Ultrasound-Assisted Synthesis and DFT Calculations of the Novel 1D Pb (II) Coordination Polymer with Thiosemicarbazone Derivative Ligand and Its Use for Preparation of PbO Clusters

In the present work, using a sonochemical method, a new lead (II) coordination 1D polymer, [Pb(L)2(CH3COO)]n (L = pyridine-4-carbaldehyde thiosemicarbazone) (1) was prepared. It was characterized structurally with different spectroscopic methods, such as SEM, IR spectroscopy, XRD, and elemental analysis. The coordination compound becomes a stair-step one-dimensional polymer in solid mode. The lead (II) ions have the coordination number of six (PbNS3O2) with two oxygen atoms from acetate anion and three sulfur atoms and one nitrogen atom from organic ligand. It contains a stereo-chemically active lone electron pair and the hemidirected coordination sphere. The high-intensity ultrasound is considered a flexible, environmentally friendly, and easy synthetic tool for the coordination compounds. PbO clusters was achieved with thermolyzing 1 at 180 ˚C with oleic acid (as a surfactant). Furthermore, the size and morphology of the created PbO clusters were assessed via SEM. The estimated gap of HOMO and LUMO is 3.275 eV based on DFT calculations.

Synthesis, Electronic Structure and Anti-Cancer Activity of the Phenyl Substituted Pyrazolo[1,5-a][1,3,5]triazines

: Background: Synthesis of a series of 2-(dichloromethyl)pyrazolo[1,5- a][1,3,5]triazines was carried out and evaluated in vitro for their anticancer activity against a panel of 60 cell lines derived from nine cancer types. The joint quantum-chemical and experimental study of the influence of the extended πconjugated phenyl substituents on the electron structure of the pyrazolo[1,5-a][1,3,5]triazines as Pharmacophores were performed. It is shown that the decrease in the barriers to the rotation of phenyl substituents in compounds 1-7 possibly leads to an increase in the anti-cancer activity, which is in agreement with the change in the parameter biological affinity ϕ0. Analysis of the S0 → S1 electronic transitions (π→π*) of the pyrazolo[1,5-a][1,3,5]triazines shows that an increase in their intensity correlates with anti-cancer activity. Thus, the introduction of phenyl substituents increases the likelihood of investigated pyrazolo[1,5-a][1,3,5]triazines interacting with protein molecules (Biomolecule) by the π stacking mechanism. In both methyl and phenyl derivatives of pyrazolo[1,5-a][1,3,5]triazines, the second electronic transition includes the n-MO (the level of the lone electron pair in two-coordinated nitrogen atoms). The highest intensity of the η→π* electronic transition is observed in pyrazolo[1,5-a][1,3,5]triazine with pyridine residue, which does not exhibit anti-cancer activity, but exhibits antiviral activity [13]. It can be assumed that the possibility of the formation of [Pharmacophore-Biomolecule] complex by hydrogen bonding ([H-B]) mechanism with protein molecules increases.

A new proposal for the electronic structure of carbon monoxide

A new proposal for the electronic structure of carbon monoxide CO is presented. The approach involves the creation of an additional half-filled 2p orbital in the oxygen atom by the transfer of an electron from the filled 2p orbital to one of two half-filled hybridized <mml:math display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> orbitals in the carbon atom. The result is a triple bond comprising one sigma bond and two pi bonds between C and O strengthened by an ionic bond contribution. The proposed structure accounts for many unusual features of the molecule CO including the observed direction of the dipole moment, which is considered anomalous based on the concept of electronegativity of the constituent atoms as well as the increased bond dissociation energy compared with isoelectronic nitrogen <mml:math display="inline"> <mml:mrow> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> . It also provides a basis for the CO molecule being a stable ligand combining with transition metals using the lone electron pair in the filled <mml:math display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> orbital of the carbon atom. The electron transfer mechanism is effectively applied to the isoelectronic compound boron monofluoride BF and predicts properties of the undetected isoelectronic molecule BeNe. Finally, the method proposes new electronic structures for the cyanide ion <mml:math display="inline"> <mml:mrow> <mml:mi>C</mml:mi> <mml:msup> <mml:mi>N</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:mrow> </mml:math> which resolves the long-standing puzzle of “charge reversal” on the molecule and the carbon monofluoride ion <mml:math display="inline"> <mml:mrow> <mml:mi>C</mml:mi> <mml:msup> <mml:mi>F</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:mrow> </mml:math> .

