Effects of Sterics and Electronic Delocalization on the Photophysical, Structural, and Electrochemical Properties of 2,9-Disubstituted 1,10-Phenanthroline Copper(I) Complexes (original) (raw)

1999, Inorganic Chemistry

The syntheses, crystal structures, electronic absorption spectra, electrochemical properties, and photophysical properties of a series of copper(I) bis(phenanthroline) complexes are reported. The phenanthroline ligands that have been prepared and investigated are the following: dop (2,9-di-(2-methylphenyl)-1,10-phenanthroline), xop (2-(2-methylphenyl)-9-(2,6-dimethylphenyl)-1,10-phenanthroline), dpep (2,9-diphenylethynyl-1,10-phenanthroline), and dmesp (2,9-dimesityl-1,10-phenanthroline). The complex [Cu(dop) 2 ](PF 6)‚Et 2 O crystallizes in space group P1 hwith a) 11.854(3) Å, b) 14.705(3) Å, c) 15.866(4) Å, R) 107.81(2)°,) 106.72(2)°, γ) 97.56(2)°, V) 2447.6(10) Å 3 , and Z) 2. For 5739 unique data with F > 4.0σ(F), R) 7.52%. The complex [Cu(xop) 2 ](PF 6)‚ 3 / 2 CH 3 OH crystallizes in space group C2/c with a) 23.096(6) Å, b) 23.387(6) Å, c) 17.873(7) Å,) 100.08(3)°, V) 9505(5) Å 3 , and Z) 8. For 5631 unique data with F > 4.0σ(F), R) 6.02%. The complex [Cu(dpep) 2 ](PF 6) crystallizes in space group P1 h with a) 13.327(7) Å, b) 14.114(7) Å, c) 15.175(5) Å, R) 87.23(4)°,) 66.48(3)°, γ) 61.84(4)°, V) 2273(2) Å 3 , and Z) 2. For 4851 unique data with F > 4.0σ(F), R) 5.47%. The complex [Cu(dmesp)(dpep)](PF 6) crystallizes in space group Pbca with a) 14.547(6) Å, b) 22.868(6) Å, c) 30.659(10) Å, V) 10199(6) Å 3 , and Z) 8. For 2281 unique data with F > 4.0σ(F), R) 9.43%. The electrochemical, spectral, and structural properties of [Cu(dop) 2 ] + and [Cu(xop) 2 ] + demonstrate that the copper coordination environment is more sterically encumbered and more rigid in these two complexes than the coordination environment in the comparison molecule [Cu(dpp) 2 ] + (dpp) 2,9-diphenyl-1,10-phenanthroline). A larger energy gap is predicted for [Cu(dop) 2 ] + and [Cu(xop) 2 ] + based on these data, and consequently, a blue-shifted emission is observed relative to [Cu(dpp) 2 ] +. The room-temperature excited-state lifetimes in dichloromethane and methanol of the dop and xop complexes are shown to be shorter than the dpp complex, and these results are interpreted as due to a reduction in ligand π-electron delocalization in the former two complexes. The complexes [Cu(dpep) 2 ] + and [Cu(dmesp)(dpep)] + are shown to have increased ligand π-electron delocalization relative to [Cu(dpp) 2 ] + ; however, neither complex displays room-temperature steady-state emission in dichloromethane.