Conjugated polymers composed of tricoordinate boron and π-conjugated units possess extended conjugation with relatively low-lying LUMOs arising from p B –π interactions. However, donor–acceptor (D–A) polymers that feature triorganoboranes alternating with highly electron-rich donors remain scarce. We present here a new class of hybrid D–A polymers that combine electron-rich dithienosiloles or dithienogermoles with highly robust tricoordinate borane acceptors. Polymers of modest to high molecular weight are readily prepared by Pd-catalyzed Stille coupling reaction of bis(halothienyl)boranes and distannyldithienosiloles or -germoles. The polymers are obtained as dark red solids that are stable in air and soluble in common organic solvents. Long wavelength UV-vis absorptions at ca. 500–550 nm indicate effective π-conjugation and pronounced D–A interactions along the backbone. The emission maxima occur at wavelengths longer than 600 nm in solution and experience further shifts to lower energy with increasing solvent polarity, indicative of strong intramolecular charge transfer (ICT) character of the excited state. The powerful acceptor character of the borane comonomer units in the polymer structures is also evident from cyclic voltammetry (CV) analyses that reveal relatively low-lying LUMO levels of the polymers, enhancing the D–A interaction. Density functional theory (DFT) calculations on model oligomers further support these experimental observations.
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Electronic perturbation effects in the presence of electric field for π‐conjugated systems: An electron‐correlation study
In this work, the Coulson‐Longuet‐Higgins response function (atom‐atomic polarizabilities [AAPs]) is used to describe the transfer of an electron perturbation in π‐conjugated systems in the presence of a static electric field. Computations are performed using different many‐electron approaches to study the effect. An accurate account of the electron correlation is shown to play a key role in the description of the interaction of a π‐shell with the external electrostatic field. Studies in this work reveal that the Hückel theory widely used in calculations of electron‐perturbation transfer is not reliable even at the qualitative level to describe the effects studies in this work. However, the π‐electron coupled cluster theory has been proven capable of providing a reliable electronic structure (among them, AAPs and excitation energies) that agree with the results obtained with the π‐electron full configuration‐interaction approach. The calculations also show that these properties have an essentially nonlinear character in terms of the strength of the applied electric field. The results obtained in the present work can provide useful information relevant to the application of π‐conjugated systems in molecular electronics.
more » « less- Award ID(s):
- 1856702
- NSF-PAR ID:
- 10457587
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- International Journal of Quantum Chemistry
- Volume:
- 120
- Issue:
- 16
- ISSN:
- 0020-7608
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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