C_s‐Symmetric Donor–Acceptor Bis(thiazole)s: Synthesis and Photophysical, Electrochemical, and Computational Studies

Abstract

We herein report the design and synthesis of Cs‐symmetric donor–acceptor (D–A) molecular systems that have electron‐donating and electron‐withdrawing groups of the type D‐π‐A‐π‐D and D‐A1‐A‐A1‐D by using a Pd‐catalyzed Sonogshira cross‐coupling and [2+2] cycloaddition–retroelectrocyclization reactions. The photophysical and electrochemical properties as well as computational studies of these systems were explored, and strong donor–acceptor interactions were found. The [2+2] cycloaddition–retroelectrocyclization reaction pathway was studied by computational calculations, which revealed that bis(thiazole)s that contain donor groups at the terminal positions were favored in the reaction with tetracyanoethene (TCNE), whereas bis(thiazole)s that contain electron‐withdrawing groups were disfavored.

The Effect of TCNE and TCNQ Acceptor Units on Triphenylamine‐Naphthalenediimide Push‐Pull Chromophore Properties

“…The UV‐vis absorption spectra are depicted in Figure 2 and the respective data are tabulated in Table 1. The UV‐vis absorption spectra of TCBD bridged NDI‐TPA‐2 and NDI‐TPA‐3 exhibits a strong intramolecular charge transfer (ICT) absorption band at 388 nm (66100 M −1 cm −1 ), 486 nm (36700 M −1 cm −1 ) and 390 (50300 M −1 cm −1 ), 484 nm (57600 M −1 cm −1 ), which can be ascribed to the strong donor‐acceptor interaction resulting from the incorporation of the TCBD as an electron acceptor unit, which was also demonstrated in DFT calculations (Figure 1 and Figure S37, S38, S39) [31,32] . Interestingly, by increasing TCBD moiety from NDI‐TPA‐2 388 nm (66100 M −1 cm −1 ) to NDI‐TPA‐3 390 (50300 M −1 cm −1 ), the redshift of 2 nm was observed as compared to mono‐substituted compound.…”

Synthesis of tetrazine-tetracyanobutadienes and their transformation into pyridazines via inverse-electron demand Diels–Alder cycloaddition (IEDDA)

“…32 Several π-conjugated systems have been developed based on porphyrin, aza-BODIPY, naphthalene diimide, diketopyrrolopyrrole, indigo, and others (Chart 1). 24,[33][34][35][36][37][38][39] However, the TCBD integrated compounds are incompatible for further structural modifications due to the high reactivity of TCBD units; thus, there have been no attempts made so far to further tune the properties of these compounds. However, amenability for such tuning is necessary in order to modulate the properties of these compounds to enhance their applicability.…”

Tetracyanobutadiene Bridged Push‐Pull Chromophores: Development of New Generation Optoelectronic Materials

“…The ethynyl linked ferrocenyl and triphenylamine bisthiazoles undergo CA‐RE reaction sequence with two equivalents of TCNE, resulting in the formation of Btz 1 and Btz 2 in 71 % and 65 % yield, respectively (Figure 18). [74] The ferrocenyl and triphenylamine functionalized bisthiazoles upon reaction with TCNE afford TCBD derivatives, however, an attempt to synthesize the TCBD derivatives of the naphthalimide‐functionalized bisthiazoles was unsuccessful. The reaction was further investigated by DFT calculations performed at B3LYP/6‐31G** level for C, H and N, and at Lanl2DZ level for Fe, which reveal that the donor functionalized bisthiazoles favour the reaction with TCNE due to a lower HOMO‐LUMO gap; on the other hand, acceptor functionalized bisthiazoles disfavour the reaction because of their large HOMO‐LUMO gap.…”