multiple bond
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2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Bassam Oudh Aljohny ◽  
Yasir Anwar ◽  
Shahid Ali Khan

Abstract In the current study, five different plants, Syzygium Cumini, Fagonia cretica, Acacia modesta, Withania coagulans, and Olea europaea aqueous extracts were prepared and applied against the anticancer and antibacterial activities. It was observed that O. Europaea extract shows the highest anticancer activity with cell viability of 21.5%. All the five plants extract was also used against the inhibition of Bacillus subtilis where O. Europaea extract shows a promising inhibitory activity of 3.2 cm followed by W. coagulans. Furthermore, W. coagulans was subjected to the process of column chromatography as a result a withanolide was isolated. The fast atom bombardment mass spectrometry (FAB-MS) and high resolution fast atom bombardment (HRFAB-MS) [M + 1] indicated molecular weight at m/z 453 and molecular formula C28H37O5. The UV–Vis. spectrum shows absorbance at 210 nm suggesting the presence of conjugated system, and Fourier-transform infrared spectroscopy (FTIR) was recorded to explore the functional groups. Similarly, 1D and 2D NMR spectroscopy techniques such as 1H, 13C NMR, correlation spectroscopy (COSY-45°), heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC) and Nuclear Overhauser effect Spectroscopy (NOESY) techniques was carried out to determine the unknown natural product. The collective data of all these techniques established the structure of the unknown compound and recognized as a withanolide.


2022 ◽  
Author(s):  
Fabian Dankert ◽  
Christian Hering-Junghans

Heavier group 13/15 multiple bonds have been under investigation since the late 80s and to date, several examples have been published, which shows the obsoleteness of the so-called double bond...


2021 ◽  
Vol 118 (52) ◽  
pp. e2113315118
Author(s):  
Jasmin Borsovszky ◽  
Klaas Nauta ◽  
Jun Jiang ◽  
Christopher S. Hansen ◽  
Laura K. McKemmish ◽  
...  

The dicarbon molecule (C2) is found in flames, comets, stars, and the diffuse interstellar medium. In comets, it is responsible for the green color of the coma, but it is not found in the tail. It has long been held to photodissociate in sunlight with a lifetime precluding observation in the tail, but the mechanism was not known. Here we directly observe photodissociation of C2. From the speed of the recoiling carbon atoms, a bond dissociation energy of 602.804(29) kJ·mol−1 is determined, with an uncertainty comparable to its more experimentally accessible N2 and O2 counterparts. The value is within 0.03 kJ·mol−1 of high-level quantum theory. This work shows that, to break the quadruple bond of C2 using sunlight, the molecule must absorb two photons and undergo two “forbidden” transitions.


