Basis Set Level Research Articles

Iodonium Polyiodide Crystals in the Framework of Periodic Calculations with Localized Atomic Basis Sets

Methodological features of the crystal structure modeling for compounds with three-center halogen bond formed by two electron donors S–I+–S in polyiodide crystals were considered within the framework of periodic calculations based on localized atomic orbitals. The analysis of applying the different basis sets, effective core potentials, density functional theory functionals, and Grimme dispersion corrections revealed their effect on the geometric, electronic and vibrational properties obtained in calculations. Distribution of S-I bond lengths in S–I+–S fragment was analyzed. The effect of hybrid functional was demonstrated in the significant elongation of S-I distance. The treatment of dispersion interactions via Grimme approach did not significantly influence obtained results. The calculated vibration modes in medium wavenumber region of characteristic cationic stretching vibrations were validated according to experimental Raman spectra and were found to be in good agreement for C-N, C-C and C=S stretching vibrations. Small-core effective potential was shown to be effective for representation of bond lengths in S–I+–S fragment and gave reasonable results for vibrational data for cationic stretching vibrations. Taking into account relativistic effect on the level of basis set led to fine reproducibility of S-I bond lengths although in polyiodides of complex structure it should be treated with caution due to possible incorrect representation of interanionic distances.

Synthesis, Antioxidant Activity and DFT Study of Some Novel N-Methylated Indole Incorporating Isoxazole Moieties

A novel series of indolyl isoxazole derivatives were synthesized and the structure of the products is confirmed on the basis of IR, 1H NMR, MS and analytical data. The synthesized compounds were evaluated for their antioxidant and anticancer activities. The results revealed clearly those compounds 4b and 4d exhibited better radical scavenging ability. The optimized structural parameters of all compounds was carried out at the B3LYP/6-311++G (d, p) level of DFT basis set implemented in Gaussian 09 program package. Theoretical calculation of the title compounds were carried out using density functional theory method (DFT).

Molecular structure of 1,4-bis(substituted-carbonyl)benzene: A combined experimental and theoretical approach

The reaction of pyrazole derivatives (pyrazole (Pz), 3-methylpyrazole (MPz) and 3,5-dimethylpyrazole (DMPz)) with terephthaloyl dichloride (TD) in the presence of Et3N afforded the desired products, 1,4-bis(pyrazolylcarbonyl)benzene (1), 1,4-bis(3-methylpyrazolylcarbonyl)benzene (2) and 1,4-bis(3,5-dimethylpyrazolylcarbonyl)benzene (3).Good quality crystals were isolated and diffraction data for single crystal were collected which revealed that compounds 1–3 are monoclinic with space group P21/n, C2/c and P21/c, respectively. These compounds were obtained as a result of C–N coupling reaction between the acid chloride and pyrazol derivatives with the intent to explore their structure in solution as well as solid state. Density function theory (DFT) calculations using B3LYP and CAM-B3LYP functionals with 6-311G(d,p) basis set were performed to explore geometric and electronic properties of compounds. The Root Mean Square Error (RMSE) has also been calculated for the values of geometric parameters, indicating a good agreement with experimental findings. Moreover, frontier molecular orbitals (FMOs) and natural bond orbitals (NBOs) analyses were carried out through B3LYP/6-311G(d,p) level of theory. The linear polarizability (α) values of nonlinear optical (NLO) analysis were calculated with the same level of theory and basis set as FMO but under different solvent conditions. Time Dependent Density Functional Theory (TD-DFT) study of these pyrazole substituted derivatives was performed aiming to investigate UV–Visible behavior. The stability of molecule has been additionally analyzed by Hirshfeld surface analysis in addition to NBO analysis. The calculated HOMO and LUMO energies from FMO assisted in calculating global reactivity parameters (Chemical hardness, chemical softness, electronegativity, EA, IP and electrophilicity). Natural population analysis (NPA) and Molecular electrostatic potential (MEP) were also performed to obtain insights about the reactivity of compounds 1–3. Theoretical calculations indicate that these compounds have considerable low reactivity and can be used for development of coordination chemistry under optimum conditions.