Unveiling the role of the lone electron pair in sesquioxides at high pressure: Compressibility of β-Sb2O3

The structural, vibrational and electronic properties of the compressed β-Sb2O3 polymorph, a.k.a. mineral valentinite, have been investigated in a joint experimental and theoretical study up to 23 GPa. The compressibility...

Localization and steric effect of the lone electron pair of the tellurium Te4+ cation and other cations of the p-block elements. A systematic study

A simple method has been developed based on pure geometrical concepts to localize lone pairs (LPs) of cations of the p-block elements and model their steric effect. The method was applied to 1185 structures containing LP cations in 2439 non-equivalent positions. For oxide crystal structures, it is observed that, going from bottom left to top right in the periodic table, LPs move away from the cation core and decrease in size. For a given kind of cation M*, the LP radius increases linearly with the M*–LP distance, the smallest rate being observed for Tl+ and the largest for Cl5+. The influence of the anion type was also studied in the case of the Te4+ cation. Overall, the same trends were observed. The smallest Te–LP distances and LP radii are found for anions of large size and small charge.

Nonlinear optical ASnX (A = Na, H; X = N, P) nanosheets with divalent tin lone electron pair effect by first-principles design

Divalent tin Sn2+ lone electron pairs can induce strong second harmonic generation density in 2D NaSnP and HSnN structures.

Towards a quantitative bond valence description of coordination spheres – the concepts of valence entropy and valence diversity coordination numbers

Two novel definitions of chemical coordination numbers – valence entropy coordination number n VECN and valence diversity coordination number n VDCN – are proposed. Their originality stems from the fact that they are the first definitions based solely on bond valences. The expressions for them are derived from their definitions and their properties are studied. The unexpected close relationship of n VECN to Shannon entropy and n VDCN to diversity are revealed and the names of the new coordination numbers are taken therefrom. Finally, as an example, a study of arsenic(III) lone electron pair stereoactivity with respect to AsIII coordination number is carried out to demonstrate the usefulness and advantages of the new definitions as well as to compare them with the existing ones.

Crystal Structure of the Disordered Non-Centrosymmetric Compound Fe0.43Mo2.56SbO9.5

Single crystals of Fe0.43Mo2.56SbO9.5 were obtained by hydrothermal techniques at 230 °C. The crystal structure was determined from single crystal X-ray diffraction data. The compound crystallizes in the non-centrosymmetric space group Pc with unit cell parameters a = 4.0003(2) Å, b = 7.3355(3) Å, c = 12.6985(6) Å, β = 90°. The crystal structure comprises five crystallographically independent M atoms and one Sb3+ atom, M atoms are of two kinds of partially occupied sites Mo6+ and Fe3+. The building blocks consist of [SbO3O0.5O0.5E] octahedra (E = lone electron pair) and [(Mo/Fe)O6] octahedra. The M = (Mo, Fe) and O atoms are arranged in a distorted hexagonal 2D-net, not the Sb atoms. The distortion of the net and consequently the symmetry reduction results mainly from the location of the Sb atoms. Disorder manifests itself as a splitting of the metal sites and as a consequent shortening of the Mo–Fe distances. Six (Mo/Fe)O6 octahedra are connected to form a pseudohexagonal channel. The Sb3+ atom is displaced from the pseudo-six-fold axis.

Lone-pair effect on carrier capture in Cu2ZnSnS4solar cells

Fast electron–hole recombination in kesterite solar cells is linked to the chemistry of the Sn lone electron pair.