Inert Pair Research Articles

Crystal structure of lead(II) with the flavonoid morin elucidating evidence of the “inert pair effect” as well as a computational study

The synthesis and structure of a lead(II) complex of the flavonoid morin is hereby reported. This is the first example of a Pb(II) complex depicting an active inert pair effect with a flavonoid (morin). The complex has an orthorhombic structure with space group P212121. The complex shows a distorted square-based pyramidal coordination geometry. The average metal ion to donor atom coordination bond length (Pb−O) is 2.553 Å for five O-donors from water, perchlorate ions, and the morin ligand. The metal is coordinated to the morin's carbonyl and the hydroxyl oxygen at position 3. The coordination sphere of the core metal ion at the site of the lone pair on Pb(II) is devoid of any donor atom. The crystal packing features an offset face-to-face intermolecular π–π interaction with morin's centroid–centroid distances averaging 3.4 Å and displacement angles of 11.81o. Theoretical calculations using density functional theory (DFT) supported the empirical results. The DFT calculations showed that the presence of an active inert electron pair in the morin-Pb(II) complex lowers its ground state energy.

A tin analogue of propadiene with cumulated C[double bond, length as m-dash]Sn double bonds.

The synthesis, structure, and properties of a stable, linear 2-stannapropadiene are reported. The identical C[double bond, length as m-dash]Sn bonds in this 2-stannapropadiene are the shortest hitherto reported C-Sn bonds. This 2-stannapropadiene features a 119Sn NMR signal at 507 ppm for the central tin atom, indicative of an unsaturated Sn4+ oxidation state. Due to the inert-pair effect, the tin atom displays a pronounced preference for the +2 oxidation state over the +4 oxidation state. Nevertheless, by employing silyl substituents, it is possible to disrupt the inert-pair effect, leading to the formation of an isolable 2-stannapropadiene with a linear structure centered on a Sn4+ atom. Treatment of this 2-stannapropadiene with SnBr2·dioxane resulted in the formation of a novel four-membered cyclic 1,1-dibromo-1,3-distannetane, which was subsequently reduced to afford the corresponding stable four-membered cyclic bis(stannylene).

Ph2Te2: An Accessible Main Group Organometallic Target for Spectral Characterization and Modeling

A straightforward protocol for the preparation of the colorful and air-stable diphenyl ditelluride is described. In one laboratory session, students isolate their product and characterize it via melting point determination, mass spectrometry, and NMR spectroscopy (1H, 13C{1H}, and 125Te{1H}). The alternative application of a Grignard reagent serves as a bridge between common organic laboratory experiences and this exercise. Students have the opportunity to see the advantages and disadvantages of the assortment of characterization techniques and, for MS and NMR, the distinctness of their application specifically to inorganic compounds. Analysis of single crystal X-ray diffraction data and molecular modeling results of Ph2Te2 and its lighter congeners (Ph2E2, E = O–Se) provide students with a data-supported understanding of the inert pair effect.

The inert pair effect on heavy noble gases: insights from radon tetroxide.

A quantum chemical survey of radon and xenon tetroxides (NgO4, Ng = Xe, Rn) is reported herein. The intermediate species, which are formed in their explosive decomposition back to their elemental states (Ng and O2), were also studied and their energetics were compared. While Td symmetric RnO4 has a minimum energy structure, its standard enthalpy of formation is 88.6 kJ mol-1 higher than for XeO4. The reason for this higher instability lies in what is known as the inert pair effect. This work establishes that the high-valent chemical trends of the sixth period of groups 13-15 are indeed extended to group 18.

Theoretical investigation on the inert pair effect of Ga on both the Ga-Ni-Mo-S nanocluster and the direct desulfurization of 4,6-dimethyldibenzothiophene

