208471-80-1Relevant academic research and scientific papers
cis-dicyanoosmium(II) diimine complexes bearing phosphine or sulfoxide ligands: Spectroscopic and luminescent studies
Lai, Siu-Wai,Chan, Queenie K.-W.,Zhu, Nianyong,Che, Chi-Ming
, p. 11003 - 11016 (2008/10/09)
A series of cis-dicyanoosmium(II) complexes [Os(PPh3) 2(CN)2(N∩N)] (N∩N = Ph2phen (2a), bpy (2b), phen (2c), Ph2bpy (2d), tBu2bpy (2e)) and [Os(DMSO)2(CN)2(N∩N)] (3a-3e, N∩N = Br 2phen (31), Clphen (3g)), were synthesized and their spectroscopic and photophysical properties were examined, and [Os(PMe3) 2(CN)2(phen)] (4) with axial PMe3 ligands was similarly prepared. The molecular structures of 2a, 2c, [2c·Zn(NO 3)2]∞, 2d, 2e, 3b, 3d, 3e, and 4 were determined by X-ray crystallographic analyses. The two CN ligands are cis to each other with mean Os-C bond distance of 2.0 A. The two PR3 (R = Ph, Me) or DMSO ligands are trans to each other with P/S-Os-P/S angles of ～77°. The UV-vis absorption spectra of 2a-2e display an intense absorption band at 268-315 nm (ε = ～(1.54-4.82) × 104 M-1 cm-1) that are attributed to π → π*(N∩N) and/or π → π*(PPH3) transitions. The moderately intense absorption bands with λmax at 387-460 nm (ε = ～ (2.4-11.3) × 103 M-1 cm-1) are attributed to a 1MLCT transition. A weak, broad absorption at 487-600 nm (ε = ～390-1900 M-1 cm-1) is assigned to a 3MLCT transition. Excitation of 2a-2e in dichloromethane at 420 nm gives an emission with peak maximum at 654-703 nm and lifetime of 0.16-0.67 μs. The emission energies, lifetimes, and quantum yields show solvatochromic responses, and plots of νmax, τ, and Φ, respectively, versus ET (solvent polarity parameter) show linear correlations, indicating that the emission is sensitive to the local environment. The broad structureless solid-state emission of 2a-2e at 298 (λmax 622-707 nm) and 77 (λmax 602-675 nm) K are assigned to 3MLCT excited states. The 77 K MeOH/EtOH (1:4) glassy solutions of 2a-2e also exhibit 3MLCT emissions with λmax = 560-585 nm. The 1MLCT absorption and 3MLCT emission of 3a-3g occur at λmax = 332-390 nm and 553-644 nm, respectively. In the presence of Zn(NO3)2, both the 1MLCT absorption and 3MLCT emission of 2c in acetonitrile blue-shift from 397 to 341 nm and 651 to 531 nm, respectively. The enhancement of emission intensity (I/Io) of 2e at 531 nm reached a maximum of ～810 upon the addition of two equivs of Zn(NO3) 2. The crystallographic and spectroscopic evidence suggests that 2c undergoes binding of Zn2+ ions via the cyano moieties.
