Effect Of Chlorine Substituents Research Articles

Unusual lanthanoid contraction in crystal structures of 1,10-phenanthroline-2,9-diamides complexes with lanthanoid and yttrium trinitrates and the effect of chlorine substituents

Two series of crystal structures of 1:1 complexes of lanthanoid (excluding Pm) and yttrium trinitrates with N,N,N',N'-tetrabutylamide of 1,10-phenanthroline-2,9-dicarboxylic acid (L1) and N,N,N',N'-tetrabutylamide of 4,7-dichloro-1,10-phenanthroline-2,9-dicarboxylic acid (L2) that we started to study in previous works, have been completed. In all complexes, the ligands L1 and L2 coordinate central ions via two phenanthroline nitrogen atoms and two amide oxygen atoms. In complexes formed by early and middle lanthanoids, all three nitrate ions are bidentate, which gives a total coordination number equal to 10. In heavy lanthanoids complexes, starting from Ho for L1 and Yb for L2, coordination number was reduced to 9 because one nitrate turns to a monodentate coordination mode or is replaced by a water molecule. The Ln-N bonds in complexes with L2 are by 0.02–0.06 Å longer that those in L1 complexes throughout the whole lanthanoid row. With a decrease in the radius of the central ion, all coordination bonds become shorter, but their shortening occurs unevenly. In complexes with L1, between Dy and Ho, along with the reduction of the coordination number, the Ln(Y)–N bond lengths decrease abruptly, whereas the bonds Ln(Y)–O(NO3) shorten to a much lesser extent, and the Ln(Y)–O(amide) distances change almost continuously. In complexes with L2, a similar sharp shortening of Ln(Y)–N bonds takes place before the coordination number decreases to 9. The observed structural changes agree with the results of DFT calculations.

Effect of Chlorine Substituents on the Photovoltaic Properties of Monocyanated Quinoxaline-Based D–A-Type Polymers

A string of monocyanated quinoxaline (Qx)-based D-A-type polymers systematically decorated with electron-attracting chlorine (Cl) atoms was created for use in non-fullerene polymer solar cells (PSCs). First, coupling of the benzodithiophene (BDT) donor and Qx acceptor with the strong electron-attracting cyano (CN) unit at its 5-position yielded the monocyanated reference polymer PB-CNQ. Subsequently, the additional Cl atoms were separately or simultaneously incorporated into the thiophene side groups of the BDT donor and Qx acceptor to create other objective polymers, PBCl-CNQ, PB-CNQCl, and PBCl-CNQCl. The Cl substituents on the BDT donor and Qx acceptor are represented by the names of the polymers. Owing to the favorable contributions of Cl substituents, the inverted-type non-fullerene PSCs based on partially chlorinated PBCl-CNQ (12.80%) and PB-CNQCl (13.93%) exhibited better power conversion efficiencies (PCEs) than the device based on unchlorinated reference PB-CNQ (11.19%). However, a significantly reduced PCE of 9.84% was observed for the device based on PBCl-CNQCl, in which Cl atoms were loaded on both the BDT donor and Qx acceptor at the same time. Hence, these results reveal that optimization of the number and position of Cl substituents in monocyanated Qx-based polymers is essential for enhancing their photovoltaic nature through the synergistic effects between two strong electron-attracting CN and Cl substituents.

The effect of molecular planarity and resonant effects on supramolecular structures of N-(5-pyrazolyl)imines by X-ray crystallographic analysis

A series of N-(5-pyrazolyl)imines 3 were synthesized in high yields (81–90%) by a solvent-free condensation reaction of 5-aminopyrazole derivatives 1 with arylaldehydes 2 under microwave irradiation. These compounds were recrystallized from methanol. X-ray diffraction analyses of N-(5-pyrazolyl)imines 3 show that substituents can affect the degree of electronic delocalization between phenyl and pyrazole rings through the bridging imine moiety. The resonance effect changes the dihedral angles of these planar rings generating conformations close or far from planarity. This effect influences the supramolecular assembly allowing or not short intermolecular hydrogen bonds involving the methoxy group in compounds 3a-c. Additionally, the degree of electronic delocalization is related to the acidic character of the hydrogen atoms in the methyl group bonded to the pyrazole ring facilitating or not the formation of short hydrogen bonds in 3a-c. In the case of 3d, the resonance effect of chlorine substituents allows the hydrogen atom in meta position to perform short intermolecular bonds. CE-B3LYP interaction energies show that, in the more planar molecules, dispersion forces act in higher proportion to build the crystals.