Non-periodic computational model for Ga-Ni-Mo-S nanocluster was established and the inert pair effect of Ga species on both the electron structures of the Ga-Ni-Mo-S nanocluster and the direct desulfurization (DDS) reaction of 4,6-dimethyldibenzothiophene(4,6-DMDBT) were systematically investigated. The stability of the established Ga-Ni-Mo-S nanocluster was enhanced due to the inert pair effect of Ga species. Moreover, the inert pair effect of Ga species makes both the electron and bonding properties of the edge active site of the Ga-Ni-Mo-S nanocluster inclined to be similar with the corner active sites. The adsorption behaviors of the reactant and the intermediates over the edge active sites changed profoundly due to the enhanced electron acceptor characteristics. The inert pair effect of Ga made it possible for the 4,6-DMDBT undergo DDS reaction because the activation energy drastically decreased from about 201.50 kJ·mol−1 over Ni-Mo-S cluster to about 154.56 kJ·mol−1 over Ga-Ni-Mo-S nanocluster at the Mo-edge active site, which would be further effectively compensated by the higher adsorption energy (about −50 kJ·mol−1) of the generated C14H13S over the edge active site than the corner active site of the established Ga-Ni-Mo-S nanocluster.

Ultrasensitive photochromism and impedance dual response to weak visible light by solvated Pb(II) modified polyoxomolybdate

Polyoxometalates (POMs) are important inorganic photochromic materials to be potentially applied in photo-induced switch, energy storage, and even the detection of light. However, due to the limited sensitivity of POMs, it is difficult to realize the photochromic response to weak visible light. In this paper, by the coordination of solvated Pb(II), a new structure-defined chain-like polyoxomolybdate complex of [(Pb(DMF)4)3(P2Mo18O62)2]n (Pb3Mo18, DMF = dimethylformamide) has been demonstrated by a facile solvent-diffusion approach. By virtue of interactions between Pb(DMF)4 and polyoxoanions, Pb3Mo18 shows an ultrasensitive photochromic response to weak visible lights and forms the reduced 'heteropoly blue' species through ligand-to-metal charge transfer (LMCT) process. A new mechanism is firstly proposed here that the 6s orbital lone electron pair on Pb(II) can effectively stabilize the generated hole of oxygen atoms as a result of O→Mo charge transfer. Through the proposed mechanism, the LMCT barrier is drastically lowered and allows the coloration to be occurred even upon weak visible light. Also, because the conductivity of Pb3Mo18 enhances with the increase of reduction extent, its electrochemical impedance signals are proportionally response to irradiation intensity. Especially, for the first time, the polyoxomolybdate composite can be used to detect weak visible light, in which the optical signal can be converted into electrical signal output. Moreover, Pb3Mo18 can be drip-coated on the surface of the screen printed chip electrode, which is facile to the detection of light by portable devices compatible with computers, mobile phones and other electronic equipment. This work not only highlights a new approach to the molecular design of photochromic POMs by the coordination of metal ions with the effect of inert electron pair, but also lays a foundation to extend the application of POMs as light signal sensors.

Topological Quantum Materials from the Viewpoint of Chemistry.

Topology, a mathematical concept, has recently become a popular and truly transdisciplinary topic encompassing condensed matter physics, solid state chemistry, and materials science. Since there is a direct connection between real space, namely atoms, valence electrons, bonds, and orbitals, and reciprocal space, namely bands and Fermi surfaces, via symmetry and topology, classifying topological materials within a single-particle picture is possible. Currently, most materials are classified as trivial insulators, semimetals, and metals or as topological insulators, Dirac and Weyl nodal-line semimetals, and topological metals. The key ingredients for topology are certain symmetries, the inert pair effect of the outer electrons leading to inversion of the conduction and valence bands, and spin–orbit coupling. This review presents the topological concepts related to solids from the viewpoint of a solid-state chemist, summarizes techniques for growing single crystals, and describes basic physical property measurement techniques to characterize topological materials beyond their structure and provide examples of such materials. Finally, a brief outlook on the impact of topology in other areas of chemistry is provided at the end of the article.

From BiF3to BiF3·H2O: diverse Bi(iii) coordination for structural transformation and birefringence regulation

BiF3·H2O with unprecedented BiF9building blocks was synthesized, which exhibits a near-isotropic Bi3+coordination and inert lone pair activity.

