Formamide Complexes Research Articles

Unveiling the Noncovalent Interactions between Formamide and Heteroaromatics: Microwave Spectroscopy of the Formamide Complexes with Furan and Thiophene.

The noncovalent interactions between formamide (FM) and the heteroaromatic compounds (furan and thiophene) were investigated through microwave spectroscopy and theoretical calculations. Each of the investigated complexes exhibits a single rotational spectrum corresponding to the lowest energy structure predicted theoretically. In the detected structures, N-H···O and C-H···O hydrogen bonds dominate the complexation between FM and furan, resulting in a planar configuration. Conversely, a superposed configuration linked by a N-H···π hydrogen bond and C═O···π contact is observed for the FM-thiophene complex. In both cases, hydrogen bonding interactions with N-H as proton donor rank as the dominant forces, and the interaction energy of N-H···O is larger than that of N-H···π. It was found that the electrostatic component is the largest contributor to the attraction between FM and furan, while the dispersion component is the most significant attractive factor in the FM-thiophene complex. These findings highlight the distinct features of hydrogen bonding interactions of amides with heteroaromatics in the studied complexes.

Weak hydrogen bonds between alkyl halides and amides: The microwave spectroscopic and theoretical study of the difluoromethane⋯formamide complex.

The pure rotational spectrum of the complex of difluoromethane with formamide was investigated by means of microwave spectroscopy supplemented with theoretical calculations. The hyperfine structure arising from the 14N nuclear quadrupole coupling effect was completely resolved. The most stable isomer that displays the Cs symmetry with the ∠HCH angle of difluoromethane being bisected by the ab-plane of formamide was detected. The two moieties in the detected isomer are connected via one N-H⋯F and one bifurcated CH2⋯O weak hydrogen bonds confirmed by the non-covalent interaction plot and natural bond orbital analyses. The distances of the NH⋯F and CH2⋯O interactions were determined to be 2.140(14) Å and 2.749(14) Å, respectively. The NH⋯F bond angle was determined to be 150.7°. Symmetry-adapted perturbation theory analysis indicates that the electrostatic component is the largest contributor to the total attractive interaction energy of the difluoromethane⋯formamide complex.

Actinyl-Modified g-C3N4 as CO2 Activation Materials for Chemical Conversion and Environmental Remedy via an Artificial Photosynthetic Route.

With the reported CO2 activation for the oxidation of benzene to phenol (-ENE → -OL) by the graphitic carbon nitride g-C3N4 (CN) via an artificial photosynthetic route as inspiration, high-valent actinyls (AnmO2)n+ (An = U, Np, Pu; m = VI, V; n = 2, 1) have been introduced for its further modification. Our calculations indicate thermodynamic spontaneity in the feasibility of g-C3N4-(AnmO2)n+ (CN-Anm) formation. The magnificent structural and electronic properties of CN-Anm are utilized for CO2 activation in terms of the rarely studied -ENE → -OL conversion. The calculated free energies show that most steps of the catalytic cycle are favored by CN-Anm complexes. The first step (carbamate formation) is slightly endothermic in all cases, where CN-U is 0.51 eV higher than CN and CN-Pu is -0.01 eV lower. All benzene addition reactions release energy, with that for CN-U being the lowest. The phenolate formation is favored by some actinyl complexes over CN, and CN-U is only 0.23 eV higher. The phenol release (resulting in formamide complexes) and CO desorption are exothermic for all CN-Anm. The overall process suggests the improved catalytic performance of actinyl-modified CN materials, and the slightly depleted uranyl-carbon nitride could be one of the promising catalysts.

The molecular electrostatic potential analysis of solutes and water clusters: a straightforward tool to predict the geometry of the most stable micro-hydrated complexes of β-propiolactone and formamide

High-resolution microwave spectroscopic studies have recently revealed the structures of six micro-hydrated complexes of β-propiolactone (BPL) as well as five micro-hydrated complexes of formamide. Complexes containing one to three water molecules were selected as model systems to set a methodological approach based on the study on the isolated partner for the identification of the most stable micro-hydrated complexes. A four-step study revealed to be particularly straightforward for the identification and characterization of water–solute complexes: (1) the topological analysis of isolated partners, to identify complementary interaction sites; (2) the proposal of possible preferable direction of approaches of both partners to allow multiple interactions between complementary interaction sites; (3) the full optimization of initial structures at the MP2 level of theory; and (4) the topological analysis of the water–solute intermolecular interactions. It is shown that the segregation of water molecules experimentally observed, the larger complexation energy of X:(H2O)n for X = formamide rather than BPL, and the larger complexation energy of the dimers compared to the monomers and the trimers could be related to the molecular electrostatic potential of isolated partners.

Molecular Dynamics Simulation of Basal Spacing, Energetics, and Structure Evolution of a Kaolinite-Formamide Intercalation Complex and Their Interfacial Interaction.

Molecular dynamics simulations were performed on kaolinite-formamide complex models with various numbers of formamide molecules loaded in the kaolinite interlayer to explore the basal spacing, energetics, and structure evolution of the kaolinite-formamide complex during the intercalation process. Additionally, the interfacial interactions of formamide with kaolinite interlayer surfaces were calculated. The calculation revealed that the basal spacing of kaolinite was enlarged to 9.6 Å at the beginning of intercalation. Formamide was arranged as a monolayer structure in the kaolinite interlayer with the molecular plane oriented at small angles with respect to the interlayer surface. With continuous intercalation, the basal spacing readily reached a stable stage at 10.6 Å, where formamide rearranged its structure by rotating the molecule plane along the C-N bond that was parallel to the interlayer surface, which resulted in the molecular plane orienting at higher angles with respect to the interlayer surface. During this process, the C═O groups oriented toward the hydroxyl groups on the interlayer octahedral surface, and one of N-H bonds progressively pointed toward the basal oxygens on the opposing interlayer tetrahedral surface. Continuous intercalation can enlarge the basal spacing to more than 14 Å with the prerequisite of overcoming the energy barrier, and then formamide evolved to a disordered bilayer structure in the kaolinite interlayer. The affinity of kaolinite interlayer surfaces for formamide motivated the intercalation process. The octahedral surface displayed a relatively larger affinity toward formamide compared to the tetrahedral surface partially due to the presence of hydroxyl groups that are more active in the intermolecular interactions with formamide.

Prediction of the rotational spectra of microsolvated complexes with low cost DFT methods

Some of the most used DFT methods together with MP2 have been tested using 6-311++G(d,p) and TZVP basis sets to probe their usefulness in prediction of the rotational spectra of several microsolvated complexes of formamide, t-N-methylformamide, glycine and β-propiolactone. Results obtained for the rotational parameters and the prediction of the spectra have been compared to experimental data previously measured by Fourier Transform Microwave Spectroscopy. Analysis of the standard deviation of the predicted rotational spectra for all the levels tested indicates that the methods which better approach to the MP2 results are mPW91LYP and B3LYP-D3.

Theoretical studies of weak interactions of formamide with methanol and its derivates

Theoretical calculations have been performed for the complexes of formamide (FA) with methanol and its derivates (MAX, X = F, Cl, Br, NO2, H, OH, CH3, and NH2) to study their structures and properties. Substituent effects on the hydrogen bond (H-bond) strength and cooperative effect by using water and its derivatives (HOZ, Z = H, NH2, and Br) as weak interaction probe were also explored. The calculation results show that electron-donating groups strengthen the weak interaction between formamide with methanol whereas electron-withdrawing groups weaken it. The cooperativity is present for the N-HiO H-bond in MAX-FA-HOZ and the cooperative effect increases in a series HONH2, HOH, and HOBr. In addition, we investigated the interaction between FA with hypohalous acids HOY (Y = F, Cl, and Br). It was found that the weak interaction between FA and HOY became stronger with the increase of the size of halogen atom. The nature of the halogen atom has negligible impact on the strength of the H-bond in MAX-FA (X = F, Cl, and Br), whereas it has an obvious influence on the strength of the H-bond in HOY-FA (Y = F, Cl, and Br).

Substituent effects in hydrogen bonding: DFT and QTAIM studies on acids and carboxylates complexes with formamide.

Four series of hydrogen bonded complexes of formamide and substituted benzoic acids and benzoates were studied in the light of substituent effect on intermolecular interactions. The analysis based on energy of interaction, geometry, QTAIM-derived properties of hydrogen bond critical point and energy of hydrogen bonds were made and discussed. The opposite effect of the substituent on hydrogen bond donor and acceptor in acid series was found and analyzed. The isodesmic reactions were used to further study the interaction preferences. Figureᅟ Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-014-2356-8) contains supplementary material, which is available to authorized users.

