Directionality of Pb²⁺ lone pair electrons dictated hemi‐directed coordination mode of methyl‐ and ferrocenylcarboxylate complexes

Abstract

The experimentally observed hemi‐directed coordination mode in 1D polymeric Pb2+ ferrocenylcarboxylate system is examined computationally for gaining better insights on the structure of polymeric systems. By considering the different size of the ligands such as methylcarboxylate (model system) and ferrocenylcarboxylates (real system), the coordination mode is systematically explored in the complexes 1–6. As expected due to the possibility of free rotation in the methylcarboxylate systems in solution, it may follow holo‐directed geometrical arrangements but interestingly, it shows only hemi‐directed geometry as observed in the experimental studies on ferrocenylcarboxylate system (N. Palanisami et al. Science of Advanced Materials, 2014, 6, 2364). The present computational studies predict that the lone pair electrons in Pb2+ play the dictating role for formation of hemi‐directed coordination mode in methylcarboxylates as well as in ferrocenylcarboxylates. The directionality of the lone pair electrons makes the remarkable differences in the structural arrangements. Notable difference observed is that the methylcarboxylate shows the linear fashion of hemi‐directed coordination whereas ferrocenylcarboxylate shows the zig‐zag fashion of hemi‐directed coordination. The quantitative and qualitative characteristics of lone pair electrons in reported systems are assessed through NBO analysis thus it shows the s‐LP character occupancy in each case varies from 96% to 93% which is the strong evidence for the availability of lone pair electrons in Pb2+ carboxylate systems. Further, frontier molecular orbital analysis, vibrational modes and hydrogen bonding pattern are explored in the complexes 1–6.

Pb–Oxo Interactions in Uranyl Hybrid Materials: A Combined Experimental and Computational Analysis of Bonding and Spectroscopic Properties

“…The coordination sphere around a Pb 2+ cation with a coordination number of 6–8, as in our compounds, can be either hemi- or holodirectional . Holodirectional means that the lead–ligand bonds are evenly distributed throughout the coordination sphere, whereas hemidirectional complexes feature a “void” where no lead–ligand bonds exist. − This “void” is a consequence of a stereochemically active 6s 2 lone pair on the lead that can then be available for interaction with the uranyl–oxo group . That said, our compounds all feature holodirectional Pb 2+ centers as evidenced by the more spherical coordination geometries and therefore do not feature this stereochemically active lone pair.…”

Photostability of amine-free CsPbBr3 perovskite nanocrystals under continuous UV illumination

“…3c). 37–39 In Pb(OA) 2 species, bonds of the ligand atoms are isotropically distributed around Pb atom, which hinder the effective approach of Pb 2+ to Br-dangling bonds (V Pb 2− ) and of oleate to Pb-dangling bonds (V Br + ) when the concentration of the lead oleate is low. Hence, high concentration of Pb(OA) 2 is requested to overcome the steric barrier and favor the passivation of some fraction of surface defects.…”

“…3c). [37][38][39] In Pb(OA) 2 species, bonds of the ligand atoms are isotropically distributed around Pb atom, which hinder the effective approach of Pb 2+ to Br-dangling bonds (V Pb…”

“…37 On the other hand, Pb(OPA) ligands, which are desorbed from the surface of the OPAcapped PNCs, presents a molecular geometry called hemidirected (Fig. 3c), [37][38][39] in which bonds of the ligand atoms are directed throughout only a part of the space around Pb 2+ . Consequently, in those complexes Pb-site is less sterically hindered.…”