Heteroleptic Copper(I) Complexes Prepared from Mono- and Tetra-phenylbenzene-substituted Phenanthroline Ligands

Phenanthroline ligands bearing two biphenyl (L1) or two tetraarylbenzene (L2) substituents have been synthetized and used to prepare bis-phenanthroline copper(I) complexes. Steric constraints are limited in the case of the biphenyl-substituted ligand and [Cu(L1)(2)](BF4) has been obtained by reaction of L1 with [Cu(CH3CN)(4)](BF4). In contrast, the tetraarylbenzene substituents of L2 are large enough to totally prevent the formation of the corresponding homoleptic bis-phenanthroline copper(I) complex. Both L1 and L2 have been also combined with 2,9-dimethyl-1,10-phenanthroline (dmp) to prepare the corresponding heteroleptic bis-phenanthroline copper(I) complexes. All the copper(I) complexes obtained from L1 and L2 revealed dynamic conformational exchange between several atropisomers. Detailed NMR studies and Density Functional Theory (DFT) calculations have been carried out to assess their conformations in solution.

Automated summary

Phenanthroline ligands with different substituents were synthesized to prepare corresponding copper(I) complexes. While biphenyl-substituted ligands can form homoleptic copper(I) complexes, tetraarylbenzene-substituted ligands cannot. The obtained copper(I) complexes exhibit dynamic conformational exchange in solution.