Hydrogen bond nature in formamide (CYHNH2···XH; YO, S, Se, Te; XF, HO, NH2) complexes at their ground and low‐lying excited states

A theoretical study on the nature of hydrogen bond for formamide and its heavy complexes (CYHNH2···XH; YO, S, Se, Te; XF, HO, NH2) was performed on the basis of density functional theory and the quantum chemistry analysis. Except for the CYHNH2···NH3 complexes, the substitution of O atom at formamide with less electronegative atoms (S, Se, and Te) is found to weaken the hydrogen bond (H‐bond). This substitution results in cyclic structure of hydrated and ammoniated formamide complexes by the formation of bifunctional H‐bonds (Y···H4X; X···H3C). Natural bond orbital analysis indicates that the H‐bond is weakened because of less charge transfer from a lone pair orbital of H‐bond acceptor to antibonding orbital of H‐bond donor. The quantum theory of atoms in molecules analysis reveals that the acyclic structure with single H‐bond stabilizes the complexes more than the cyclic structure formed by bifunctional H‐bonds. Natural energy decomposition analysis (NEDA) and block‐localized wavefunction energy decomposition (BLW‐ED) analyses show that the H‐bond stabilization energies of NEDA and BLW‐ED have good correlation with the dissociation energy of formamide complexes and charge transfer from donor to acceptor atom play an important role in H‐bonding. We have also studied the low‐lying electronic excited states (T1, T2, and S1) for CYHNH2···H2O complexes to explore the nature of H‐bond on the basis of electronegativity and found that NEDA also establishes a good correlation with relative electronic energy (with respect to their ground state) and H‐bond strength at their excited states. Copyright © 2014 John Wiley & Sons, Ltd.

Zinc and cadmium iodide complexes with (thio)amides: Transformations of formamide complexes and effects of substitution on structure and bonding

Complexes of formamide and dimethylacetamide with cadmium iodide, [Cd(HCONH2)2I2], [Cd(HCONH2)4I2], [Cd3(HCONH2)2I6], and [Cd(MeCONMe2)6][Cd2I6] and of 5-acetyl-6-methyl-1,2,3,4-tetrahydropyrimidine-2-thione (MP) with zinc iodide, [Zn(MP)(H2O)I2], were synthesized; their crystal structures were studied by X-ray diffraction. Unique transformations of cadmium iodide complexes with formamide were observed. Structural diversity of zinc and cadmium iodide complexes with (thio)amides is discussed in terms of donating ability of the ligands, steric requirements and sizes and polarizing power of the cations.

Communication: Frequency shifts of an intramolecular hydrogen bond as a measure of intermolecular hydrogen bond strengths

Infrared-ultraviolet double resonance spectroscopy has been applied to study the infrared spectra of the supersonically cooled gas phase complexes of formic acid, acetic acid, propionic acid, formamide, and water with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. In these complexes each binding partner to 9HFCA can function as both proton donor and acceptor. Relative to its frequency in free 9HFCA, the 9-hydroxy (9OH) stretch is blue shifted in complexes with formic, acetic, and propionic acids, but is red shifted in the complexes with formamide and water. Density functional calculations on complexes of 9HFCA to a variety of H bonding partners with differing proton donor and acceptor abilities reveal that the quantitative frequency shift of the 9OH can be attributed to the balance struck between two competing intermolecular H bonds. More extensive calculations on complexes of glycolic acid show excellent consistency with the experimental frequency shifts.

Vibrational study on the solvates formed during interactions of amide with alkaline earth metal ions

We present in this paper very interesting vibrational data for formamide (FA) complexes with Mg and Ca ions. The νCO and νCN modes of FA are shifted to lower (45cm−1) and higher (30cm−1) wavenumbers, respectively, in the presence of Mg(II), whereas both modes are upshifted (∼15cm−1) as Ca(II) is present. The shifts observed for the system containing Mg(II) indicate that the HC−ON+H2 form is majority due to the coordination through the O atom. On the other hand, the HCONH2 form is dominant because of the coordination to Ca(II) via both O and N atoms. Such differences may be explained based on the ionic radii of Mg and Ca, which lead to the formation of FA complexes with coordination numbers equal to 6 and 8, respectively. The results here presented may help us for a better understanding about amide bond hydrolysis reactions catalyzed by metal ions, since the ionic and molecular FA forms have been recognized as active and inactive intermediates, respectively, in the hydrolysis mechanisms proposed so far.

