Surface Enhanced Second Harmonic Generation from Macrocycle, Catenane, and Rotaxane Thin Films:  Experiments and Theory

Abstract

Surface enhanced second harmonic generation (SE SHG) experiments on molecular structures, macrocycles, catenanes, and rotaxanes, deposited as monolayers and multilayers by vacuum sublimation on silver, are reported. The measurements show that the molecules form ordered thin films, where the highest degree of order is observed in the case of macrocycle monolayers and the lowest in the case of rotaxane multilayers. The second harmonic generation activity is interpreted in terms of electric field induced second harmonic (EFISH) generation where the electric field is created by the substrate silver atoms. The measured second order nonlinear optical susceptibility for a rotaxane thin film is compared with that obtained by considering only EFISH contribution to SHG intensity. The electric field on the surface of a silver layer is calculated by using the Delphi4 program for structures obtained with TINKER molecular mechanics/dynamics simulations. An excellent agreement is observed between the calculated and the measured SHG susceptibilities.

Linear and nonlinear optical properties of transfer ribonucleic acid (tRNA) thin solid films

“…4 This behavior was attributed to the surface interaction to orient molecules. 49,50 Note that we took all the measurements in a laboratory environment maintained at a temperature of ∼20 °C, and humidity of 40–50%. However, these films may be subject to gradual changes in the thickness and refractive index due to interactions with the biological substances.…”

Au10(SG)10: A Chiral Gold Catenane Nanocluster with Zero Confined Electrons. Optical Properties and First-Principles Theoretical Analysis

“…[25]Also catenane structures were found to present large optical nonlinearites. [26][27][28] The asymmetry in the ground and excited states topology plays an essential role in the observed nonlinear optical properties. A high charge transfer character may be observed for catenanes, where charge transfers from one part of the molecule (macrocycle, thread) to the other causes large asymmetries in the molecule and large changes of the dipolar moment in the ground and the excited states.…”

“…Mechanically interlocked molecules such as catenanes present remarkable structural and chiroptical properties. , The chirality of catenanes can originate either from the presence of chiral elements or from directionality in both rings . Also catenane structures were found to present large optical nonlinearites. − The asymmetry in the ground- and excited-state topology plays an essential role in the observed NLO properties. A high charge transfer character may be observed for catenanes, where charge transfers from one part of the molecule (macrocycle, thread) to the other cause large asymmetries in the molecule and large changes of the dipolar moment in the ground and the excited states.…”

Superimposed Arrays of Nanoprisms for Multispectral Molecular Plasmonics

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