Dual Luminescent Tetranuclear Organogold(I) Macrocycles of 5,5′-Diethynyl-2,2′-bipyridine and Their Efficient Sensitization of Yb(III) Luminescence

Reaction of (AuCCbpyCCAu)n (HCCbpyCCH = 5,5′-diethynyl-2,2′-bipyridine)
with diphosphine ligands Ph2P­(CH2)nPPh2 (n = 1 dppm, 3 dppp,
5 dpppen, 6 dpph), 1,1′-bis­(diphenylphosphino)­ferrocene (dppf),
and 1,2-bis­(diphenylphosphino)­benzene (bdpp) in CH2Cl2 afforded the corresponding dual luminescent gold­(I) complexes
[(AuCCbpyCCAu)2(μ-dppm)2] (1), [(AuCCbpyCCAu)2(μ-dppp)2] (2), [(AuCCbpyCCAu)2(μ-dpppen)2] (3), [(AuCCbpyCCAu)2(μ-dpph)2] (4), [(AuCCbpyCCAu)2(μ-dppf)2] (5), and [(AuCCbpyCCAu)2(μ-bdpp)2] (6). The solid structures
of complexes 1 and 2 are confirmed to be
tetranuclear macrocyclic rings by single crystal structure analysis,
and those of complexes 3–6 are proposed
to be similar to those of complexes 1 and 2 in structure because their good solubility in CH2Cl2, their HRMS results, and the P···P separations
of 20.405–20.697 Å in the same linear rigid PAuCCbpyCCAuP
unit are all favorable to form such 2:4:2 macrocycles. Each of the
absorption spectral titrations between complexes 1–6 and Yb­(hfac)3(H2O)2 (Hhfac
= hexafluoroacetylacetone) gives a 2:1 ratio between the Yb­(hfac)3 unit and the complex 1–6 moieties. The energy transfer occurs efficiently from the gold­(I)
alkynyl antennas 1–6 to Yb­(III) centers
with the donor ability in the order of 1 ∼ 2 ∼ 3 ∼ 4 > 6 > 5.