Teaching Practice and Experience of 6<i>s</i><sup>2</sup> Inert Pair Effect in Inorganic Chemistry Course

Teaching Practice and Experience of 6<i>s</i><sup>2</sup> Inert Pair Effect in Inorganic Chemistry Course

A comparison of structural and luminescence properties of lead(II) coordination polymers with isomeric thiophenecarboxylate ligands

Abstract Two new lead(II) coordination polymers with isomeric thiophenecarboxylates, namely [Pb(2tpCOO)2]n (1) and [Pb(3tpCOO)2(H2O)]n (2) (2tpCOO− = thiophene-2-carboxylate, 3tpCOO− = thiophene-3-carboxylate), were synthesized and characterized. Single crystal X-ray crystallography revealed a distorted pentagonal pyramidal geometry {PbO6} around Pb in 1 and a distorted dodecahedral geometry {PbO8} in 2. The distortion derived from the presence of 6 s2 inert electron pair on lead(II), which was confirmed by DFT calculations. The topological classification of obtained polymers has been performed, disclosing the SP 1-periodic net (4,4)(0,2) and gek1 topology in 1 and 2, respectively. Interactions stabilising crystal structures were also confirmed by Hirshfeld surface analysis. Fluorescence properties allowed to distinguish the type of thiophene-monocarboxylic acid isomers. The luminescence intensity which derived from π → π∗ and/or n → π∗ transitions is higher in 2tpCOOH. Photoluminescent properties of complexes 1 and 2 are much more enhanced in comparison to starting ligands. The emission bands in the complexes can be attributed to the ligand-to-metal charge transfer (LMCT) as a change in the intraligand transitions. Additional low energy emissions with large Stokes shifts appeared and were assigned to the metal-centered (MC) transitions involving s and p lead(II) orbitals, which were also confirmed by DFT calculations. Moreover, both complexes were characterized by infrared spectroscopy and thermal stability analysis.

Ab Initio Investigating the Bonding and Electronic Structure in Bismuth Calixarene Complexes

The geometric and electronic structures of calixarene bismuth(III) complexes have been investigated by ab initio method in this study. Three conformations (cone shape conformation with C2v symmetry, 1,2-alternative conformation with C2h symmetry and 1,3-alternative conformation) are investigated as possible binding modes between bismuth fragment and calixarene fragment. The optimized geometries are then compared with the recent reported crystal structure. Two bis-muth(III) fragments are needed to bind with calixarene ligand due to the inert-pair effect. Co-crystalized LiCl-DMSO fragment plays a crucial role in stabilizing the bismuth calixarene crystal, where the binding energy ΔH is estimated to be 55.3 kcal/mol or 56.1 kcal/mol with zero-point energy correction. The estimated ΔG is -28.2 kcal/mol for the complex, which is consistent with the strong HC4Bi-ClLi interactions. The trans effect is evidenced by two slight longer Bi-O bond lengths.

CO synthesized from the central one-carbon pool as source for the iron carbonyl in O2-tolerant [NiFe]-hydrogenase

Hydrogenases are nature's key catalysts involved in both microbial consumption and production of molecular hydrogen. H2 exhibits a strongly bonded, almost inert electron pair and requires transition metals for activation. Consequently, all hydrogenases are metalloenzymes that contain at least one iron atom in the catalytic center. For appropriate interaction with H2, the iron moiety demands for a sophisticated coordination environment that cannot be provided just by standard amino acids. This dilemma has been overcome by the introduction of unprecedented chemistry-that is, by ligating the iron with carbon monoxide (CO) and cyanide (or equivalent) groups. These ligands are both unprecedented in microbial metabolism and, in their free form, highly toxic to living organisms. Therefore, the formation of the diatomic ligands relies on dedicated biosynthesis pathways. So far, biosynthesis of the CO ligand in [NiFe]-hydrogenases was unknown. Here we show that the aerobic H2 oxidizer Ralstonia eutropha, which produces active [NiFe]-hydrogenases in the presence of O2, employs the auxiliary protein HypX (hydrogenase pleiotropic maturation X) for CO ligand formation. Using genetic engineering and isotope labeling experiments in combination with infrared spectroscopic investigations, we demonstrate that the α-carbon of glycine ends up in the CO ligand of [NiFe]-hydrogenase. The α-carbon of glycine is a building block of the central one-carbon metabolism intermediate, N10-formyl-tetrahydrofolate (N10-CHO-THF). Evidence is presented that the multidomain protein, HypX, converts the formyl group of N10-CHO-THF into water and CO, thereby providing the carbonyl ligand for hydrogenase. This study contributes insights into microbial biosynthesis of metal carbonyls involving toxic intermediates.

