Effect of the donor units on the properties of fluorinated acceptor based systems

Abstract

A new series of monomers in the donor-acceptor-donor array, namely 5-fluoro-4,7-di(furan-2-yl)benzo [c][1,2,5] thiadiazole (F 2 BT-F), and 5-fluoro-4,7-di(selenophen-2-yl)benzo [c][1,2,5] thiadiazole (S 2 BT-F), bearing 5-fluorobenzo[c][1,2,5]-thiadiazole as the acceptor moiety and furan and selenophene as the electron donating groups was synthesized and polymerized electrochemically. To compare heteroatom effect, thiophene analogue of newly synthesized F 2 BT-F and S 2 BT-F namely, (5-fluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5] thiadiazole (T 2 BT-F)) and its corresponding polymer were also synthesized. Effect of donor units on the electrochemical and optical properties of fluorinated acceptor based systems was investigated in terms of the effect of different sized heteroatoms in five-membered rings on the dihedral angle and planarity. Theoretical calculations also suggested a deviation from planarity upon fluorination. Moreover, electrochemically obtained polymers possess low bandgap values (1.62 eV-1.68 eV for PF 2 BT-F and PS 2 BT-F, respectively) and exhibited electrochromic properties with relatively low switching times.

Structural‐Functional Properties of Asymmetric Fluoro‐Alkoxy Substituted Benzothiadiazole Homopolymers with Flanked Chalcogen‐Based Heterocycles

“…This can be explained in terms of the aromaticity of the heterocycle, the aromaticity decreases when the heterocycle has larger chalcogen atoms that result in poor overlap with the diene carbon p z orbitals. [47,63,64] The same trend was detected for homopolymers containing the electron-deficient spacers, HPOx and HPTzC2, the substitution of oxazole for thiazole, lead to a bathochromic shift of 39 nm in solution and 17 nm in thin film. In addition, a blueshift in the absorbance maxima 𝜆 max in solution and thin film, as well as, an increase in the vibronic shoulder of the solidstate was detected between HPTzC5 and HPTzC2.…”

Effects of polymer precursor conjugation length on the optoelectronic properties of fluorinated benzothiadiazole-based D–A systems

“…Monomers and polymers undergo a blue shift in their electronic spectra with increasing fluorine atom substitution on the BT unit, due to deviation from planarity upon fluorination. In this regard, they further synthesized two new D–A–D-type monomers utilizing 5-fluorobenzo[ c ][1,2,5]-thiadiazole as the acceptor unit 23 and furan and selenophene as the donor units. As prepared fluorinated polymers possess a low band gap (1.62–1.68 eV) and exhibit electrochromic properties with relatively low switching times.…”

Toward High-Performance Electrochromic Conjugated Polymers: Influence of Local Chemical Environment and Side-Chain Engineering

“…PDT6FBT exhibited comparative values at all three wavelengths with a range value of 86–97 cm 2 C −1 . The above electrochromic performance demonstrated that PDT6FBT was on a par with its analogues PT2BT-1F (thiophene as terminal groups), PF2BT-F (furan as terminal groups), PS2BT-F (selenophene as terminal groups), and PE2BTD-F (EDOT as terminal groups) [ 34 , 35 , 36 ].…”

“…[ 32 , 33 ]. Önal et al reported 5-fluoro-2,1,3-benzothiadiazole-based ECPs [ 34 , 35 , 36 ], and analyzed the influence of a fluorine atom on the optical and electrical properties of a conjugated polymer. As we all know, alkyl side chains influence the redox behavior and electrochromic properties of the electrodeposited polymers [ 24 , 37 ].…”