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Werner Kaminsky, Edgar Weckert, Hartmut Kutzke, A. Michael Glazer, Helmut Klapper

Non-linear optical properties and absolute structure of metastable 4-methyl benzophenone

Keywords: Absolute structure, Three-beam method, Optical rotation, Second-harmonic generation, Dipole-dipole interaction

Metastable 4-methyl benzophenone (4-MBP, C₁₄H₁₂O) crystallizes in the polar (pyroelectric) and enantiomorphic space groups (SG) P3₁ and P3₂. The optical rotation tensor has been measured for 670 nm and the material was tested for evidence of phase-matchability. The absolute structure was determined via three-beam diffraction, showing that the structural right-hand screw 3₁ is combined with positive (right-handed, i.e. clockwise when looking towards the light source) optical rotation, for both tensor components ρ₁₁ = ρ₂₂ = 26(5)°/mm, ρ₃₃ = 8.3(5)°/mm (contrary to low-quartz which shows negative optical rotation for ρ₃₃ and positive rotation for ρ₁₁ in right-hand SG P3₁2).
The non-linear optical tensors for optical rotation, d-coefficients, electro-optic effect and electrogyration have been calculated using a set of electronic polarizabilities as input parameters for a dipole-dipole interaction model that reproduces the experimental refractive indices and optical rotation. Unusually high polarizability volumes are needed for hydrogen atom bonding to aromatic carbons in order to model the optical tensors. The non-linear optical coefficients are of medium size.

Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0044-2968
Volume: 221, 04/2006
Pages: 294 - 299

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