Brahma Rinki, Singh Munendra Pal, Baruah Jubaraj B
Department of Chemistry, Indian Institute of Technology Guwahati Guwahati 781 039 Assam India
RSC Adv. 2019 Oct 17;9(57):33403-33412. doi: 10.1039/c9ra07602f. eCollection 2019 Oct 15.
Clip-like arrangements of molecules in the cocrystals of phenazine with hydroxy-aromatics in their respective self-assemblies and photophysical properties were presented. Phenazine cocrystals with 1,2-dihydroxybenzene provided assembly with butterfly-like arrangements. In these cocrystals, the phenazine molecules occurred in parallel pairs having extensive π-stacking. The clip-like cocrystals with 1,3-dihydroxybenzene also exhibited parallel pairs of phenazine molecules that were parallel cofacial π-stacked. The hydrated cocrystals of phenazine with 1,2,3-trihydroxybenzene had chains of parallel cofacial phenazine rings having three distinguishable π-separation distances among the centroids of the phenazine rings. Also, 2,7-dihydroxynaphthalene formed a clip-like cocrystal with phenazine, which encapsulated an additional molecule of phenazine. This cocrystal also provided chain-like parallel arrangements of the phenazine molecules. The emission and quantum yields of the cocrystals were determined by the integrating sphere method, which indicated that only the cocrystal of phenazine with 2,7-dihydroxynaphthalene showed monomer-like emission of phenazine and the rest of the cocrystals were in a quenched state. In the solution phase, quenching of the emission of hydroxynaphthalene was observed when phenazine was added to an independent solution of 2,7-dihydroxynaphthalene or another hydroxynaphthalene. However, when hydroxybenzenes were added to a solution of phenazine, fluorescence enhancements of phenazine occurred due to photo-electron transfer.
介绍了吩嗪与羟基芳烃共晶体中分子的夹子状排列及其各自的自组装和光物理性质。吩嗪与1,2 - 二羟基苯的共晶体提供了蝴蝶状排列的组装结构。在这些共晶体中，吩嗪分子以具有广泛π堆积的平行对形式出现。与1,3 - 二羟基苯形成的夹子状共晶体也表现出平行的吩嗪分子对，它们是平行共面π堆积的。吩嗪与1,2,3 - 三羟基苯的水合共晶体具有平行共面吩嗪环的链，在吩嗪环的质心之间有三个可区分的π - 分离距离。此外，2,7 - 二羟基萘与吩嗪形成了夹子状共晶体，其中包裹了一个额外的吩嗪分子。这种共晶体也提供了吩嗪分子的链状平行排列。通过积分球法测定了共晶体的发射和量子产率，结果表明只有吩嗪与2,7 - 二羟基萘的共晶体表现出吩嗪的单体状发射，其余共晶体处于猝灭状态。在溶液相中，当将吩嗪添加到2,7 - 二羟基萘或另一种羟基萘的独立溶液中时，观察到羟基萘发射的猝灭。然而，当将羟基苯添加到吩嗪溶液中时，由于光电子转移，吩嗪的荧光增强。
