The Use of Structure Analysis Methods in Combination with Semi-empirical Quantum-Chemical Calculations for the Estimation of Quadratic Nonlinear Optical Coefficients of Organic Crystals

Abstract

An effective search for new organic crystals for prospective use in nonlinear optical (NLO) applications requires quantitative and fast experimental determination of their NLO properties at a molecular level. However, the growth of sufficiently large single crystals, which are needed for structural analysis and refinement by X-ray methods, is a time-consuming and sometimes impossible task. Single crystals of a considerably smaller size may be effectively used for complete structural analysis by electron diffraction combined with simulation methods. When the crystal structure of a given compound is known, its NLO properties may be estimated using quantum-chemical methods for calculation of the molecular nonlinearity tensor and the relationships between its components and the macroscopic coefficients of the crystalline nonlinearity tensor. In the present work, the semiempirical PM-3 method was employed for this aim.

Role of Donor−Acceptor Strengths and Separation on the Two-Photon Absorption Response of Cytotoxic Dyes: A TD-DFT Study

“…Single-crystal X-ray analysis shows "equatorial", "axial", and intermediate structures. 49,50,57,62,64 The energy difference between two conformations, estimated through B3LYP/6-31G** or HF/6-31G** calculations, does not exceed 3 kJ/mol, which may imply that in solution at roomtemperature one could find a statistical mixture of both conformers. Therefore, we study both "equatorial" and "axial" structures of compounds 5-8 with strong TPA absorbancies to consider the impact of the conformational geometry on the optical properties of the chromophores.…”

“…Several examples of such compounds were found in series of cyclohexanones (Figure 1a). [46][47][48][49][50] Significant TPA absorbancies of cyclohexanones were reported in ref 51. It is remarkable that series of compounds with similar molecular structure (piperidones, in neutral and protonated form, Figure 1a) was identified as cytotoxic chemotherapeutic agents.…”

Electron crystallography and non-linear optics

“…If the experiment is performed under different polarisation conditions of the fundamental laser and the collected light, it is possible to determine five independent terms containing products of ␤ components. We have described details about these calculations on DMACB, CNBA, and NPHU in the specialised literature (VoigtMartin et al, 1995a(VoigtMartin et al, ,b, 1997aYakimanski et al, 1997) and have combined the results in a teaching course on crystallography (Voigt-Martin and . If only one ␤ component is significant (as is the case in many linear molecules with delocalised -systems), the molecular fixed frame may be chosen such that the tensor components that finally emerge after some calculation are ␤ xxx , ␤ yyy or ␤ zzz .…”

“…14. Relate molecular ␣, µ, ␤ to crystal co-ordinates and calculate macroscopic optical susceptibility (VoigtMartin et al, 1995a(VoigtMartin et al, ,b, 1997bYakimanski et al, 1997). …”

“…13. Ab initio structure determination using ME approach (Voigt-Martin et al, 1995a,b, 1997bYakimanski et al, 1997). 14.…”