Sensitivity of semiclassical vibrational spectroscopy to potential energy surface accuracy: A test on formaldehyde

A set of permutationally invariant potential energy surfaces for the electronic ground state of formaldehyde is built at several levels of electronic theory and atomic orbital basis sets starting from a database of more than 34,000 ab initio energies. Preliminarily, the reliability of the fitted surfaces is determined by comparing the calculated harmonic frequencies with the corresponding ab initio values. Then, semiclassical estimates of the quantum frequencies of vibration are presented, and their dependence on the employed level of theory, type of atomic orbital basis set, and complexity of the fit is investigated. Comparisons of semiclassical results to experimental data provide a further assessment of the quality of the analytical surfaces and show that anharmonic frequencies are influenced by the precision of the fit, while accurate frequency values are obtained also with density functional theory. Results and conclusions support the use of ab initio “on-the-fly” semiclassical dynamics as a means of spectroscopic investigation when high-level analytical potential energy surfaces are not available.

Theoretical and Experimental Study of the α‐ and β‐Phase of Diammonium 5,5′‐Bistetrazole‐1,1′‐Diolate (ABTOX)

AbstractTwo new phase of diammonium 5,5′‐bistetrazole‐1,1′‐diolate (α‐ and β‐ABTOX) were prepared, and its structure were characterized by FT‐IR spectroscopy and single X‐ray diffraction. The thermal decomposition processes of α‐ and β‐ABTOX were studies by means of the DTA‐TG and TG‐MS technologies, the crystal morphology of α‐ and β‐ABTOX were studied by SEM technology. The results show thermal stability of α‐ABTOX is better than β‐ABTOX, the crystal morphology of α‐ and β‐ABTOX are rhombus and square. Finally, front orbital energies and the molecular electronic potential (MEP) of α‐ and β‐ABTOX were studied using density functional theory (DFT) B3LYP/6‐311G(d, p) basis set level.

Understanding the Formation of Novel Hydrated Gallic Acid-Creatinine Molecular Salt: Crystal Structure, Hirshfeld Surface and DFT Studies

Creatinine, an aliphatic hetero monocyclic compound, plays an important role in the protein metabolism and change in its physiological normal concentration leads to diabetic nephropathy, renal failure and muscle disorder. In this work, a novel molecular salt form (ionic cocrystal) of creatinine (CR) with gallic acid (GA) has been obtained and preliminarily characterized by PXRD, FTIR and the crystal structure was confirmed by X-ray diffraction method. The presence of a single C–O stretching band in the place of two stretching bands [C=O and C–O] in the infrared spectrum confirms the formation of molecular salt. The asymmetric unit of GA–CR ionic cocrystal [(C7H5O5)− (C4H8N3O)+ 3(H2O)] comprises of a molecule of gallic acid, a molecule of creatinine and three water molecules. The structural analysis reveals the strong hydrogen bond DDAA environment of water molecules which confirms the presence of different supramolecular architectures. Thermal gravimetric analysis was carried out to investigate the presence of water/solvent molecules in the molecular salt. Further, the intermolecular interactions in stabilizing the molecular salt were analyzed using Hirshfeld surfaces. Furthermore, the coordinates of molecular salt were optimized by DFT calculations using APFD hybrid functional with 6-311 + G(d,p) level basis set. Frontier molecular orbitals, energy gap and related molecular properties were also analyzed. GA–CR pharmaceutical molecular salt form is found to be more reactive than CR and therefore offers an innovative approach for the futuristic drug design. Strong hydrogen-bond DDAA environment (D: donor, A: acceptor) exhibited by the water molecules in the GA–CR molecular salt play a major role in stabilizing the crystal structure.

