Synthesis, structural characterization and luminescent properties of a series of Cu(i) complexes based on polyphosphine ligands

Abstract

A series of Cu(I) complexes with a [Cu(NN)(PP)](+) moiety, [Cu(phen)(pba)](BF(4)) (1a), [Cu(2)(phen)(2)(pbaa)](BF(4))(2) (2a), [Cu(2)(phen)(2)(pnaa)](BF(4))(2) (3a), [Cu(2)(phen)(2)(pbbaa)](BF(4))(2) (4a), [Cu(dmp)(pba)](BF(4)) (1b), [Cu(2)(dmp)(2)(pbaa)](BF(4))(2) (2b), [Cu(2)(dmp)(2)(pnaa)](BF(4))(2) (3b) and [Cu(2)(dmp)(2)(pbbaa)](BF(4))(2) (4b) (phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, pba = N,N-bis((diphenylphosphino)methyl)benzenamine, pbaa = N,N,N',N'-tetrakis((diphenylphosphino)methyl)benzene-1,4-diamine, pnaa = N,N,N',N'-tetrakis((diphenylphosphino)methyl)naphthalene-1,5-diamine and pbbaa = N,N,N',N'-tetrakis((diphenylphosphino)methyl)biphenyl-4,4'-diamine), were rationally designed and synthesized. These complexes were characterized by (1)H and (31)P NMR, electrospray mass spectrometry, elemental analysis and X-ray crystal structure analysis. Introduction of different central arene spacers (phenyl, naphthyl, biphenyl) into ligands, resulting in the size variation of these complexes, aims to tune the photophysical properties of the complexes. Each Cu(I) ion in these complexes adopts a distorted tetrahedral geometry constructed by the chelating diimine and phosphine groups. Intermolecular C-H···π and/or π···π interactions are involved in the solid states. The dmp-containing complex exhibits better emission relative to the corresponding phen complex due to the steric encumbrance of bulky alkyl groups. Furthermore, for complexes with identical diimine but different phosphine ligands, the tendency of increased emission lifetime as well as blue-shifted emission in the solid state follows with the decrease in size of complexes. Intermolecular C-H···π interactions have an influence on the final solid state photophysical properties through vibrationally relaxed non-radiative energy transfer in the excited state. Smaller-sized complexes show better photophysical properties due to less vibrationally relaxed behavior related to flexible C-H···π bonds. Nevertheless, the tendency for increased quantum yield and emission lifetime, as well as blue-shifted emission in dilute solution goes with the increase in size of complexes. The central arene ring (phenyl, naphthyl or biphenyl) has an influence on the final photophysical properties. The larger the π-conjugated extension of central arene ring is, the better the photophysical properties of complex are. The rigid and large-sized complex 3b, with a high quantum yield and long lifetime, is the best luminophore among these complexes.

Synthesis, structure, characterization and luminescent properties of copper(I) complexes based on bis-diimine bridging ligands

“…Accounting for this, the selected DFT calculation of complexes 1, 2 and 3 have recently been carried out to investigate the electronic properties in the Dmol 3 package. Similarly to the previously report [11] , calculation results indicate that the HOMOs in these complexes are mainly comprised of copper d-orbital with admixed phosphane ligand character, while the LUMOs are mainly located on the π-electron system of pmb or pmbb (Figs. S1-S3).…”

“…To obtain Cu(I) complexes suitable for photoelectrochemical applications, an important consequence of typically addition of bulky substituents will avoid the conformational change and maintain the pseudotetrahedral Cu(I) at the excited state, which leads to extending the lifetime for photoprocess. As we previously reported [11] , the introduction of bulky phosphine groups can minimize effectively the geometric relaxation of copper(I) complexes at the excited state as well as solvent attack, demonstrating unprecedented higher quantum yield and longer lifetime at room temperature.…”

Synthesis, structures and photoluminescent properties of Cu+ complexes with extended π-systems

“…But in 2 and 3, each Cu + adopts a distorted tetrahedral geometry consisting of two P atoms from one pba and two N atoms from one phenanthroline moiety. The average bond distances of Cu\N and Cu\P, as well as the bite angles of P\Cu\P and N\Cu\N are 2.07 Å, 2.24 Å, 103.8°and 80.7°, respectively, which have no significant difference compared with the corresponding values in the previously studied [Cu(NN)(PP)] systems [7]. In 1, the pz ring has a weak intramolecular π-π interaction with one phenyl ring attached to the P atom (Fig.…”

Poly[di-μ3-chlorido-di-μ2-chlorido-{μ4-N,N,N′,N′-tetrakis[(diphenylphosphanyl)methyl]benzene-1,4-diamine-κ4P:P′:P′′:P′′′}tetracopper(II)]

“…Recently, Cu I complexes containing multiphosphine ligands have received much attention so far due to their special structures, novel reactivity, as well as catalytic and luminescent properties (Kohl et al, 2006;Wang et al, 2008;Hou et al, 2011;Ni et al, 2011). However, synthesis of Cu I complexes with tetraphosphine ligands have been virtually not explored, though a great number of Cu(I) complexes with diphosphines were reported (Saravanabharathi et al, 2002;Sivasankar et al, 2004;Li et al, 2009 (Li et al, 2009).…”

“…For the structures and properties of Cu I complexes containing polyphosphine ligands, see: Li et al (2009) ;Kohl et al (2006); Wang et al (2008); Hou et al(2011);Ni et al (2011). For the synthesis of Cu(I) complexes with diphosphine ligands, see: Saravanabharathi et al (2002); Sivasankar et al (2004).…”