title: 3,5-Diarylimidazo[1,2-a]pyridines as Color-Tunable Fluorophores.
abstract: A new protocol for the synthesis of color-tunable fluorescent 3,5-diarylimidazo[1,2-a]pyridines has been achieved via palladium-catalyzed C-H amination of pyridinium zwitterions. Based on experimental results and computational analysis, we extracted a high correlation of photophysical properties with the theoretical concept and predicted emission wavelengths of 3,5-diarylimidazo[1,2-a]pyridines. The emission wavelengths of imidazo[1,2-a]pyridines increase as a function of the electron-withdrawing nature of the substituent on the C5-aryl group of imidazo[1,2-a]pyridine as a result of inductive effects on the LUMO levels. Varying the substituent on the C3-aryl group imidazo[1,2-a]pyridine changes the HOMO levels. Combining these two sites, the HOMO and LUMO levels can be tuned fairly decoupled from each other. This conceptual trend is demonstrated across a series where the C3 and C5 positions were functionalized independently and then utilizes a combination strategy where both sites are used to prepare fluorophores with a large window of emission wavelengths. In view of the biological properties of imidazo[1,2-a]pyridines, the developed method provides an efficient approach for understanding and preparing strongly fluorescent bioprobes.
authors.affiliation: Department of Chemistry, Kangwon National University , 1 Kangwondaehak-gil, Chuncheon 24341, South Korea.
authors.forename: Ju Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Kangwon National University , 1 Kangwondaehak-gil, Chuncheon 24341, South Korea.
authors.forename: Jae Yul
authors.initials: JY
authors.lastname: Shim
authors.affiliation: Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS) , Daejeon 34141, South Korea.|Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, South Korea.
authors.forename: Hong Ki
authors.identifier: 0000-0002-6115-384X
authors.initials: HK
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Kangwon National University , 1 Kangwondaehak-gil, Chuncheon 24341, South Korea.
authors.forename: Donguk
authors.initials: D
authors.lastname: Ko
authors.affiliation: Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS) , Daejeon 34141, South Korea.|Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141, South Korea.
authors.forename: Mu-Hyun
authors.identifier: 0000-0002-8832-8187
authors.initials: MH
authors.lastname: Baik
authors.affiliation: Department of Chemistry, Kangwon National University , 1 Kangwondaehak-gil, Chuncheon 24341, South Korea.
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Yoo