| Abstract
| - Four dinuclear and trinuclear Cu(I) complexes that contain 2-(2‘-pyridyl)benzimidazolyl derivative ligands including1,4-bis[2-(2‘-pyridyl)benzimidazolyl]benzene (1,4-bmb), 1,3-bis[2-(2‘-pyridyl)benzimidazolyl]benzene (1,3-bmb), 1,3,5-tris[2-(2‘-pyridyl)benzimidazolyl]benzene (tmb), and 4,4‘-bis[2-(2‘-pyridyl)benzimidazolyl]biphenyl (bmbp) have beensynthesized. The formulas of these complexes are [Cu2(1,4-bmb)(PPh3)4][BF4]2 (1), [Cu2(1,3-bmb)(PPh3)4][BF4]2(2), [Cu3(tmb)(PPh3)6][BF4]3 (3), and [Cu2(bmbp)(PPh3)4][BF4]2 (4), respectively. The crystal structures of 2−4 havebeen determined by single-crystal X-ray diffraction analyses. The Cu(I) ions in the complexes have a distortedtetrahedral geometry. For 3, two structural isomers (syn and anti) resulted from two different orientations of thethree 2-(2‘-pyridyl)benzimidazolyl chelating units were observed in the crystal lattice. Variable-temperature 1H NMRexperiments established the presence of syn and anti isomers for 1−3 in solution which interconvert at ambienttemperature. Complexes 1−4 have a weak MLCT absorption band in the 350−450 nm region and display a yellow-orange emission when irradiated by UV light. One unexpected finding is that the yellow-orange emission of complexes1−4 has a very long decay lifetime (∼200 μs) at 77 K. An electroluminescent (EL) device using 4 as the emitterand PVK as the host was fabricated. However, the long decay lifetime of the copper complexes may limit theirapplications as phosphorescent emitters in EL devices.
- Dinuclear and trinuclear Cu(I) complexes based on either a linear or a star-shaped ligand containing two or three 2-(2‘-pyridyl)benzimidazolyl groups have been found to display structural isomerism, phosphorescence with a long decay lifetime, and the possible use as emitters in EL devices.
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