An efficient method was developed for the preparation of a series of zinc Schiff base complexes. Introduction of a pyridyl group as a bridging unit as well as incorporation of ethynyl and electron-donating groups into the salicylidene moiety of these complexes moderately enhances the photoluminescence intensity and quantum yield. Electron-rich palladium groups possibly influence the photophysical character through the bridging C[triple bond]C bond. The crystal structure of the pyridine adduct of a salen Zn complex is determined by X-ray diffraction analysis.

Two series of chiral salicylaldimine-based liquid crystals which differ from each other in the position of the (S)-2-octyloxy tail have been synthesized and characterized by polarizing optical microscopy, differential scanning calorimetry, and electrical switching. Compounds OH I (n = 6-7) having (S)-2-octyloxy tail close to the salicylaldimine core and compounds OH II (n = 6-11) having (S)-2-octyloxy tail far from the salicylaldimine core exhibit polymorphism of mesophases including frustrated blue phase and antiferroelectric (SmC*(A)) phases. Notably, as compared with structurally similar Schiff base compounds H I (n = 7), intramolecular hydrogen bonding in antiferroelectric salicylaldimine-based compounds OH I (n = 7) induces the frustrated blue phase. However, as compared with structurally similar Schiff base compounds OH II (n = 8), the lack of intramolecular hydrogen bonding in Schiff base compounds H II (n = 8) suppresses antiferroelectric properties.

A new series of photo-luminescent Zn(II) and Mg(II) Schiff base complexes were prepared by treatment of the arylethynyl-substituted salicylaldehydes obtained from the Sonogashira reaction with the metal salt followed by addition of the different diamines. Most square-planar Zn(II) complexes exhibited good quantum efficiencies. The Mg(II) complexes displayed even higher quantum yields than the corresponding Zn-complexes. Unsymmetrical Zn(II) Schiff base complexes were also successfully prepared from organic monoimines obtained as intermediates in the formation of the Mg metal Schiff base complex. The monoimine can also be prepared from the reaction of salicylaldehydes with excess diaminoarene. Two crystal structures featuring the zinc atom are reported, one with a rare four-coordinate square planar geometry and the other with a five-coordinate square pyramidal geometry.

Incorporation of fluorene groups into the salicylidene moiety significantly enhances the luminescence of a number of multinuclear alkynylated Zn(II)-salophen complexes. Preparation of these complexes was achieved by a synthetic strategy with facile handling of the reactants, simple purification of the products, and one-pot reaction process. Two synthetic methods are used for the preparation of different types of multinuclear salophen complexes. The introduction of a bis- or a tris-salicylaldehyde as a bridging unit in the presence of various alkynyl substituted monoimines in the reaction mixture containing zinc acetate resulted in the preparation of di- and tri-nuclear Zn(II)-salophen complexes of type 1, respectively. For a different type, treatment of tetraminobenzene with various arylethynyl-substituted salicylaldehyde afforded dinuclear Zn(II) alkynylated salophen complexes of type 2 with a different structure. The photophysical behaviors of these multinuclear metal salophen complexes were investigated. Particularly, the dinuclear complex 9b of type 1 having ethynylfluorene groups in salophen moieties and dialkoxyl groups in the bridging moiety exhibits higher quantum efficiency than that of other complexes in this report. In addition, the bis-Zn(II) alkynylated salophen complex 11e bearing nitrogen donor groups displays more red-shifted pattern than those with other functional substituents both in absorption and emission spectra.

Four simple rodlike Schiff base mesogens with tolane moiety were synthesized and applied to stabilize cubic blue phases (BPs) in simple binary mixture systems for the first time. When the chiral additive or was added into a chiral salicylaldimine-based compound, the temperature range of the cubic BP could be extended by more than 20 °C. However, when the chiral Schiff base mesogen was blended with chiral dopant possessing opposite handedness, , BPs could not be observed. Interestingly, the widest temperature range of the cubic BPs (∼35 °C) could be induced by adding the rodlike chiral dopant or into the rodlike racemic Schiff base mesogen with hydroxyl group. On the basis of our experimental results and molecular modeling, the appearance and temperature range of the BPs are affected by the dipole moment and the biaxiality of the molecular geometry. Accordingly, we demonstrated that the hydroxyl group and the methyl branch in this type of Schiff base mesogen play an important role in the stabilization of BPs.