Experimental and theoretical study on the 1:1 supramolecular complexes of formamide with adrenaline

The electron transfer properties were investigated for supramolecular complexes of formamide (FA) with adrenaline (Ad) at graphite electrode and paraffine soaked graphite electrode using cyclic voltammetry (CV). The experimental results show that FA affected the electron transfer properties of Ad. The formed supramolecular complexes by hydrogen bond (H-bond) interaction between FA and Ad slowed down the diffusion ability of adrenaline, which makes it hard to donate electron and be oxidized.The H-bond interaction energies calculation for the supramolecular complexes of FA with Ad at MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) level have also been performed. The calculational results confirm the experimental fact that FA can form stable supramolecular complexes with Ad.

Electron collisions with hydrogen-bonded complexes

We investigated elastic collisions of low-energy electrons with the hydrogen-bonded formic-acid dimer, formamide dimer, and formic-acid--formamide complex. We focused on how the ${\ensuremath{\pi}}^{*}$ shape resonances of the isolated monomers are affected when bonded to another molecule. The scattering cross sections were computed with the Schwinger multichannel method with pseudopotentials in the static-exchange and static-exchange-plus-polarization approximations, for energies ranging from 1 to 6 eV. The present results support the existence of two low-lying ${\ensuremath{\pi}}^{*}$ shape resonances for the formic-acid dimer, as suggested in previous theoretical and experimental studies. We also found low-lying ${\ensuremath{\pi}}^{*}$ shape resonances for the formamide dimer and for the formic-acid--formamide complex. For the dimers, the presence of a center of inversion is key to understanding how these resonances arise from linear combinations of the ${\ensuremath{\pi}}^{*}$ anion states of the respective monomers. For the formic-acid--formamide complex, the resonances are more localized on each unit, lying at lower energies with respect to the isolated monomers. The present results suggest that if there is no delocalization of the ${\ensuremath{\pi}}^{*}$ resonances over the pair for hydrogen-bonded molecules, then their positions would lie below those of the units.

A Mild and Efficient Route to 2-Azetidinones Using the Cyanuric Chloride-DMF Complex

Efficient conversion of Schiff bases and carboxylic acids to β-lactams can be carried out at room temperature in CH2Cl2, using a cyanuric chloride-N,N-dimethyl formamide complex. The complex is easily prepared by reaction of cyanuric chloride and DMF, an inexpensive reagent, at room temperature. Optimization of conditions and comparison of yield with cyanuric chloride were performed.

Strength and Nature of Hydrogen Bonding Interactions in Mono- and Di-Hydrated Formamide Complexes.

In this work, mono- and di-hydrated complexes of the formamide were studied. The calculations were performed at the MP2/6-311++G(d,p) level of approximation. The atoms in molecules theory (AIM), based on the topological properties of the electronic density distribution, was used to characterize the different types of bonds. The analysis of the hydrogen bonds (H-bonds) in the most stable mono- and di-hydrated formamide complexes shows a mutual reinforcement of the interactions, and some of these complexes can be considered as "bifunctional hydrogen bonding hydration complexes". In addition, we analyzed how the strength and the nature of the interactions, in mono-hydrated complexes, are modified by the presence of a second water molecule in di-hydrated formamide complexes. Structural changes, cooperativity, and electron density redistributions demonstrate that the H-bonds are stronger in the di-hydrated complexes than in the corresponding mono-hydrated complexes, wherein the σ- and π-electron delocalization were found. To explain the nature of such interactions, we carried out the atoms in molecules theory in conjunction with reduced variational space self-consistent field (RVS) decomposition analysis. On the basis of the local Virial theorem, the characteristics of the local electron energy density components at the bond critical points (BCPs) (the 1/4∇ (2)ρ(b) component of electron energy density and the kinetic energy density) were analyzed. These parameters were used in conjunction with the electron density and the Laplacian of the electron density to analyze the characteristics of the interactions. The analysis of the interaction energy components for the systems considered indicates that the strengthening of the hydrogen bonds is manifested by an increased contribution of the electrostatic energy component represented by the kinetic energy density at the BCP.

