Extremely bulky copper(i) complexes of [HB(3,5-{1-naphthyl}2pz)3]- and [HB(3,5-{2-naphthyl}2pz)3]- and their self-assembly on graphene.

Abstract

The synthesis and characterization, using NMR (1H and 13C), infrared spectroscopy, and X-ray crystallography, of the ethene and carbon monoxide copper(i) complexes of hydridotris(3,5-diphenylpyrazol-1-yl)borate ([TpPh2]-) and the two new ligands hydridotris(3,5-bis(1-naphthyl)pyrazol-1-yl)borate ([Tp(1Nt)2]-) and hydridotris(3,5-bis-(2-naphthyl)pyrazol-1-yl)borate ([Tp(2Nt)2]-) are described. X-ray crystal structures are presented of [Cu(TpPh2)(C2H4)] and [Cu(Tp(2Nt)2)(C2H4)]. The compound [Cu(TpPh2)(C2H4)] features interactions between the protons of the ethene ligand and the π-electron clouds of the phenyl substituents that make up the binding pocket surrounding the copper(i) center. These dipolar interactions result in strongly upfield shifted signals of the ethene protons in 1H-NMR. [Cu(Tp(1Nt)2)(CO)] and [Cu(Tp(2Nt)2)(CO)] were examined using infrared spectroscopy and were found to have CO stretching vibrations at 2076 and 2080 cm-1 respectively. The copper(i) carbonyl complexes form self-assembled monolayers when drop cast onto HOPG and thin multilayers of a few nanometers thickness when dip coated onto graphene. General macroscopic trends such as the different tendencies to crystallize observed in the complexes of the two naphthyl-substituted ligands appear to extend well to the nanoscale where a well-organized monolayer could be observed of [Cu(Tp(2Nt)2)(CO)].