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1.
The crystal structures of four organoselenium compounds, viz. bis(2-formylphenyl)diselenide (5), bis(2-methylnaphthyl)diselenide (6), organoselenenyl sulfide (7), and spiroselenurane (8) are described. Crystal data for 5: space group Pca21, crystal system orthorhombic, a=7.9969(4) Å, b=20.8794(12) Å, c=15.8307(13) Å, Z=8, R=0.0292. Owing to the presence of a strong Se···O interaction in compound 5 the geometry around the selenium atom may be considered as T-shaped. Crystal data for 6: space group Pna21, crystal system orthorhombic, a=18.2253(12) Å, b=13.0714(8) Å, c=7.7355(5) Å, Z=4, R=0.0570. The molecule has a cisoid conformation. Crystal data for 7: space group Pbcn, crystal system orthorhombic, a=22.2144(13) Å, b=8.0255(4) Å, c=15.4496(9) Å, Z=8, R=0.0292. Due to intramolecular Se···N interaction in 7 the geometry around selenium is T- shaped. Crystal data for 8: space group P21/c, crystal system monoclinic, a=7.4585(5) Å, b=19.5634(13) Å, c=8.0428(5) Å, β=97.1320(10)°, Z=4, R=0.0254. The O?Se?O angle is 172.86(6)°.  相似文献   

2.
Five 4-dicyanomethylene derivatives 6–10, N-cyanoacetyl-cis-2,6-diphenylpiperidin-4-one 11 and 4-cyano(ethoxycarbonyl)-methylene-cis-2,6-bis(o-chlorophenyl)piperidine 12 were synthesised by condensing the appropriate piperidin-4-ones 13–17 with malononitrile/ethylcyanoacetate and their 1H and 13C NMR spectra were recorded. The 1H-1H COSY spectrum for 6 and NOESY spectra for 8, 10, and 11 were also recorded. Based on coupling constants and the results obtained from NOESY spectra boat conformation for 10 and epimerised chair conformations for 8 and 9 have been proposed. Other derivatives adopt normal chair conformations. Theoretical calculations and the 1H and 13C chemical shifts also support the above conformations. Mass spectra were also recorded for 6–12.  相似文献   

3.
This paper describes the hydrothermal synthesis, full characterization, and architectural diversity of three intriguingly bioactive cobalt–organic frameworks, namely, 3D [Co(HL ? )2(BPY)] n ·4nH2O (1), 2D [Co(HL ? )2(BPE)] n (2), and 2D [Co(HL ? )2(DPP)] n (3) coordination polymers, synthesized through a mixed ligand strategy using H 2 L (1-H-indazole-3-carboxylic acid) as a main structural block and the flexible bipyridine and its derivatives (BPY = 4,4′-bipydine, BPE = 1,2-bis(4-pyridyl)ethane, DPP = 1,3-bis(4-pyridyl)propane) as auxiliary ligand sources. Complexes 13 were isolated as air stable and slightly soluble crystalline solids and characterized using elemental analysis, FT-IR, electrochemical technique, thermogravimetric analysis, powder X-ray diffractometer, and single-crystal X-ray crystallography. The bipyridine derivatives played key roles in defining the structural space group and dimensionality feature of the obtained networks. The abundant H-bonding and ππ stacking interactions in complexes 13 gave rise to their intricate metal–organic structures of 3D (1), 2D (2), and 2D (3). In addition, the solutions of complexes 13 showed profound antifungal activities against the selected strain of Colletotrichum musae compared with the controlled group using benomyl as a traditional agrochemical fungicide.  相似文献   

4.
Metal(II) complexes of 4-(((2-hydroxynaphthalen-1-yl)methylene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (HL) were prepared, and their compositions and physicochemical properties were characterized on the basis of elemental analysis, with1HNMR, UV–Vis, IR, mass spectroscopy and thermogravimetric analysis. All results confirm that the novel complexes have a 1:1 (M:HL) stoichiometric formulae [M(HL)Cl2] (M = Cu(II)(1), Cd(II)(5)), [Cu(L)(O2NO)(OH2)2](2), [Cu(HL)(OSO3)(OH2)3]2H2O(3), [Co(HL)Cl2(OH2)2]3H2O(4), and the ligand behaves as a neutral/monobasic bidentate/tridentate forming a five/six-membered chelating ring towards the metal ions, bonding through azomethine nitrogen, exocyclic carbonyl oxygen, and/or deprotonated phenolic oxygen atoms. The XRD studies show that both the ligand and Cu(II) complex (1) show polycrystalline with monoclinic crystal structure. The molar conductivities show that all the complexes are non-electrolytes. On the basis of electronic spectral data and magnetic susceptibility measurements, a suitable geometry has been proposed. The trend in g values (g ll > g  > 2.0023) suggest that the unpaired electron on copper has a \(d_{{x^{2} - y^{2} }}\) character, and the complex (1) has a square planar, while complexes (2) and (3) have a tetragonal distorted octahedral geometry. The molecular and electronic structures of the ligand (HL) and its complexes (15) have been discussed. Molecular docking was used to predict the binding between HL ligand and the receptors of the crystal structure of Escherichia coli (E. coli) (3t88) and the crystal structure of Staphylococcus aureus (S. aureus) (3q8u). The activation thermodynamic parameters, such as activation energy (E a), enthalpy (ΔH), entropy (ΔS), and Gibbs free energy change of the decomposition (ΔG) are calculated using Coats–Redfern and Horowitz–Metzger methods. The ligand and its metal complexes (15) showed antimicrobial activity against bacterial species such as Gram positive bacteria (Bacillus cereus and S. aureus), Gram negative bacteria (E. coli and Klebsiella pneumoniae) and fungi (Aspergillus niger and Alternaria alternata); the complexes exhibited higher activity than the ligand.  相似文献   

5.
The biological activities of two binuclear copper(II) complexes containing S-alkenyl derivatives of thiosalicylic acid are reported [alkenyl = propenyl (L1), isobutenyl (L2)]. The structure of the complex with the S-isobutenyl derivative (C2) was confirmed by single-crystal X-ray structure analysis, which revealed that the structure consists of centrosymmetric, dinuclear complex molecules [Cu2(S-i-butenyl-thiosal)4(DMSO)2] containing two Cu(II) centers bridged by four S-isobutyl-thiosalicylate ligands in a paddle-wheel type structure. The Cu(II) atom is situated in a distorted square-pyramidal environment formed by carboxylate oxygen atoms in the basal plane and a DMSO ligand in the axial position. The reactivities of the complexes toward guanosine-5′-monophosphate (5′-GMP) were investigated. Complex C2 ([Cu2(S-i-butenyl-thiosal)4(H2O)2]) reacted more rapidly with 5′-GMP than complex C1. The interactions of complexes C1 and C2 with calf thymus DNA (CT-DNA) were examined by absorption (UV–Vis) and emission spectral studies (ethidium bromide displacement studies), revealing good DNA interaction abilities. The antimicrobial activities of the free ligands and their complexes were tested by microdilution method, and both minimal inhibitory and microbicidal concentrations were determined. All the tested substances demonstrated selective and moderate antibacterial activity on gram-positive bacteria, but low antibacterial activity on gram-negative bacteria. Also, the tested substances demonstrated low antifungal activity.  相似文献   

6.
A series of novel coumarin substituted amide derivatives were synthesized and evaluated for their antibacterial activities. Result indicated that compounds 3f, 3g, 3h, 3i, 3j, 3k, 3l, 3m, 3n, 3o and 3q exhibited excellent antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas citri subsp. Citri (Xcc) in vitro, which were better than those of commercial agricultural antibacterial thiodiazole-copper. The title compounds with electron-withdrawing group showed better antibacterial activities than those of compounds with electron-donating group, and the title compounds bearing the same substituent group exhibited better antibacterial activities against Xcc than antibacterial activities against Xoo.  相似文献   

7.
A computational Petra/Osiris/Molinspiration and Density Functional Theory based model has been developed for the identification of physic–chemical parameters governing the bioactivity of chiral amides derivatives of diacetyl-L-tartaric acid and aromatic amines 4–9 containing combined antifungal pharmacophore sites. The six compounds 4–9 analyzed here were previously experimentally and now virtually screened for their antibacterial/antifungal activity. The highest antifungal activity was obtained for compound 6, which exhibited excellent % inhibition, comparable to Terbinafine. Compound 5, represents increased activity as compared to its isomer 6. The increase of bioactivity from 5 to 6 could be attributed to the existence of pi-charge transfer from para-Bromo-phenyl to its amid group (COδ?--NHδ+), which plays a crucial template role in the organization of antifungal O,O-phramacophore sites. Moreover, it is cheap, has fewer side effects, and its possible inclusions in selective fungal/viral media such as Fusarium, HIV, and Hepatitis B/C have to be questioned.  相似文献   

8.
A 3 × 3 isomer grid of nine Methylphenyl-N-pyridinylcarbamates (CxxM) is reported with seven CxxM crystal structures at 294 K (xx = pp, pm, po, mp, op, om, oo; x = para-, meta-, ortho), where Cx = pyridinyl ring (as C5NH4NH-) and xM is representative of –C(=O)OC6H4CH3. All seven carbamate crystal structures aggregate via N–H…N intermolecular interactions with the three CpxM carbamates having C(6) zigzag chains, CmpM with C(5) zigzag chains and three ortho-pyridine CoxM structures as hydrogen-bonded dimers with graph set \(R_{2}^{2}\) (8) and augmented by flanking C–H…O contacts. The CpoM crystal structure crystallises with 0.25 CHCl3 per carbamate molecule and solvent channels aligning along the a-axis direction. Conformational analyses of the nine minimised CxxM structures in gas phase are detailed for comparisons with the solid-state structures and demonstrate similarities between both structural methods. The modelling results also demonstrate the problems associated with pendant ortho-groups sterically clashing in the CmoM and CooM structures and methods to find a reasonable estimate of the CxxM conformational landscape.  相似文献   

9.
N-pyridinium salt derivatives (15) were prepared and investigated as corrosion inhibitors for mild steel in 1 M H2SO4 solution at 30°C for 24 h. The corrosion inhibiting action was studied using weight loss measurements. The results demonstrated that the corrosion rate decreases, inhibition efficiencies increase, and surface coverage degree increases with increasing inhibitor concentration. Inhibition efficiencies for prepared N-pyridinium salt derivatives have highest inhibiting efficiency for even low concentration. The values of ΔGads° showed physisorption effect for all prepared compounds. Molecular modeling systems were achieved for suggested inhibitors 1–5. Theoretical calculations could be used as a useful tool to obtain information for explaining the mechanism and nature of interaction between the metal surface and the organic molecule as a corrosion inhibitor.  相似文献   

10.
A new triazole-substituted ligand H2L (H2Trza = 3-amino-1H-1,2,4-triazole-5-acetate) and its two new isomorphic compounds [M(HTrza)2(H2O)2] ? 2H2O (Co(I) and Mn(II)) have been synthesized and characterized structurally. Their X-ray crystal structures (CIF files CCDC nos. 906893 for I and 906892 for II) show that H2L belongs to a tetragonal system; space group P43 with a = b = 5.0445(13), c = 27.054(10) Å; Z = 4. Complex I belongs to a monoclinic system; space group P21/n with a = 7.6543(8), b = 7.3453(8), c = 13.6283(14) Å; β = 91.5990(10)°, Z = 2. Complex II belongs to a triclinic system; space group with a = 6.8550(15), b = 8.0630(18), c = 15.173(4) Å; α = 84.794(4)°, β = 79.005(3)°, γ = 73.779(4)°, Z = 2. X-ray analysis demonstrates that compound H2L is found to contain a H2Trza and a lattic water molecule; complexes I and II are discrete mononuclear species. The central Co(II) and Mn(II) atoms exhibit octahedral coordinations, type 4 + 2. In two compounds, the coordination entities are further organized via hydrogenbonding interactions to generate uniform supramolecular networks. Thermal stabilities of two compounds were examined by thermogravimetric analysis.  相似文献   

11.
The rate of substitution of aqua ligands from three mononuclear platinum(II) complexes, namely [Pt{2-(pyrazol-1-ylmethyl)pyridine}(H2O)2](ClO4)2, [Pt(H 2 Py)]; [Pt{2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine}(H2O)2](ClO4)2, [Pt(dCH 3 Py)] and [Pt{2-[(3,5-bis(trifluoromethyl)pyrazoly-1-ylmethyl]pyridine}(H2O)2](ClO4)2, [Pt(dCF 3 Py)] by thiourea, N,N-dimethylthiourea and N,N,N′,N′-tetramethylthiourea, was studied in aqueous perchloric acid medium of constant ionic strength. The substitution reactions were investigated under pseudo-first-order conditions as a function of nucleophile concentration and temperature using UV/Visible and stopped-flow spectrophotometries. The observed pseudo-first-order rate constants, \( k_{{{\text{obs }}\left( {1/2} \right)}} \), for the stepwise substitution of the first and second aqua ligands obeyed the rate law: \( k_{{{\text{obs}}\left( {1/2} \right)}} = k_{{2 \left( { 1 {\text{st/2nd}}} \right)}} \left[ {\text{Nu}} \right] \). The first substitution reaction takes place trans to the pyrazole ligand, while the second entering nucleophile is stabilised at the reaction site trans to the pyridine ligand. The rate of substitution of the first aqua ligand from the complexes followed the order: Pt(dCF 3 Py) > Pt(H 2 Py) > Pt(dCH 3 Py), while that of the second was Pt(H 2 Py) ≈ Pt(dCF 3 Py) > Pt(dCH 3 Py). Lower pK a values were found for the deprotonation of the aqua ligand cis to the pyrazole ring. Density functional theory calculations were performed to support the interpretation of the experimental results.  相似文献   

12.
Novel platinum(II) organometallic dinuclear complexes and oligomers with two types of phenanthroline ligands, namely 3,8-diethynylphenanthroline (L1) and 3,8-bis-(4-ethynyl-phenylethynyl)-1,10-phenanthroline (L2), were synthesized from trans-Pt(PBu3)2(1-ethynyl-4-methyl-benzene)Cl and trans-Pt(PBu3)2Cl2 by transmetalation of copper ion. The alternative procedure targeted platinum oligomer termination selection of either chloride or respective phenanthrolines and was successfully performed with different purifications by extraction and column chromatography. The structural formulae of these platinum complexes and oligomers were revealed with by analysis of both 31P{1H}-NMR and 1H-NMR spectral data. Alternative preparations of platinum oligomers with two types between chloride and respective phenanthroline termination are very useful for the selective synthesis for hybrid polymers with the coupling reaction with two different platinum oligomers with different diethynylaryl ligands. The platinum organometallic compounds showed similar absorption bands in the UV–Vis region. Those prepared with L1 had a strong absorption band at around 400 nm, assignable to the lowest energy metal-perturbed 1[ππ*] transitions, while in compounds prepared with L2, the strong band appeared around 410 nm, because L2 has an extended π conjugation relative to L1. No distinct differences were observed in the absorption spectra of these platinum oligomers between the different terminal structures, chloride or various phenanthrolines. The luminescence spectra of the platinum compounds prepared with either L1 or L2, however, showed a distinct difference. Those with L1 showed only a phosphorescence assignable to a typical metal-perturbed 3[ππ*] transition with vibronic progressions centered at around 530 nm in deoxygenated CH2Cl2 at room temperature, while those with L2 showed weak dual emissions assignable to a mixture of typical metal-perturbed 1[ππ*] and 3[ππ*] transitions in the visible region.  相似文献   

13.
The existence of the [SrF0.8O0.1]2.5[Mn6O12] = Sr2.5Mn6O12.5 ? δF2 compound was established in the SrO-Mn2O3-SrF2 system at 900°C and p(O2) = 1 atm. The crystal structure of strontium fluoromanganite was determined from the X-ray powder diffraction data, electron diffraction, and high-resolution electron microscopy. It can be described in the monoclynic system with four Miller hklm indices: hklm: H = h a* + k b* + l c 1 * + m q 1, q 1, q 1 = c 2 * = γc 1 * , γ ≈ 0.632, aa ≈ 9.72 Å, b ≈ 9.55 Å, c 1 ≈ 2.84 Å, c 2 ≈ 4.49 Å, monoclinic angle γ ≈ 95.6°. The electromotive force method with a solid fluorine ion electrolyte was used to refine the composition of fluoromanganite and determine the thermodynamic functions of its formation from phases neighboring in the phase diagram (SrMn3O6, Mn2O3, SrF2, and oxygen), ΔG°, kJ/mol = ?(111.7 ± 1.9) + (89.5 ± 1.5) × 10?3 T.  相似文献   

14.
In continuation of a systematic study of bis(citrate)germanates, we synthesized a number of heterometallic germanium(IV) and 3d metal complexes based in citric acid (H4Cit) with the molecular formula [M(H2O)6][Ge(HCit)2] · nH2O, where M = Fe, n = 4 (I); Co, n = 2 (II); Ni, n = 2 (III); Cu, n = 1 (IV); Zn, n = 3 (V). The complexes were characterized by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The X-ray diffraction analysis of compound I was performed. Crystals are monoclinic, a = 10.091(4) Å, b = 11.126(4) Å, c = 10.996(4) Å, β = 100.966(6)°, V = 1212.1(8) Å3, Z = 4, space group P21/n, R1 = 0.0561 for 2266 reflections with I > 2σ(I). Compound I is composed of centrosymmetric octahedral complexes-[Ge(HCit)2]2? anions and [Fe(H2O)6]2+ cations—and crystallization water molecules. Structural units in compound I are combined by a hydrogen bond system.  相似文献   

15.

Background

Thiazolidinedione is a pentacyclic moiety having five membered unsaturated ring system composed with carbon, oxygen, nitrogen and sulfur molecules at 1 and 3 position of the thiazole ring and widely found throughout nature in various form. They favourably alter concentration of the hormones secreted by adipocytes, particularly adiponectin. They also increase total body fat and have mixed effects on circulating lipids. Thiazolidinedione nucleus is present in numerous biological moieties and has different pharmacological activities likes, e.g. antimalarial, antimicrobial, antimycobacterial, anticonvulsant, antiviral, anticancer, anti-inflammatory, antioxidant, anti-HIV (human immunodeficiency virus) and antituberculosis.

Results and discussion

The synthesized compounds were screened for their in vitro antimicrobial potential against Gram (positive and negative) bacterial and fungal strains by tube dilution technique. In this series, compound 10 exhibited significant antimicrobial activity against B. subtilis and S. aureus with MIC?=?4.2?×?10?2 µM/ml, compound 15 showed significant activity against K. pneumonia with MIC?=?2.60?×?10?2 µM/ml and compound 4 displayed potent antibacterial activity against E. coli with MIC?=?4.5?×?10?2 µM/ml. Compound 10 had most potent antifungal activity against C. albicans and A. niger with MIC?=?4.2?×?10?2 µM/ml. Compounds 12 and 15 were found as most active antidiabetic agents having IC50?=?27.63 μg/ml and 22.35 μg/ml, respectively, using DPPH assay. Antioxidant activity results indicated that compounds 3 and 9 displayed good antioxidant agent with IC50?=?29.04 μg/ml and 27.66 μg/ml respectively, using α amylase assay.

Conclusion

All the synthesized derivatives exhibited good antimicrobial, antidiabetic and antioxidant activities using specific methods then compared with mentioned standard drugs. Especially, compounds 3, 4, 9, 10, 12 and 15 displayed highest activity. Structure activity relationship demonstrated that presence of electron withdrawing group (o-NO2, p-Cl, p-Br) enhanced the antibacterial activity against E. coli as well as increased the antioxidant activity while the presence of electron releasing group (o/p-OCH3, 3,4,5-trimethoxy) enhanced the antibacterial activity against S. aureus, B. subtilis, S. typhi, K. pneumonia, C. albicans and A. niger as well as the antidiabetic activity.
  相似文献   

16.
Cis-Pt(II) complexes, namely [Pt{2-(phenylthiomethyl)pyridine}(H2O)2](CF3SO3)2 Pt(pyS Ph ), [Pt{2-(4-tert-butylphenylthiomethyl)pyridine}(H2O)2](CF3SO3)2 Pt(pyS Ph( t -But) ) and [Pt{2-(4-fluorophenylthiomethyl)pyridine}(H2O)2](CF3SO3)2 Pt(pyS PhF ), were synthesised and characterised. The pK a1 and pK a2 values of the complexes were determined titrimetrically. Substitution of the aqua ligands from these complexes by thiourea nucleophiles was studied at a pH of 2 and ionic strength of 0.1 M under pseudo-first-order conditions using stopped-flow and UV–visible spectrophotometric techniques. Substitution of the aqua ligands depends on both the nature and concentration of the incoming ligand, with low enthalpy and negative entropy of activation values. Substitution of the first and second aqua ligands occurs sequentially and fits the rate laws: k obs (1/2) = k (1/2) [Nu]. The second-order rate constant, k 1, relates to the substitution trans to sulphur, while k 2 is the second-order rate constant for the subsequent substitution of the aqua ligand trans to pyridine. The rate of substitution of the first aqua ligand decreases in the order: Pt(pyS Ph( t -But) ) > Pt(pyS PhF ) > Pt(pyS Ph ), while that of the second decreases in the order: Pt(pyS Ph( t -But) ) > Pt(pyS Ph ) > Pt(pyS PhF ), reflecting the influence of the substituents on the spectator ligands. 195Pt NMR spectra of aged solutions of complexes with the thiourea nucleophile suggest a subsequent but rapid concentration-independent ring opening of the N,S-bidentate ligand to form a PtS 4 species. The crystal structure of Pt(pyS PhF )Cl 2 was elucidated by X-ray diffraction analysis.  相似文献   

17.
Novel organophosphorus compounds, containing Nicotinamide, with formula C5H4NC(O)NHP(O)R2, R=Cl (1), OH (2), N(C2H5)2 (3), N(C3H7)2 (4), N(n-C4H9)2 (5), NHC3H5 (6), NHC5H9 (7), were synthesized and characterized by 1H, 13C, 31P, NMR, IR, spectroscopy and elemental analysis. Single crystal structures of 3 7 were determined by X-ray crystallography. 1HNMR spectra of compounds 2, 3, 68 demonstrated interesting long-range coupling constant, n J P,H (n = 5 7). Crystallographic data revealed that in both molecules 3 and 7, the phosphoryl and the carbonyl groups have anti-configurations and the phosphorus atoms in these structures have distorted tetrahedral configuration. All the hydrogen bonds and electrostatic interactions make a three dimensional polymeric network for both 3 and 7. Interestingly, two independent conformers were detected in the unit cell of compound 7. The two conformers of the title compound can be observed in a solid phase but only one compound defined in a solution. These two conformers are connected to each other by a short contact, N (amine)···H–C (pyridine) with 2.626 Å distance. The molecular geometry of 7 was calculated by DFT/B3LYP (6–31+G**) quantum chemical calculations. The computational optimized geometric parameters and vibrational frequencies showed a good agreement with the experimental results, considering reasonable variations arising from the differences between solid and gaseous phases. Theoretical calculations revealed that the more stable conformer of the title compound is conformer 1 with the energy of ?1335.723996 a.u., which is about 1.17 kcal/mol lower than the energy of conformer 2.  相似文献   

18.
Two ethylenediamine derivatives—N-(2-ammoniumethyl)carbamate HN(COO?)CH2CH2N+H3 (I) and tetraacetylethylenediamine (H3CC(O))2NCH2CH2N(C(O)CH3)2 (II) (synthesized for the first time)—have been synthesized and characterized by X-ray crystallography. Compounds I and II are isolated as minor admixtures upon an attempt to synthesize ethylenediamine complexes of lanthanum and neodymium nitrates, respectively. The crystals of I and II are monoclinic: a = 7.778 Å, b = 8.060 Å, c = 7.568 Å, β = 95.73°, Z = 4, space group P21/c (I); a = 5.946, b = 10.255, c = 9.343 Å, β = 95.72°, Z = 2, space group P21/c (II). The bond lengths and bond angles lie within the corresponding standard values. Compounds I and II have different conformations of the N-C-C-N ethylenediamine moiety: gauche in I and trans in II, and the corresponding torsion angles are equal to 66.6° and 180°, respectively.  相似文献   

19.
Sterically hindered meso-tetramethyl-meso-tetraarylcalix[4]pyrroles 1-4 where aryl is p-fluorophenyl 1, p-chlorophenyl 2, and p-methylphenyl 3, 4 (configurational isomers) are synthesized and purified by the recrystallization technique. They are characterized by IR, 1H and 13C NMR, and mass spectroscopy. Configurational isomers ααββ (3) and αααα (4) of meso-tetramethyl-meso-tetramethylphenylcalix[ 4]pyrroles are assigned by the 1H NMR studies and confirmed by the X-ray diffraction analysis. The single crystal X-ray diffraction analysis reveals that the ethanol adduct of 1, the acetone adduct of 2 and 3 adopt the 1,2-conformation while the acetone-water adduct of 1 and the acetone adduct of 4 adopt partial cone and cone conformations respectively. The conformational diversity is due to non-covalent interactions among the encapsulated guest, pyrrolic NH protons, and meso- substituents. Anion binding studies (F, Cl, CH3COO, HSO 4 ? ) are carried out through 1H NMR titrations; the binding constants are evaluated using the EQNMR program, displaying that they are more selective towards fluoride rather than other anions with the 1:1 stoichiometry. The configuration of compounds drastically influences the ion-recognition processes.  相似文献   

20.
Density functional theory and ab initio computations elucidated the ring-opening of substituted (R = –CF3, –CN, –CH3, –H, –NH2, –OCH3, –OH, –SiH3) 1-bromo–1-lithiosilirane 1 and 2-bromo–2-lithiosilirane 2 to LiBr complexes of 2-silaallene and 1-silaallene, respectively. Formally, two competitive pathways can be considered. The ring-opening reaction can take place through a concerted manner via TS3. Alternatively, the reaction may proceed in a stepwise fashion with the intermediacy of a free silacyclopropylidene–LiBr complex 7. In both cases, the position of the substituents determines the kinetic of the reactions. The structures with an electron-donating group are generally unstable, whereas the silacyclopropylidenoids bearing electron-withdrawing substituents are particularly stable species. Here, we propose the ring-opening of 5ah to corresponding LiBr complexes of 2-silaallenes can proceed in both concerted and stepwise mechanism except for –H, –CH3, and –SiH3. The obtained activation energies for the ring-openings of 5ah to related 2-silaallenes are too high for a reaction at room temperature with up to 61.4 kcal/mol. In contrast, the activation energy barriers for the isomerization of 6ah to the LiBr complexes of 1-silaallenes was determined to be relatively low at the B3LYP/6-31+G(d,p), M06/6-31+G(d,p), and MP2/6-31+G(d,p) levels. Moreover, we have also investigated the solvent effect on the unsubstituted models using both implicit and explicit solvation models. The energy barriers of the solvated models are found to be slightly higher than the results of gas phase calculations. Additionally, the ring-opening of dimer 6 (6Dim) is also calculated for the ring-opening mechanism with the energy barrier of 3.7 kcal/mol at B3LYP/6-31+G(d,p) level of theory.  相似文献   

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