Preparation And Property Investigation Of The Organic Donor-acceptor Complexes

Organic charge transfer complexes,which are generally referred to molecular solids consisted of donor and acceptor through non-covalent bond interactions and have emerged as an efficient and versatile route to construct novel multifunctional materials,due to the simple preparation process,low cost and collaborative strategy in the distinct constituent units.Currently,organic charge transfer cocrystals are attracted increasing attentions in the fields of organic field effect transistors(OFETs),organic photodetectors(OPs),organic light-emitting transistors(OLETs),nonlinear optics(NLOs),stimulus-response materials,and pharmaceuticals,etc.Although they reveal unique physical features,their synthesis still faces many drawbacks for the introduction of more potential semiconductors,different components of the structure,energy level mismatch,and even the preparation of poor conditions often have an important impact on the functionality of the complexes.Therefore,how to control the stacking mode,morphology,or polymorphism of cocrystals through molecular design,optimizing preparation conditions or controlling a certain stoichiometric ratio to effectively control the optical,electrical,mechanical,and ferromagnetic aspects of the complex prformance is still a huge challenge.This paper focuses on the preparation and properties of novel organic charge transfer complexes,including the following two aspects:(1)Novel complexes consisting of soluble pentacene derivative and DTTCNQ were successfully prepared via solution-evaporation method,and the transport properties were investigated with single crystal field effect transistors.Obtained from the chlorobenzene solution,cocrystal P1 consisted of 1:1:1 TMTES-P,DTTCNQ and an inserted xylene molecule,and in DTTCNQ,the thiophene units were disordered with sulfur atoms appearing in the 1,2,4 and5-positions of the quinoid ring with 50%occupancy.However,the cocrystal P2 prepared by toluene solvent formed a more tightly slipping structure and additional directional short-contacts to eliminate carbon-sulfur disorders.Electrical characterizations of both these complexes demonstrated that the cocrystals exhibited charge transport from p-type(P1)to n-type(P2)as tailored structures.Devices based on cocrystal P1 exhibited a hole-dominating transport feature with the highest mobility of 5.5×10^-3 cm² V^-1 s^-1,on the contrary,the cocrystal P2 exhibited n-type semiconducting behaviour,and the electron mobility reached to 0.06 cm² V^-1 s^-1.Theoretical calculations show that the transfer integrals of holes and electrons of the cocrystal P1 and P2 along the mixed stacking direction are 34.895 and-41.306 me V,respectively,suggesting the n-type and p-type nature.(2)Based on the same acceptor molecule Me-NDI,two novel host-guest complexes with similar mixed stacked structures were designed and synthesized by solution and mechanical grinding methods,and their thermophysical properties and electrical properties were characterized.Upon thermal treatment,TMTES-P/Me-NDI complex revealed an in-situ cocrystal to crystal conversion and gradual receptor release behavior,while Perylene/Me-NDI cocrystal disassembled like a single-component compound.Crystal structure analysis and theoretical simulation show that the realization of an in-situ cocrystal-to crystal transition via a cocrystal strategy is attributed to anisotropic attachment energies as well as the good stability of host component.On the other hand,the fundamental packing directions bore comparable attachment energies,leading to the escape of supramolecules from the PMC cocrystals as a whole.Meanwhile,as a novel organic semiconductor,TMC microcrystals exhibited a good hole-transport property.