Heteroleptic Copper(I) Complexes Prepared from Phenanthroline and Bis-Phosphine Ligands

Abstract

Preparation of [Cu(NN)(PP)](+) derivatives has been systematically investigated starting from two libraries of phenanthroline (NN) derivatives and bis-phosphine (PP) ligands, namely, (A) 1,10-phenanthroline (phen), neocuproine (2,9-dimethyl-1,10-phenanthroline, dmp), bathophenanthroline (4,7-diphenyl-1,10-phenanthroline, Bphen), 2,9-diphenethyl-1,10-phenanthroline (dpep), and 2,9-diphenyl-1,10-phenanthroline (dpp); (B) bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)benzene (dppb), 1,1'-bis(diphenylphosphino)ferrocene (dppFc), and bis[(2-diphenylphosphino)phenyl] ether (POP). Whatever the bis-phosphine ligand, stable heteroleptic [Cu(NN)(PP)](+) complexes are obtained from the 2,9-unsubstituted-1,10-phenanthroline ligands (phen and Bphen). By contrast, heteroleptic complexes obtained from dmp and dpep are stable in the solid state, but a dynamic ligand exchange reaction is systematically observed in solution, and the homoleptic/heteroleptic ratio is highly dependent on the bis-phosphine ligand. Detailed analysis revealed that the dynamic equilibrium resulting from ligand exchange reactions is mainly influenced by the relative thermodynamic stability of the different possible complexes. Finally, in the case of dpp, only homoleptic complexes were obtained whatever the bis-phosphine ligand. Obviously, steric effects resulting from the presence of the bulky phenyl rings on the dpp ligand destabilize the heteroleptic [Cu(NN)(PP)](+) complexes. In addition to the remarkable thermodynamic stability of [Cu(dpp)2]BF4, this negative steric effect drives the dynamic complexation scenario toward almost exclusive formation of homoleptic [Cu(NN)2](+) and [Cu(PP)2](+) complexes. This work provides the definitive rationalization of the stability of [Cu(NN)(PP)](+) complexes, marking the way for future developments in this field.

Binuclear Copper(I) Borohydride Complex Containing Bridging Bis(diphenylphosphino) Methane Ligands: Polymorphic Structures of [(µ2-dppm)2Cu2(η2-BH4)2] Dichloromethane Solvate

“…The formation of the [(μ2-dppm)2Cu2][η 2 -BH4]2 dimer from two molecules of monomeric (η 1 -dppm)Cu(η 2 -BH4) is energetically favourable, ∆GDCM°form being −19.3 kcal/mol (M06) and −24.0 kcal/mol (B3LYP-D2) (Table S5). This is in agreement with only a few examples of Cu(I) complexes reported in which dppm acts as a chelate ligand (η 2 -dppm, Scheme 1) [114]; the dinuclear Cu(I) complexes with two bridging dppm ligands are by far more common [115]. The majority of all three Boat-Boat structures (basic, distorted, and twisted) contains a bridging ligand (µ-R 2 S; µ-R 2 CO; RPy-O; µ-NO 3 ; µ-RCOO) and is characterized by rather short Cu(1)···Cu (2) distances (2.679-3.852 Å).…”

“…The formation of the [(µ 2 -dppm) 2 (Table S5). This is in agreement with only a few examples of Cu(I) complexes reported in which dppm acts as a chelate ligand (η 2 -dppm, Scheme 1) [114]; the dinuclear Cu(I) complexes with two bridging dppm ligands are by far more common [115].…”

Origin of a counterintuitive yellow light-emitting electrochemical cell based on a blue-emitting heteroleptic copper(i) complex

“…In detail, 1 shows three quasi-reversible oxidation waves at +1.02, +1.28, and +1.51 V, as well as a quasi-reversible reduction wave at −2.32 V. As a complement, the electronic structure of the ground state (GS) of 1 was optimized via DFTTables S5 and S6 and Fig. S3 2,9,11,12,14,17,18,20,21,28 the frontier molecular orbitals of 1 in the GS, i.e. HOMO (highest-occupied molecular orbital) and LUMO (lowest-unoccupied molecular orbital), are both located at the impy ligand - Fig.…”

“…[1][2][3][4][5][6][7][8]19 Encouraged by the aforementioned, heteroleptic copper(I) complexes based on diimine (N^N) and diphosphine (P^P) ligands, i.e., [Cu(N^N)(P^P)] + , have been recently revisited by several groups. 2,9,12,14,17,18,20,21 They have established several simple guidelines for enhancing both the synthesis protocol 20,21 and the ligand design 2,17,18 to take full advantage of the photoluminescence and electrochemical features of these materials. More striking, these guidelines have also proven to be useful for enhancing their electroluminescence features.…”

“…Here, the selection of the ancillary impy ligand was based on its simple one-pot synthesis and its absorption features in the ultraviolet region that might provide emission responses in the deep-blue region of the visible spectrum, [29][30][31] while the POP was selected as its bite angle stabilizes the tetrahedral coordination sphere in the excited state and avoids the formation of di-nuclear species. 20,21 Although 1 shows a deep-blue emission (λ = 450 nm) in solution, thin films, and crystalline powder, the device shows a yellow electroluminescence centered at ∼550 nm. This cannot be rationalized by standard arguments, such as the degradation of the emitter during device fabrication and/or under operation conditions, driving conditions, active layer composition, and changes in the excited states due to polarization effects.…”