Hydrogen-bonded Dimers Research Articles

Density functional theory studies on a non-covalent interaction system: hydrogen-bonded dimers of zoledronate.

A computational study was carried out to characterize the hydrogen-bonded dimers of Zoledronate (ZOL), which is used widely in treating skeletal diseases. The stable conformations, hydrogen bonding interactions, IR spectra, thermodynamic properties, and electronic characteristics of nine possible ZOL dimers were studied using density functional theory (DFT) at the B3LYP/6-311++G** level. The stability of dimers was determined according to the analyses of total electronic energies and hydrogen bonding interactions. The results showed that both the number and intensity of hydrogen bonds played an important role in determining the stability order of dimers, and the hydrogen bonding interactions in dimers resulted in a red shift of hydroxyl vibration with a corresponding increase in intensity. The calculated thermodynamic properties illustrated that the dimerization process can take place spontaneously at room temperature. Natural bond orbital and atoms in molecules analyses revealed that the nature of hydrogen bonding interactions was attributed to the interactions from lone pair orbital n(A) to the antibonding orbital σ*(D-H), and the interactions were closed-shell interactions in hydrogen-bonded dimers of ZOL. Graphical abstract Changes in Gibbs free energy and infrared spectra of ZL in the dimerization process.

Insight into the interaction between hydrogen bonds in brown coal and water

The hydrogen bonds between water and oxygen-containing functional groups are key factors controlling water re-adsorption and drying behaviour of brown coal. However, the changes of hydrogen bonds are hard to investigate because of the overlap of H2O IR vibration bands with those due to coal hydrogen bonds. Thus, D2O was innovationally used instead of H2O to interact with brown coal. The interaction between re-adsorbed water and the hydrogen bonds of brown coal was investigated by studying the IR spectra changes and the release of D2O, HDO, H2O and CO2 during drying of brown coals containing adsorbed D2O. The Gibbs free energies of reactions involving hydrogen bonds were calculated to complement the findings of IR measurements. The effect of re-adsorbed water on hydrogen bonds of brown coal and the interaction among them during drying process were revealed for the first time. The results show that the OH–π and COOH dimer hydrogen bonds in dried brown coal are easily disrupted by re-adsorbed water. During the brown coal drying process, the re-adsorbed water cannot be completely removed, but some of it participates in the rearrangement of hydrogen bonds. The remaining re-adsorbed water is hydrogen-bonded to the free OH and free COOH groups at higher temperature. The free OH groups are obtained from the decomposition of cyclic OH tetramer and OH–ether hydrogen bonds, and the free COOH groups from the disruption of COOH dimer disrupted by re-adsorbed water. The self-associated n-mers (n > 3) and OH–N hydrogen bonds are formed during the brown coal drying process. The infrared peak positions of COD bonds formed by D2O molecules bonded to free OH groups and free COOH groups are found to be 2575 and 2490 cm−1, respectively. Some O–D bonds remain intact at temperatures as high as 330 °C. Thus in situ DRIFT spectrum analysis combined with isotopic substitution provides a rapid and direct method for research on water behaviour in brown coal.

Stable Mixed-Valent Complexes Formed by Electron Delocalization Across Hydrogen Bonds of Pyrimidinone-Linked Metal Clusters.

Electron transfer across a mixed-valent hydrogen-bonded self-dimer of oxo-centered triruthenium clusters bridged by a pair of 4(3 H)-pyrimidinones is reported. Spectroelectrochemical studies in methylene chloride reveal that 1 rapidly self-dimerizes upon one-electron reduction, forming the strongly coupled mixed-valent hydrogen-bonded dimer (12)-. In the mixed-valent state, significantly broadened, partially coalesced ν(CO) bands are observed, allowing estimation of the electron transfer rate ( kET) by an optical Bloch line shape analysis. Simulation of the FTIR line shapes provides an estimate of kET on the order of 1011 s-1, indicating a highly delocalized electronic structure across the hydrogen bonds. These findings are supported by the determination of the formation constant ( KMV) for (12)-, which is found to be on the order of 106 M-1, or nearly 4 orders of magnitude higher than that for the neutral isovalent dimer (12). This represents a stabilization of approximately 5.7 kcal/mol (1980 cm-1) arising from electron exchange across the hydrogen bonds in the mixed-valent state. Significantly, an enormous intensity enhancement of the amide ν(NH) band (3300 cm-1) of (12)- is observed, supporting strong mixing of the bridging ligand vibrational modes with the electronic wave function of the mixed-valent state. These findings demonstrate strong donor-bridge-acceptor coupling and that highly delocalized electronic structures can be attained in hydrogen-bonded systems, which are often considered to be too weakly bound to support strong electronic communication.