One-pot synthesis, spectroscopic characterizations, quantum chemical calculations, docking and cytotoxicity of 1-((dibenzylamino)methyl)pyrrolidine-2,5-dione

Abstract The investigations of stabilization energy, bond order, intra-molecular interactions and energy gap of pharmaceutical drugs are useful for understanding their behaviour. A new Mannich base molecule 1-((dibenzylamino)methyl)-pyrrolidine-2,5-dione (SBF) was synthesized through sequential Mannich reactions of an imide with an aldehyde and the intermediate obtained are reacted with secondary amine to get the desired product. The entire molecular geometry of the SBF molecule was confirmed by single crystal XRD studies. The crystal structure of SBF molecule was found symmetrical and planar with anti-periplanar orientation of C O group and nitrogen atom. The theoretical computations were performed using B3LYP/6-31G(d, p) level of basis set. The chemical environment of carbon and protons were shown with 13C and 1H NMR spectral analysis, respectively. The molecular weight of the title molecule was determined by mass spectrum. The thermal stability of the SBF molecule up to 270 °C was exposed by thermogravimetric (TG) and differential scanning analysis (DSC). The natural bonding orbital (NBO) analysis data revealed the highest stabilization value of E(2) for transfer of electron density from succinimide to the antibonding molecular orbital of the dibenzyl ring were found to be 51.51 and 50.31 kJ/mol. The energy of HOMO-LUMO, PDOS, OPDOS, RDG of the title molecule have also been carried out. The protein-ligand relationship was well revealed by molecular docking studies. The cytotoxic activity of the SBF molecule was evaluated by MTT assay on cell line A549.

On the structural-optical correlation of ZnO nanospheres synthesized using thermal evaporation technique

Zinc oxide clusters of different sizes and geometrical shapes have been synthesized and characterized experimentally and theoretically. The ZnO cluster models have been built and presented to study the evolution of physico-chemical properties of the metal oxide semiconductor upon reduction of size. However, most of the theoretical models are lack of support from the experimental details. This article aims to correlate the geometry of the theoretical models with their optical properties. The ZnO thin films were synthesized by thermal evaporator at vacuum pressures of 5 × 10−5 Torr. Cluster models of the synthesized ZnO were built based on its crystal structure. The clusters were evaluated as realistic using geometry optimization, and harmonic frequency calculations at the level of B3LYP functional and lanl2dz basis set. We observed that the fabricated ZnO thin film was constructed by small ZnO spherical clusters, which revealed by the Field Emission Electron Microscopy (FESEM) . This observation is in good agreement with our theoretical simulations, which were established based on its crystal structure – characterized by the X-ray diffractometer.

Synthesis, characterization and hydrogen bonding attributes of halogen bonded O-hydroxy Schiff bases: Crystal structure, Hirshfeld surface analysis and DFT studies

Abstract Halogen bond has been the focus of crystal engineering for many decades. The role of intra molecular halogen bonds on adjacent intramolecular hydrogen bonding attributes has hardly been investigated. The O-hydroxy Schiff bases offer a good platform to shed light on these bonding aspects. The halogen bonded O-hydroxy Schiff bases were synthesized by the reaction of aldehydes with primary amines. Compounds were then characterized using mass, FTIR and NMR spectroscopic methods. Finally, the three dimensional molecular structures of all the Schiff base compounds were confirmed through single crystal X-ray diffraction studies. The crystal structures exhibit both inter and intramolecular hydrogen bond interactions. The O–H⋯N intramolecular interactions form the six membered pseudo chelate rings. The structures are also stabilized by C–O···π, N–O···π and π···π interactions. These molecular interactions were then quantified using Hirshfeld surface analysis. Further, the density functional theory calculations were employed using B3LYP hybrid functional with 6-311G+(d, p) level basis set to optimize the structural coordinates. The chemically active regions of the Schiff base molecules were identified by the analysis of molecular electrostatic potential surface.

