Influence of lone-pair activity on the bond parameters of lead bromide, lead chloride and lead oxide

Abstract

Lead Pb(II) is challenging environment to study because it has electron lone pair, coordination number would vary from 2 to 10. The current study chooses chlorine, oxygen and bromine as coordination atoms because it bonded with one type of element in single crystal. The present research work is focused, to study the impact of electron lone pair on coordination number (CN), bond length and bond valence sum(BVS). The coordination number is the number of atom attachment with cation, which represents the central atom. The sample of the study includes 388 sites of Pb(II). Analysis of those sites consist of three types of single crystals; 44 of single-crystal Pb-O, 24 of single crystal Pb(II)-Cl and 18 of single crystal Pb(II)-Br (Uses for that different programs like Origin, Excel, Avogadro and Crystal Maker). Deduced through the graph (coordination number-frequency) lead prefers to bond with two or eight atoms of oxygen. Also, it is noted that lead prefers to bond with two atoms of chlorine while prefer to bond with five or six atoms of bromine. The pattern that lead follows in (coordination number-frequency), (bond length-frequency) and (bond valence sum-frequency) indicate that high value of bond length offset low bond valence sum and high coordination number while the low value of bond length offset high bond valence sum and low coordination number. This interpretation is according to distortion theory. Study correlations (LP magnitude –coordination number), (LP magnitude – bond length R) and (LP magnitude – bond valence sum) lead to confirm that the presence electron lone pair spread the values of coordination number, bond length and bond valence sum. The graph of coordination number energy is confirm on the fact that the crystal prefers a specific coordination number to be stable(less energy). Lone pair divided in two types active lone pair and non-active lone pair. When LP magnitude = 0, lone pair will not be active and there are symmetric bonds while when LP magnitude > 0, LP will be active and non –symmetric bonds.