Compound-model morphed potential for the hydrogen bond HCN⋯HF

ABSTRACTA 5-D compound-model morphed potential has been generated for the prototype hydrogen-bonded dimer HCN⋯HF. The potential includes the intermolecular degree of freedom and the HF stretching vibration. Only five morphing parameters are optimised, correcting for inadequacies in the underlying ab initio potentials. Band origin fundamental vibrational frequencies are fitted to an average absolute error of 0.01 cm−1. The calculated value of the ground state dissociation energy, D0 = 1969 cm−1, is in excellent agreement with the experimental value of 1970(10) cm−1 [Oudejans and Miller, Chem. Phys. 239 (1998) 345]. Additional vibrational frequencies are predicted with an average absolute error of 1.61 cm−1. Application of the morphing methodology to characterise hydrogen-bonded complexes is discussed.

Graphene-induced bi-tilted two-component smectic CG phase with bulk ferroelectricity in hydrogen-bonded dimer liquid crystals

Nanocomposites of the hydrogen-bonded dimeric liquid crystal heptyloxybenzoic acid (7OBA) with admixture of graphene flakes (GFs) are investigated with microtexture polarization analysis for new effects in their electro-optical behavior and characterized with Raman spectroscopy. In the nanocomposite with GF concentration of 3 × 10−4 wt% we establish as lowest-temperature LC state the triclinic smectic CG phase featuring chirality and ferroelectricity, previously found only in 7OBA nanocomposites with carbon nanotubes and in large banana-like bent-core molecules even though pure 7OBA is typically achiral. In the present study we find the CG phase manifested as two detached sub-structures with a smooth transition between them. For the appearance of the CG phase with its substructures denoted as CGcl and CGln we propose an explanation based on the π–π interaction of the 7OBA molecules with graphene and different coupling combinations of the clinic and leaning degree of freedom of the doubly tilted molecular geometry in the CG ordering. We examine the response of these structures to electric field, and demonstrate the presence in both of them of ferroelectric polarization with polar vector pointing out of the smectic layer planes. Molecular models are proposed for the 7OBA ordering in the substructures CGcl and CGln which are supported by the Raman spectroscopy results. The dispersion of the GFs in the nanocomposite bulk is confirmed by scanning electron microscopy in the solid state.

Energy Decomposition Analysis for Excimers Using Absolutely Localized Molecular Orbitals within Time-Dependent Density Functional Theory and Configuration Interaction with Single Excitations.

We present an improved energy decomposition analysis (EDA) scheme for understanding intermolecular interactions in delocalized excited states, especially in excimers. In the EDA procedure, excited states are treated with linear response theory such as configuration interaction singles (CIS) or time-dependent density functional theory (TDDFT), and absolutely localized molecular orbitals (ALMOs) are used to define the intermediate (frozen, excitonic coupling, and polarized) states. The intermolecular interaction energy is thereby separated into frozen, excitonic splitting, polarization, and charge transfer contributions. The excitonic splitting term describes the delocalization effect as two or more degenerate local excitations coupled with each other, which is often an important binding force in excimers. A maximum overlap state-tracking procedure is introduced to connect the initial fragment excitations to the constrained intermediate states and finally to the unconstrained delocalized states of the complex. The EDA scheme is applied to several excimer systems, including the He2* and Ne2* noble gas excimers, the doubly hydrogen-bonded 2-pyridone dimer, and the aromatic benzene and perylene excimers. We are able to gain some useful insights into the role each term is playing in the formation of these excimers, and the resulting method may also be useful for understanding a range of other complexes in excited states.

