Syntheses and Characterizations of Platinum Complexes with New Pyrene-based Salicylaldiminato-type Ligand Substituted at 7-Position of Pyrene

Abstract

Many experimental data show that bulky substituents on the molecules enhance solubility, catalytic activity, and photophysical properties due to the prevention of π-π stacking in metal salicylaldimines. In order to understand the effect of bulkiness of substituents on the properties of the obtained molecules, the author researched and synthesized two new pyrene-based salicylaldiminato-type ligands that were substituted at 7-position and functionalized on imine group with bulky substituents. After the introduction of  the tert-butyl group at 7-position of pyrene by Friedel-Crafts reaction, the syntheses of new ligands 1-hydroxy-2-[((2,6-dimethylphenyl)-imino)methyl]-7-(tert-butyl)-pyrene 3, 2-hydroxy-1- [((2,6-dimethylphenyl)imino)methyl]-7-(tert-butyl)-pyrene 4 and corresponding platinum complexes 3(Pt), 4(Pt) were performed in the different ways with the synthetic processes of the complexes 1(Pt) and 2(Pt). The new ligands and complexes were characterized by ¹H NMR, IR spectroscopy, mass spectroscopy, elemental analysis and X-ray diffraction, only for 3(Pt). In addition to measurements of the absorption and emission spectra, TDDFT calculations using the B3LYP functions were also performed. The complexes 3(Pt) and 4(Pt) exhibit good solubility and red-shift in absorption and emission spectra because of tert-butyl group at 7-position of pyrene and extension of the delocalized π-orbitals to the 2,6-dimethylphenyl on imine group. The change of functional groups also induces the upfield shift of the protons affected by ring currents of phenyl groups Ar-3, Ar-4 on imine groups. Introduction of t-butyl groups in pyrene moieties can stabilize radical forms in oxidation processes.