Stacking-Induced Diamagnetic/Paramagnetic Conversion of Imidazo[1,2-<i>a</i>]pyridin-2(3 <i>H</i>)-one Derivatives: Near-Infrared Absorption and Magnetic Properties in the Solid State
作者:Guoping Yong、Xuerui Zhang、Yumei Zhao、Wenlong She
DOI:10.1002/asia.201300400
日期:2013.9
Herein, we present three imidazo[1,2‐a]pyridin‐2(3 H)‐one derivatives that are diamagnetic in solution, but paramagnetic in the solid state, possibly owing to a stacking‐induced formation of phenoxide‐type radicals. Notably, a larger bathochromic shift of the absorption (even up to the near‐ infrared region) of these three compounds was observed in the solid state than in solution, which was attributable
在这里,我们提出了三种咪唑并[1,2 - a ]吡啶-2-2(3 H)-一衍生物,它们在溶液中是反磁性的,但在固态是顺磁性的,这可能是由于堆积诱导形成的酚盐型自由基所致。值得注意的是,在固态下观察到这三种化合物的吸收(甚至到近红外区域)的红移都比在溶液中大,这归因于有序的柱状堆积排列或它们作为自由基的单电子特性在固态。有趣的是,与溶液中的相比,(E)-3-(吡啶-4′-亚甲基)咪唑并[1,2- a ]吡啶2(3 H)-在固态下显示出很大的红移发射(中心在660 nm,拖尾在800 nm以上)。发射的较大的红移(260 nm)表示固态有更好的有序性和紧密堆积,这是由刚性和极性受体引起的。这三种化合物在300 K时也显示出不同的磁化率,因此暗示它们具有各种柱状堆积结构。最有趣的是,这三个自由基表现出不寻常的铁磁-反铁磁相变,这可归因于柱状堆积链的各向异性收缩和不均匀滑动。