Network formation and photoluminescence in copper(i) halide complexes with substituted piperazine ligands

Abstract

The synthesis, X-ray structures and photophysics of ten complexes of CuX (X = I or Br) with bridging N-substituted and N,N'-disubstituted piperazines (Pip) are presented. Depending on the steric demand of the Pip substituents, the complexes fall into four categories: (CuX)(4)(Pip)(2), which are networks of linked Cu(4)X(4) cubane units, (CuX)(2)(Pip), which are chains of linked Cu(2)X(2) rhombs, and (CuX)(2)(Pip)(2) or (CuX)(4)(Pip)(4), which are simple rhomboid dimers and cubane tetramers. A combination of spectroscopic studies and DFT calculations was used to investigate the luminescence of the products. The results suggest that the relatively high energy emission seen in dimers is due to cluster-centred (XMLT/metal-centred) excitations for the aliphatic amines and MLCT (d →π*) for aromatic amines, and low energy emission seen in the tetramers is the result of cluster-centred transitions. The (CuI)(2)(Pip) complexes act as sensor materials, undergoing irreversible reaction with aliphatic and aromatic amines (Nu) in the vapour state, irreversibly producing cubanes (CuI)(4)Nu(4), with corresponding production of long wavelength emission.

Cu(I) hybrid inorganic–organic materials with intriguing stimuli responsive and optoelectronic properties

“…The linkage isomerization reaction is accompanied by a significant increase of the Cu···Cu separation, from 2.721 Å in 66 to 2.7961 Å in 67·MeOH, however, in 67 relevant π−π interactions between phenyl and pyridyl planes takes place lowering the LUMO energy level and resulting in a red shift of the emission with respect to 66. [67]. The structures of the compounds consist of chains with piperazine-linked Cu 2 I 2 rombs.…”

Luminescent Complexes Containing Halogeno-bridged Dicopper(I) Unit {Cu2(µ-X)2} (X = Cl, Br, and I)

“…3,10 As another aliphatic amine complexes, complexes with piperazine derivatives have been reported to show emission around 450 nm, which is also ascribed to the same transition in the {Cu 2 X 2 } unit. 24 As complexes with P donor atoms, complexes with diphosphine ligand, dppbz (bisdiphenylphosphinobenzene) [Cu 2 X 2 (dppbz) 2 ] (X = Cl, Br, and I) have been reported as strongly emissive material. 25 The complexes show emission with max at around 520 nm and the quantum yields are 0.60.8.…”

“…3,10 Thereafter, several discrete and polymeric complexes composed of {Cu 4 I 4 } have been prepared with ligands having N donor atoms, to show the clustercentered emission at around 550600 nm. 19,24,31,32 Recently, a number of complexes containing {Cu 4 (¯3-X) 4 } with thioether ligands have been prepared by the direct reaction of copper(I) iodide and the thioether ligand. 27,28,33 For these thioether complexes, the emission resulting from the intracluster transition is observed in the range of 500600 nm without CT emission.…”

“…While the luminescent d 6 and d 8 metal complexes prefer specific types of ligands, such as polypyridines and their derivatives and octahedral or square-planar geometry, the d 10 metal complexes of gold(I) and copper(I) are known to be emissive with various ligands such as phosphine derivatives, pyridine derivatives, acetylides, and chalcogenides as well as halides and to assume structures with various nuclearities and linkage modes due to the flexible coordination geometry of d 10 metal ions. 24 In accordance with the diverse coordination circumstances, the emissive excited states of d 10 metal complexes include the ds transition on the metal center(s), the charge transfer (CT) between metal center and ligands, and inter-and intraligand transfer depending on the metal and ligand combinations. 2 The relation between ligand sets and their emissive properties, therefore, should be clarified to design and utilize the d 10 emissive materials.…”

Transition‐Metal Complexes with Ferrocene‐Bridged Bis(imidazolin‐2‐imine) and Bis(diaminocyclopropenimine) Ligands

“…The resulting Cu 2 I 2 moieties display Cu-Cu distances of 2.6015(8) and 2.5907(8) Å. Cu-I-Cu′ angles of 60.820 (16)°and 60.393(16)°w ere observed along with Cu-I distances between 2.5365(5) and 2.6127(5) Å, which is expected for such types of structural motifs. [25] …”