Benzoxazine Monomers and Polymers Based on 3,3'-Dichloro-4,4'-Diaminodiphenylmethane: Synthesis and Characterization.

To reveal the effect of chlorine substituents in the ring of aromatic amine on the synthesis process of benzoxazine monomer and on its polymerization ability, as well as to develop a fire-resistant material, a previously unreported benzoxazine monomer based on 3,3′-dichloro-4,4′-diaminodiphenylmethane was obtained in toluene and mixture toluene/isopropanol. The resulting benzoxazine monomers were thermally cured for 2 h at 180 °C, 4 h at 200 °C, 2 h at 220 °C. A comparison between the rheological, thermal and fire-resistant properties of the benzoxazines based on 3,3′-dichloro-4,4′-diaminodiphenylmethane and, for reference, 4,4′-diaminodimethylmethane was made. The effect of the reaction medium on the structure of the oligomeric fraction and the overall yield of the main product were studied and the toluene/ethanol mixture was found to provide the best conditions; however, in contrast to most known diamine-based benzoxazines, synthesis in the pure toluene is also possible. The synthesized monomers can be used as thermo- and fire-resistant binders for polymer composite materials, as well as hardeners for epoxy resins. Chlorine-containing polybenzoxazines require more severe conditions for polymerization but have better fire resistance.

The role of chlorine substituents in lichexanthones properties: the ionic and halogen bond interactions

The effects of chlorine substituents (Cl substituents) on the structural and electronic properties of lichexanthones (LXs) such as aromaticity of rings, the intramolecular interactions and the complexation of LXs with Mg2+ and NH3 (the ionic and halogen bond interactions) have been investigated by the quantum mechanical calculations at the M06-2X/6-311++G(d,p) level of theory. The effects of Cl substituents on the intramolecular H-bond interactions strongly depend on their positions on the ring. The Cl substituents increase the E2 values of nX → π*CC interactions, obtained from the natural bond orbital analysis, reduce the electron densities on the center of the substituted ring, ρRCP in the results of atoms in molecules analysis, and decrease the aromaticity of the rings with respect to the aromatic fluctuation index. The stabilities of compounds depend on the aromaticity of rings, the O···H-bond strength, and especially the Cl···H interaction. Also, the effects of substituents on the local minimum values of electrostatic potential around the O atoms (Vmin) and therefore the binding energies of [LX···Mg]2+ and [LX···Mg·4H2O]2+ complexes strongly depend on the positions of the substituents. The aromaticity of rings A and C decrease and that of B increases after complexation with the Mg2+ ion. The electronic effects (and in some cases the steric effects) play a special role in the formation and stability of LX···NH3 complexes. The stabilities of the LX···NH3 complexes increase by increasing the natural charges and the local maximum electrostatic potential (Vmax−Cl) calculated, respectively, on and around the Cl atoms, and the ρCl−N values calculated at the Cl···N BCPs.

Effect of chlorine substituent on cytotoxic activities: Design and synthesis of systematically modified 2,4-diphenyl-5H-indeno[1,2-b]pyridines

In continuation of our previous work, six hydroxylated 2,4-diphenyl-5H-indeno[1,2-b]pyridine analogs were modified by introducing one chlorine functionality at ortho, meta or para position of the 2- or 4-phenyl ring. Eighteen new chlorinated compounds were thus prepared and assessed for topoisomerase inhibitory activity and cytotoxicity against HCT15, T47D, and HeLa cancer cell lines. All of the chlorinated compounds displayed significant cytotoxic effect, revealing potent anticancer activity against T47D breast cancer cells. This functional group modification allowed us to explore the importance of chlorine group substitution for the cytotoxic properties. The information reported here provides valuable insight for further study to develop new anticancer agents using related scaffolds.