Synthesis, characterization crystal and molecular structure studies of 5-(3-Methylbenzoyl)-4-methyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepin-2-one: Hirshfeld surface analysis and DFT calculations

Abstract Benzodiazepines derivatives have been reported for their broad spectrum of biological applications. These derivatives are also being investigated for their supporting activity against human cancers. The title compound 5-(3-Methylbenzoyl)-4-methyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepin-2-one has been synthesized, characterized using 1H NMR, 13C NMR, IR techniques and finally the structure was confirmed by single crystal X-ray diffraction studies. The single crystals of the compound were obtained using ethanol as crystallization solvent. The compound C18H18N2O2 crystallizes in the orthorhombic crystal system with P212121 space group. The crystal structure of the title compound is stabilized by N H···O intermolecular hydrogen bond and π···π interactions. The structure also exhibits one dimensional chain stacking along a-axis through intermolecular interactions. These molecular interactions were then quantified using Hirshfeld surface analysis to understand their nature of involvement in interaction with other molecules. The analysis of the fingerprint plots revealed that the H…H (58.7%) interactions has the major contribution to the total molecular surface. Further, the electronic properties of the title compound were studied by computing the frontier molecular orbital energies using density functional theory calculations with B3LYP/6-311 + G (d, p) level basis set. Finally, the molecular electrostatic potential map was generated and the chemical reactive sites were identified to understand the molecular surface properties.

Thermal analysis, structure, spectroscopy and DFT calculations of a pharmaceutical cocrystal of salicylic acid and salicylamide

The pharmaceutical cocrystal of salicylic acid (C7H6O3 or H2Sal) and salicylamide (C7H7NO2 or SAM) was synthesized and characterized by various techniques. The differential scanning calorimetry results confirmed the eutectic fusion showing the characteristic of the endothermic sharp peak of the solidus temperature at 108 °C. X-ray crystal structure of cocrystal is orthorhombic with space group Pna2(1). Cocrystal consists of H2Sal and a distorted phenolic group of SAM. The packing diagram of cocrystal H2Sal·SAM clearly confirmed the $$R_{8}^{2}$$ acid–amide dimer heterosynthons and other inter- and intramolecular interaction bonds to stabilize the structure. In addition, the strength of the hydrogen bonds is studied using the vibrational spectral measurements, confirming the band shifting due to the intermolecular interactions. The identity of compounds by matching the absorbance spectrum was confirmed by ultraviolet spectroscopy technique. Furthermore, the experimental studies were supported by calculation results using density functional B3LYP methods with the standard 6-311++G(d,p) basis set level. The parameters such as bond lengths, bond angles and Mulliken atomic charges values have been calculated and compared, confirmed the interactions and charge transfers. The frontier molecular orbitals (HOMO–LUMO) illustrated the lower band-gap value suggesting the possible pharmaceutical activity of this as obtained H2Sal·SAM cocrystal.

Chiral Self Recognition: Interactions in Propylene Oxide Complexes.

We elucidate the subtle energetic effects that give rise to chiral recognition in the propylene oxide dimer. Specifically, we investigate six homochiral (RRx) and six heterochiral (RSx) structures of this complex, with the RRn-RSn pair sharing the same pattern of weak O···H-C hydrogen bonds but subtly differing in energy due to chiral effects. The interaction energies for the 12 structures are computed at various levels of electronic structure theory and basis set up to the complete basis set limit of the coupled-cluster approach with single, double, and perturbative triple excitations (CCSD(T)). These benchmark interaction energies are compared to the results of various approximate approaches, both density functional theory-based and wave function-based. We find that while the RRn-RSn diastereomeric energy differences exhibit a great deal of error cancellation between the individual interaction energies, most approximate methods have a hard time even reproducing the correct signs of these differences consistently. The origins of the RRn-RSn differences are elucidated by several symmetry-adapted perturbation theory (SAPT) analyses ranging from ordinary intermolecular SAPT to a functional-group SAPT (F-SAPT) decomposition of direct and indirect H → CH3 substitution effects leading from achiral ethylene oxide complexes to chiral propylene oxide ones. It is shown that the largest diastereomeric energy differences are correlated to the variations in the electrostatic and dispersion SAPT contributions. Finally, the effect of chiral interactions on the vibrational frequencies of a propylene oxide molecule is investigated, showing that the interaction results in largest frequency shifts, splittings, and chiral discrimination effects in the lowest, torsional vibrational mode of the noninteracting monomer.

