Application Of Pb-204m Perturbed Angular Correlation Of Gamma-Rays Spectroscopy In Coordination Chemistry

Pb-204m perturbed angular correlation of gamma-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 ([AsPh4](4)[Pb-2(i-mnt)(4)])]. The recorded parameters from a powder crystalline sample are nu(Q) = 0.178(1) GHz and eta = 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 Pb-204m PAC spectroscopy as a novel technique to elucidate the electronic and molecular structures of lead-containing complexes and biomolecules are presented.