Constructing soft-conjugated materials from small molecules to polymers: a theoretical study

Construction of organic materials with harmonized optoelectronic properties and processabilities is important for the practical applications, especially for the solution-processed devices. Herein, three series of soft-conjugated materials designed with rigid planar molecular structures in solid state for promising optoelectronic properties and flexible non-planar conformation in solution for facile processing were constructed and theoretically investigated using thiophene and/or furan aromatic rings as the backbone and 10 pairs of non-bonding interactions as the soft bonding to conformationally lock the molecules. Computational results indicate that soft-conjugated small molecules and polymers can be efficiently established on 5–5 aromatic ring architectures with various non-bonding interaction pairs, and furan is more efficient than thiophene in constructing soft-conjugated materials due to the strong conjugation effects and low rotation hindrance between the adjacent furan-based rings. High optical and electronic properties of the soft-conjugated materials can be also achieved, showing delocalized frontier molecular orbitals with favorable energy levels for conventional device applications, strong absorption and emission bands that are comparable to the corresponding rigid-conjugated materials. These findings highlight that soft-conjugation feature would be inspirational for the development of organic electronics to overcome the intrinsic contradiction between high optoelectronic properties and good processability in organic π-conjugated small molecules and polymers.