Synthesis and Properties of Salicylaldehydes Fine‐Tuned by Modular Assembly using “Plug‐and‐Socket”‐Type Extendibility

Abstract

A salicylaldehyde derivative bearing four pyridine arms, 3,5-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-2,4-dihydroxybenzaldehyde (Hbpsal) as a "socket", was prepared and used to derive a series of zinc complexes with various extra anions "plugged" into their vacant site. The crystal structure and H NMR spectra were noticeably influenced by the extra anions, allowing fine-tuning of the properties by "plug-and-socket"-type modification. Similar to unsubstituted salicylaldehyde, the zinc complexes reacted with primary amines to afford Schiff-base compounds. Because of the potential chirality around the coordination sphere, reaction with a chiral amine resulted in an equilibrium system between diastereomers, the potential of which as chiral sources tunable by the extra anions is discussed. Some of the complexes were further converted into zinc- or nickel-salphen (=N,N-bis(salicylidene)-1,2-phenylenediamine) complexes. The electrochemical properties of the nickel complex were slightly modified by the extra anions, whereas the photophysical properties of the zinc complex appeared unchanged.

Acrylic Polymers Containing a Nickel Salphen Complex: An Approach to Supramolecular and Macromolecular Systems

“…beyond the typical binding site design based on adjusting the interplay between steric hindrance and ligand shape by trial and error is still unexplored. Therefore, these Salphen complexes with a nickel atom have mostly found uses in catalytic systems, where the role of the metal has mostly remained in terms of its redox activity, with a few multirole cases, for instance, as a guest‐binding regulator in molecular tweezers [22] or as an oxidation loci translocation agent [23] in plug‐and‐socket multinuclear complexes. Besides, in spite of the rich portfolio of accessible non‐covalent interactions for Ni‐Salphen structures to address control of matter using simple host‐guest chemistry, the potential of these complexes as supramolecular scale modulators of macroscale properties in the design of functional polymers, has remained limited.…”