“Push–pull” 1,8-naphthalic anhydride with multiple triphenylamine groups as electron donor

Photophysical properties and stimuli-responsive crystal-state luminescence switching of morpholine-modified naphthalic anhydride derivative

Stimuli-response organic solid-state luminescence switching materials are attracting increasing interest due to their smart photophysical properties. In this study, a morpholine-modified naphthalic anhydride derivative, 4-(4-morpholinyl)naphthalic anhydride (MBC), was synthesized and studied. Its two crystal polymorphs, MBC-G and MBC-O, were obtained under different crystallization conditions. These two distinct crystals show significantly different solid-state luminescence behaviors: a green emission at 535 nm for MBC-G, and an orange emission at 572 nm for MBC-O. Upon fiercely grinding the MBC-G crystal or melting and then quickly cooling it, a phase transition occurs from MBC-G to MBC-O, accompanied by a fluorescence change from green to orange. The reverse transformation from MBC-O to MBC-G can be achieved by recrystallization. The X-ray single crystal structures show that the green emission should be attributed to molecular J-aggregation in the crystal packing, and the orange emission may originate from molecular H-aggregation. This switchable color nature gives MBC the promising candidate for potential smart anti-counterfeiting and light-emitting materials.

Synthesis and fluorescence properties of two dendritic molecules based on naphthalimide and triphenylamine

Artificial light-harvesting systems have attracted great interest in biological photosynthesis and photo-voltaic devices areas due to their unique structures, easy purification, low-cost, and convenient processing abilities. Here, two dendritic molecules based on triphenylamine and naphthalimide have been designed and synthesized, their structures were confirmed by ¹ H NMR, ESI-MS, and high resolution mass spectrometry. In these molecules, triphenylamine units perform as the electron donor moiety, and naphthalimide units perform as the electron acceptor. The obvious quenched fluorescence intensity and considerably shortened lifetime of the dendritic molecules combined with the molecular frontier orbital energy levels proved that the dendritic molecules not only are good candidates as hole-transporting materials but also are two excellent photo-induced electron transfer materials. Therefore, it is believed that these dendritic molecules have potential application value in photo-voltaic devices.