Synthesis, structural, thermal, mechanical, laser damage threshold and DFT investigations on bis (2-methylimidazolium-4-aminobenzoate) single crystal

An organic salt, bis (2-methylimidazolium-4-aminobenzoate) (MIAB) was synthesized and single crystals grown successfully by slow solvent evaporation solution growth technique using ethyl acetate as solvent at room temperature. Fourier transform infrared (FTIR) spectral analysis was carried out to detect the presence of functional groups in the MIAB salt crystal. 1H and 13C spectra were recorded to confirm the presence of various kinds of proton and carbon environments thereby establish the molecular structure of MIAB crystal. Single crystal X-ray diffraction analysis (SCXRD) reveal that the crystal belongs to monoclinic system centrosymmetric space group, P21/c. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) confirms that the MIAB crystal is thermally stable up to 250 °C. The mechanical properties of the grown crystal were determined by Vickers Microhardness test. Computational studies were performed using Gaussian 09 software by 6.31 g basis set level. The calculated first order hyperpolarizability (β) of MIAB from computational studies is 5.01 times that of Potassium dihydrogen phosphate (KDP). The laser damage threshold value of the MIAB is found to be 1.44 GW/cm2. Z-scan technique reveals the optical non-linearity of the crystal.

Efficiently Transplanting Potential Energy Interpolation Database between Two Systems: Bacteriochlorophyll Case with FMO and LH2 Complexes.

Generating a reliable potential energy surface (PES) is an important issue for studying the dynamics of any system with computational simulations. Interpolation mechanics/molecular mechanics (IM/MM) based on a PES interpolation scheme is a useful tool in that regard as it provides an accuracy of a quantum chemistry (QC) level while maintaining its computational cost comparable to conventional MM force fields. Despite this benefit, constructing the database for interpolation itself is still challenging and time-consuming. Here, we present a method with which we can construct the IM database of one system based on a preexisting data set for another related system. We adopt the case of constructing bacteriochlorophyll PESs for the light-harvesting 2 (LH2) complex by utilizing already available IM database for the BChls from the Fenna-Matthews-Olson (FMO) complex. In this method, the IM database from FMO is first transplanted to LH2 by considering BChl displacement vectors that take into account the geometry differences induced by the protein scaffolds. From this transplanted primitive database entries, a relatively small number of effective ones are selected by a survival process based on a genetic algorithm such that the IM energies evaluated at geometries in a conveniently collected prediction set can closely match with the reference QC energies. The selection process is expedited by using two different levels of basis sets for the QC calculations. To demonstrate the utility of the PES thus constructed, we carry out 1 ns of IM/MM dynamics simulations with the finally optimized BChl database for LH2. Indeed, the energy profiles of the snapshots are found to be closely matching with the reference QC calculation data, with only ∼0.07 eV of errors in the ground- and excited-state energies and ∼0.008 eV of errors in the transition energies. We also show that properly selecting data points is actually quite important for generating an IM PES toward performing molecular dynamics simulations.