Homo and Dinuclear Heteroleptic Zn, Cd & Pb Complexes Derived from FcCOOH and DTBbpy Ligands: Structural, Luminescence and Electrochemical Studies

Mononuclear [Zn(FcCOO)(DTBbpy)2]ClO4.(H2O)3 (1) and dinuclear [Cd2(FcCOO)2(DTBbpy)4]ClO4·(H2O) (2), [Pb2(FcCOO)2(DTBbpy)2(H2O)2]·ClO4 (3) (FcCOO = ferrocenecarboxylate, DTBbpy = 4,4′-di-tert-butyl-bipyridyl) metal complexes have been synthesized and characterized by single crystal X-ray diffraction. It reveals that the Zn(II), Cd(II) and Pb(II) metal complexes have different coordination geometries [Zn and Pb = distorted octahedral, Cd = distorted pentagonal bipyramidal]. The compound 3 shows the hemidirected mode of coordination in the geometrical system due to the inert pair effect of the lone pair of an electron on Pb(II) metal atom. The molecules are further forms 2D & 3D framework structure via intermolecular hydrogen bonding. All the three compounds exhibit strong fluorescence emission bands in the liquid state at ambient temperature, of which the emission maxima show red-shifted and the solution-state electrochemistry of compounds 1–3 in CH3CN has been investigated.

Pb2+—N Bonding Chemistry: Recycling of Polyaniline–Pb Nanocrystals Waste for Generating High-Performance Supercapacitor Electrodes

Understanding of Pb—N bonding chemistry is not only fundamentally important in the view of relativistic inert-pair effect but also is important for therapeutic as well as environmental applications. In the present study, an unusual reactivity of N-containing π-conjugated polyaniline emeraldine base (EB) toward aqueous Pb2+ ions has been identified. In the course of sequestering Pb2+ ions by EB, cuboid-shaped nanocrystals were isolated. Synchrotron-based X-ray absorption near-edge structure and extended X-ray absorption fine structure techniques were employed to understand Pb–N bonding chemistry in EB-Pb nanocrystals. The adopted methodology of slow exposure of HCl vapor to EB-Pb nanomaterial facilitated the isolation of polyaniline emeraldine-salt (ES) with unique morphological patterns, porosity and electrical conductivity. The electrochemical device based on recycled ES showed high-capacitance value (∼606 F/g @1 A/g and ∼663 F/g @10 mV/s), high-energy density (∼14.8 Wh/kg at power density of ∼663 W/kg) ...

An unusual assembled Pb(ii) meso-helicate that shows the inert pair effect.

A dinuclear Pb(ii) mesocate has been prepared with an unprecedented four-coordinated kernel in which the Pb(ii) lone pair is stereochemically active. This is the first time that this effect has been observed in a supramolecular Pb(ii) helicate or meso-helicate.

Assembly of one 2D layer and two 3D pillared-layer structures derived from metal ions and 5-(pyridin-4-yl)isophthalic acid with or without pillars

Three new coordination polymers, [Mn(L)(H2O)2]2·5H2O (1), [Cu(L)(4,4′-bipy)]2·H2O (2) and [Pb(L)(4,4′-bipy)0.5] (3) (H2L=5-(pyridin-4-yl)isophthalic acid; 4,4′-bipy=4,4′-bipyridine) have been synthesized and characterized by IR, thermogravimetric analysis, X-ray powder diffraction and X-ray single crystal diffraction. Complex 1 shows a 2D layer structure which stacks with the other ones to form 1D channels to hold 1D water chains. Complex 2 displays a 3D+3D→3D polycatenation network. 3 shows a unique 2D+2D→3D polycatenation net in which each Pb center has a hemidirected coordination geometry due to the existence of “inert pair effect”. The thermal and luminescent properties of 1–3 were also examined.

