K. Muthu

Optical, vibrational, NBO, first-order molecular hyperpolarizability and Hirshfeld surface analysis of a nonlinear optical chalcone.

The synthesis of (1E,4E)-1,5-di-p-tolylpenta-1,4-dien-3-one (DTDO) was done and its single crystals were grown by slow evaporation solution technique from 4-methylbenzaldehyde, acetone solution at room temperature. Crystal structure is determined by single crystal X-ray diffraction analysis and reveals that it belongs to the monoclinic system with four molecules in the unit cell (space group C2). The emission of green light from the sample confirms the second harmonic generation (SHG) of the specimen responsible for nonlinear optical property. The various vibration patterns of the specimen have been investigated by Fourier transform infrared and Fourier transform Raman spectroscopy. Optimized molecular geometry, vibrational patterns of DTDO are derived from density functional theory (DFT) calculations and the results are compared with experimental one. The molecular stability and bond strengths were investigated by applying the natural bond orbital analysis. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density with molecular electrostatic potential (MEP). Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gaps were calculated. The other molecular properties like charge transfer are explained using Mulliken population analysis and the first-order molecular hyperpolarizability (β) of the specimen is also estimated and SHG efficiency of DTDO was found to be 3.9 times that of KDP. Fingerprint plots and Hirshfeld surfaces were used to locate and analyze the molecular surface and bonding interactions in various methodologies utilized in the establishment of the relative energies.

Growth and characterization of Fe3+-doped bis(thiourea)zinc(II) chloride crystals.

Fe3+-doping at ∼10 mol% in aqueous medium during crystal growth by slow evaporation solution method in bis(thiourea)zinc(II) chloride (BTZC) leads to form a new compound C2H8Cl2N4S2Zn0.93Fe0.07 (BTZCF) which crystallizes in orthorhombic structure with centrosymmetric space group Pnma though the parent compound BTZC crystallizes in noncentrosymmetric structure with space group Pn2(1)a. The interesting feature observed in this new crystal is that though it crystallizes in centrosymmetric structure, it exhibits positive SHG result (weak signal), quite likely due to possible surface effects or internal stress. The calculated first-order hyperpolarizability is 1.457×10(-30) esu which is ∼5.5 times that of urea. Fe3+-doping enhances the transmittance to a significant extent. Comparison of the thermal analysis results by DSC reveals the incorporation of dopant into the crystalline matrix. The high resolution XRD studies reveal that the crystalline quality is improved considerably when the doping level is reached to ∼10 mol%.

Crystal growth, characterization and theoretical studies of 4-aminopyridinium picrate.

Single crystals of 4-aminopyridinium picrate (APP) were grown by slow evaporation of a mixed solvent system methanol-acetone (1:1, v/v) containing equimolar quantities of 4-aminopyridine and picric acid. Structure is elucidated by single crystal XRD analysis and the crystal belongs to monoclinic system with four molecules in the unit cell (space group P21/c) and the cell parameter values are, a=8.513 Å (±0.015), b=11.33 Å (±0.02), c=14.33 Å (±0.03) and β=104.15° (±0.019), V=1340 A(3) (±6) with refined R factors R1=0.0053 and wR2=0.0126. The electron density mapping is interpreted to find coordinates for each atom in the crystallized molecules. The various functional groups present in the molecule are confirmed by FT-IR analysis. UV-visible spectral analysis was used to determine the band gap energy of 4-aminopyridinium picrate. Powder X-ray diffraction pattern reveals the crystallinity of the as-grown crystal and it closely resembles the simulated XRD from the single crystal XRD analysis. Scanning electron microscopy reveals the surface morphology of the grown crystal. Optimized geometry is derived by Hartree-Fock theory calculations and the first-order molecular hyperpolarizability (β), theoretically calculated bond length, bond angles and excited state energy from theoretical UV-vis spectrum were estimated.

Synthesis, crystal growth, characterization and theoretical studies of 4-aminobenzophenonium picrate.

Single crystals of 4-aminobenzophenonium picrate (4ABPP) were grown by slow evaporation of a mixed solvent system methanol-acetone (1:1,v/v) containing equimolar quantities of picric acid and 4-aminobenzophenone. The proton and carbon signals are confirmed by nuclear magnetic resonance spectroscopy. The various functional groups present in the molecule are identified by FT-IR analysis. Optimized geometry, first-order molecular hyperpolarizability (β), polarizability (α), bond length, bond angles and excited state energy from theoretical UV were derived by Hartree-Fock calculations. The complete assignment of the vibrational modes for 4-aminobenzophenonium picrate was performed by the scaled quantum mechanics force field (SQMFF) methodology using potential energy distribution. Natural bond orbital (NBO) calculations were employed to study the stabilities arising from charge delocalization and intermolecular interactions of 4ABPP. The atomic charge distributions of the various atoms present in 4ABPP are obtained by Mulliken charge population analysis. The as-grown crystal is further characterized by thermal and optical absorbance studies.

Optical, thermal and dielectric properties of Sr(II)-doped bis(thiourea)zinc(II) chloride crystals

The influence of strontium doping on the properties of bis(thiourea)zinc(II) chloride (BTZC) crystals has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. The incorporation of Sr(II) into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy (EDS). Surface morphological changes due to doping of the alkaline earth metal are observed by scanning electron microscopy (SEM). The crystal is transparent in the entire visible region having a lower optical cut-off at ~308 nm with a band gap energy of 4.06 eV. The DSC studies reveal the purity of the materials and no decomposition is observed up to the melting point. Dielectric studies show that the isovalent ion Sr(II)-doping altered the dielectric properties of the host crystal.

