[Pt]2Pb Trinuclear Systems: Impact of the Anionic Platinum Fragment on the Lead Environment and Photoluminescence
摘要:
A comparison of the solid structures of three novel trinuclear sandwich Pt2Pb systems (NBu4)(2)[(Pt(C=CTol)(4)}(2)Pb(OH2)(2)] 1, [(Pt(bzq)(C CPh)(2))(2)Pb] 2, and (NBu4)[{Pt(bzq)(C CC6H4-CF3-4)(2)}(2)Pb(O2ClO2)] 4 (NBu4[3 center dot(O2ClO2)]) with that of the previously reported (NBu4)(2)[Pt(C6F5)(4))(2)Pb] 5 showed that the local environment of Pb-II is highly sensitive to the nature of the anionic platinate(II) precursors. The photoluminescence (PL) studies of all 1-5 complexes revealed a dependence of PL on the structure type. Thus, complexes 1 and 5 exhibit metal centered emissions (1, 497 nm, 77 K; 5, 539 nm, phi = 0.43, 298 K) related to the linear (5) or bent (1 Pt-Pb-Pt 149.9 degrees) trinuclear entities. However, in complexes 2-4, that have unprecedented Pb-II... eta(1)(C CR) bonding interactions and very short Pt center dot center dot center dot Pb and Pt center dot center dot center dot Pt distances, the emissive state in solid state (77 K) is attributed to a (MLM)-M-3'CT [Pt(1)pi(C CR)-> Pt(2)/Pb(sp)pi*(C CR)] state mixed with some pi pi* excimeric character in neutral complexes 2 (R = Ph) and 3 (R = C6H4-CF3-4), and in the case of the adduct (NBu4)[{Pt(bzq)(C CC6H4-CF3-4)(2)}(2)Pb(O2ClO2)] 4 modified also by Pb-II center dot center dot center dot O (O2ClO2-) contacts.
Neutralization reactions of (NBu4)[Pt(bzq)(C CR)(2)] (bzq = 7A-benzoquinolinyl) with [Pb(HBpz(3))]Cl (pz = pyrazolyl) afford tetranuclear neutral Pt2Pb2 derivatives [Pt(bzq)(CE CR),}Pb(HBpz(3))}](2). Ph, 1; C6H4OMe3, 2) or the anionic trinuclear Pt2Pb cluster (NBu4):[Pt(bzq)-. (CT CC6H4CP3-4)(2)}(2)Pb(HBpZ(3))}], 3, stabilized by Pt Pb and Pb172-(C CR) bonding interactions in the solid state, as confirmed by X-ray crystallography. The variable-temper attire 1HNMR spectra of 3 confirm the existence of a dynamic equilibrium that averages the "Pt(bzq)(C CC6H4CP3-4)2 groups in solution. 1D 1HPGSE-NMR, 2D DOSY, and 21-1 variable-temperature NMR experiments "for the tetranuclear. clusters 1 and 2 indicate that in solution these dimers generate mainly binuclear [Pt(bzq)(G=CR)2}Pb(EIBPZ3)}] units by cleavage of the Pb-II center dot center dot center dot eta center dot(C CR) interactions. All clusters exhibit phosphorescent emission in rigid media (solid; glasses) and 3 also in CH2Cl2 solution. The emission maxima of 1 and 2 are slightly blue-shifted in relation to the precursors, being assigned to a mixed 3.(MLCTLC)-L-3 = bzq) excited state, perturbed by the Pt Pb bond. However, the emission maximum of 3 coincides withthat of its indicating little or no involvement of the Pt Pb bonds in the emissive state.