A Visually Attractive “Interconnected Network of Ideas” for Organizing the Teaching and Learning of Descriptive Inorganic Chemistry

A visually attractive interconnected network of ideas that helps general and second-year inorganic chemistry students make sense of the descriptive inorganic chemistry of the main-group elements is presented. The eight network components include the periodic law, the uniqueness principle, the diagonal effect, the inert-pair effect, the metal–nonmetal line, the acid–base character of metal and nonmetal oxides in aqueous solution, trends in reduction potentials, and dπ–pπ bonding involving elements of the second and third periods. dπ–pπ bonding is advocated for these courses in lieu of an extensive presentation of molecular orbital theory. Each component is given its own colorful icon and a distinctive visual image that is added atop and among the fabric of the periodic table. This colorful, iconographic, and symbolic building process makes it easier to organize the many facets of descriptive inorganic chemistry in a meaningful and memorable manner. When a new group of elements is presented, students can place the group data in perspective and integrate it into their own expanding network of interconnected ideas for understanding the periodic table.

ChemInform Abstract: Pentavalent Organobismuth Reagents in Organic Synthesis: Alkylation, Alcohol Oxidation and Cationic Photopolymerization

AbstractReview: 102 refs.

(IP)2GaIII Complexes Facilitate Net Two-Electron Redox Transformations (IP = α-Iminopyridine)

Reaction of M(+)[(IP(2-))(2)Ga](-) (IP = iminopyridine, M = Bu(4)N, 1a; (DME)(3)Na, 1b) with pyridine N-oxide affords two-electron-oxidized (IP(-))(2)Ga(OH) (2) in reactions where the product outcome is independent of the cation identity, M(+). In a second example of net two-electron chemistry, outer sphere oxidation of M(+)[(IP(2-))(2)Ga](-) using either 1 or 2 equiv of the one-electron oxidant ferrocenium afforded [(IP(-))(2)Ga](+) (3) in either 44 or 87% yield, respectively. Reaction with 1 equiv of TEMPO, a one-electron oxidant, afforded the two-electron-oxidized product (IP(-))(2)Ga(TEMPO) (4). Reduction of 2IP by 3Na and subsequent reaction with GaCl(3) yielded a 1:1 mixture of (IP(-))(2)GaCl and 1. Most remarkably, all of these reactions are overall two-electron processes and only the (IP(-))(2)GaX and [(IP(2-))(2)Ga](-) oxidation states are thermodynamically accessible to us. Analogous aluminum chemistry previously afforded either one-electron or two-electron reactions and mixed-valent states. The thermodynamic accessibility of the mixed-valent states of (IP(2-))(IP(-))E, where E = Al or Ga, can be compared using cyclic voltammetry measurements. These measurements indicated that the mixed-valent state [(IP(2-))(IP(-))Ga](+) is not significantly stabilized with respect to disproportionation on the time scale of the electrochemistry experiment. The electrochemically observed differences in thermodynamic stability of the mixed-valent state [(IP(2-))(IP(-))E](+) can be rationalized by the observation that the dihedral angle between the ligand planes containing the π-system of IP is roughly 5° larger in all gallium complexes compared with aluminum analogs. Presumably, a larger dihedral angle provides weaker electronic coupling between the π-systems of IP via the E-X σ* orbital. Alternatively, the observed difference may be a result of the "inert pair effect": a contracted Ga component in the E-X σ* orbital would also afford weaker electronic coupling.

Hemidirected one-dimensional lead(II) coordination polymers containing NSAIDs as ligands: Spectroscopic and structural characterization of [Pb(C9H7O4)2(H2O)]n, [Pb(C13H17O2)2(H2O)]n and [Pb(C14H10Cl2NO)2

Combination of the nonsteroidal anti-inflammatory drugs (NSAIDs) aspirin (1), ibuprofen (2) and meclofenamic acid (3) with lead(II) nitrate gave metal complexes of the composition [Pb(C9H7O4)2(H2O)]n (4), [Pb(C13H17O2)2(H2O)]n (5) and [Pb(C14H10Cl2NO2)2]n (6). The compounds have been characterized by IR and NMR spectroscopy, mass spectrometry and single-crystal X-ray diffraction analysis. The complexes crystallized in the monoclinic and triclinic space groups P21/n (4), P21 (5) and P1¯ (6), respectively. All compounds are coordination polymers with a highly distorted coordination geometries. The polyhedra of the [PbO7] (4 and 5) and [PbO6] (6) cores are hemidirected as indicated by a vacant site, which can be attributed to an active inert pair of electrons.