Catalytic oxidation of chlorinated benzenes over V2O5/TiO2 catalysts: The effects of chlorine substituents

Chlorobenzene and 1,3,5-trichlorobenzene were chosen as model pollutants of chlorinated benzenes. Catalytic (kinetic) studies and in-situ FTIR experiments were conducted over V2O5/TiO2 catalysts to investigate the oxidation behavior of these two chlorinated benzenes. Different oxidation rates were observed in the catalytic study, which was ascribed to their molecular structural properties. Oxidation products and by-products were analyzed both on-line by GC and off-line by GC-MS, and slight difference was observed for these two chlorinated benzenes. Similar surface species on the catalysts could be easily identified in the in-situ FTIR curves. Supported by these results, a possible reaction pathway for catalytic oxidation of 1,3,5-trichlorobenzene was accordingly proposed. Noteworthy, the effect of the chlorinated degree on the catalytic oxidation was discussed, and it is well demonstrated that the structural and electronic factors of the chlorinated benzenes, and the influence of chlorine to the active vanadium sites, play important roles in the oxidation process.

Theoretical Study of the Molecular Geometries, Electronic and Thermodynamic Properties of Chlorinated Dipyrido‐(3,2‐a:2′,3′‐c)‐Phenazine

Theoretical study of the molecular geometries, electronic and thermodynamic properties of dipyrido‐(3,2‐a:2′,3′‐c)‐phenazine (dppz) was carried out in the gas phase under standard conditions using PM6 Hamiltonian in semiempirical model. Effects of chlorine substituents on these properties were also investigated. The results showed that all the electronic and thermodynamic properties investigated were affected by the number and relative position of chlorine substituents. Variations in some properties are not significant for some isomeric congeners, having the same number of chlorine substituents, while a number of properties showed general variation with both the number and position of chlorine substituents. Successive addition of one chlorine atom after the other at adjacent position to the last chlorine substituent increases the total energy by 241 eV and decreases the LUMO‐HOMO gap by an average value of 0.124 eV. Geometry and energy optimization show that all the molecules considered are planar.

Structure–reactivity relationships and substituent effect additivity in the aqueous oxidation of chlorophenols by cerium(iv)

The oxidation of all 19 chlorophenols and unsubstituted phenol by cerium(IV) was studied in an acidic aqueous solution in order to carry out a systematic test of chlorine substituent effects on the reactivity. All reactions were found to show 2 ∶ 1 cerium(IV) ∶ phenol stoichiometry and a simple second-order rate equation. Rate constants did not correlate well with characteristic parameters such as pK values, carbon-13 NMR chemical shifts or Hammett substituent constants. Nevertheless, a strict additivity of chlorine substituent effects was found in both characteristic and reactivity parameters. The data suggest that a proton-coupled electron transfer mechanism could be operative. 2,4,6-Trichlorophenol was found to show exceptionally high reactivity towards cerium(IV).

ChemInform Abstract: Nucleophilic Displacement in Polyhalogenoaromatic Compounds. Part 14. Chloroazulenes.

Methoxydechlorination of 5,6-dichloroazulene in NaOMe–MeOH shows second-order kinetics, apparently proceeding by the SNAr mechanism in which the attack of the nucleophile, and not the loss of chloride ion, is rate-determining. No evidence of a Meisenheimer-type intermediate is found. The rate of the reaction is not affected by light, nor by the presence of nitrobenzene; radical contributions to the process are therefore unlikely. The corresponding reactions of 4,5,6,7- and 1,3,5,6-tetrachloroazulene, and of 1- and 3-nitro-5,6-dichloroazulene all show second-order kinetics and are all accelerated compared to the parent compound; 1,3,4,5,6,7-hexachloroazulene reacted too rapidly for measurement. As expected, the extent of such acceleration is conditioned not only by the nature of the substituent but also by its position. Unexpectedly, chlorine substituent effects are clearly greater from the five-membered ring than from the ring undergoing attack.Semi-empirical all-valence-electron SCF–MO calculations are presented which rationalise the orientation of attack and describe the observed substituent effects.

