Synthesis And Characterization Of A-(?)-D-(?)-A-type Small Molecule Photoelectric Materials Based On Indacenodithiazole With Aromatic Fused Ring

In this paper,we designed and synthesized a series of A-(?)-D-(?)-A type aromatic fused ring small molecules with indacenodithiazole(IDTz)as the core.Photophysical and electrochemical properties based on the indacenodithiazole small-molecule fused-ring system were systematically studied from UV/Vis absorption and electrochemical tests and theoretical calculation.The IDTz C6 which were modified by four n-hexyl side chains were used as the donor core unit.2-(1,1-dicyanomethylene)rhodamine(RCN),1,1-dicyanomethylene-3-indanone(DC)were used as terminal electron-deficient units(A).Then,two kinds of A-D-A type aromatic fused ring small molecules,IDTz C₆-RCN and IDTz C₆-IC,were obtained by Hydroformylation and Knoevenagel condensation reaction.Compared with IDTz C6-RCN,the maximum absorption peak of IDTz C6-IC in solution and film is red-shifted by 95 nm and 52 nm,respectively.The optical band gap of IDTz C6-RCN and IDTz C6-IC is 1.75 e V,1.60 e V,respectively.Compared with IDTz C6-RCN,the HOMO and LUMO level of the IDTz C6-IC downshift 0.03 e V and 0.44 e V,respec-tively.Combined with the theoretical calculations,we find that both compounds are planar molecules and their HOMO energy levels are mainly concentrated on the core IDTz C6,while the LUMO energy levels are distributed in the entire molecular skeleton.Good planarity,suitable optical bandgap and energy level,indicate that two molecules have potential application value in the field of organic photoelectric materials.On the basis of IDTz C6 core unit,through the stille coupling reaction and the Knoevenagel condensation,we have synthesized two novel aromatic fused ring small molecules IDTz C6-T-IC and IDTz C6-TOEH-IC with IDTz C6 as a central building block,DC as electron-withdrawing end groups,and thiophene or alkoxy-substituted thiophene as?-bridges.The insertion of the?-bridge increases the conjugation of the molecular skele-ton and enhances the light harvesting ability of molecular materials.Both the IDTz C6-T-IC and the IDTz C6-TOEH-IC exhibit broad and strong spectral absorption abilities in chloroform solutions and solid films.Compared to IDTz C6-T-IC,the molecule IDTz C6-TOEH-IC has a red-shift absorption and narrower optical bandgap.The LUMO level of IDTz C6-TOEH-IC is comparable to that of IDTz C6-T-IC,but the HOMO level is 0.16 e V higher than that of IDTz C6-T-IC.Through theoretical calcula-tion,we find that the two A-(?)-D-(?)-A type aromatic fused ring small molecules have good planarity.The weak non-covalent interaction of N…S in the molecular framework can lock the molecular conformation.These studies are of guiding significance for structural design and performance regulation of linear fused ring small molecule accep-tor materials based on indacenodithiazole(IDTz).