Structures of the Copper(I) and Copper(II) Complexes of 2,9-Diphenyl-1,10-phenanthroline:  Implications for Excited-State Structural Distortion

Abstract

The syntheses, crystal structures, and electronic absorption spectra of the copper(I) and copper(II) complexes of 2,9-diphenyl-1,10-phenanthroline (dpp) are reported. The complex [Cu(dpp)(2)](PF(6)) (1) crystallizes in space group P2(1)/c with a = 11.081(4) Å, b = 25.491(8) Å, c = 14.263(5) Å, beta = 92.84(3) degrees, Z = 4, and V = 4024(2) Å(3). For 4813 unique data with F > 4.0sigma(F), R = 5.41% and R(w) = 6.43%. The coordination geometry about the copper(I) center in [Cu(dpp)(2)](+) is best described as distorted tetrahedral with approximate C(2) symmetry. The structure of [Cu(dpp)(2)](+) is largely determined by interligand pi-stacking interactions that occur between the phenyl groups of one ligand and the phenanthroline moiety of the other ligand. Solution-state absorption and (1)H NMR spectra indicate that the [Cu(dpp)(2)](+) complex is fluxional in solution, rocking between two enantiomeric structures of C(2) molecular symmetry through an intermediate of C(s)() symmetry. The complex [Cu(dpp)(2)](ClO(4))(2) (2) crystallizes in space group P&onemacr; with a = 7.809(3) Å, b = 13.027(6) Å, c = 20.344(10) Å, alpha = 87.68(4) degrees, beta = 89.16(4) degrees, gamma = 79.26(4) degrees, Z = 2, and V = 2032(1) Å(3). For 4943 unique data with F > 4.0sigma(F), R = 5.22% and R(w) = 5.37%. The coordination geometry about the copper(II) center in [Cu(dpp)(2)](2+) is best described as flattened tetrahedral with approximate D(2) symmetry. There are no interligand pi-stacking interactions in the structure of [Cu(dpp)(2)](2+). The four-coordinate geometry in [Cu(dpp)(2)](2+) persists in solution on the basis of solution-state and solid-state absorption spectroscopy. Structural distortion in the metal-to-ligand charge-transfer excited state of [Cu(dpp)(2)](+) is discussed on the basis of the structures of 1 and 2.

Dynamic Study of Metal-Ion Incorporation into Porphyrins Based on the Dynamic Characterization of Metal Ions and on Sitting-Atop Complex Formation

“…[76][77][78] However, the EXAFS spectrum of the Cu(II)-SAT complex was satisfactorily reproduced by the model with an axial Cu-N(an) interaction, and the result is in agreement with that observed for the structure parameters around the Cu 2+ ion in the Cu(II)/Hg (II) heterodinuclear porphyrin intermediate (see 4·2). 66 Furthermore, the fact that the R value of Cu-N(an)eq is almost the same as that of Cu(an)6 2+ strongly indicates that the AN molecules coordinate to the Cu 2+ ion at the equatorial sites in the distorted octahedral environment because the bond distance in the tetrahedral analogue with a reduced coodination number should be shortened, as indicated by the structural data of the solvated metal ions with a reduced solvation number in bulky solvents.…”

The Versatile SALSAC Approach to Heteroleptic Copper(I) Dye Assembly in Dye-Sensitized Solar Cells

“…As expected, the presence of the 6,6 -diphenyl substituents extends the absorption range giving two bands in the visible region (435 and 585 nm) as observed for the bromo-analogue [Cu(2) 2 ][PF 6 ] [40]. Similar dual bands in the visible have been described for [Cu(dpp) 2 ] + (dpp = 2,9-diphenyl-1,10-phenanthroline) and arise from the highly distorted and flattened structure caused by intramolecular π-stacking involving the phenyl substituents [37,38]. Interestingly, when a CH 2 Cl 2 solution of [Cu(4) 2 ][PF 6 ] was left standing at room temperature, the colour changed from dark red to yellow over a 10 day period, and the dual absorptions in the visible were replaced with one, lower intensity maximum at 452 nm ( Figure 3).…”

“…Methyl groups are often selected, but use of 6,6 -diphenyl-2,2 -bipyridine has the advantage of extending the absorption range of the copper(I) complex towards the red as observed in the absorption spectrum of [Cu(dpp) 2 ] + (dpp = 2,9-diphenyl-1,10-phenanthroline) [37,38]. The second design feature to consider is the anchoring domain.…”

Two Neutral Copper(I) Complexes Bearing 2‐(4‐Nitrophenyl) Imidazole[4,5‐f]‐1,10‐Phenanthroline: Synthesis, Crystal Structure, and Luminescence Properties

“…[3][4][5] However, the series [Cu (1,10-phen) 2 ] + are not emissive because a distortion from tetrahedral toward square-planar geometry may accelerate nonradiative decay of the excited state. 6,7 This distortion is efficiently prevented by replacing one 1,10-phen by a sterically hindered phosphine ligand. 8 Another effective strategy involves the chemical functionalization of 1,10-phen at various ring positions.…”