Synthesis, structure, growth and characterization of an organic crystal: 1,5-diphenylpenta-2,4-dien-1-one

1,5-Diphenylpenta-2,4-dien-1-one (DDO) chalcone single crystals, synthesized by a base-catalysed aldol condensation reaction between cinnamaldehyde and acetophenone, have been grown by the slow evaporation of an ethanol solution. The crystals belong to the orthorhombic system with centrosymmetric space group Pbca. The DDO crystals are transparent in the visible region and have a lower optical cut-off at ∼445 nm with a band-gap energy of 2.87 eV. Thermogravimetry/differential scanning calorimetry thermal analysis shows that the crystal is stable up to 375 K and it has a good chemical stability. The vibrational patterns of the chalcone have been investigated by Fourier transform IR and Fourier transform Raman spectroscopy. Microhardness studies were also carried out to elucidate the mechanical behaviour. Theoretical calculations were performed using the Hartree–Fock method with 6-31G(d,p) as the basis set, and the first-order hyperpolarizability is 7.077 × 10−30 electrostatic units, which is >25 times that of urea. The crystalline perfection evaluated by high-resolution X-ray diffraction analysis reveals multiple peaks. The molecular packing leads to a centrosymmetric arrangement, resulting in zero second harmonic generation [χ(2) = 0] efficiency. Interestingly, the bromo- and chloro-substituted chalcones are good nonlinear optical materials.

Growth, crystalline perfection, spectral, thermal and theoretical studies on imidazolium L-tartrate crystals.

Transparent optical quality single crystals of imidazolium L-tartrate (IMLT) were grown by conventional slow evaporation solution growth technique. Crystal structure of the as-grown IMLT was determined by single crystal X-ray diffraction analysis. Thermal analysis reveals the purity of the crystal and the sample is stable up to the melting point. Good transmittance in the visible region is observed and the band gap energy is estimated using diffuse reflectance data by the application of Kubelka-Munk algorithm. The powder X-ray diffraction study reveals the crystallinity of the as-grown crystal and it is compared with that of the experimental one. An additional peak in high resolution X-ray diffraction (HRXRD) indicates the presence of an internal structural low angle boundary. Second harmonic generation (SHG) activity of IMLT is significant as estimated by Kurtz and Perry powder technique. HOMO-LUMO energies and first-order molecular hyperpolarizability of IMLT have been evaluated using density functional theory (DFT) employing B3LYP functional and 6-31G(d,p) basis set. The optimized geometry closely resembles the ORTEP. The vibrational patterns present in the molecule are confirmed by FT-IR coinciding with theoretical patterns.

Synthesis, structure, spectral, thermal and first-order molecular hyperpolarizability of 4-benzoylpyridine isonicotinyl hydrazone monohydrate single crystals.

Single crystals of 4-benzoylpyridine isonicotinyl hydrazone monohydrate were grown by slow evaporation solution growth technique from ethanol at room temperature. It belongs to triclinic system with space group P1¯ and the cell parameters are, a=8.9250(2) Å, b=9.1540(2) Å, c=10.87500(10) Å and V=797.88(3) Å(3). Powder XRD closely resembles with that of simulated pattern from single crystal XRD. The characteristic functional groups present in the molecule are confirmed by FT-IR and FT-Raman analyses. The crystal is transparent in the visible region having a lower optical cut-off at ∼420 nm and the band gap energies are estimated by the application of Kubelka-Munk algorithm. Thermal analysis by TG/DTA indicates the stability of the material. The scanning electron microscopy studies reveal the surface morphology of the as-grown crystal. Mass spectrometry provides information pertaining to the structure and molecular weight of the compound. Theoretical calculations were performed using Hartree-Fock method with 6-31G(d,p) as the basis set for to derive the optimized geometry, dipole moment and first-order molecular hyperpolarizality (β) values.

Spectroscopic (FTIR, FT-Raman, NMR and UV) and molecular structure investigations of 1,5-diphenylpenta-2,4-dien-1-one: a combined experimental and theoretical approach

The title molecule 1,5-diphenylpenta-2,4-dien-1-one (cinnamylideneacetophenone, CA) has been synthesised and characterised by FTIR, FT-Raman, NMR and UV–vis spectral analyses. The possible stable conformers of the CA molecule were searched by potential energy surface scan at B3LYP level of theory. The molecular geometry from X-ray determination of the CA molecule in the ground state has been compared using the density functional theory (DFT) with 6-31G(d,p) basis set. The harmonic vibrational modes, the corresponding wavenumbers and IR and Raman intensities of most stable conformer were calculated by the DFT method. The assignments of the fundamentals were proposed on the basis of total energy distribution calculations. The calculated 13C and 1H NMR chemical shifts using gauge including atomic orbitals approach are in good agreement with the observed chemical shifts. The molecular stability and bond strength have been investigated by applying natural bond orbital analysis. Using the time-dependent DFT method, the electronic absorption spectrum of the title compound has been predicted and the electronic transitions within the molecule have been interpreted. The molecular electrostatic potential map was used for predicting possible hydrogen and oxygen bonding sites in the CA molecule.

Growth and characterization of 2-amino-5-nitrobenzophenonium picrate crystals

Single crystals of 2-amino-5-nitrobenzophenonium picrate (ANBP) were grown by slow evaporation solution growth technique from a mixed solvent system ethanol–chloroform–acetic acid (1:1:1, v/v). The 1H and 13C signals of the grown crystal are identified by the nuclear magnetic resonance analyses. Fourier transformed infrared spectroscopy confirms the presence of characteristic functional groups present in the grown crystal. Powder X-ray diffraction was carried out to determine the structure and crystallinity. The crystal belongs to monoclinic system. The optical properties of the grown crystals were analyzed by UV–Vis spectroscopy. Thermogravimetric and differential thermal analysis studies reveal no decomposition up to the melting point. The surface morphology of the as-grown crystals was studied by scanning electron microscopy.