2021 ◽  
Author(s):  
◽  
Struan Cummins

<p>This thesis describes the synthesis, structures and reactivities of gallium and aluminium complexes supported by β-diketiminato ligands ([CR{C(R)N(R’)}₂]-, abbrev. [(BDIR’)]-).  Chapter 1 gives a general introduction into the trends and properties that distinguish the heavier p-block elements from their lighter counterparts. An introduction into the theory of multiple bond formation, both homonuclear and heteronuclear, in the heavy p-block elements is provided and a summary of the sterically demanding ligands required to stabilise these complexes is introduced. The β-diketiminato ligand framework utilised in this study is introduced and the methods of generation of low valent gallium and aluminium complexes supported by the BDIDIPP ligand are discussed.  Chapter 2 discusses the reactivity of the complex BDIDIPPGa with diazo- compounds in the quest to isolate a complex with a formal gallium-carbon double bond. BDIDIPPGa reacts with two equivalents of both trimethylsilyldiazomethane and diazofluorene, presumably through the target gallium-carbon double bond intermediate. No reaction is observed with di-tert-butyldiazomethane, while BDIDIPPGa catalyses the decomposition of diphenyldiazomethane into tetraphenylethene. Three new β-diketiminato gallium(I) complexes were synthesised: ArBDIDIPPGa, BDIAr*Ga and BDIAr’Ga. ArBDIDIPPGa also reacted with two equivalents of trimethylsilyldiazomethane, presumably through the target gallium-carbon double bond intermediate. BDIAr*Ga and BDIAr’Ga both inserted into the C-H bond of trimethylsilyldiazomethane to give BDIAr*Ga(H)C(N2)SiMe₃ and BDIAr’Ga(H)C(N2)SiMe₃ respectively. Upon addition of diazofluorene to BDIAr*Ga, one of the aromatic protons of the BDIAr* ligand was abstracted by the diazofluorene, resulting in coordination of one of the flanking phenyl groups to the gallium centre.  Chapter 3 discusses an investigation into the formation of formal double bonds between aluminium and phosphorus, and gallium and phosphorus. The proposed ‘deprotonation/elimination’ method, reacting BDIDIPPM(PHAr)Cl (M = Al, Ga Ar = Ph, Mes) with nBuLi, resulted in the formation of intractable mixtures of products. Direct synthesis by the addition of MesPLi₂ to BDIDIPPMCl₂ (M = Al, Ga) resulted in the formation of BDIDIPPM(PHMes)Cl (M = Al, Ga). Changing the elimination product to TMS-Cl, through the synthesis of BDIDIPPM(P(TMS)Ph)Cl (M = Al, Ga), resulted in the synthesis of BDIDIPPAl(P(TMS)Ph)Cl, which showed no signs of elimination occurring upon heating to 110 °C. BDIDIPPGa(P(TMS)Ph)Cl could not be isolated, potentially as the complex was undergoing the desired elimination of TMS-Cl, but the resulting complex was decomposing. Changing the elimination product to ethane, through the synthesis of BDIDIPPAl(PHMes)Et, resulted in no sign of elimination occurring upon heating to 110 °C. Reduction of BDIDIPPMCl₂ (M = Al, Ga) in the presence of bistrimethylsilylacetylene, as part of the synthesis of BDIDIPPMLi₂ (M = Al, Ga) salts, was unsuccessful, as was the reaction of BDIDIPPGa with bistrimethylsilylacetylene. Reduction of MesPCl₂ with potassium metal in the presence of BDIDIPPGa resulted in an intractable mixture of products, reduction with magnesium resulted in the formation of (MesP)₃ and (MesP)₄. Addition of MesPH₂ to BDIDIPPGa resulted in the formation of BDIDIPPGa(H)P(H)Mes, which did not undergo H₂ elimination at 110 °C. The synthesis of BDIDIPPAl was unsuccessful as the product could not be isolated cleanly. The synthesis of ArBDIDIPPAl resulted in the intramolecular rearrangement of the ligand to give a five-membered aluminium containing ring. The synthesis of BDIAr*Al stalled at the formation of BDIAr*Al(Me)I due to the steric bulk of the ligand blocking the second substitution of iodine from occurring.  Chapter 4 discusses the reactivity of the primary phosphanide complexes BDIDIPPAl(PHMes)Cl, BDIDIPPAl(PHMes)Et and BDIDIPPGa(H)P(H)Mes with phenyl acetylene, 4-nitro-phenyl isocyanate, phenyl isothiocyanate, dicyclohexyl carbodiimide, cyclohexene, benzophenone, benzaldehyde, selenium, sulfur, and methyl iodide. Reactivity was not observed for phenyl acetylene, dicyclohexyl carbodiimide or benzophenone with any of the phosphanides. Reactivity with the phosphanides was observed with cyclohexene, however rapid decomposition of the products occurred and they were unable to be identified. BDIDIPPAl(PHMes)Cl and BDIDIPPGa(H)P(H)Mes showed no reactivity with benzaldehyde, however, the ethyl ligand of BDIDIPPAl(PHMes)Et reacted with the aldehyde proton, eliminating ethane and substituting the PhC(O)- ligand onto the aluminium centre. Reactivity with the phosphanides was observed with both sulfur and selenium, however multiple different products were formed, none of which were successfully isolated. Reactivity between the phosphanides and methyl iodide was observed, with the P-M bond appearing to be cleaved and formation of a M-I bond occurring. 4-nitro-phenyl isocyanate and phenyl isothiocyanate underwent insertion reactions into the M-P bond, however only BDIDIPPAl(Cl)N(4-NO₂-Ph)C(O)P(H)Mes was able to be isolated and fully characterised.  Finally, chapter 5 summarises the results of this research and provides an outlook at the future direction of this field of research.</p>