The crystal structure, linear and nonlinear optical properties of 3-Aminonitrobenzene for photonic application — A combined experimental and theoretical investigation

Optically transparent good quality single crystal of 3-Aminonitrobenzene (3-ANB) was grown by slow evaporation technique using methanol as solvent. The grown crystal was subjected to single crystal X-ray diffraction analysis in order to reveal its cell parameters, crystal structure and space group. Powder X-ray diffraction analysis was carried out in order to verify the crystalline nature. UV-Vis study was carried out to measure the optical transparency of the title material and also optical band gap was determined from the transmittance window. The existence of second harmonic generation (SHG) in the title material was confirmed by Kurtz–Perry powder technique. In order to throw light on the crystal structure, linear and nonlinear optical properties at molecular level, Density Functional Theory (DFT) was employed using B3LYP/6[Formula: see text]G (d, p) level of basis set. The DFT study illustrates the HOMO–LUMO energy gap analysis and the existence of SHG behavior of 3-ANB at molecular level.

Crystal structure, Hirshfeld surface analysis, DFT calculations and molecular docking studies on pyridine derivatives as potential inhibitors of NAMPT

Abstract The crystal structure of 4-(4-fluorophenyl)-2-(1H-indol-3-yl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile (Ia) and 2-(1H-indol-3-yl)-4-(thiophen-2-yl)-5,6,7,8,9,10-hexahydrocycloocta[b]pyridine-3-carbonitrile (Ib) were elucidated by single crystal X ray diffraction. The central piperidine ring adopts twisted conformation, the piperidine of octahydroindolizine ring is in half chair conformation and the pyrrole ring is in twisted envelope conformation in both the compounds (Ia) and (Ib). Details of the preparation, crystal structure determination and intra- and inter- molecular interactions of the compounds are given. Intermolecular interactions were also studied by Hirshfeld surface analysis. The structures of both compounds were optimized by density functional theory (DFT) calculations using B3LYP hybrid functional with 6–311G(2d,2p)level basis set. The molecular docking study of synthesized compound with an enzyme, namely, Nicotinamidephosphoribosyltransferase (NAMPT) which increases sensitivity to apoptosis in both NAMPT-expressing cells and tumorspheres has also been carried out.

Synthesis and DFT calculations of new ruthenium(II) nitrosyl complexes using cis-fac-dichlorotetrakis(dimethylsulfoxide)ruthenium(II) precursor and different oximes as sources of nitrosyl ligand

Three NO+-ruthenium(II) complexes were prepared by using cis-[RuCl2(DMSO)4] as precursor, P, and the compounds benzohydroxamic acid (BHA), 1′, anti-diphenylglyoxime (H2dpg), 2′, and dimethylglyoxime (H2dmg), 3′, as sources of NO moiety. The three complexes [RuCl2(DMSO)3(NO)]+(BA)−, 1, [RuCl2(DMSO)3(NO)]+(Hdpg)−, 2, and [RuCl2(DMSO)3(NO)]+(Hdmg)−, 3, were characterized by (FT-IR, NMR, UV-Vis) spectroscopy, thermogravimetry, and microanalysis. From FT-IR spectral data, two modes of coordination of DMSO to Ru atom through both S and O atoms were detected for 1 and 2. For 3, only S coordination was reported. Computational studies on the [RuCl2(DMSO)3(NO)]+ cationic parts, 1″, 2″ and 3″, of the investigated complexes 1, 2 and 3 were carried out by DFT. The molecular geometry and mode of attachment of Ru(II) with DMSO were performed with the B3LYP/LANL2DZ level of theory and basis set. Theoretical to the experimental agreement was achieved for analysis of IR data of the investigated complexes. Additional information about binding between the ruthenium atom and the DMSO ligand has been obtained by NBO analysis.