Di-μ-chlorido-bis[chlorido(dimethylformamide-κN)(3,5-diphenyl-1H-pyrazole-κN2)copper(II)

The title compound, [Cu2Cl4(C15H12N2)2(C3H7NO)2], Cu2(μ-Cl)2Cl2(3,5-diphenyl-1H-pyrazole)2(DMF)2, where DMF isN,N-dimethylformamide, crystallizes in the monoclinic space groupP21/n. The five-coordinate CuIIions have a distorted square-pyramidal geometry and are joinedviatwo μ-Cl anions. The coordination environment of each CuIIion is completed by a terminal chloride anion, a nitrogen-coordinated 3,5-diphenyl-1H-pyrazole molecule, and a DMF molecule. Two intramolecular hydrogen bonds exist in the molecule as the H atom of the protonated N atom of the 3,5-diphenyl-1H-pyrazole bonds to a terminal chloride anion of the adjacent CuIIcation. In addition, molecules are linked into a two-dimensional sheetviaweak C—H...Cl intermolecular hydrogen bonds. Each dimer hydrogen bonds to four neighboring molecules as the H atom of the C atom in the fourth position of the pyrazole ring bonds to a μ-Cl on a neighboring molecule.

Crystal structure analysis of [5-(4-meth-oxy-phen-yl)-2-methyl-2H-1,2,3-triazol-4-yl](thio-phen-2-yl)methanone.

The title compound, C15H13N3O2S, crystallizes in the monoclinic space group P21/n and its mol-ecular conformation is stabilized via intra-molecular C-H⋯O and C-H⋯N contacts. The supra-molecular structure is mainly governed by C-H⋯N hydrogen-bonded centrosymmetric dimers, C-H⋯O and C-H⋯S hydrogen bonds and S⋯π and π-π stacking inter-actions which, together, lead to the formation of a layered crystal packing. The inter-molecular inter-actions were further evaluated through the mol-ecular electrostatic potential map and Hirshfeld fingerprint analysis.

Benchmarking of the R-7 Anisotropic Dispersion Energy Term on the S22 Dimer Test Set.

The effects of including the anisotropic E7 term to the dispersion energy in addition to the leading E6 term are examined by using the effective fragment potential (EFP) method on the S22 test set. In this study, the full anisotropic E7 term is computed whereas the isotropic and spherical approximations are used for the E6 term. It is found that the E7 term is positive for hydrogen-bonded complexes and has a magnitude that can be as large as 50% of E6, giving rise to larger intermolecular distances than those obtained with E6 alone. The large positive value of E7 is analyzed for the hydrogen-bonded uracil dimer; it is found to originate from the large magnitude of the dynamic polarizability tensors as well as the proximity of the LMOs involved in hydrogen bonding. Conversely, E7 tends to be negative for dispersion-dominant complexes, and it has a very small magnitude for such complexes. The optimized geometries for these systems are therefore not greatly affected by the presence of the E7 term. For the mixed systems in the S22 test set, an intermediate behavior is observed. Overall, the E7 term is most important for systems with hydrogen bonding interactions and mixed systems. A full anisotropic treatment of the E6 term and higher order terms may need to be included to obtain more accurate interaction energies and geometries.

An efficient water force field calibrated against intermolecular THz and Raman spectra.

A polarizable water model is presented which has been calibrated against experimental THz and Raman spectra of bulk water. These low-frequency spectra directly probe the dynamics, and thereby intermolecular interactions, on time scales relevant to molecular motions. The model is based on the TL4P force field developed recently by Tavan and co-workers [J. Phys. Chem. B 117, 9486 (2013)], which has been designed to be transferable between different environments; in particular, to correctly describe the electrostatic properties of both the isolated water molecule in the gas-phase and the liquid water at ambient conditions. Following this design philosophy, TL4P was amended with charge transfer across hydrogen-bonded dimers as well as an anisotropic polarizability in order to correctly reproduce the THz and Raman spectra. The thermodynamic and structural properties of the new model are of equal quality as those of TL4P, and at the same time, an almost quantitative agreement with the spectroscopic data could be achieved. Since TL4P is a rigid model with a single polarizable site, it is computationally very efficient, while the numerical overhead for the addition of charge transfer and the anisotropic polarizability is minor. Overall, the model is expected to be well suited for, e.g., large scale simulations of 2D-Raman-THz spectra or biomolecular simulations.

Evaluation of N-H...S and N-H...π interactions in O,O'-diethyl N-(2,4,6-trimethylphenyl)thiophosphate: a combination of X-ray crystallographic and theoretical studies.

