Functionalized Benzothiadiazole Non‐Fused A−D−A’−D−A Small Molecules for Effective Electron Mobilities and Metal‐free Photocatalysis

Abstract

Three non-fused AÀ DÀ A'À DÀ A π-conjugated metalfree small molecules BT-IT1, BT-IBT2 and BT2F-IBT3 have been synthesized and their absorption characteristics and redox properties, as well as charge carrier mobilities have been investigated. The resultant molecules exhibited broad absorption in the range of 325-600 nm in solutions and in thin films the absorption range is 350-700 nm. These new conjugated small molecules showed low-lying HOMO energy levels (À 5.49 to À 5.50 eV), deep LUMO energy levels (À 3.67 to À 3.69 eV) and narrow bandgaps of (E g CV ) ~0.79 eV. Appreciable electron mobilities for compounds BT-IBT2 and BT2F-IBT3 were 4.56 × 10 À 3 and 1.12 × 10 À 3 cm 2 V À 1 s À 1 , respectively, obtained by space-charge limited current (SCLC) measurements. Additionally, excellent photocatalytic performances of BT-2T (6), BT2F-2T (10), BT-IT1, BT-IBT2 and BT2F-IBT3 for highly selective oxidation of thioanisole to desired sulfoxides under visible light irradiation were observed.

Tripodal Triazine and 1,8‐Naphthalimide‐based Small Molecules as Efficient Photocatalysts for Visible‐light Oxidative Condensation

“…Fluorescence quantum yields were determined by relative method using 4',6-diamidino-2-phenylindole (DAPI) as a reference dye [59,60] and fluorescence quantum yields (φ) of 0.55 and 0.19 were obtained from Tr-Np3 and Tr-T-Np3 respectively (Table S2).…”

“…In compound Tr-T-Np3, emission maximum was hypsochromically shifted minimally from ~505 nm to 500 nm (Figure S2) upon increasing the temperature. To determine the ratiometric temperature analysis [60,61] of Tr-Np3 and Tr-T-Np3, temperature-dependent emission data were fitted with linear functions with goodness of fit (R 2 ) values of 0.98 and the calculated temperature sensitivities obtained were À 0.19 % °CÀ 1 and 0.50 % °CÀ 1 for Tr-Np3 and Tr-T-Np3 respectively (Figure S2, Table S3).…”

Dithienopyrrolobenzothiadiazole and Naphthalimide-Based Donor–Acceptor Triads for Charge Transport and Photocatalytic Synthesis of Benzimidazoles

“…We intend to study the influence of a thiophene spacer in the D−A backbone on the optical, redox, and photocatalytic properties of triad 1 and triad 2. Moreover, a detailed study on the charge transport behavior (i.e., electron mobility, hole mobility, and conductivities) of these triads has been undertaken in this work unlike our previous work, 47 thereby highlighting the ambipolar charge transport behavior of these triads. Triad 1 and triad 2 demonstrated broad absorption within the 300−600 nm range in solutions and 350−700 nm range in thin films.…”

“…Furthermore, we utilized those molecules for metal-free selective oxidation of thioanisole to sulfoxide under visible light irradiation. 47 Herein, we report the synthesis of two A−D−A small molecules, triad 1 and triad 2 (Scheme 1), containing DPBT as a donor and Np as an acceptor, both without and with a thiophene spacer. We intend to study the influence of a thiophene spacer in the D−A backbone on the optical, redox, and photocatalytic properties of triad 1 and triad 2.…”

“…In our recent study, we synthesized nonfused A–D–A′–D–A π-conjugated small molecules based on thiophene and bithiophene as a donor and utilized 2,1,3-benzothiadiazole (BT) and hemi-isoindigo as primary and secondary acceptors, respectively, and investigated only their electron mobilities by the SCLC method. Furthermore, we utilized those molecules for metal-free selective oxidation of thioanisole to sulfoxide under visible light irradiation . Herein, we report the synthesis of two A–D–A small molecules, triad 1 and triad 2 (Scheme ), containing DPBT as a donor and Np as an acceptor, both without and with a thiophene spacer.…”