Application of ^204mPb Perturbed Angular Correlation of γ-rays Spectroscopy in Coordination Chemistry

Abstract

(204m)Pb perturbed angular correlation of γ-rays (PAC) spectroscopy has been applied successfully for the first time to detect the nuclear quadrupole interaction in a lead(II) coordination compound in a molecular crystal [tetraphenylarsonium lead(II) isomaleonitriledithiolate ([AsPh(4)](4)[Pb(2)(i-mnt)(4)])]. The recorded parameters from a powder crystalline sample are ν(Q) = 0.178(1) GHz and η = 0.970(7). The electric field gradient (EFG) was determined at the PW91/QZ4P level including relativistic effects using the two-component zeroth-order regular approximation method for both the [Pb(i-mnt)(2)](2-) monomer and the [Pb(2)(i-mnt)(4)](4-) dimer. Only the EFG for the latter compares favorably with the experimental data, indicating that the picture of this complex as a prototypical hemidirected coordination geometry with a stereochemically active lone pair on lead(II) is inadequate. Advantages and limitations of (204m)Pb PAC spectroscopy as a novel technique to elucidate the electronic and molecular structures of lead-containing complexes and biomolecules are presented.

Structural Diversity of Iso-Maleonitrile Dithiolate d10s2 Metal Complexes of Lead and Bismuth

“…The structure of ( n Pr 4 N) 4 [Pb 2 ( i -mnt) 4 ] can be compared to the related (Ph 4 As) 4 [Pb 2 ( i -mnt) 4 ] dimer, , with the main difference that in (Ph 4 As) 4 [Pb 2 ( i -mnt) 4 ], each Pb­(II) center is described as six-coordinate, with all six sulfur atoms within the sum of the van der Waals radii (2.704–3.597 Å), , i.e., both S3 and S4 donors in the μ- i -mnt ligands show bridging interactions between both Pb­(II) centers, while in ( n Pr 4 N) 4 [Pb 2 ( i -mnt) 4 ] the S4 donor does not bridge (Pb1–S4 = 4.833(1) Å). Other dimeric metal-bridging μ- i -mnt motifs have been previously reported, including a zinc­(II) complex with two μ- i -mnt ligands bridging two ZnL 2 units (L = 4-methylpyridine, 1,3-diaminopropane) , and the dimeric Hg 2 ( i -mnt) 4 .…”

“…Given the soft donor nature of the sulfur atoms, it was of interest to expand the scope of i -mnt CPs to other soft metal cations, in particular, to Pb­(II) and Bi­(III), which provide access to a range of useful chemical and physical properties as well as unusually diverse coordination geometries as a result of their stereochemically active lone pairs. ,− Crystallographically, a distorted coordination geometry with inequivalent bond lengths and a vacancy in the inner coordination sphere are the observable structural consequences of such stereochemically active lone pairs. − This tunable structural feature may introduce an element of noncentrosymmetry, which is often leveraged to engineer materials with functional properties such as piezo/pyroelectricity and nonlinear optical behavior. − There are currently 166 structurally characterized S-bound metal i -mnt complexes (Cambridge Structural Database, accessed 22 February 2024), almost all of which contain late transition metals. Comparatively, there are very few i -mnt-containing structures incorporating p-block metals, and none include bismuth.…”

TDPAC andβ-NMR applications in chemistry and biochemistry

“…The angular correlation of the γ-γ cascade 374-158 keV of the 199m Hg/Hg probe has been successfully used for chemistry and biochemistry studies at ISOLDE for decades [13]. More recently, 204m Pb/Pb has also appeared as a probe in chemical applications of TDPAC spectroscopy [23]. It may become useful because of its greater sensitivity to deviations of the EFG from axial symmetry than other usual TDPAC probes [24].…”