Correlating Structural Features and ²⁰⁷Pb NMR Parameters with the Stereochemical Activity of Pb^II Lone Pairs in Birefringent Pb[2,6‐bis(benzimidazol‐2‐yl)pyridine] Complexes

Abstract

A series of PbII materials containing the highly anisotropic tridentate ligand 2,6‐bis(benzimidazol‐2‐yl)pyridine (bbp) and [Au(CN)2]–, Hg(CN)2 or halide bridging units, [Pb(bbp)Br2]·2H2O, Pb(bbp)I2, [Pb(bbp)I]2(µ‐I)[Au(CN)2], [Pb(bbp)Br]2(µ‐Br)[Au(CN)2], [Pb(bbp)Br2][Hg(CN)2], Pb(bbp)Cl[Au(CN)2]·0.25H2O and Pb(H2O)(bbp)2[Au(CN)2]2, have been prepared, structurally characterised and investigated spectroscopically by 207Pb solid‐state NMR spectroscopy. Of these, five possess similar coordination geometries, providing an ideal series to investigate structural parameters as indicators for stereochemical activity by correlation with the 207Pb chemical shift span parameter (Ω). The bond length of the substituent opposite to the stereochemically active lone pair and the angle between axial ligands were found to correlate weakly with Ω for these compounds (R2 = 0.85 and 0.66, respectively) and an expanded set of compounds with varying components and structures (R2 = 0.60 and 0.67, respectively), which indicates that these (or similar) structural parameters or Ω can be used to estimate the degree of lone‐pair activity. Compounds were also found to be highly birefringent with values ranging from 0.31(5) for Pb(H2O)(bbp)2[Au(CN)2]2 to 0.660(4) for [Pb(bbp)Br2]·2H2O, the latter being amongst the most birefringent compounds reported.

Synthesis, spectroscopic findings and crystal engineering of Pb(ii)–Salen coordination polymers, and supramolecular architectures engineered by σ-hole/spodium/tetrel bonds: a combined experimental and theoretical investigation

“…Thus, the lead( ii ) preferred hemi-directed coordination over the holo-directed coordination sphere. 76–79 The hemi-directed coordination sphere is comparable to previously reported X-ray characterized lead( ii ) complexes (Table S2 † ). The coordination of the hydroxyl group from an adjacent complex results in forming a unique hetero-bimetallic one-dimensional (1D) polymer.…”

Hybrid Inorganic–Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand

“…In comparison to zinc and cadmium, the coordination chemistry of main group metals is less developed for the soft N-heterocyclic ligands and is illustrated by pseudo-octahedral complexes of Pb­(II), forming 1D polymeric chains [Pb­(diimine)­(μ-X) 2 ] n , − the emission energy of which is regulated by aromatic system …”

Sn2B5O9Cl: A Material with Large Birefringence Enhancement Activated Prepared via Alkaline‐Earth‐Metal Substitution by Tin

“…To analyze the origin that the amazing birefringence of SBOC is about 16 times that of BBOC, the first‐principles calculations were carried out using the CASTEP package. Birefringence arises when the refractive index varies depending on the direction of light propagation through a crystal, and it can be traced to the anisotropic arrangement of the atoms and molecules within the crystal. The metal cations with SCALP can exert a strong structural influence and impact the observed properties such as birefringence.…”