In the crystal structure of O,O'-diethyl N-(2,4,6-trimethylphenyl)thiophosphate, C13H22NO2PS, two symmetrically independent thiophosphoramide molecules are linked through N-H...S and N-H...π hydrogen bonds to form a noncentrosymmetric dimer, with Z' = 2. The strengths of the hydrogen bonds were evaluated using density functional theory (DFT) at the M06-2X level within the 6-311++G(d,p) basis set, and by considering the quantum theory of atoms in molecules (QTAIM). It was found that the N-H...S hydrogen bond is slightly stronger than the N-H...π hydrogen bond. This is reflected in differences between the calculated N-H stretching frequencies of the isolated molecules and the frequencies of the same N-H units involved in the different hydrogen bonds of the hydrogen-bonded dimer. For these hydrogen bonds, the corresponding charge transfers, i.e. lp (or π)→σ*, were studied, according to the second-order perturbation theory in natural bond orbital (NBO) methodology. Hirshfeld surface analysis was applied for a detailed investigation of all the contacts participating in the crystal packing.

Controlling Self-Assembly of Switchable Azobenzene Derivatives on Highly Oriented Pyrolytic Graphite at Ambient Conditions

Ultrathin films prepared at the solid/air interface of azobenzene (AB), 4-(phenylazo) benzoic acid (PABA), 3,4′-azodibenzoic acid (meta-ADB), and 4,4′-azodibenzoic acid (para-ADB) have been studied on highly oriented pyrolytic graphite using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). While AB molecules form compact herringbone pattern stabilized via van der Waals interaction, AB derivatives with carboxyl groups show patterns formed through strong dimeric hydrogen bonds. Depending on the numbers and the positions of carboxyl group(s), we show that the assembly can be controlled at a global level. Due to the right balance of weak and strong intermolecular interactions, PABA molecules show a unique growth at global levels. meta/para-ADB molecules form chains stabilized through carboxyl groups; however, possible adsorption-induced isomers influence the growth behavior and restrict it to limited size on the surface.

Schiff base of isoniazid and ketoprofen: synthesis, X-ray crystallographic, spectroscopic, antioxidant, and computational studies

Ketoprofen and isoniazid together are a potential combination of a nonsteroidal antiinflammatory drug and an antitubercular medicine to treat tuberculosis and associated symptoms like fever and fatigue. The Schiff base of isoniazid with ketoprofen is synthesized in this research. Infrared spectroscopy (IR) and X-ray diffraction (XRD) analysis of the crystal packing proved the formation of the Schiff base and the existence of N-H$\cdot \cdot \cdot $O hydrogen bonds between the hydrogen-bonded dimer of the Schiff base. The complete geometrical optimization of the monomer and hydrogen-bonded dimer of the Schiff base is performed utilizing M06-2X/6-31G(d,p) level theory and compared with the experimental data to optimize the molecular structure. The effect of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity shows that the synthesized Schiff base has improved antioxidant activity. Molecular docking studies against Mycobacterium tuberculosis (Mtb) RNA polymerase-related targets with PDB codes 2M6O and 4KBJ and lung surfactant protein A (SP-A) with PDB ID 5FFT suggest that it can be screened as a potent drug against Mtb infection of the lungs. Frontier orbital theory analysis shows a high energy gap between the HOMO and LUMO, which suggests that the reported Schiff base might be a bioactive compound. Different experimental (XRD, IR, thermal gravimetric analysis, differential scanning calorimetry) and computational studies correlate and validate findings related to this novel Schiff base.

2-(Hydroxyimino)aldehydes: Photo- and Physicochemical Properties of a Versatile Functional Group for Monomer Design.

In the context of our research on stimuli-responsive polymers bearing the 2-(hydroxyimino)aldehyde (HIA) group, we have explored the photochemical behavior and physicochemical properties of a number of HIAs. Interpretation of the experimental data is supported by quantum mechanical calculations. HIAs are expected to undergo photoisomerization, chelate metal ions, yield hydrogen-bonded dimers or oligomers, exhibit relatively low pKa s, and form >C=NO. radicals through OH hydrogen abstraction or oxidation of the oximate ion. Besides the well-established E/Z oxime photoisomerism, we observed a Norrish-Yang cyclization resulting in cyclobutanol oximes, to our knowledge not previously described in the literature. The acidity, bond dissociation enthalpies, and electrochemical properties of the HIAs are compared with literature data of simple oximes. The results are discussed in relation to the many potential applications for HIAs, with emphasis on the synthesis of novel HIA-containing responsive polymers.

