Synthesis And Properties Of Corannulene-Based Organic Materials

Organic seimiconductors have attracted much attention in recent years due to their potential applications in low-cost,high-performance,and flexible electronic devices.The design and synthesis of new conjugated motifs have always been "fountains of innovations" in the field of organic electronics.In this thesis,starting from a new type of bowl-shaped conjugated molecule,we developed several types of organic semiconducting materials based on corannulene through rational design,and investigated their intermolecular electronic couplings and charge-transport properties.The research content and conclusions are listed as following:(1)We introduce two chiral carbon atoms bearing bulky groups into the molecular backbone of imide-fused corannulene derivatives to produce four stereoisomers(RS,,STR,RR,and SS,where S and R are the chirality of chiral carbons).These four isomers are separated into two portions through column chromatography over silica gel.Portion 1 contains one pair of enantiomers(SS and RR)and Portion 2 contains one pair of diastereomers(SR and RS).The orientation of bulky groups significantly alters the molecular packing of imide-fused corannulene derivatives.Portion 1 adopts layered packing,and Portion 2 shows a columnar packing motif.The molecular packing modes modulate-the intermolecular electronic couplings and thus charge transport of the stereoisomers of imide-fused corannulene derivatives.Combining with theoretical calculations,we found that the Portion 1 shows hole-dominated transport,while the Portion 2 exhibits electron-dominated transport.These results indicate that the stereoisomerization will alter the arrangement and thus charge-transport properties of molecules in the solid state,in some cases,which may even change the charge-transport polarity.(2)Corannulene,a curved fragment of fullerene C60,have similar curvatures with C60.Their shape-size complementarity facilitates forming host-guest complexes through concave-convex ?-? interaction.For corannulene/C60 binary complexes,however,most work focused on their binding properties and only one example demonstrated their utilizations in OFETs.Herein,we mixed the Portion 2(obtained as a mixture of SR and RS isomers from the first part)and C60 at a molar ratio of 1:1 to grow cocrystals and investigated the intermolecular electronic couplings and charge transport of the cocrystal.The molecule with the exposed concave surface,i.e.the SR isomer,has a higher binding energy with C60 than that of the RS isomer whose concave surface is buried by the bulky groups.Hence,only the SR isomer is observed in the cocrystal because all RS molecules were converted to SR molecules.SR molecules and C60 form a 1:1 segregated packing motif with alternating donor and acceptor layers in cocrystal.In the donor layer,SR isomer show strong ?-? interaction with themselves along a axis,while C60 which are organized in a zigzag manner along a and c axes also have strong ?-? intermolecular interactions in acceptor layer.Theoretical calculations show that the cocrystal exhibits anisotropic electronic couplings,ie,large hole transfer integrals(originating from the corannulene derivative layer)along the a axis,and large electron transfer integrals along the a and c axes(originating from the C60 layer).Organic field-effect transistor measurements confirm that the pathway along the c axis indeed facilitate electron transport with an electron mobility of 0.0008 cm2V-1 s-1.This research provides a reference for the subsequent design of complex materials based on interconvertible molecules,and confirms that complexes of bowl-shaped molecules and fullerenes can be applied in organic electronics.(3)In the third part,two methods are also tried to synthesize the corannulene-based diradicals.We couldn't obtain the target molecule through the method which starts from the tetrabromocorannulene,and we could get the biradical through another method.Preliminary results indicate that the biradical based on corannulene are unstable and are easily oxidized to diketone in air.