New2-((2-(2,4-dinitrophenyl)hydrazineeylidene) derivatives: design, synthesis, in silico, and in vitro anticancer studies.

A series of novel hydrazone compounds have been synthesized by the condensation of hydrazines and different substituted salicylaldehydes at a molar ratio of 1:1 in one step reaction and characterized by FT-IR, ESI-MS, 1H NMR, and single crystal x-ray diffraction. The crystal structure of the compound shows a trans configuration around the C = N bond and triclinic system with P -1/-p 1. Synthesized compounds were screened for cytotoxicity activities against A375 (melanoma), HT-29 (Colon), and A549 (lung) cancer cell lines. Among them, compound 2 exhibited the highest cytotoxic effect against the A375 cell line (IC50 = 0.30 µM) and HT-29 cell line (1.68 µM), compared to those of apatinib as a reference standard drug (0.28, 1.49 µM, respectively). The cytocompatibility assay on the L929 normal cell line and the hemolysis assay on human RBC were used to validate the non-toxic action. From DFT calculation, the various parameters such as HOMO-LUMO energies, Hirshfeld, and MEP have been studied. Furthermore, in silico molecular docking with three receptors was studied. Among four compounds, compound 2 has the lowest binding energy against cyclin dependent kinase (ΔGb = -9.3 kcal/mol). In addition to this, molecular dynamics (MD) simulation was also performed. Based on this study, these novel hydrazones can be considered a promising anticancer agent due to their potent cytotoxicity activities and computational analysis.Communicated by Ramaswamy H. Sarma.

Recent Advances in BODIPY Compounds: Synthetic Methods, Optical and Nonlinear Optical Properties, and Their Medical Applications.

Organoboron compounds are attracting immense research interest due to their wide range of applications. Particularly, low-coordinate organoboron complexes are receiving more attention due to their improbable optical and nonlinear optical properties, which makes them better candidates for medical applications. In this review, we summarize the various synthetic methods including multicomponent reactions, microwave-assisted and traditional pathways of organoboron complexes, and their optical and nonlinear properties. This review also includes the usage of organoboron complexes in various fields including biomedical applications.

ENDOR characterization of an iron-alkene complex provides insight into a corresponding organometallic intermediate of nitrogenase.

A bio-organometallic intermediate, denoted PA, was previously trapped during the reduction of propargyl alcohol to allyl alcohol (AA) by nitrogenase, and a similar one was trapped during acetylene reduction, representing foundational examples of alkene binding to a metal center in biology. ENDOR spectroscopy led to the conclusion that these intermediates have η2 binding of the alkene, with the hydrogens on the terminal carbon structurally/magnetically equivalent and related by local mirror symmetry. However, our understanding of both the PA intermediate, and of the dependability of the ENDOR analysis on which this understanding was based, was constrained by the absence of reference iron-alkene complexes for EPR/ENDOR comparison. Here, we report an ENDOR study of the crystallographically characterized biomimetic iron(i) complex 1, which exhibits η2 coordination of styrene, thus connecting hyperfine and structural parameters of an Fe-bound alkene fragment for the first time. A tilt of the alkene plane of 1 from normal to the crystallographic Fe-C2-C1 plane causes substantial differences in the dipolar couplings of the two terminal vinylic protons. Comparison of the hyperfine couplings of 1 and PA confirms the proposed symmetry of PA, and that the η2 interaction forms a scalene Fe-C-C triangle, rather than an isosceles triangle. This spectroscopic study of a structurally characterized complex thus shows the exceptional sensitivity of ENDOR spectroscopy to structural details, while enhancing our understanding of the geometry of a key nitrogenase adduct.

The Mechanism of N-N Double Bond Cleavage by an Iron(II) Hydride Complex.

The use of hydride species for substrate reductions avoids strong reductants, and may enable nitrogenase to reduce multiple bonds without unreasonably low redox potentials. In this work, we explore the N═N bond cleaving ability of a high-spin iron(II) hydride dimer with concomitant release of H2. Specifically, this diiron(II) complex reacts with azobenzene (PhN═NPh) to perform a four-electron reduction, where two electrons come from H2 reductive elimination and the other two come from iron oxidation. The rate law of the H2 releasing reaction indicates that diazene binding occurs prior to H2 elimination, and the negative entropy of activation and inverse kinetic isotope effect indicate that H-H bond formation is the rate-limiting step. Thus, substrate binding causes reductive elimination of H2 that formally reduces the metals, and the metals use the additional two electrons to cleave the N-N multiple bond.

