New Acceptor–Donor–Acceptor Systems Based on Bis-(Imino-1,8-Naphthalimide)

Abstract

In this paper, six novel symmetrical bis-(imino-1,8-naphthalimides) differing in core and N-substituent structure were synthesized, and their thermal (TGA, DSC), optical (UV-Vis, PL), electrochemical (DPV, CV) properties were evaluated. The compounds were stable to 280 °C and could be transferred into amorphous materials. Electrochemical investigations showed their ability to occur reductions and oxidations processes. They exhibited deep LUMO levels of about −3.22 eV and HOMO levels above −5.80 eV. The optical investigations were carried out in the solutions (polar and non-polar) and in films and blends with PVK:PBD. Bis-(imino-1,8-naphthalimides) absorbed electromagnetic radiation in the range of 243–415 nm and emitted light from blue to yellow. Their capacity for light emission under voltage was preliminarily tested in devices with an active layer consisting of a neat compound and a blend with PVK:PBD. The diodes emitted green or red light.

Luminescence and Electrochemical Activity of New Unsymmetrical 3-Imino-1,8-naphthalimide Derivatives

“…The two emission bands, about 390 nm of the matrix and in the lower energy, were seen in blends (cf. Figure S7 ), as reported earlier in [ 33 , 36 ]. In the matrix (host) and the guest (compounds), the energy transfer from the host to the guest in the ground state can take place (by Dexter (exchange) or Förster (dipole–dipole interactions) mechanism) [ 46 ].…”

“…AzNI were absorbed with λ max in the range 330–440 nm (cf. Table 3 ) with λ max about 330 nm belonging to π → π* naphthalimide [ 33 , 36 ]. The PL emission of AzNI in the chloroform solution ranged from 514 to 524 nm, while in the remaining non-protic solvents, a shift of the wavelength to a higher energy, covering the range of 492–511 nm, was noted (cf.…”

“…In the matrix (host) and the guest (compounds), the energy transfer from the host to the guest in the ground state can take place (by Dexter (exchange) or Förster (dipole–dipole interactions) mechanism) [ 46 ]. Full effective energy transfer can be seen when the emission intensity of the host decreases and the guest increases (the host presence is needed) and the host emission overlaps with the absorption spectrum of the guest [ 36 , 46 ]. For the N -hexyl-1,8-naphthalimides, the partial overlap, and two PL bands were seen, as presented in Figure S7 in the SI .…”

“…In our previous works, for the first time, our group described properties of the 3-C substituted 1,8-naphthalimides containing an imine and β-ketoamine bond, and their applicability in OLED devices and cell imaging [ 28 , 33 , 34 , 35 , 36 ]. The 1,8-naphthalimide derivatives described in our publications were used for cellular imaging, including salicyl imine analogues undergoing hydrolysis [ 28 ] or were susceptible to aggregation-induced emission (the β-ketoenamines) [ 34 , 35 ].…”

“…The 1,8-naphthalimide derivatives described in our publications were used for cellular imaging, including salicyl imine analogues undergoing hydrolysis [ 28 ] or were susceptible to aggregation-induced emission (the β-ketoenamines) [ 34 , 35 ]. In turn, the use of iminonaphthalimides in organic electronics included the structures of mono- and bis-iminonaphthalimides [ 33 , 35 , 36 ]. Most of the compounds tested showed the ability to electroluminescence, which is the first time our research showed this.…”