A HeI photoelectron spectroscopy and theoretical study of 2,6-dichloropyrazine, 2,3-dichloropyrazine, 4,6-dichloropyrimidine and 3,6-dichloropyridazine

The electronic structures of C 4H 2Cl 2N 2 isomers have been studied by HeI photoelectron spectroscopy (PES) combined with the outer valence Green’s function (OVGF) calculations at 6-311++G(d,p) basis sets. The vertical first ionization potentials for 2,6-dichloropyrazine, 2,3-dichloropyrazine, 4,6-dichloropyrimidine and 3,6-dichloropyridazine are determined to be 9.93, 9.89, 10.45 and 10.07 eV, respectively, and the PE spectra were assigned based on molecular orbital analysis and by comparison with related compounds. The effects of chlorine substituent and different positions of nitrogen atoms in these C 4H 2Cl 2N 2 isomers have been carefully analyzed by comparing the C 4H 2Cl 2N 2 isomers with their matrixes (pyrazine, pyridazine, pyrimidine). The inductive effect of chlorine substituent leads to the stabilization of the nitrogen lone pair orbitals. The resonance effect predominates over the inductive effect, and the consequence is the destabilization of the π orbitals. Owing to the different positions, the effects of nitrogen atoms are different and lead to the different sequence of π orbitals.

Raman spectral analysis of phenoxyacetic acid and some chloro substituted phenoxyacetic acids

Raman spectra of phenoxyacetic acid and chlorine substituted phenoxyacetic acids viz., o-chlorophenoxyacetic acid, p-chlorophenoxyacetic acid and 2,6-dichlorophenoxyacetic acid have been analysed with the aid of abinitio theoretical calculations. The effect of chlorine substituents on the Raman spectra of phenoxyacetic acid have also been analysed by considering some important vibrational modes.

Conformational and substituent effects in the 19F spectra of C7-C10 straight-chain chlorofluoroalkanes.

One- and two-dimensional fluorine NMR spectra of straight-chain chlorofluoroalkanes having 7-10 carbons were obtained and interpreted. Spectral assignments were based primarily on indirect spin-spin correlations. A scale of chlorine substituent effects was developed. The effects of asymmetric CFCl centers on chemical-shift differences in nearby CF2 groups were analyzed in terms of molecular conformational effects. Spin-spin coupling patterns of CF3 groups were elucidated.

Influence of chlorine substituents on rates of oxidation of chlorinated biphenyls by the biphenyl dioxygenase of Burkholderia sp. strain LB400.

Biphenyl dioxygenase from Burkholderia (Pseudomonas) sp. strain LB400 catalyzes the first reaction of a pathway for the degradation of biphenyl and a broad range of chlorinated biphenyls (CBs). The effect of chlorine substituents on catalysis was determined by measuring the specific activity of the enzyme with biphenyl and 18 congeners. The catalytic oxygenase component was purified and incubated with individual CBs in the presence of electron transport proteins and cofactors that were required for enzyme activity. The rate of depletion of biphenyl from the assay mixture and the rate of formation of cis-biphenyl 2,3-dihydrodiol, the oxidation product, were almost equal, indicating that the assay accurately measured enzyme-specific activity. Four classes of CBs were defined based on their oxidation rates. Class I contained 3-CB and 2,5-CB, which gave rates that were approximately twice that of biphenyl. Class II contained 2,5,3',4'-CB, 2,3,2',5'-CB, 2,3,4,5-CB, 2,3,2',3'-CB, 2,4, 5,2',5'-CB, 2,5,3'-CB, 2,5,4'-CB, 2-CB, and 3,4,5-CB, which gave rates that ranged from 97 to 35% of the biphenyl rate. Class III contained only 2,3,4,2',5'-CB, which gave a rate that was 4% of the biphenyl rate. Class IV contained 2,4,4'-CB, 2,4,2',4'-CB, 3,4,5, 2'-CB, 3,4,5,3'-CB, 3,5,3',5'-CB, and 3,4,5,2',5'-CB, which showed no detectable depletion. Rates were not significantly correlated with the aqueous solubilities of the CBs or the number of chlorine substituents on the rings. Oxidation products were detected for all class I, II, and III congeners and were identified as chlorinated cis-dihydrodiols for classes I and II. The specificity of biphenyl dioxygenase for the CBs examined in this study was determined by the relative positions of the chlorine substituents on the aromatic rings rather than the number of chlorine substituents on the rings.

