Synthesis, physical properties, and anion recognition of two novel larger azaacenes : benzannelated hexazaheptacene and benzannelated N,N'-dihydrohexazaheptacene

Abstract

Two novel larger azaacenes with six or ten N atoms in their backbones, benzannelated 9,11,13,22,24,26-hexazatetrabenzo[a,c,l,n]heptacene (HATBH, 1) and benzannelated 9,26-dihydro-9,11,13,22,24,26-hexaza-tetrapyrido[3,2-a: 2′,3′-c: 3′′,2′′-l: 2′′′,3′′′-n]heptacene (DHATPH, 2), have been successfully synthesized in two steps. The theoretical band gaps estimated through DFT calculations for HATBH (1) and DHATPH (2) are 1.949 eV and 2.278 eV, which are close to the experimentally obtained optical band gaps (2.14 eV and 2.39 eV). Interestingly, HATBH (1) can act as efficient anion sensor for F− and H2PO4−, while DHATPH (2) selectively responds to F− among the ten different anions used (F−, Cl−, Br−, I−, PF6−, HSO4−, NO3−, BF4−, AcO−, and H2PO4−). Our synthetic strategy could offer a promising and easy way to obtain even larger azaacenes.