2021 ◽  
Author(s):  
◽  
Struan Cummins

<p>This thesis describes the synthesis, structures and reactivities of gallium and aluminium complexes supported by β-diketiminato ligands ([CR{C(R)N(R’)}₂]-, abbrev. [(BDIR’)]-).  Chapter 1 gives a general introduction into the trends and properties that distinguish the heavier p-block elements from their lighter counterparts. An introduction into the theory of multiple bond formation, both homonuclear and heteronuclear, in the heavy p-block elements is provided and a summary of the sterically demanding ligands required to stabilise these complexes is introduced. The β-diketiminato ligand framework utilised in this study is introduced and the methods of generation of low valent gallium and aluminium complexes supported by the BDIDIPP ligand are discussed.  Chapter 2 discusses the reactivity of the complex BDIDIPPGa with diazo- compounds in the quest to isolate a complex with a formal gallium-carbon double bond. BDIDIPPGa reacts with two equivalents of both trimethylsilyldiazomethane and diazofluorene, presumably through the target gallium-carbon double bond intermediate. No reaction is observed with di-tert-butyldiazomethane, while BDIDIPPGa catalyses the decomposition of diphenyldiazomethane into tetraphenylethene. Three new β-diketiminato gallium(I) complexes were synthesised: ArBDIDIPPGa, BDIAr*Ga and BDIAr’Ga. ArBDIDIPPGa also reacted with two equivalents of trimethylsilyldiazomethane, presumably through the target gallium-carbon double bond intermediate. BDIAr*Ga and BDIAr’Ga both inserted into the C-H bond of trimethylsilyldiazomethane to give BDIAr*Ga(H)C(N2)SiMe₃ and BDIAr’Ga(H)C(N2)SiMe₃ respectively. Upon addition of diazofluorene to BDIAr*Ga, one of the aromatic protons of the BDIAr* ligand was abstracted by the diazofluorene, resulting in coordination of one of the flanking phenyl groups to the gallium centre.  Chapter 3 discusses an investigation into the formation of formal double bonds between aluminium and phosphorus, and gallium and phosphorus. The proposed ‘deprotonation/elimination’ method, reacting BDIDIPPM(PHAr)Cl (M = Al, Ga Ar = Ph, Mes) with nBuLi, resulted in the formation of intractable mixtures of products. Direct synthesis by the addition of MesPLi₂ to BDIDIPPMCl₂ (M = Al, Ga) resulted in the formation of BDIDIPPM(PHMes)Cl (M = Al, Ga). Changing the elimination product to TMS-Cl, through the synthesis of BDIDIPPM(P(TMS)Ph)Cl (M = Al, Ga), resulted in the synthesis of BDIDIPPAl(P(TMS)Ph)Cl, which showed no signs of elimination occurring upon heating to 110 °C. BDIDIPPGa(P(TMS)Ph)Cl could not be isolated, potentially as the complex was undergoing the desired elimination of TMS-Cl, but the resulting complex was decomposing. Changing the elimination product to ethane, through the synthesis of BDIDIPPAl(PHMes)Et, resulted in no sign of elimination occurring upon heating to 110 °C. Reduction of BDIDIPPMCl₂ (M = Al, Ga) in the presence of bistrimethylsilylacetylene, as part of the synthesis of BDIDIPPMLi₂ (M = Al, Ga) salts, was unsuccessful, as was the reaction of BDIDIPPGa with bistrimethylsilylacetylene. Reduction of MesPCl₂ with potassium metal in the presence of BDIDIPPGa resulted in an intractable mixture of products, reduction with magnesium resulted in the formation of (MesP)₃ and (MesP)₄. Addition of MesPH₂ to BDIDIPPGa resulted in the formation of BDIDIPPGa(H)P(H)Mes, which did not undergo H₂ elimination at 110 °C. The synthesis of BDIDIPPAl was unsuccessful as the product could not be isolated cleanly. The synthesis of ArBDIDIPPAl resulted in the intramolecular rearrangement of the ligand to give a five-membered aluminium containing ring. The synthesis of BDIAr*Al stalled at the formation of BDIAr*Al(Me)I due to the steric bulk of the ligand blocking the second substitution of iodine from occurring.  Chapter 4 discusses the reactivity of the primary phosphanide complexes BDIDIPPAl(PHMes)Cl, BDIDIPPAl(PHMes)Et and BDIDIPPGa(H)P(H)Mes with phenyl acetylene, 4-nitro-phenyl isocyanate, phenyl isothiocyanate, dicyclohexyl carbodiimide, cyclohexene, benzophenone, benzaldehyde, selenium, sulfur, and methyl iodide. Reactivity was not observed for phenyl acetylene, dicyclohexyl carbodiimide or benzophenone with any of the phosphanides. Reactivity with the phosphanides was observed with cyclohexene, however rapid decomposition of the products occurred and they were unable to be identified. BDIDIPPAl(PHMes)Cl and BDIDIPPGa(H)P(H)Mes showed no reactivity with benzaldehyde, however, the ethyl ligand of BDIDIPPAl(PHMes)Et reacted with the aldehyde proton, eliminating ethane and substituting the PhC(O)- ligand onto the aluminium centre. Reactivity with the phosphanides was observed with both sulfur and selenium, however multiple different products were formed, none of which were successfully isolated. Reactivity between the phosphanides and methyl iodide was observed, with the P-M bond appearing to be cleaved and formation of a M-I bond occurring. 4-nitro-phenyl isocyanate and phenyl isothiocyanate underwent insertion reactions into the M-P bond, however only BDIDIPPAl(Cl)N(4-NO₂-Ph)C(O)P(H)Mes was able to be isolated and fully characterised.  Finally, chapter 5 summarises the results of this research and provides an outlook at the future direction of this field of research.</p>


