Pt]2Pb trinuclear systems: impact of the anionic platinum fragment on the lead environment and photoluminescence

A comparison of the solid structures of three novel trinuclear sandwich Pt 2Pb systems (NBu 4) 2{Pt(C identical withCTol) 4} 2Pb(OH 2) 2] 1, {Pt(bzq)(C identical withCPh) 2} 2Pb] 2, and (NBu 4){Pt(bzq)(C identical withCC 6H 4-CF 3-4) 2} 2Pb(O 2ClO 2)] 4 (NBu 4 3.(O 2ClO 2)]) with that of the previously reported (NBu 4) 2{Pt(C 6F 5) 4} 2Pb] 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, varphi = 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 identical withCR) bonding interactions and very short Pt...Pb and Pt...Pt distances, the emissive state in solid state (77 K) is attributed to a (3)MLM'CT Pt(1)pi(C identical withCR)-->Pt(2)/Pb(sp)pi*(C identical withCR)] state mixed with some pipi* excimeric character in neutral complexes 2 (R = Ph) and 3 (R = C 6H 4-CF 3-4), and in the case of the adduct (NBu 4){Pt(bzq)(C identical withCC 6H 4-CF 3-4) 2} 2Pb(O 2ClO 2)] 4 modified also by Pb (II)...O (O 2ClO 2 (-)) contacts.