Steric and electronic effects of CF3 conformations in acene(CF3) derivatives

PAH/PAH(CF3)n Donor/Acceptor Charge‐Transfer Complexes in Solution and in Solid‐State Co‐Crystals

“…[38,39] However,C F 3 is am uch stronger electron-withdrawing group (EWG) than F. [22,40,41] For example, the DFT-predicted EAso fp erfluoroanthracene (ANTH(F) 10 )a nd ANTH(CF 3 ) 10 are 1.84 [29,30] and 4.01 eV, [24] respectively.W ith only six CF 3 groups,t he experimental EA of 2,3,6,7,9,10-ANTH(CF 3 ) 6 (ANTH-6-1), at 2.81(2) eV, [26] is more than 1eVh ighert han ANTH(F) 10 and is the same as the 2.78 (6) eV EA of the common charge-transfer electron acceptor chloranil (2,3,4,5-tetrachlorobenzoquinone; Cl 4 BQ). [42] Another differenceb etween CF 3 and Fs ubstituents on PAHs is exemplified by the order of photostability of 9,10-ANTH(X) 2 derivatives in aerated cyclohexane:C F 3 > H > F. [43] Al-thoughP AH/PAH(F) n co-crystals have been studied for many years (e.g.,c o-crystals of perfluoronaphthalene with pyrene [44] and fluorene [45] ), to our knowledge there are no reports of PAH/PAH(CF 3 ) n co-crystals other than our briefc ommunication of the structures of co-crystals containing pyrene and either 1,2,3,5,7-azulene(CF 3 ) 5 (AZUL-5-1) [46] or ANTH-6-1 [47] (both of which will be discussed in greater detail in this paper) and the co-crystal structure of two complementary p-bowls, corannulene/1,3,5,7,9-corannulene(CF 3 ) 5 . [48] We have studied the synthesis and physicochemical properties of 53 PAH(CF 3 ) n derivatives prepared by substituting H atoms in twelve unsubstituted PAHs using CF 3 radicals generated from CF 3 Ia th igh temperature (n = 1-8).…”

“…The cyclic voltammograms of ANTH‐6‐2, PYRN‐6‐2, and CORO are shown in Figure S3. The recently published UV spectra of ANTH and ANTH‐6‐1 are shown in Figure S4 . The similarity in λ max values for ANTH and ANTH‐6‐1 shows that the HOMO–LUMO gaps for these two compounds must be similar, even though they have EA s that differ by nearly 2.3 eV (0.53(2) eV for ANTH and 2.81(2) eV for ANTH‐6‐1).…”

“…The crystal structureso ft he recently reported donor/acceptor (D/A) co-crystals of PYRN with AZUL-5-1 [46] and PYRN with ANTH-6-1 (the 1/2 structure PYRN/(ANTH-6-1) 2 ), [47] andt he seven X-ray D/A co-crystal structures we reporth ere represent combinationso ff our PAHd onors, ANTH,C ORO, PERY,a nd PYRN,a nd six PAH(CF 3 ) n acceptors, ANTH-5-1,A NTH-6-1, ANTH-6-2, AZUL-5-1, PYRN-6-2, and TRPH-6-1. Table 1l ists their formulas (with IUPAC locants), ionization energies (IEs) and/or electron affinities( EAs), E 1/2 (+ /0) and/or E 1/2 (0/À)v alues, and, for D/A mixtures, charge-transfer (CT) l max and E(l max )v alues.…”

“…Relevant geometric parameters for the D x /A y structures are listed in Ta ble 4, including, for comparison, the corresponding parameters for the previously reported 1/1 structures of PYRN/AZUL-5-1 [46] and ANTH/NAPH(F) 8 , [44] and the 1/2 structure of PYRN/ (ANTH-6-1) 2 . [47] Thermale llipsoid plotsf or one D/A pair in ANTH/ANTH-6-2 and PYRN/PYRN-6-2, the CT complex co-crystals tructures with the two new PAH(CF 3 ) 6 acceptors, are shown in Figure 7. Ther-mal ellipsoid plots fort he other structures are shown in Figures S10-S12.A ll of the structures exhibit nearly-parallel donor and acceptor nearest neighbours with significant p-p overlap.…”

“…Another difference between CF 3 and F substituents on PAHs is exemplified by the order of photostability of 9,10‐ANTH(X) 2 derivatives in aerated cyclohexane: CF 3 >H>F . Although PAH/PAH(F) n co‐crystals have been studied for many years (e.g., co‐crystals of perfluoronaphthalene with pyrene and fluorene), to our knowledge there are no reports of PAH/PAH(CF 3 ) n co‐crystals other than our brief communication of the structures of co‐crystals containing pyrene and either 1,2,3,5,7‐azulene(CF 3 ) 5 (AZUL‐5‐1) or ANTH‐6‐1 (both of which will be discussed in greater detail in this paper) and the co‐crystal structure of two complementary π‐bowls, corannulene/1,3,5,7,9‐corannulene(CF 3 ) 5 …”