Polycyclic motif engineering in cyanostilbene-based donors towards highly efficient modulable emission properties in two-component systems

Abstract

Molecular engineering schemes are essential for the construction of highly efficient and tunable long-wavelength fluorescent materials from the perspective of crystal engineering. Herein, three charge transfer (CT) cocrystals (Ia, Ib, and Ic) are successfully fabricated using cyanostilbene (CS) derivatives with various polycyclic motifs (naphthalene, anthracene, or pyrene) as the donor compounds and 1,2,4,5-tetracyanobenzene (TCNB) as the acceptor unit to tune their photophysical characteristics. The three CT cocrystals exhibit mixed stack arrangements in which the donor and acceptor align in a face-to-face fashion (Ia: DADA, Ib, and Ic: DAD–DAD) as revealed by single-crystal X-ray diffraction (SCXRD). These organic hybrid materials display tunable multicolor luminescence from yellow (Ia: 554 nm) to red (Ib: 650 and Ic: 620 nm) in the solid state depending on the polycyclic motif ionization potential (IP) as well as the organization of the donor species in the framework. Furthermore, the results of density functional theory (DFT) calculations also support the observed red-shifted emission of the three products. These results demonstrate that the engineering of CS is an effective approach for the development of future two-component multicolor fluorescent complexes, which could find applications in optoelectronic and electronic devices.