Imidazo[1,5‐a]quinolines emit intense blue luminescence, suggesting their possible use as emitter molecules in organic light‐emitting diodes. We synthesized several new imidazo[5,1‐a]isoquinolines and found they possessed a characteristic hypsochromic effect and even increased quantum efficiency compared to the homolog imidazo[1,5‐a]quinolines, as measured by UV‐vis‐ and fluorescence spectroscopy in solution. The energies of the highest occupied and lowest unoccupied molecular orbitals were calculated using density functional theory and experimentally determined by cyclic voltammetry in solution. We obtained a maximum fluorescence quantum yield of 48% at 446 nm for the newly synthesized 3‐(4‐cyanophenyl)‐1‐(pyridyl)imidazo[5,1‐a]isoquinoline with an optimized substitution pattern. For 1‐phenyl‐3‐(2‐pyridinyl)imidazo[5,1‐a]isoquinoline, a quantum yield of 33% was obtained at an even shorter emission wavelength of 431 nm.

中文翻译：

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咪唑并[5,1-a]异喹啉和咪唑并[1,5-a]喹啉的合成、光学和理论表征

咪唑并[1,5-a]喹啉发出强烈的蓝色发光，表明它们可能用作有机发光二极管中的发射体分子。我们合成了几种新的咪唑并[5,1-a]异喹啉，并通过紫外可见光谱和荧光光谱测量，发现与同系物咪唑并[1,5-a]异喹啉相比，它们具有特有的减色效应，甚至提高了量子效率在溶液中。使用密度泛函理论计算最高占据和最低未占据分子轨道的能量，并通过溶液中的循环伏安法进行实验测定。新合成的3-(4-氰基苯基)-1-(吡啶基)咪唑并[5,1-a]异喹啉具有优化的取代模式，在446 nm处获得了48%的最大荧光量子产率。对于1-苯基-3-(2-吡啶基)咪唑并[5,1-a]异喹啉，在更短的431 nm发射波长下获得了33%的量子产率。