Structural Regulation And Photophysical Properties Investigation Of The Organic Donor-Acceptor Complexes

As an intelligent design strategy of functional materials,organic cocrystal has attracted extensive attention in the scientific field in recent years.Various molecular arrangements and intermolecular interactions,especially the intrinsic charge transfer in organic cocrystal,describe such materials as ideal systems to control and adjust their physical properties for use in the field of luminescence.In recent years,organic donor-acceptor complex has attracted great attention due to their luminescent applications in organic waveguides,lasers,nonlinear optics,room temperature phosphorescence,and even light-emitting transistors.By wisely selecting various component materials,emission properties and other optoelectronic properties can be tailored through intermolecular charge transfer interactions.Furthermore,the fabrication of multicolour photoluminescent materials with tunable luminescence properties is an attractive research goal due to the wide range of applications of organic donor-acceptor complexes in materials science and optical engineering.Compared to covalent synthesis,supramolecular chemistry provides a more competitive and promising strategy for the preparation of organic materials and the regulation of their photophysical properties.By using dynamic and reversible non covalent bond interactions,the supermolecule strategy can not only simplify the design and preparation of organic materials,but also give them dynamic reversibility and stimulus responsiveness,which makes it easier to adjust the structure and properties of materials.In some cases,organic donor-receptor complexes may also exhibit new properties that the donor or receptor does not possess,thus expanding their potential applications.This paper focuses on organic donor-acceptor complexes.By selecting common luminescent donor and acceptor materials,new donor-acceptor complexes with unique luminescent properties are prepared.Through research on fluorescence changes,analysis of crystal structure,and photophysical properties characterisation,the relationship between crystal structure and function was systematically elaborated.The specific research content mainly involves the following two aspects:（1）Three new donor-acceptor complex forms（z BC）containing a helical-shape dibenzocarbazole analog（DBCz）as the electron donor and 1,2,4,5-tetracyanobenzene（TCNB）as the electron acceptor via a simple solution-processing strategy.The begining components self-assembled into supramolecular frameworks with glamorous alignment modes and different molar ratios:～1:1 P or M-enantiomer forα-cocrystal,alternated P/M-column stacking in mesmeric 2:3β-cocrystal,and segregated stacking ofγ-cocrystal.As a result,α-cocrystal exhibits bright solid-state red fluorescent,β-cocrystal shows significant optical waveguide behavior with a low optical loss coefficient of～0.018d B/μm,and no visual light emission is observed forγ-cocrystal under ultraviolet radiation.Interestingly,theα-z BC crystal is not only emissive but also chiroptically active with g_lum of 0.004.This study on chiral stacking tailoring paves a way for functional design of organic charge-transfer complex towards application in high-performance organic optoelectronics.（2）Organic cocrystals formed by two or more components throughπ-π,charge-transfer interactions and hydrogen/halogen bondings were of great interest for their applications in organic optoelectronics.Here,three charge-transfer cocrystals were prepared by solution-process self-assembly method which used coronene and pyrene as donors,N,N’-dimethyl-1,4,5,8-naphthalenetetracarboxylic diimide（NDI-1）and N,N’-Bis（ethyl）-1,4,5,8-naphthalenetetracarboxylic diimide（NDI-2）as acceptors.Detailed structural characterizations clarified the mixed stacking mode in charge-transfer cocrystals,and the supramolecular network was stabilized by C-H···O hydrogen bonds andπ-πinteractions.Interestingly,compared with the originating donors,three cocrystals show different fluorescence emission,which is related to the formation of charge-transfer states between donor and acceptor.This cocrystal strategy provides a new opportunity for the design of new organic light-emitting charge-transfer complexes.