Amidate-bridged diplatinum(ii) entities [Pt2(bpy) 2(μ-amidato)2]2+ (amidate = pivalamidate and/or benzamidate; bpy = 2,2′-bipyridine) were covalently linked to one or two Ru(bpy)32+-type derivatives. An amide group was introduced at the periphery of Ru(bpy)32+ derivatives to give metalloamide precursors [Ru(bpy)2(BnH)]2+ (abbreviated as RuBnH, n = 1 and 2), where deprotonation of amide BnH affords the corresponding amidate Bn, B1H = 4-(4-carbamoylphenyl)-2,2′-bipyridine, and B2H = ethyl 4′-[N-(4-carbamoylphenyl)carbamoyl]-2,2′- bipyridine-4-carboxylate. From a 1:1:1 reaction of [Pt2(bpy) 2(μ-OH)2](NO3)2, RuBnH, and pivalamide, trinuclear complexes [Pt2(bpy)2(μ-RuBn) (μ-pivalamidato)]4+ (abbreviated as RuBn-Pt2) were isolated and characterized. Tetranuclear complexes [Pt2(bpy) 2(μ-RuBn)2]6+ (abbreviated as (RuBn) 2-Pt2) were separately prepared and characterized in detail. The quenching of the triplet excited state of the Ru(bpy) 32+ derivative (i.e., Ru*(bpy)3 2+) upon tethering the Pt2(bpy)2(μ-amidato) 22+ moiety is strongly enhanced in RuB1-Pt2 and (RuB1)2-Pt2, while it is only slightly enhanced in RuB2-Pt2 and (RuB2)2-Pt2. These are partly explained by the driving forces for the electron transfer from the Ru*(bpy)32+ moiety to the Pt2(bpy) 2(μ-amidato)22+ moiety (ΔG° ET); the ΔG°ET values for RuB1-Pt2, (RuB1)2-Pt2, RuB2-Pt2, and (RuB2) 2-Pt2 are estimated as -0.01, 0.00, +0.22, and +0.28 eV, respectively. The considerable difference in the photochemical properties of the B1- and B2-bridged systems were further examined based on the emission decay and transient absorption measurements, which gave results consistent with the above conclusions.
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry