Aniline Complexes Research Articles

TCNE-aniline charge transfer complex: ab initio and TDDFT investigations in gas phase

The geometric and electronic structure of tetracyanoethylene (TCNE)-aniline (donor-acceptor type) complex has been investigated in gas phase using ab initio and time dependent density functional theory calculations. Both the above calculations predict a composed structure for the complex, in which the interacting site is a C[triple bond]N and C=C bond center in the TCNE and, -NH(2) and pi-electrons of aniline. The N atom of aniline is oriented toward the TCNE molecule. The charge transfer transition energy, estimated by calculating the ground-to-excited state transition electric dipole moments of the complex, agree well with the reported experimental value in chloroform medium.

Combined experimental and computational study of W(II), Ru(II), Pt(IV) and Cu(I) amine and amido complexes using 15N NMR spectroscopy

Abstract Using 2D proton-coupled gHSQC pulse sequences in addition to 1D 15 N NMR experiments of 15 N labeled systems, 15 N NMR chemical shifts of a range of transition metal amido and amine complexes were determined. Tungsten(II), ruthenium(II), platinum(IV) and copper(I) complexes with aniline and their anilido variants were studied and compared to free aniline, lithium anilido and anilinium tetrafluoroborate. Upon coordination of aniline to transition metals, upfield chemical shifts of 20–60 ppm were observed. Deprotonation of the amine complexes to form amido complexes resulted in downfield chemical shifts of 40–60 ppm for all of the complexes except for the tungsten d 4 system. For the tungsten(II) complexes, the cationic aniline complex displayed a downfield shift of approximately 56 ppm relative to the neutral anilido complex. The change in chemical shift for amine to amido conversion is proposed to depend on the ability of the amido ligand to π-bond with the metal center, which influences the magnitude of the paramagnetic screening term.

Evaluation of the association constants of molecular complexes by electronic and NMR spectroscopy - First evidence for association constants measured by NMR spectroscopy being independent of the methods used

Modified Benesi-Hildebrand and Hanna-Ashbaugh equations have been used for the evaluation of association constants of the charge-transfer complexes by electronic spectroscopy and NMR spectroscopy, respectively. Association constants of charge-transfer complexes of aniline with various dinitrobenzenes have been calculated by electronic spectroscopy using the existing methods and compared with those calculated by the new method. Results show that the new equation has the advantages of measuring K directly rather than evaluating it from the product Ke leading to increased accuracy and being obeyed in cases where Foster-Hammick-Wardley and Scott equations fail. Similarly, association constant of dinitrotoluene-diphenylamine charge-transfer complex has been calculated by NMR spectroscopy using the existing and the new equations. Values of K measured by NMR spectroscopy using different methods are nearly the same, a fact not borne by other workers. This is perhaps the first report where equal values of K are obtained by different methods. The modified Ilanna-Ashbaugh equation also has the advantage of measuring K directly without recourse to evaluating it from the product KΔ 0 ,

H-Bonded Complexes of Aniline with HF/F−and Anilide with HF in Terms of Symmetry-Adapted Perturbation, Atoms in Molecules, and Natural Bond Orbitals Theories

The hydrogen-bonded isoelectronic complexes of aniline with HF/F- and an ionic form of aniline with HF were investigated by use of computational methods: Symmetry-Adapted Perturbation Theory (SAPT), Atoms in Molecules (AIM), and Natural Bond Orbitals (NBO) approaches. All computations were based on structural models previously generated at the B3LYP/6-311+(d,p) level. The differences between neutral (Ph-NH2...HF)and anionic (Ph-NH2...F- and Ph-NH-...HF) complexes were clearly outlined. The discussed charged complexes serve as Lewis acids and base, HF and F-, respectively. It was found that electrostatic and induction energy terms, obtained as a result of the SAPT method, are most dependent on the type of H-bonding (i.e.,charged or neutral). The electrostatic term is the most distinctive between the neutral and charge-assisted hydrogen bonds in the investigated two-body systems, whereas the latter is more significant in the case of weaker interactions (larger H...B distances). Application of Principal Component Analysis (PCA) to energy components obtained from the SAPT procedure indicated that all of them are relatively well intercorrelated.The above-mentioned terms together with the exchange energy terms are the most important contributions ofthe main principal component, which describes 95% of the total variance. Comparison of AIM parameters in bond critical points for modeled H-bond systems shows a good agreement with those from equilibrium complexes, both experimental and calculated ones. It was found that charged H-bonded complexes exhibit larger fluctuation of electron density and its Laplacian in bond critical points, in line with SAPT analysis. NBO results confirmed the effect of the strength of interaction on property changes both in the region of H-bonding and outside of it. The latter, more distant consequences follow the Bent-Walsh rule for all studied complexes.

Time-Dependent Density Functional Theory Study on Electronically Excited States of Coumarin 102 Chromophore in Aniline Solvent: Reconsideration of the Electronic Excited-State Hydrogen-Bonding Dynamics

The time-dependent density functional theory method was performed to investigate the electronically excited states of the hydrogen-bonded complex formed by coumarin 102 (C102) chromophore and the hydrogen-donating aniline solvent. At the same time, the electronic excited-state hydrogen-bonding dynamics for the photoexcited C102 chromophore in solution was also reconsidered. We demonstrated that the intermolecular hydrogen bond CO...H-N between C102 and aniline molecules is significantly strengthened in the electronically excited-state upon photoexcitation, since the calculated hydrogen bond energy increases from 25.96 kJ/mol in the ground state to 37.27 kJ/mol in the electronically excited state. Furthermore, the infrared spectra of the hydrogen-bonded C102-aniline complex in both the ground state and the electronically excited state were also calculated. The hydrogen bond strengthening in the electronically excited-state was confirmed for the first time by monitoring the spectral shift of the stretching vibrational mode of the hydrogen-bonded N-H group in different electronic states. Therefore, we believed that the dispute about the intermolecular hydrogen bond cleavage or strengthening in the electronically excited-state of coumarin 102 chromophore in hydrogen donating solvents has been clarified by our studies.

Synthesis and X‐ray Crystal Structures of Acenaphthenequinone‐based α‐Diimine Palladium Complexes and a Novel V‐shape Tripalladium Cluster

AbstractPartially fluorinated 1,4‐Diazadiene (α‐Diimine) ligand 3,5‐CF3‐BIAN (1) formed from 3,5‐bis(trifluoromethyl)aniline and acenaphthenequinone was used in the synthesis of palladium dichlorido complex 2 and its mono methyl chlorido palladium complex 3. Both complexes as well as side products of the reaction with methyl lithium such as trans‐bis(3,5‐bis(trifluoromethyl)aniline complex 4 and an interesting mixed valent trinuclear V‐shaped palladium cluster 5 with two bridging μ2,η3‐N,CN′ non‐innocent BIAN ligands were structurally characterized by the single‐crystal XRD method.

Structural aspects of the intermolecular hydrogen bond strength: H‐bonded complexes of aniline, phenol and pyridine derivatives

AbstractThis short review is devoted to the description of the effect of the nature and the strength of intermolecular hydrogen bonds on structural properties of H‐bonded complexes of aniline, phenol and pyridine derivatives. Several hundreds of such complexes, playing an important role in organic chemistry and biochemistry, have been identified and described in the literature. In the introductory part, the idea of the H‐bond is discussed in terms of its historical development, followed by presently accepted classification of H‐bonds. Critical review of quantum methods usually used for the calculations of the geometry of H‐bonded complexes and the energies of H‐bonds is then presented. In the second part, the H‐bond‐induced geometrical, hybridization and aromaticity index changes are discussed. All correlations based on quantum calculations are compared with those derived from the available crystal structure data. Although the experimental data are more scattered than the calculated ones, their agreement is impressive. This unequivocally shows the power of the calculation methods developed in recent years. Copyright © 2008 John Wiley & Sons, Ltd.

ChemInform Abstract: Baeyer—Villiger Oxidation of Ketones with Hydrogen Peroxide Catalyzed by Sn—Aniline Complex.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Substituent effects on the hydrogen-bonded complex of aniline–H2O: a computational study

Substituent effects (X = –CH3, –NH2, –OH, –F, –SiH3, –PH2, –H, –Cl, –CN, –NO2, –CHO) on the hydrogen-bonded complex of para-substituted aniline with one water molecule are studied at the B3LYP/6-311++G(d,p) level of theory. The nature of H-bond interactions and the origin of substituent effects are explored by means of natural bond orbital (NBO) and atoms in molecules (AIM) analysis as well as a series of good correlation equations obtained. The result suggests that the substitution induces changes in the electron density transfer from the water molecule to the aniline derivative by means of influencing the interaction of nO → σ*N–H while the change in the electron density transfer would give rise to the variation on the electron densities in the proton donating N–H bond and the N–H⋯O hydrogen bond, and ultimately, influence the length and the frequency of the N–H bond, the H⋯O distance, the binding energies of complexes, the pKa of the substituted aniline and the 1H chemical shift. In addition, the correlations obtained reveals that the H-bond parameters calculated (such as ∇2ρH⋯O, ρH⋯O, RH⋯O), reflecting both the intramolecular (substituent effects) and intermolecular (water effects) interactions, are found to perform better than substituent constants in rationalizing the substitution induced variations on the structure, the binding energy, 1H chemical shift and experimental pKa.

Dependence of 35Cl NQR on hydrogen bonding and temperature in dichlorophenol–aniline charge transfer complexes

The hydrogen-bonded charge transfer complexes of aniline with pi-acceptors (or proton donors) such as 2,5-, 2,6-, 3,4- and 3,5-dichlorophenol were prepared. The (35)Cl nuclear quadrupole resonance (NQR) frequencies of these charge transfer complexes in the temperature range 77-300 K were measured to ascertain the existence or otherwise of a phase transition upon complex formation. Further, the NQR frequency and asymmetry parameter of the electric field gradient at the site of quadrupole nucleus were used to estimate the chemical bond parameters, namely ionic bond, double bond character of the carbon-chlorine(C--Cl) bond and the percentage charge transfer between the donor-acceptor components in charge transfer complexes. The effect of hydrogen bonding and temperature on the charge transfer process is analysed.

Homogeneous solvation controlled photoreduction of cobalt(III) complexes in aqueous 2-methyl-2-propanol solutions: Linear solvation energy relationship and cyclic voltammetric analyses

The effect of solvent participation on the ligand-to-metal charge transfer (LMCT, L → Co III) reduction of the of Co III(en) 2Br(RC 6H 4NH 2) 2+ where R = m-OCH 3, p-F, H, m-CH 3, p-CH 3, p-OC 2H 5 and p-OCH 3 were examined in aqueous 2-methyl-2-propanol (Bu t OH) solutions. The change in the reduction behavior of Co III centre was also examined through cyclic voltammetric studies. The observed reduction in quantum yield due to LMCT excitation can mainly be accounted using linear solvation energy relationship (LSER) comprising model correlation equations. These consist of empirical parameters such as Grunwald–Winstein's solvent ionizing power, Y, Dimroth–Richardt's solvent micro-polarity parameter, E T N , Gutmann's donor number, DN N, along with Kamlet–Taft's solvatochromic parameters (hydrogen bond acceptor acidity/basicity α/ β and solvent dipolarity/polarizability, π*). The origin of solvent effect is found to be due to microscopic interaction between the solvent donor and the nitrogen-bound hydrogen of the ligand. Cyclic voltammograms show an irreversible reduction of Co III in DMF using Glassy Carbon Electrode, GCE, the redox peaks for the aniline complexes appear at −0.20 and 0.525 V. Irradiation of the complexes with UV light ( λ = 254 nm) in binary mixtures produce Co II aq and the concentration of this species are highly dependent on x alc ( x alc = mole fraction of alcohol). The observed quantum yield (log Φ Co(II)) is found to be linearly related to mole fraction of organic co-solvent added in the mixture, therefore, log Φ Co(II) = 26.41 × 10 −2 when x 2 = 0.0094 and 43.75 × 10 −2 when x 2 = 0.076 for a typical complex Co III(en) 2Br( p-OCH 3C 6H 4NH 2) 2+ in aqueous 2-methyl-2-propanol at 300 K. Cyclic voltammetry and LSER analyses illustrate the variation of reduction property of Co(III) by the aryl ligand and homogeneous solvation of the excited state of the complex Co III(en) 2Br(RC 6H 4NH 2) 2+ in H 2O/Bu t OH mixtures.

Fluorescent Tagged Probing Agent and Structure-Directing Amphiphilic Molecular Design for Polyaniline Nanomaterials via Self-Assembly Process

We have designed and developed a unique amphiphilic dopant molecule, 4-[4-hydroxy-2((Z)-pentadec-8-enyl)phenylazo]-benzenesulfonicacid, from a renewable resource, cardanol, which acts as a fluorescent probe and structure-directing agent for polyaniline nanomaterials. The amphiphilic dopant is fluorescing in water and forms stable emulsion for a wider composition of dopant:aniline ratio from 1:1 to 1:1500 (in moles), which is rarely noticed in the polyaniline synthesis. The azobenzene dopant exists in two supramolecular aggregates, such as bi-layer or micelle, depending upon its concentration in water, and the critical micelle concentration (CMC) is directly obtained from the emission properties. Above the CMC, the dopant−aniline complex exists as either aggregated or isolated micelles, and subsequent oxidation produces polyaniline nanomaterials such as hollow spheres (1−2 μM), dendritic nanofibers, and linear nanofibers of 8−10 μM length with a diameter of 130−180 nm. Below the CMC, the dopant aggregated in the form of bi-layers which produce mixtures of nanotubes plus nanofibers or nanotubes of 60 nm pore and 80 nm wall thicknesses. The WXRD patterns of nanofibers showed a sharp peak at 2θ = 6.4 (d-spacing = 13.6), which corresponds to the highly ordered polyaniline chain followed by the effective interdigitations of dopant molecules. The intensity and percent (%) crystallinity of the ordered peak increase and reach a maximum up to CMC and then decrease gradually. It reveals that above CMC, the dopant effectively penetrates into the polymer interlayer and produces highly three dimensionally ordered solid-state nanofibers. Below the CMC, the dopant molecule loses the collective penetration ability to form highly ordered fibers. The polyaniline nanofibers showed enhanced emission in water, and the amount of the dopant in the nanomaterial plays a crucial role in luminescent intensity and quantum yield of the nanofibers. In a nutshell, by understanding the mechanistic aspects of renewable resource amphiphilic dopant−aniline complex by fluorescent spectroscopy, the properties of polyaniline nanomaterials were precisely controlled in a single system.

Structure and Dynamics of the Aniline−Argon Complex as Derived from its Potential Energy Surface

The structure and dynamics of the van der Waals (vdW) complex of aniline (An) with argon (Ar) are studied using ab initio methods. The inversion potential of the aniline-argon (AnAr) complex perturbed by the weak vdW interaction is calculated taking into account subtle corrections from the zero-point energy of the vdW modes and from the frequency shifts of the An normal modes modified by the complexation. The intermolecular potential energy surface (PES) of the AnAr complex is determined by performing a large-scale computation of the interaction energy and the fitting of the analytical many-body expansion to the set of single-point interaction energies. The PES determined shows two deep local minima corresponding to the anti and syn AnAr conformers. The difference in the energies of these two minima is only 15 cm-1, but it is sufficient to localize the inversion wave functions and to form the two conformers. In the conformer anti (syn) of lower (higher) energy, Ar is bound to the An ring opposite (adjacent) the amino-hydrogens. In the additional local minima higher in energy, Ar approaches the aniline ring between the C-H bonds near its plane. An additional local minimum is located opposite of nitrogen between the two N-H bonds. The high-energy minima are, however, too flat to form stable conformers. The perturbation of the interaction of Ar with the phenyl ring by the NH2 group is described by the vdW hole, which is responsible for unusually strong intermode mixing in the excited intermolecular vibrational states. The analysis of these states calculated for the ground (S0) as well as the first excited electronic state (S1) resolves difficulties faced earlier with the assignment of the observed vibronic bands of AnAr.

Baeyer–Villiger oxidation of ketones with hydrogen peroxide catalyzed by Sn–aniline complex

Sn–aniline complex was prepared by a simple procedure. Cyclic and acyclic ketones were oxidized into lactones or esters with very high selectivity and yield with 30% hydrogen peroxide in the presence of Sn–aniline complex.

Substituent Effects in C6F6C6H5X Stacking Interactions

Parallel displaced and sandwich configurations of hexafluorobenzene-substituted benzene dimers are studied by ab initio molecular orbital methods up to the MP2(full)/aug-cc-pVDZ level of theory to reveal how substituents influence pi-pi interactions. Two minimum energy configurations are found, one with the substituent group away from the pi-face of the hexafluorobenzene ring (2a-f) and the other with the substituent group on top of the pi-face of the hexafluorobenzene (3a-f). Higher binding energies are predicted for dimers with the substituent on the pi-face (3a-f). All sandwich dimers (4a-e) are found to be saddle points on the potential energy surfaces. A parallel-displaced minimum energy configuration is also predicted for the parent complex, C6F6-C6H6, which is in contrast to predictions based on quadrupole moments of benzene and hexafuorobenzene. The preference for the parallel displaced, rather than the sandwich configuration, is rationalized based on the smaller interplanar distance in the former. The closeness of contact in the parallel-displaced dimers leads to greater binding energies. The shape of the electron density isosurface of the monomers is suggested to provide a guide for the prediction of how arenes stack with one another. A large difference in binding energy between the C6F6 complex of aniline (3e) and N,N-dimethylaniline (3f) is calculated, and charge-transfer interactions are suggested to play a role in the latter.

Reactivity of [Cp ∗Rh(η 6-C 6H 3NH 2-2,6- i-Pr 2)](OTf) 2 toward phosphines and alkynes

The cationic aniline complex [Cp ∗Rh(η 6-2,6-(Me 2CH) 2C 6H 3NH 2)](OTf) 2 ( 1) was prepared from either [Cp ∗Rh(η 2-NO 3)(η 1-OTf)] or [Cp ∗Rh(OH 2) 3](OTf) 2 and 2,6-diisopropylaniline. Complex 1 underwent substitution with phosphines or phosphites, indicating the labile character of the η 6-aniline ligand. Complex 1 mediated cycloaddition reactions of several alkynes in refluxing ethanol: the [2 + 2] dimerization for Ph C C Ph and the [2 + 2 + 1] trimerization for Ph C C H and CH 3C 6H 4 C C H. The unexpected cyclobutadiene complex [Cp ∗Rh(η 4-C 4(C(O)CH 3) 2H(SiMe 3))] was obtained from complex 1 and Me 3Si C C C C SiMe 3 and structurally characterized by X-ray diffraction.

Synthesis, Characterization of Mixed Ligand Palladium(II) Complexes of Triphenylphosphine and Anilines and their Enzyme Inhibition Studies against β-glucuronidase. The Crystal Structure of trans-dichloro-(m-chloroaniline)(triphenylphosphine)palladium(II)

A number of palladium(II) complexes with Ph3P and aromatic amines as ligands having the general formula [(Ph3P)Pd(Ph3P)(NH2R)Cl2] {where R = Ph (1), m-ClC6H4 (2), p-ClC6H5 (3)} and [Pd(CH3NHPh)Cl2] (4), have been synthesized and characterized by elemental analysis, IR, 1H and 13C NMR. The X-ray crystal structure of [(Ph3P)Pd(m-ClC6H4NH2)Cl2] · CH2 Cl2 (2) shows a distorted square planar environment around the Pd(II) ion with the P–Pd–N and Cl(1)–Pd–Cl(2) bond angles of 174.88(5)° and 176.77(2)° respectively. The complexes were screened for enzyme inhibition activity against β-glucuronidase and found to be active.

Phosphane-free C–C Heck couplings catalyzed by Pd(II) fluorinated aniline complexes of the type trans-[PdCl 2(NH 2Ar F) 2

A series of palladium fluoro-aniline complexes of the trans-[PdCl 2(NH 2Ar F ) 2] type were synthesized in good yields by direct reaction of trans-[PdCl 2(C 6H 5CN)] with Ar F NH 2; Ar F = C 6H 3-2,3-F 2 ( 1), C 6H 3-2,5-F 2 ( 2), C 6H 3-3,4-F 2 ( 3), C 6H 3-3,5-F 2 ( 4), C 6H 2-2,3,4-F 3 ( 5), C 6H 2-2,3,6-F 3 ( 6), C 6H 2-2,4,5-F 3 ( 7), C 6H 2-2,4,6-F 3 ( 8), C 6F 4-4-H ( 9), C 6F 5 ( 10). The crystal structures of complexes 3, 4 and 5 were determined. Heck coupling reactions were carried out using complexes 1–10 as catalysts in order to examine the effect of the fluorinated anilines in the reaction of bromobenzene and styrene.

35Cl NQR for the SbCl3 complex with aniline, SbCl3·NH2C6H5

The temperature dependence of the 35Cl NQR frequencies and spin-lattice relaxation times has been investigated for a trigonal-bipyramidal vn complex SbCl3·NH2C6H5. Thermally activated motion of chlorine atoms (pseudorotation) was not revealed in the complex, in contrast to the vπ complexes of SbCl3 with related molecular structures. The high potential barrier of pseudorotation in the aniline complex is likely to be due to the unusually high nonequivalence of Sb-Cl chemical bonds.

Synthesis, characterisation and properties of polyanilines containing transition metal ions

Polyanilines containing transition metal ions were synthesized by oxidizing the complex of aniline with the corresponding metal chloride in solution. The influence of the synthetic conditions such as reaction medium, the molar ratio of reactants, temperature and time on the polymer yield and electrical conductivity was discussed. The products were characterized by elemental analysis, FT-IR spectroscopy and in-situ UV/Vis spectroscopy. Scanning electron micrograph was employed to examine the morphology of polyanilines synthesized in the presence of different transition metals. Experimental results showed that transition metal ions had been successfully incorporated into the polymer, and there was a strong interaction between the transition metal ions and polyaniline chains. Thermogravimetric analysis demonstrated that the thermal stability of polyaniline containing transition metal ions was lower than that of emeraldine base of polyaniline.