Effect of substituents on crystal packing of functionalized 4,4′-bis(benzylideneamino)diphenyl ether(s) and their reduced benzyl forms: Synthesis, characterization, optical and thermal properties

In this paper we report the synthesis of 4,4′-bis(benzylideneamino)diphenyl ether (1), 4,4′-bis(p-methoxybenzylideneamino)diphenyl ether (2), 4,4′-bis(p-nitrobenzylideneamino)diphenyl ether (3), 4,4′-bis(benzylamino)diphenyl ether (4) and 4,4′-bis(p-methoxybenzylamino)diphenyl ether (5). The new compounds were characterized by using standard spectroscopic techniques. Supramolecular structures of 1–4 have been studied by using single-crystal X-ray diffraction to gauge the influence of substituents, present on para-positions of peripheral phenyl rings, on the association of molecules in the solid state. The study showed that introduction of p-OCH3 and p-NO2 substituents on peripheral phenyl rings, successfully switches off CH⋯π synthons seen in compound 1 and 4 and that the new compounds adopt other packing strategies based on CH⋯O (2) and CH⋯N, CH⋯O and π⋯π (3) interactions. The optical band gaps (Eg), calculated by optical absorption method fall in the range of 2.16–3.0 eV and demonstrate a wide band gap semiconducting nature of these compounds. The thermogravimetric study of these compounds suggests the total destruction of the molecules up to 550 °C with a remaining mass of <10%, except the 3.