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 ga ve the cyclometalated complex [Hg(C AND N-dpp)Cl]2. X-ray crystal anal ysis revealed a dimeric molecular structure: [HgC24H15N2Cl]2, fw = 567 .48 X 2, P2(1)/n, a = 11.79(1) angstrom, b = 17.80(1) angstrom, c = 18 .84(1) angstrom, beta = 99.23(6)-degrees, V = 3904(5) angstrom3, Z = 4 . The long Hg-N distances (2.60-3.85 angstrom) and proton chemical shi fts 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 A N-dpp)Cl] 2 at room temperature is evidenced by its facile transformation into the proton ated salt of dpp (Hdpp+) in dichloromethane. The low-temperature emiss ion spectrum of [Hg(C AND N-dpp)Cl] 2 is almost identical to that of d pp. The photophysical and emission properties of [Hg(C AND N-dpp)Cl]2 are compared with those of the related cyclometalated Pt(II) and Au-(I II) complexes, viz. [Pt(C AND N AND N-dpp)(NCCH3)]+ and [Au(C AND N AN D N-dpp)Cl]+.