usually face complex and subtle processes, which may bring great uncertainty to the accuracy of the results.…”