Tommy Geisler

New Chiral Bis(dipolar) 6,6′‐Disubstituted Binaphthol Derivatives for Second‐Order Nonlinear Optics

Macro- and microscopic nonlinear optical properties of 6,6′-diacceptor-substituted binaphthol derivatives with C2 symmetry were measured by the Kurtz–Perry powder test (scheme, right) and electric field induced second harmonic generation (EFISHG). These derivatives are axially chiral and possess two equal donor–acceptor systems linked together, to give a V-shaped bis(dipolar) system. The use of this type of chirality (atropisomerism) ensures noncentrosymmetric packing in crystals necessary for second-harmonic generation in bulk.

Third-harmonic generation in organometallic ruthenium(II) derivatives containing coordinated p-substituted benzonitriles

A family of η5-monocyclopentadienylruthenium(II) derivatives possessing coordinated p-substituted benzonitriles has been studied by optical third-harmonic generation (THG) at the fundamental wavelength of λ= 1064 nm. Thin films of the compounds in a polymer matrix of poly(methyl methacrylate)(PMMA) were studied using the Maker fringe technique. For the compound possessing the p-NCC6H4C6H4NO2 coordinated nitrite the second hyperpolarizability, γ(–3ω;ω,ω,ω), was determined to be 2.3 × 10–33 esu. Spectroscopic results show evidence of π back-donation resulting in an extension of the electronic π-system. We propose that this π back-donation is the origin of this significant value of γ.

Donor-acceptor interfaces in langmuir-blodgett films. Structural and optical features related to nonlinear optical properties

Abstract The linear optical properties of Langmuir-Blodgett films of alternating layers of the electron acceptor, octadecylthiobenzoquinone, and the electron donor 7-( N -octadodecylaminomethyl)-8-16-dioxadibenzo [f,g]perylene indicate that only a weak intermolecular contact is formed at the interface between donors and acceptors. Structural data based on linear dichroism and X-ray diffraction show that the intermolecular contact between donor and acceptor layers is possible due to the carbonyl lonepairs in the acceptor, which are directed towards the interface. The prospects for donor-acceptor interfaces in nonlinear optical materials are discussed.

Nonlinear optical phenomena due to donor–acceptor interfaces created in Langmuir–Blodgett films

Langmuir–Blodgett films consisting of two-dimensional interfaces between corbiene donor and quinone acceptor molecules show a significant nonlinear optical property (second-harmonic generation) that can be attributed to the intermolecular contact across the interface between the donor and acceptor molecules in the film.

Saturation effects in the nonlinear optical response of regioregular, highly conjugated poly(3-alkyl-thiophene) thin films

Abstract Third harmonic generation measurements on highly conjugated regioregular poly(3-dodecylthiophene) thin films using a fundamental wavelength of 1907 nm give an absolute value of χ(3)(-3ω;ω,ω,ω) = 4×10−11 esu. This value is the nonlinear susceptibility of the most highly conjugated polythiophene film reported to date (λmax= 555 nm). Comparison to less conjugated samples reveals a saturation in the dependence of χ(3) the effective conjugation length.

Large Nonlinear Optical Response of Acceptor Substituted bis(N-phenyldithiocarbimato)Nickel(II) Complexes and the Relation to Intramolecular Charge Transfer Transitions

Abstract The second molecular hyperpolarizability, γ, for bis(N-(4-nitrophenyl)dithiocarbimato)Ni(II) complexes incorporating two p-nitroaniline moieties in a centrosymmetric fashion is found from third harmonic generation measurements to be two orders of magnitude higher than the simple sum of the p-nitroaniline contributions. The molecules with γ values as high as 2×10 −33 esu were designed to have efficient “periphery-to-centre” charge transfer transitions demonstrated to be of paramount importance for the nonlinear response by comparison with similar complexes without efficient intramolecular charge transfer transitions.