Synthesis and characterization of Copper (I) complexes

Synthesis and Characterization of Cu(I) complexes

Enrico Casamassa,

_{Giorgio Volpi,}

_{Claudia Barolo,}

_{Guido Viscardi,}

_{Michael D. Weber}

_{and Rubén D. Costa}

a _{Dipartimento di Chimica e Centro Interdipartimentale NIS, Università degli Studi di Torino, Via Pietro Giuria 7, 10125-Torino, Italy} b _{Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg (FAU), Egerlandstr. 3, D-91058 Erlangen, Germany.}

INTRODUCTION

In the last years, Cu(I) complexes have been identified as favourable candidates as active materials in light-emitting electrochemical cells (LECs). In particular, the copper(I) complexes are an alternative to iridium(III) complexes. The N,N-bidentate ligands such as 2,2’-bipyridine and 1,10-phenanthroline play a pivotal role in synthesis of copper(I) complexes. In others kind of complex, ligands based on imidazo[1,5-a]pyridines have been used.

In this work we present the optimized preparation of a series of six N^N ligands, 1-pyridylimidazo[1,5-a]pyridines, and for each ligand both the corresponding heteroleptic and homoleptic complexes.

LIGANDS: 1-pyridylimidazo[1,5-a]pyridines

N,N-bidentate ligands with mixed five- and six-membered heterocycles are desirable class of compounds in the pursuit of structural diversity for property performance. In particular, 1-pyridylimidazo[1,5-a]pyridines possess a bidentate structural feature with a pyridyl unit directly next to a fused imidazole and have emerged as a new class of ligands.

The synthesis of desirable N,N-bidentate ligands is based on a direct cyclization of 2,2’-dipyridyl ketone with aldehydes in the presence of ammonium acetate in glacial acetic acid.

Classical synthesis:

• 1:2:5 molar ratio of ketone/aldehyde/NH4OAc • stirred at 110°C under N₂ in 5h

Microwave synthesis: optimization of reaction time and use of less reagents!

• 1:1:5 molar ratio of ketone/aldehyde/NH4OAc • stirred at 180°C for 1h L1 R = t-butyl R’=H L2 R = CF₃ R’=H L3 R = H R’=H L4 R = CN R’=H L5 R = OMe R’=H L6 R = H R’=OMe Spectroscopic Characterization Heteroleptic complexes:

• starting reagent: [Cu(NCCH₃)₄]PF₆ , commercially available

• most hindered ligand: POP (bis[2-diphenylphosphino)-phenyl]ether), a P,P-bidentate ligand commercially available

• two step: 30’ each step, 1h reaction time • room temperature

• under N_2(g) flux

Homoleptic complexes:

• starting reagent: [Cu(NCCH₃)₄]PF₆ , commercially available • two molecules of N,N-bidentate ligand

• one step: 30’ reaction time • room temperature

• under N_2(g) flux