Synergistic Effects of Conjugation and Polarization on Dual Amide Hydrogen-bonding in CCl4: Theory and Experiment

The doubly hydrogen-bonded dimer of pyrrolidinone (γ-lactam) is used as a benchmark for the effect of conjugation on the strength and extent of hydrogen-bonding of the compounds Oxindole and Isoxindole. The experimental portion of this project consists of collecting the FTIR spectrum of γ-lactam, Oxindole and Isoxindole in CCl4. The concentrations and temperatures were varied to determine the thermodynamic properties of ΔHd, ΔSd and Kd. In addition, the spectroscopic parameters of the difference of the monomer and dimer N-H stretching frequencies (Δν) and the ratio of the molar extinction coefficients of the dimer and monomer (ed/em) are experimentally determined. The values of ΔHd, ΔSd, Δν and ed/em are computed using MP2 and B3LYP methods with 6-31G** and 6-31+G** basis sets. The experimental values are best described by B3LYP/6-31G**with the incorporation of the dielectric effect (PCM) of CCl4. The experimental and computational results support the results of increased or decreased hydrogen-bond strength due to conjugation effects on the polarization of the monomers in forming dimers.

Local energy decomposition analysis of hydrogen-bonded dimers within a domain-based pair natural orbital coupled cluster study.

The local energy decomposition (LED) analysis allows for a decomposition of the accurate domain-based local pair natural orbital CCSD(T) [DLPNO-CCSD(T)] energy into physically meaningful contributions including geometric and electronic preparation, electrostatic interaction, interfragment exchange, dynamic charge polarization, and London dispersion terms. Herein, this technique is employed in the study of hydrogen-bonding interactions in a series of conformers of water and hydrogen fluoride dimers. Initially, DLPNO-CCSD(T) dissociation energies for the most stable conformers are computed and compared with available experimental data. Afterwards, the decay of the LED terms with the intermolecular distance (r) is discussed and results are compared with the ones obtained from the popular symmetry adapted perturbation theory (SAPT). It is found that, as expected, electrostatic contributions slowly decay for increasing r and dominate the interaction energies in the long range. London dispersion contributions decay as expected, as r−6. They significantly affect the depths of the potential wells. The interfragment exchange provides a further stabilizing contribution that decays exponentially with the intermolecular distance. This information is used to rationalize the trend of stability of various conformers of the water and hydrogen fluoride dimers.

Towards the synthesis of prenylated phloroglucinol derivatives: An X-ray crystallographic and DFT study of unexpected reaction products

Owing to their bioactivity and prevalence in medicinal plant extracts, prenylated phloroglucinols have garnered significant interest. Towards the synthesis of prenylated phloroglucinol derivatives, 2,4,6-trihydroxy-3-(3-methylbut-2-enyl)acetophenone is required as an intermediate. Herein, this was synthesised by a tandem Claisen-Cope rearrangement reaction on 2,4-bis(methoxymethoxy)-6-(3-methylbut-2-enyloxy)acetophenone and a subsequent hydrolysis to remove protecting groups. This reaction yielded the desired product as well as three by-products. Two of these by-products were isomeric chromane derivatives (2 and 3) and the third was a methoxy derivative (4). These compounds have been studied by single crystal X-ray crystallography and DFT methods. Compound (2) crystallised in the P21/c space group with two hydrogen-bonded molecules in the asymmetric unit (Z = 8). Compound (4) crystallised in the Pbca space group with a single molecule in the asymmetric unit (Z = 8). Both compounds formed extensive supramolecular structures supported by hydrogen bonds in the solid state. Compound (2) forms a simple one-dimensional hydrogen-bonded chain co-linear with the a-axis. Compound (4) forms a two-dimensional supramolecular structure comprising “pentameric” hydrogen-bonded motifs linked by additional H-bonds to form the supramolecular structure. Both structures showed intramolecular hydrogen bonds between the acetyl oxygen and adjacent OH group. DFT simulations were used to probe the relative energies of the molecules and hydrogen bonds. These simulations showed that the intramolecular hydrogen bond has a substantial stabilising effect with an interaction strength of 70.64 kJ mol−1. The formation of the hydrogen-bonded dimer of (2) from which the supramolecular structure is formed has a ΔHassoc constant of −42.32 kJ mol−1, illustrating that the formation of the hydrogen-bonded structure is energetically favourable.

DFT-SAPT Intermolecular Interaction Energies Employing Exact-Exchange Kohn-Sham Response Methods.

Intermolecular interaction energies have been calculated by symmetry-adapted perturbation theory based on density functional theory monomer properties (DFT-SAPT) employing response functions from time-dependent exact-exchange (TDEXX) kernels. Combined with a new asymptotic correction scheme for the exchange-correlation (xc) potentials of the monomers, which is similar in its performance to standard asymptotic correction methods, it is shown that this DFT-SAPT[TDEXX] method delivers highly accurate intermolecular interaction energies for the S22, S66, and IonHB benchmark databases by Hobza et al. A corresponding DFT-SAPT approach employing the adiabatic TDEXX kernel in the response calculations has also been tested. This DFT-SAPT[ATDEXX] method performs almost as well as DFT-SAPT[TDEXX] for dispersion-dominated dimer systems but less accurately for hydrogen-bonded dimers. Compared to this, DFT-SAPT[TDEXX] yields a balanced description of the interaction energies for various interaction-type motifs, similar to the standard DFT-SAPT method that utilizes the ALDA xc kernel to compute the response functions.

Highly accurate equilibrium structure of the C2h symmetric N1-to-O2 hydrogen-bonded uracil-dimer

The highly accurate ab initio equilibrium geometry of the hydrogen-bonded uracil dimer is derived using a composite geometry extrapolation scheme based on all-electron, complete basis set extrapolated Møller–Plesset perturbation theory using the jun-pwCV[T,Q]Z basis sets combined with a valence CCSD(T)/cc-pVTZ high-level correction. Geometrical changes on dimerization are discussed and the performance of the several density functional approximations (among others SCAN, ωB97M-V, DSD-PBEP86-D3(BJ), and DSD-PBEP86-NL) is evaluated. Orbital-optimized MP2.5 is discussed as a reduced-cost alternative to the CCSD(T) gradient in the composite scheme. A new reference interaction energy is calculated with explicitly correlated F12-CCSD(T).

Spectroscopic investigation on structure (monomer and dimer), molecular characteristics and comparative study on vibrational analysis of picolinic and isonicotinic acids using experimental and theoretical (DFT & IVP) methods

In this investigation, the monomeric structure is determined for picolinic and isonicotinic acids based on geometry optimization for one of the four possible conformers and intramolecular hydrogen bond of OH⋯O using density functional theory (DFT) employing B3LYP functional supplemented with 6–311++G(d,p) basis set. Using this optimized monomeric form, the dimer structure is determined based on minimum energy and length of hydrogen bonds obtained for two possible dimeric forms yielded due to head-to-tail intermolecular OH⋯N hydrogen bond (dimer 1) linkage and tail-to -tail intermolecular OH⋯O hydrogen bond (dimer 2) linkage between pyridine ring and carboxyl group. The structure parameters obtained for monomer and dimer forms are in good agreement with the experimental literature values. The vibrational assignments have been made unambiguously for all the vibrations from FTIR and FT-Raman spectra based on the potential energy distribution (PED) and eigen vectors obtained in DFT and inverse vibrational problem (IVP) computations. The rms error between the observed and scaled frequencies is 7.7 and 9.4 cm−1 for PIA and INA, respectively. A 74-element modified valence force field is derived by Wilson's GF matrix method using 58 experimental frequencies of the two molecules in overlay least-squares technique. The average error between observed and computed frequencies by this method is calculated to be 10.39 cm−1. The results of both DFT and IVP computations yielded good agreement between observed and calculated frequencies. The NLO behaviour using hyperpolarizability values; and HOMO and LUMO energies; of the two molecules are investigated by DFT. Charge density distribution and site of chemical reactivity of the molecules are studied by molecular electrostatic surface potential (MESP). Stability of the molecules arising from hyper conjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The 13C and 1H NMR chemical shifts of the molecules are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. UV–visible (UV–Vis) spectra of the compounds are also recorded in the region 200–400 nm. Thermodynamic parameters and rotational constants are also determined and found that they are comparable with experimental literature values for these molecules.