2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Elliot Y. Makhani ◽  
Ailin Zhang ◽  
Jered B. Haun

AbstractNanoparticles have drawn intense interest as delivery agents for diagnosing and treating various cancers. Much of the early success was driven by passive targeting mechanisms such as the enhanced permeability and retention (EPR) effect, but this has failed to lead to the expected clinical successes. Active targeting involves binding interactions between the nanoparticle and cancer cells, which promotes tumor cell-specific accumulation and internalization. Furthermore, nanoparticles are large enough to facilitate multiple bond formation, which can improve adhesive properties substantially in comparison to the single bond case. While multivalent binding is universally believed to be an attribute of nanoparticles, it is a complex process that is still poorly understood and difficult to control. In this review, we will first discuss experimental studies that have elucidated roles for parameters such as nanoparticle size and shape, targeting ligand and target receptor densities, and monovalent binding kinetics on multivalent nanoparticle adhesion efficiency and cellular internalization. Although such experimental studies are very insightful, information is limited and confounded by numerous differences across experimental systems. Thus, we focus the second part of the review on theoretical aspects of binding, including kinetics, biomechanics, and transport physics. Finally, we discuss various computational and simulation studies of nanoparticle adhesion, including advanced treatments that compare directly to experimental results. Future work will ideally continue to combine experimental data and advanced computational studies to extend our knowledge of multivalent adhesion, as well as design the most powerful nanoparticle-based agents to treat cancer.


