Modulation of the solid-state luminescent properties of conjugated polymers by changing the connecting points of flexible boron element blocks

Abstract

A flexible molecule is known to be unfavorable for designing a luminescent dye because its excitation state would be rapidly decayed through molecular motions. Meanwhile, we recently found that some of flexible boron complexes, which potentially show larger degree of structural relaxation in the excited state, and their polymers exhibit unique optical properties with high environmental sensitivity by adding structural restriction, such as aggregation-induced emission (AIE) and luminochromism triggered by external stimuli. Moreover, it was shown that these optical properties were drastically changed by modulating the connecting points in polymers. In this review, recent progresses in the developments of luminescent polymer films with stimuli-responsiveness are illustrated. In particular, influence of the alteration of connecting points on luminescent behaviors is explained. It is demonstrated that polymerization is a versatile strategy not only for transforming a class of non-emissive molecules to luminescent dyes but also for precisely regulating optical properties of film materials which are promised to be applied as a scaffold for advanced chemical sensors.

Vapochromic Luminescent π‐Conjugated Systems with Reversible Coordination‐Number Control of Hypervalent Tin(IV)‐Fused Azobenzene Complexes

“…Heteroatom-containing building blocks are effective in constructing functional and unique materials. [28][29][30] As examples, we discovered cubic silica and boron cluster compounds named polyhedral oligomeric silsesquioxane (POSS) [31,32] and ocarborane, [33,34] respectively, have been applicable to main scaffolds for creating functional materials showing superior luminescence behaviors with high durability or stimuli-responsiveness. We recently reported the series of solid-state luminescent complexes and polymers containing boron-fused azomethine (À C=NÀ ) [35][36][37][38][39] and azo (À N=NÀ ) [40][41][42][43][44] complexes with the tridentate ligands, o-salicylideneaminophenol or 2,2'-dihydroxyazobenzne scaffold, respectively.…”

Modulation of stimuli‐responsiveness toward acid vapor between real‐time and write‐erase responses based on conjugated polymers containing azobenzene and Schiff base moieties

“…[9][10][11] For instance, we have proposed the idea on the material design based on an "element-block", which is the minimum functional units containing heteroatom, as a scaffold. [12][13][14] On the basis of this idea, various film-type sensors for detecting acid/base vapors, 15 reactive oxygen species, 16 and mechanical stresses 17,18 were obtained with conjugated polymers involving boron "element-blocks" having environment-responsive luminochromic characters. Except for our examples, although many researchers have realized unique sensing materials with heteroatom-containing conjugated polymers, in order to obtain advanced sensing materials, establishment of precise controls of stimuli-responsivity toward environmental changes and external stimuli is still one of relevant topics in this research field.…”

Preparation of Near‐Infrared Emissive π‐Conjugated Polymer Films Based on Boron‐Fused Azobenzene Complexes with Perpendicularly Protruded Aryl Substituents

“…Recently, we have proposed the design concept based on “element‐blocks” which is a minimum functional unit containing heteroatoms. [ 39–41 ] By employing unique properties of heteroatoms, various types of luminescent dyes and polymers have been developed. [ 42–54 ] As a luminescent “element‐block,” we focused on the complexes having a tetracoordinated boron atom.…”