Through-bond versus through-space T1 energy transfers in organometallic compound-metalloporphyrin pigments

The preparation and characterization of two d9−d9 M2-bonded Pt2(dppm)2(C≡CC6H4-M(P))2 complexes (where M = Zn or Pd, and P = diethylhexamethylporphyrin) were achieved. The central [Pt2(dppm)2(C≡CC6H4)2] organometallic unit appears to be an independent chromophore and is suspected to be luminescent at 77 K (in 2MeTHF) in the porphyrin-containing complexes, as this is the case for the unfunctionalized Pt2(dppm)2(C≡CPh)2 parent compound. However, when this spacer is connected (by a single C−C bond) to either M(P) (M = Zn, Pd), even in the absence of conjugation (as the computed dihedral angle between the C6H4 and porphyrin planes is ∼84.5°), total quenching of the luminescence of the [Pt2(dppm…