Structure and hydrogen bond vibrations of the jet-cooled 1:1 complex between 7-azaindole and formamide: A laser-induced fluorescence spectroscopy study

Laser-induced fluorescence spectra of 7-azaindole ⋯ formamide complex are measured in a supersonic free jet expansion. Calculation at MP2/6-311++G ∗∗ level predicts a cyclic doubly hydrogen-bonded structure for the complex is favoured most in the ground state. The complex emits only UV fluorescence from the locally excited state and tautomerization is inhibited under the jet-cooled environment. This photophysical behavior is consistent with the predictions of CIS/6-311++G ∗∗ and TDDFT/6-311++G ∗∗ calculations. The low-frequency bands in the fluorescence spectra are assigned to different hydrogen bond modes of the complex, and the spectra reveal signatures of mixing between inter- and intra-molecular vibrational modes in the excited state.

Chemo- and stereospecific solid-state dimerization of lithium trans-2-butenoate and lithium trans-2-butenoate formamide solvate

60Co γ-irradiation of both lithium trans-2-butenoate (11) and lithium trans-2-butenoate·formamide (12) affords the same dimer, dilithium trans-5-methyl-2-heptenedioate (13). However, stereochemical analysis of products 22 and 24 from the analogous trans-2-butenoate-2-d salts 21 and 23 established that C–C and C–H bond formation occur stereospecifically by syn addition to the double bond in lithiumtrans-2-butenoates 11 and 21 and anti addition to the double bond in lithium trans-2-butenoate·formamide complexes 12 and 23. These reactions, which provide an unprecedented, chemospecific one step synthesis of dicarboxylate 13, add significantly to the synthetic scope of the γ-ray induced reactions of crystalline metal trans-2-butenoates that lead to cyclic and acyclic dimers and acyclic trimers by γ-ray initiated radical chain reactions. The stereochemistry of products 22 and 24 is that predicted by analysis of crystal packing, consistent with least-motion principles of the topochemical postulate as shown in Fig. 12 and 13. Analysis of the crystal structures, with respect to nearest neighbors, is consistent with the hypothesis that formation of carbon–carbon bonds in propagation step 1 and hydrogen atom transfer in propagation step 2 are topochemical and controlled by the crystal lattice. Analysis of the packing diagrams provides a pathway for chain propagation throughout the crystal that consumes all the molecules in the unit cell. The dimerization of 12 is much more rapid and proceeds in much higher yield than that of 11, probably as a result of significantly shorter C⋯C contacts and a more robust pathway for hydrogen transfer.

Accounting for non-optimal interactions in molecular recognition: a study of ion–π complexes using a QM/MM model with a dipole-polarisable MM region

For a quantitative understanding of molecular structure, interaction and dynamics, accurate modelling of the energetics of both near-equilibrium and less optimal contacts is important. In this work, we explore the potential energy surfaces of representative ion-π complexes. We examine the performance of a semi-empirical QM/MM approach and the corresponding QM/MMpol model, where inducible point dipoles are additionally employed in the MM region. The predicted potential energy surfaces of cation-benzene complexes are improved by inclusion of explicit MM polarisation of the π-molecule. For cation-formamide complexes, inducible dipoles appreciably improve energetic estimates at geometries forming non-optimal interactions. Energetic component analysis suggests that the implicit MM polarisation of the fixed charge QM/MM model mirrors the behaviour of the QM/MMpol dipole model for the energetics of near-equilibrium conformations. However, for complexes at less optimal orientations, the QM/MM model exhibits higher errors than the QM/MMpol approach, being unable to capture orientation-dependent variations in polarisation energy.

Monitoring the 1160 cm−1 band of pyridazine to investigate complexes with formamide

Hydrogen bonding between pyridazine (PRD) and formamide (FA) molecules has been investigated both experimentally by Raman spectroscopy on their binary mixtures and theoretically by DFT calculations on various gas-phase PRD:FA clusters. The band at 1160cm−1 of PRD was used for the first time as a marker for monitoring the degree of complexation. Upon dilution with FA, a new band at 1169cm−1 is observed and attributed to hydrogen-bonded PRD. The Raman experiments were complemented by DFT calculations and the corresponding structures, vibrational spectra and binding energies were determined. The most stable species were found to be the 1:2 PRD:FA complexes and such stoichiometry is in excellent agreement with the experimental determination. The shift to higher frequency observed to the prominent modes of PRD may be related to a shortening of the NC and CC bonds, upon complexation, which causes a decrease in the electron delocalization in PRD ring.