Article

Theoretical and experimental study of optical second harmonic generation in new chiral thiolates salts

University of Angers, Angers, Pays de la Loire, France
Chemical Physics (Impact Factor: 2.03). 11/2006; 330:387 - 393. DOI: 10.1016/j.chemphys.2006.09.008

ABSTRACT The second harmonic generation ability of new chiral thiolate salts is investigated. Aromatic thiolate anions ArS− are expected from semi-empirical calculations with PM3 parameterization of the MNDO Hamiltonian to possess higher intrinsic polarizabilities than the parent neutral thiols ArSH. Salts associating (hyper)polarizable aromatic thiolate anions with chiral cations, which ensure the noncentrosymmetry necessary to have second-order nonlinear optical effects have been synthesized. The first hyperpolarizabilities, β, of the salts are measured using hyper-Rayleigh scattering technique. Second harmonic generation powder tests (Kurtz and Perry method) carried out on various salts studied, were positive indicating that these materials crystallize in noncentrosymmetric space groups.

0 Followers
 · 
62 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: An intramolecular S(N)Ar mechanism has been identified in the unexpected aryl migration observed in a mesomeric betaine. The process changes drastically the optical and spectroscopic properties and should be a valuable model for related heteroaromatic systems.
    The Journal of Organic Chemistry 06/2010; 75(12):4300-3. DOI:10.1021/jo100350t · 4.64 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 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%.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 06/2011; 79(5):1648-53. DOI:10.1016/j.saa.2011.05.029 · 2.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 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.
    Journal of Applied Crystallography 10/2012; 45(5). DOI:10.1107/S0021889812030403 · 3.95 Impact Factor
Show more