ChemSusChem ◽  
2021 ◽  
Author(s):  
Marta Piquero ◽  
Cristina Font ◽  
Natalia Gullón ◽  
Pilar López‐Alvarado ◽  
J. Carlos Menéndez

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5479
Author(s):  
Sachikazu Omura ◽  
Yoshinori Kawazoe ◽  
Daisuke Uemura

We developed non-toxic, harmless adhesives composed of all-natural and renewable resources, of which one was composed of tannin and gelatin, which unfortunately was lacking water resistance, and the other of tannin and ε-poly-l-lysine. In this study, we analyzed the chemical structures of these adhesives by two-dimensional nuclear magnetic resonance (2D-NMR) to explain the difference in water-resistance of the two glues. The results showed that only one proton was left in the benzene ring of tannin after mixing. This suggests that the amino group of the protein was directly attached to the benzene ring by a Michael addition-type reaction, and not to the hydroxyl group. In addition, the heteronuclear multiple bond correlation spectrum of the tannin-poly-l-lysine compound indicated that the hydroxyl groups of the tannin oxidized, suggesting the improvement of its water resistance.


2021 ◽  
Vol 9 (2) ◽  
pp. 161-169
Author(s):  
E. T. Oganesyan ◽  
S. S. Shatokhin

The quantum-chemical parameters of 52 derivatives related to flavanones, flavanonoles, flavones and flavonoles with a phloroglucinic type of the A ring and containing electron-donating substituents in the B ring were studied.The aim is the analysis of the dynamics of changes in the electron density, bond numbers, free valence indices and unsaturation indices on carbon atoms C-7 → C-8 of the vinyl group of the main conjugation chain in relation to the position and number of substituents in the “B” ring and the type of the pharmacological activity.Materials and methods. The quantum-chemical parameters of the 4 analyzed groups of the compounds, have been calculated by the semi-empirical method PM7 (WinMopac 2016 program) on the workstation with an Intel Xeon E5-1620 3.5 GHz processor, 20 GB of RAM.Results and discussion. When comparing the quantum chemical parameters of the analyzed compounds, it was established that when the C-7 → C-8 multiple bond is formed, the free valency and unsaturation indices increase on both carbon atoms of the vinylene group in flavones and flavonols compared to the corresponding flavanones and flavanonols. This is explained by the fact that the value of the bond numbers Nµ on these atoms, on the contrary, decreases (Fµ = 4.732-Nµ). The transition from flavanone to flavone is accompanied by the formation of a vinyl group C-7 → C-8, and therefore both atoms from the sp3-hybridized state go into the sp2-state. The consequence of this transformation is a change in the electronegativity value and an increase in the unsaturation index of C-7 and C-8 atoms: C sp3 = 2.5;  Csp2 = 2.8. At the same time, the transition from flavanone to flavone leads to the formation of a conjugated system with the participation of π-electrons of the aromatic system “B”, C-7, C-8 atoms and the carbonyl group, which is commonly called the “main conjugation chain”. These structural changes, namely, the transition from a less oxidized flavanone to a more oxidized flavone, contribute to a decrease in the electron density on C-7 and C-8 atoms, and an increase in the total unsaturation of the molecules in general. Mulliken charges on C-7 of all groups of compounds are characterized by a positive value. As for the carbon atoms of the B fragment, the following features are revealed here: in the presence of one substituent -OH or -OCH3 on the carbon atom to which the substituent is bounded, the Mulliken charge is positive; if there are two substituents in the B ring -OH or -OCH3, as well as two -OCH3 groups, then the carbon atoms bonded to the indicated substituents also have a positive Mulliken charge; in the case of trihydroxy substituted in the C-2, C-3 and C-4 B ring, all three carbon atoms are characterized by a positive Mulliken charge; if there are methoxy groups in positions C-2, C-3 and C-4, then the positive Mulliken charge is concentrated only on C-2 and C-4 atoms, and on C-3 atom this charge has a negative value.Conclusion. The above data on the quantum-chemical parameters of the main conjugation chain indicate that the transition of C-7 and C-8 atoms to the sp2-hybrid state, leads to a decrease in the electron density and a decrease in the bond numbers, with a simultaneous increase in the indices of unsaturation and free valence on these atoms. Thus, the trigger mechanism of the anti-radical activity, primarily with respect to the HO • radical, is determined by the fact that this particle, electrophilic in its properties, will attach in the C-8  atom during an initial attack. 


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