Spectroscopic properties and molecular structure of a luminescent cyclometalated mercury(II) complex of 2,9-diphenyl-1,10-phenanthroline

The reaction of mercuric acetate with 2,9-diphenyl-1,10-phenanthroline (dpp) in refluxing ethanol and in the presence of lithium chloride gave the cyclometalated complex [Hg(C ∧ N-dpp)Cl]2. X-ray crystal analysis revealed a dimeric molecular structure: [HgC24H15N2Cl]2, fw = 567.48 × 2, P21/n, a = 11.79(1) Å, b = 17.80(1) Å, c = 18.84(1) Å, β = 99.23(6)°, V = 3904(5) Å3, Z = 4. The long Hg-N distances (2.60-3.85 Å) and proton chemical shifts of the metalated dpp suggest that the 1,10-phenanthroline ring is weakly coordinated to the Hg-phenyl moiety. The complex is luminescent at both 77 and 298 K. Photosensitivity of [Hg(C ∧ N-dpp)Cl]2 at room temperature is evidenced by its facile transformation into the protonated salt of dpp (Hdpp+) in dichloromethane. The low-temperature emission spectrum of [Hg(C ∧ N-dpp)Cl]2 is almost identical to that of dpp. The photophysical and emission properties of [Hg(C ∧ N-dpp)Cl]2 are compared with those of the related cyclometalated Pt(II) and Au(III) complexes, viz. [Pt(C ∧ N ∧ N-dpp)(NCCH3)]+ and [Au(C ∧ N ∧N-dpp)Cl]+. © 1994 American Chemical Society.link_to_subscribed_fulltex