Synthesis and structural analysis of titanatranes bearing terminal substituted aryloxo ligands of the type [Ti(OAr){(O-2,4-Me2C6H2-6-CH2)2(OCH2CH2)N}]n (n = 1, 2): effect of aryloxo substituents in the ethylene polymerization.

A series of titanatranes containing both chelate bis(aryloxo)-(alkoxo)amine and the terminal aryloxo ligands of type [Ti(OAr)(L)](n) [n = 1 or 2, Ar = 2,6-Me(2)C(6)H(3) (1), 2,6-(i)Pr(2)C(6)H(3) (2), 2,6-Ph(2)C(6)H(3) (3), 2-FC(6)H(4) (4), 2,6-F(2)C(6)H(3) (5), C(6)F(5) (6); L = (O-2,4-Me(2)C(6)H(2)-6-CH(2))(2)(OCH(2)CH(2))N)] have been prepared, and their structures (1, 3-6) were determined by X-ray crystallography. The ortho-substituents in the terminal aryloxo ligand directly affect the structure in the solid state; the structures of 1-3 possessed monomeric form and fold a distorted trigonal bipyramidal geometry around Ti, whereas the structure of 4-6 were of dimeric form and fold a distorted octahedral around Ti bridged with oxygen in the alkoxo arm expressed as [Ti(OAr){(O-2,4-Me(2)C(6)H(2)-6-CH(2))(2)(mu(2)-OCH(2)CH(2))N)}](2). The Ti-O(Ar) bond distances and the Ti-O-C(Ar) bond angles are highly influenced by the terminal aryloxo substituents especially in the ortho-position. The 2,6-(i)Pr(2)C(6)H(3) analogue (2), the C(6)F(5) analogue (6), and the 2,6-Me(2)C(6)H(3) analogue (1) showed moderate/notable catalytic activities for ethylene polymerization in the presence of MAO especially at 80-100 degrees C, whereas both the 2,6-Ph(2)C(6)H(3) analogue (3) and 2-FC(6)H(4) analogue (4) showed the negligible catalytic activities, clearly indicating that the activity was strongly affected by the terminal aryloxo substituents especially in the ortho-position.

From unstable to stable: half-metallocene catalysts for olefin polymerization.

The reaction of LAlMeOH [L = CH(N(Ar)(CMe))2, Ar = 2,6-i-Pr2C6H3] with CpTiMe3, Cp*TiMe3, and Cp*ZrMe3 was investigated to yield LAlMe(mu-O)TiMe2Cp (2), LAlMe(mu-O)TiMe2Cp* (3), and LAlMe(mu-O)ZrMe2Cp* (4), respectively. The resulting compounds 2-4 are stable at elevated temperatures, in contrast to their precursors such as CpTiMe3 and Cp*ZrMe3, which already decompose below room temperature. Compounds 2-4 were characterized by single-crystal X-ray structural analysis. Compounds 2 and 3 were tested for ethylene polymerization in the presence of methylaluminoxane. The half-metallocene complex 3 has higher activity compared to 2. The polydispersities are in the range from 2.8 to 4.2. A copolymerization with styrene was not observed.

Oxygen-bridged hybrid metallocene-nonmetallocene polymetallic catalysts of group 4 metals for bimodal activity in olefin polymerization: synthesis, characterization, and theoretical investigation.

