A Study of π – π Stacking Interactions in Rhenium Carbonyl Complexes Based on Backbone Functionalized Bis(pyrazolyl)methane Ligands

Abstract

π – π Stacking interactions are one of the most important non-covalent inter-molecular forces, which play an important role in the architecture of 1D and 2D networks of supramolecular chemistry. This associative contact involves the attractive interactions of aromatic molecules with each other. To describe and study the strength of the π – π stacking interactions, four new bis(pyrazolyl)ethanamine ligands having different aromatic groups (1-pyrenyl, 1-naphthyl, 2-naphthyl, and 9-anthracenyl) known for their propensity to be involved in π – π stacking interactions were prepared by the reaction of one equivalent of bis(pyrazolyl)ethanamine with one equivalent of the corresponding aromatic aldehyde. One equivalent of these ligands reacted with one equivalent of Re(CO)5Br to give their corresponding metal complexes.

The ligands and their metal complexes were characterized in solution state by 1H NMR and IR spectroscopic methods. To confirm the formation of metal complexes, ESI-mass spectra were taken. DOSY spectra were taken to study π – π stacking and this spectral data suggested that only the 2-naphthyl and 9-anthracenyl ligands were π-stacked, while for the complexes only the 9-anthracenyl and 1-pyrenyl complexes were π-stacked. X-ray diffraction analysis of the 9-anthracene-CH=NCH2CH(pz)2-Re(CO)3Br complex showed a dimer of two Re complexes with π – π stacking. Unfortunately, suitable crystal structures of the remaining complexes and ligands were not obtained.

Date of Award	2022
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Radu Semeniuc (Supervisor)