Synthesis, characterization, and photophysics of a new trinuclear mercury(II) complex of 1,3,5-triethynylbenzene

A new trinuclear mercury(ii) complex of 1,3,5-triethynylbenzene [(MeHgC?C)3(1,3,5-C6H3)] 1 was prepared in good yield by Hagihara's dehydrohalogenation reaction of HgMeCl with [(HC?C)3(1,3,5-C6H3)] under ambient conditions. This trimercury triacetylide complex's structure was confirmed by common spectroscopic techniques and its photophysical properties were examined and compared with the isolobal gold(i) congener [{(PPh3)AuC?C}3(1,3,5-C6H3)] 2. Our investigations indicate that the organic triplet emissions can be harvested by the heavy-atom effect of mercury which enables efficient intersystem crossing from the S1singlet excited state to the T1triplet excited state. The influence of Hg and Au centres on the phosphorescence efficiency and evolution of the lowest electronic singlet and triplet excited states is critically characterized. Both complexes 1 and 2 possess high-energy triplet states of 2.77?2.82 eV, in which the order of intersystem crossing rate follows the order Au > Hg.