Solid-state fluorescence of zwitterionic imidazolium pyridinolates bearing long alkyl chains: Control of emission properties based on variation of lamellar alignment
作者:Atsushi Yoshida、Masahiro Ikeshita、Naruyoshi Komiya、Takeshi Naota
DOI:10.1016/j.tet.2017.08.045
日期:2017.10
Herein, the control of the crystalline-state fluorescence of zwitterionic imidazolium 2-pyridin-3-olate 1 bearing linear alkyl chains via morphological variations is described, along with a mechanistic rationale. Crystals of 1a-e prepared from CH3CN exhibited intense blue fluorescence under UV irradiation at 298 K, whereas crystals of le prepared from i-PrOH/Et2O were less emissive under the same measurement conditions. Temperature-dependent emission spectra showed that emissive crystals of 1a-e experienced minimal emission decay with increasing temperature, whereas crystalline 1e, having a different polymorphism, was highly heat-quenchable. Single-crystal XRD established that less emissive, heat quenchable crystal le had a lamellar structure supported by consecutive face-to-face arrangement with 7c-stacking interactions between imidazolium and pyridinolate moieties, whereas highly emissive, heat-resistant crystals ld and le had a face-to-edge lamellar structure with CH-7r interactions between the heteroaromatic rings. (C) 2017 Elsevier Ltd. All rights reserved.