Light Induced Elimination of Mono- and Polychlorinated Phenols from Aqueous Solutions by PW12O403-. The Case of 2,4,6-Trichlorophenol

Light induced catalytic decomposition of several mono-, di-, and trichlorophenols and phenol in the presence of PW12O403- in aqueous solutions (pH 1) leads to mineralization of substrates. The method is an example of Advanced Oxidation Processes (AOP) that cause mineralization of organic pollutants through the generation of very active, mainly OH, radicals. Generally, chlorination of phenolic ring enhances the decomposition, whereas the effect of chlorine substituents in the ortho position is less pronounced. However, the rates of decomposition of chlorinated phenols are very much the same. Dioxygen's main function seems to be the regeneration of the catalyst, with limited participation in the initial stages of the photoreactions. A detailed study of 2,4,6-trichlorophenol (2,4,6-TCP) photodecomposition showed that key reactions involved were hydroxylation, substitution of chlorine by OH radicals mainly in the ortho and para positions, and breaking of the aromatic ring. Ring-opened products detected were m...

Effects of chlorine substituents upon the formation, reactivity and electrochemical properties of platinum(II) and platinum(IV) metallacycles

The reactions of [Pt 2Me 4( μ-SMe 2) 2] ( 1) with chlorinated ligands Me 2NCH 2CH 2NCHAr (Ar=C 6Cl 5 ( 2a); 2,3,6-C 6H 2Cl 3 ( 2b); 2,3,5-C 6H 2Cl 3 ( 2c); 2,4-C 6H 3Cl 2 ( 2d); 3,5-C 6H 3Cl 2 ( 2e) and 3-C 6H 4Cl ( 2f)) yield either cyclometallated [C,N,N′] platinum(IV) complexes [PtMe 2Cl(Me 2NCH 2CH 2NCHR–C, N, N′)], arising from C–Cl bond activation, or cyclometallated [C,N,N′] platinum(II) complexes [PtMe(Me 2NCH 2CH 2NCHR– C, N, N′)], arising from C–H bond activation, followed by methane elimination. These processes occur at room temperature except for the formation of compound [PtMe{Me 2NCH 2CH 2NCH(3,5-C 6H 2Cl 2)}] ( 4e) which is produced in refluxing toluene, since at room temperature cyclometallation of ligand 2e is not achieved. Compound [PtMe 2{Me 2NCH 2CH 2NCH(3,5-C 6H 3Cl 2)– N, N′)}] ( 3e), arising from coordination of the ligand to the platinum center, is obtained at room temperature. The reactions of 1 with ligands PhCH 2NCHAr (Ar=2,3,6-C 6H 2Cl 3 ( 2g) and 2,3,5-C 6H 2Cl 3 ( 2h)) produce cyclometallated [C,N] platinum(IV) complexes. The reactivities of the platinum complexes towards phosphines and methyl iodide have been studied. All complexes have been characterized by NMR spectroscopy and the X-ray crystal structure of [PtMe 2Cl{Me 2NCH 2CH 2NCH(3,5-C 6H 2Cl 2)– C, N, N′}] ( 4c) has been determined. The electrochemical properties of the compounds based on cyclic voltammetry have also been studied. While the first reduction step is nearly reversible for cyclometallated platinum(II) compounds, coordination complex 3e and cyclometallated platinum(IV) compounds exhibit an irreversible reduction wave. In all cases oxidation occurs in an irreversible manner. The processes involved and the influence of the chlorine substituents are discussed.

