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Structural and Photophysical Study on Alkynyl Cyclometalated Pt<sub>2</sub>Pb<sub>2</sub> and Pt<sub>2</sub>Pb Clusters
No full textNeutralization reactions
of (NBu<sub>4</sub>)Ā[PtĀ(bzq)Ā(Cī¼CR)<sub>2</sub>] (bzq = 7,8-benzoquinolinyl)
with [PbĀ(HBpz<sub>3</sub>)]ĀCl
(pz = pyrazolyl) afford tetranuclear neutral Pt<sub>2</sub>Pb<sub>2</sub> derivatives [{PtĀ(bzq)Ā(Cī¼CR)<sub>2</sub>}Ā{PbĀ(HBpz<sub>3</sub>)}]<sub>2</sub> (R = Ph, <b>1</b>; C<sub>6</sub>H<sub>4</sub>OMe-3, <b>2</b>) or the anionic trinuclear Pt<sub>2</sub>Pb cluster (NBu<sub>4</sub>)Ā[{PtĀ(bzq)Ā(Cī¼CC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4)<sub>2</sub>}<sub>2</sub>Ā{PbĀ(HBpz<sub>3</sub>)}], <b>3</b>, stabilized by PtāPb and Pb<sup>II</sup>Ā·Ā·Ā·Ī·<sup>2</sup>-(Cī¼CR) bonding interactions in the solid state, as
confirmed by X-ray crystallography. The variable-temperature <sup>1</sup>H NMR spectra of <b>3</b> confirm the existence of a
dynamic equilibrium that averages the āPtĀ(bzq)Ā(Cī¼CC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4)<sub>2</sub>ā groups
in solution. 1D <sup>1</sup>H PGSE-NMR, 2D DOSY, and <sup>1</sup>H
variable-temperature NMR experiments for the tetranuclear clusters <b>1</b> and <b>2</b> indicate that in solution these dimers
generate mainly binuclear [{PtĀ(bzq)Ā(Cī¼CR)<sub>2</sub>}Ā{PbĀ(HBpz<sub>3</sub>)}] units by cleavage of the Pb<sup>II</sup>Ā·Ā·Ā·Ī·<sup>2</sup>-(Cī¼CR) interactions. All clusters exhibit phosphorescent
emission in rigid media (solid, glasses) and <b>3</b> also in
CH<sub>2</sub>Cl<sub>2</sub> solution. The emission maxima of <b>1</b> and <b>2</b> are slightly blue-shifted in relation
to the precursors, being assigned to a mixed <sup>3</sup>MLCT/<sup>3</sup>LC (L = bzq) excited state, perturbed by the PtāPb
bond. However, the emission maximum of <b>3</b> coincides with
that of its precursor, indicating little or no involvement of the
PtāPb bonds in the emissive state