This article describes the syntheses of two covalently linked oxygen-bridged hybrid metallocene-nonmetallocene polymetallic catalysts bearing two different catalytically active group 4 metals. The reactions of Cp*2(Me)Zr(OH) (2) with Ti(NMe2)4 and Hf(NMe2)4 led to the formation of a heterobimetallic compound Cp*2(Me)Zr(micro-O)Ti(NMe2)3 (7) and a trimetallic derivative Cp*2(Me)Zr(micro-O)Hf(NMe2)2(micro-O)Zr(Me)Cp*2 (9), respectively, under the elimination of Me2NH. The crystal data confirm the molecular structures of 7 and 9, which crystallize in the space groups P and P21/n, respectively. 9 is the first example of a crystallographically characterized heterotrimetallic complex having a Zr-O-Hf-O-Zr core. 7 bearing two active catalytic centers, namely, zirconium and titanium, exhibits bimodal activity in olefin polymerization when activated with methylalumoxane (MAO). It produces polyethylene largely controlled by the zirconium center, and polystyrene seems to be formed predominantly by the titanium center. DFT calculations were performed on the supposed cationic intermediates, revealing that a cation generated on the titanium center is sterically more accessible for monomer binding, though it is energetically less-favorable than that generated on the zirconium center.

Synthesis and structures of heteroleptic silylenes.

The reaction of benzamidinato silicon trichloride [{PhC(NR)2}SiCl3] [R = Bu(t) (1), SiMe3 (2)] with 2 equiv of potassium in THF afforded mononuclear chlorosilylene [{PhC(NBu(t))2}SiCl] (3) and [{PhC(NSiMe3)2}2SiCl2] (4), respectively. Compound 4 was formed by the disproportionation of unstable [{PhC(NSiMe3)2}SiCl]. The reaction of [{PhC(NBu(t))2}SiCl3] (1) with 1 equiv of LiR (R = NMe2, OBu(t), OPr(i), PPr(i)2) in THF yielded [{PhC(NBu(t))2}SiCl2R] [R = NMe2 (5), OBu(t) (6), OPr(i) (7), PPr(i)2 (8)]. Treatment of 5-8 with 2 equiv of potassium in THF resulted in the novel heteroleptic silylene [{PhC(NBu(t))2}SiR] [R = NMe2 (9), OBu(t) (10), OPr(i) (11), PPr(i)2 (12)]. Compounds 4, 9, and 12 have been analyzed by X-ray crystallography.

Synthesis, structural characterization, and theoretical investigation of compounds containing an Al-O-M-O-Al (M=Ti, Zr) core.

We report a facile route to the first molecular compounds with the Al-O-M-O-Al (M=Ti, Zr) structural motif. Synthesis of L(Me)Al(mu-O)M(NMe2)2(mu-O)Al(Me)L [L=CH{N(Ar)(CMe)}2, Ar=2,6-iPr2C6H3; M=Ti (7), Zr (8)] was accomplished by reacting the monometallic hydroxide precursor L(Me)Al(OH) (1) with Ti(NMe2)4 or Zr(NMe2)4 under elimination of Me2NH in good yield. The crystal structural data confirm the trimetallic Al-O-M-O-Al core in both 7 and 8. Preliminary investigation on catalytic activity of these complexes reveals low activity of these complexes in ethylene polymerization as compared to the related oxygen-bridged metallocene-based heterobimetallic complexes L(Me)Al(mu-O)M(Me)Cp2 (M=Ti, Zr) which could be attributed to the relatively lower stability of the supposed cationic intermediate as revealed by DFT calculations.

Synthesis, structural characterization, catalytic properties, and theoretical study of compounds containing an Al-O-M (M = Ti, Hf) core.

Two single oxygen-bridged heterobimetallic oxides of Al(III) with group 4 metals (Ti, Hf) have been prepared. The reaction of LAlMeOH (1) [L = CH(N(Ar)(CMe))2, Ar = 2,6-iPr2C6H3] with dimethylmetallocenes of Ti and Hf in toluene (80 degrees C) and ether (room temperature), respectively, resulted in the formation of LAl(Me)(mu-O)M(Me)Cp2 [M = Ti (2), Hf (3)] in moderate to good yield. Compounds 2 and 3 were characterized by elemental analysis, IR, NMR (1H and 13C), EI-MS, and single-crystal X-ray structural analysis. Furthermore, compound 2 showed good catalytic activity in ethylene and styrene homopolymerization, while compound 3 is less active in ethylene polymerization. The styrene polymerization yields atactic polystyrene.