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A new imidazole derivative, 2-(4-bromophenyl)-1-(3-fluoro-4-methylphenyl)-4,5-diphenyl-1H-imidazole (I) was synthesized and characterized by IR, Mass, NMR (1H and 13C), Single crystal X-ray diffraction, and elemental analysis techniques. Hirshfeld surface analysis was performed to find out the intercontacts in the crystal structure. Density functional theorem (DFT) based calculations viz. optimized geometry, frontier molecular orbital analysis and vibrational analysis were performed using Gaussian09 software at B3LYP functional and 6–31G* level basis set and compared with experimental values. The calculated geometric parameters are consistent with XRD data. Stability and charge transfer within the compound was explained by frontier molecular orbital calculations. Molecular electrostatic surface analysis revealed that positive potential is concentrated on the nitrogen atoms of the imidazole ring. Molecular docking of the compound to the active site of Candida albicans dihydrofolate reductase (PDB ID: 4HOE) revealed that the molecule is tightly bound to the target protein, with good docking score compared to standard ciprofloxacin.

Surface-enhanced Raman scattering and quantum chemical studies of 2-trifluoroacetylpyrrole chemisorbed on colloidal silver and gold nanoparticles: A comparative study

Surface-enhanced Raman scattering (SERS) studies of 2-trifluoroacetylpyrrole (TFAP) molecule adsorbed on synthesized colloidal silver nanoparticles (SNPs) and gold nanoparticles (GNPs) were reported and compared to the normal Raman spectra (nRs) of TFAP molecule in solid and liquid states. The experimental results were validated with the simulated nRs and SERS spectra of the molecule using density functional theory (DFT) calculations. The structures of the TFAP, TFAP-Ag3 and TFAP-Au4 molecular systems were optimized at different level of basis sets. HR-TEM analysis reveals that the colloidal SNPs and GNPs were monodispersed in spherical shape with average particle size were predicted as ~20 and ~25 nm, respectively. The observed red shift and decreased intensity behavior in the UV–visible spectral analysis confirm that the TFAP molecule chemisorbed on the colloidal SNPs and GNPs surface. Frontier molecular orbitals (FMOs) analysis points out the charge transfer from silver cluster to molecule and gold cluster to molecule in the TFAP-Ag3 and TFAP-Au4 molecular systems, respectively. The molecular electrostatic potential surface and Fukui functions analysis further validated the charge transfer interaction in the molecular systems. SERS spectral analysis confirms that the TFAP molecule was adsorbed on colloidal SNPs and GNPs surface with tilted orientation through the lone pair electrons on oxygen atom in the CO group, pyrrole ring π electrons and lone pair electrons on fluorine atom in the trifluoro group. Moreover, the calculated SERS enhancement factor values indicate that the title molecule chemisorbed on colloidal GNPs surface with higher affinity than that of colloidal SNPs surface. Hence, the present study paves the way for the designing of SERS active colloidal silver and gold substrates, which will be useful for the development of pyrrole related biosensors.

Cocrystals of Gallic Acid with Urea and Propionamide: Supramolecular Structures, Hirshfeld Surface Analysis, and DFT Studies

AbstractThe exploitation of new crystal forms with controlled properties of the active pharmaceutical ingredients (APIs) has a significant role in the pharmaceutical industry. Cocrystallization technique is a powerful strategy to modify the physicochemical properties of APIs. In the present work, two pharmaceutical cocrystals—gallic acid‐urea (GA‐UR) and gallic acid‐propionamide (GA‐PR)—have been obtained by mechanochemical grinding method. Novel cocrystals are characterized by powder X‐ray diffraction, Fourier‐transform infrared spectroscopy, and their structures are confirmed by single crystal X‐ray diffraction method. The structural analysis confirms the formation of various supramolecular architectures. Thermal gravimetric analysis is carried out to investigate the presence of water/solvent molecules in the cocrystals. Further, the intermolecular interactions in stabilizing the cocrystals are analyzed using Hirshfeld surfaces. Furthermore, the coordinates of cocrystals are optimized by density functional theory (DFT) calculations using B3LYP hybrid functional with 6–31+G(d,p) level basis set. Frontier molecular orbitals (HOMO‐LUMO), energy gap, and related molecular properties are also analyzed.