NMR Spectra of Some Chlorinated Diphenyliodonium Salts and Iodobenzenes

1H and 13C NMR chemical shifts and nJ(C,H) coupling constants of symmetrical polychlorinated diphenyliodonium salts and polychlorinated iodobenzenes were measured and analysed to obtain information about chlorine substituent effects on aromatic tri- and monovalent iodo compounds. The chlorine substituent effects on the chemical shifts and the direct 1J(C,H) coupling constants were studied by multiple linear regression analysis.

CH and CCl bond activation in the formation of cyclometallated platinum(II) and platinum(IV) compounds with chlorinated N-benzylidenebenzylamines

Platinum substrate [Pt 2Me 4(μ-SMe 2) 2] ( 1) reacts with chlorinated imines 3,5-Cl 2C 6H 3CHNCH 2C 6H 5 ( 2a) and 3-ClC 6H 4CHNCH 2C 6H 5 ( 2b) to yield cyclometallated platinum(II) compounds [PtMe(3,5-Cl 2C 6H 2CHNCH 2C 6H 5)(SMe 2)] ( 4a) and [PtMe(3-ClC 6H 3CHz.dbnd;NCH 2C 6H 5)(SMe 2)] ( 4b), arising from CH bond activation followed by loss of methane. A react intermediate [PtMe 2(3,5-Cl 2C 6H 3CHNCH 2C 6H 5)(SMe 2)] ( 3a) was detected by 1H NMR. The reaction of [Pt 2Me 4(μ-SMe 2) 2] ( 1) with chlorinated imine 2,4,-Cl 2C 6H 3CHNCH 2C 6H 5 ( 2c) produces a mixture of cyclometallated platinum(II) compound [PtMe(2,4- Cl 2C 6H 2CHNCH 2C 6H 5)(SMe 2)] ( 4c) and cyclometallated platinum(IV) compound [PtMe 2Cl(4-ClC 6H 3CHNCH 2C 6H 5)(SME 2)] ( 4c′) arising respectively from aryl CH and aryl CCl bond activation. The reaction of complex 4a with triphenylphosphine produces metallacycle cleavage and [PtMe(3,5-Cl 2C 6H 2CHNCH 2C 6H 5)PPh 3) 2] ( 5a) is formed with the imine acting as a [C −] unidentate ligand. 5a crystallizes in the monoclinic space group P2 1/ n with a = 10.899(5) A ̊ , b = 22.953(5) A ̊ and c = 17.588(9) A ̊ , β =95.14(5)° and Z = 4. Compounds 4b, 4c and 4c′ react with PPh 3 to give cyclometallated compounds [PtMe(3-ClC 6H 3CHNCH 2 C 6H 5)(PPh 3)] ( 5b), [PtMe(2,4-Cl 2C 6H 2CHNCH 2C 6H 5)(PPh 3)] ( 5c), and [PtMe 2Cl(4-ClC 6H 3CHNCH 2C 6H 5)(PPh 3)]( 5c′) respectively. The stereo-electronic effect of chlorine substituents, as well as the NMR parameters, are discussed in relation to the observed reactivity of these compounds.

Substituent effects on 13C NMR parameters of chlorinated diphenyl ethers. A multiple linear regression analysis

Abstract13C NMR chemical shifts and nJ(C,H) coupling constants of polychlorinated diphenyl ethers (PCDEs) were measured and analysed. The chlorine substituent effects on the chemical shifts and the coupling constants were determined by a multiple linear regression analysis. The 13C NMR chemical shifts depend on the conformational preferences in PCDEs. In addition to single substituent effects, corrective terms reflecting the conformational state of the molecule and the mutual steric interactions of two chlorine atoms had to be taken into account for the reliable prediction of the 13C chemical shifts. In contrast to chemical shifts, conformational effects play a minor role in the substituent effects of the nJ(C,H) coupling constants. Coupling constants are approximately additive in terms of ‘simple sum rules’.

ChemInform Abstract: Substituent Effects in Chemical Shifts of Tryptophan Derivatives. Part 3. Chlorine Substituent Effects for Indole and Tryptophan in 13C NMR.

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