Zinc Chalcogenolate Complexes as Precursors to ZnE and Mn/ZnE (E = S, Se) Clusters

The ternary clusters (tmeda)6Zn14–xMnxS13Cl2 (1a–d) and (tmeda)6Zn14–xMnxSe13Cl2 (2a–d), (tmeda = N,N,N′,N′-tetramethylethylenediamine; x ≈ 2–8) and the binary clusters (tmeda)6Zn14E13Cl2 (E = S, 3; Se, 4;) have been isolated by reacting (tmeda)­Zn­(ESiMe3)2 with Mn­(II) and Zn­(II) salts. Single crystal
X-ray analysis of the complexes confirms the presence of the six “(tmeda)­ZnE2” units as capping ligands that stabilize the clusters,
and distorted tetrahedral geometry around the metal centers. Mn­(II)
is incorporated into the ZnE framework by substitution of Zn­(II) ions
in the cluster. The polynuclear complexes (tmeda)6Zn12.3Mn1.7S13Cl2 1a, (tmeda)6Zn12.0Mn2.0Se13Cl2 2a, and (tmeda)6Zn8.4Mn5.6Se13Cl2 2d represent
the first examples of “Mn/ZnE” clusters with structural
characterization and indications of the local chemical environment
of the Mn­(II) ions. The incorporation of higher amounts of Mn into 1d and 2d has been confirmed by elemental analysis.
Density functional theory (DFT) calculations indicate that replacement
of Zn with Mn is perfectly feasible and at least partly allows for
the identification of some sites preferred by the Mn­(II) metals. These
calculations, combined with luminescence studies, suggest a distribution
of the Mn­(II) in the clusters. The room temperature emission spectra
of clusters 1c–d display a significant
red shift relative to the all zinc cluster 3, with a
peak maximum centered at 730 nm. Clusters 2c–d display a peak maximum at 640 nm in their emission spectra.