Synthesis, Crystal Structure, and Second-Order Nonlinear Optical Properties of a New Phase-Matchable Cyanine Dye

Abstract

A new chiral hemicarboxonium salt, (ephem)(BF4), was synthesized by action of α-1-((methylamino)ethyl)benzyl alcohol, (−)-ephedrine, on a carboxonium tetrafluoroborate salt. The compound crystallizes in monoclinic space group P21. a = 11.153(1) Å, b = 8.187(1) Å, c = 16.104(1) Å, β = 91.26(1)°, Z = 2. The molecular origin of the nonlinearity was calculated using the INDO/SCI-SOS approach. The static molecular hyperpolarizability (β0) is equal to 10.7 × 10-30 cm5 esu-1. The compound is phase matchable and exhibits an efficiency around 20 times that of urea at 1.097 μm. The orbital description of the electronic transitions reveals that the carbon skeleton is mainly responsible for the NLO response. The possibility of growing large single crystals (>0.5 mm3) associated with a good transparency (λmax = 420 nm) suggests that pentamethinium salts may be an interesting family of materials for second-order optical nonlinearities.

Investigation of the grafting of fluorophores onto double-walled carbon nanotubes: The influence of the geometry of the molecules

“…Please note that considering the rings to be parallel in the case of Hemicarboxonium is an approximation that reduces the number of configuration to simulate. Indeed, contrarily to the Streptocyanine 5Me(NEt ) 2 2 , the Hemicarboxonium does not own parallel rings [11][12][13], nevertheless, our calculations indicated that the energy of such a configuration is close enough to the real configuration's energy (typically the difference is less than 2 kcal mol −1 ) to be considered a good approximation, and considerably reduce the number of our calculations.…”

“…Then, hoping to pave the way toward a better understanding of the parameters that influence the grafting efficiency of the fluorophores onto DWNTs, we chose to study the influence of the geometry by investigating the grafting of a fluorescent molecule owning a very different geometry, the streptocyanine 5Me(NEt 2 ) 2 [11][12][13][14][15]. Indeed, the streptocyanine 5Me(NEt 2 ) 2 exhibits two parallel aromatic 6-carbon rings that are perpendicular to the main carbon chain in witch both nitrogen atoms are not included in conjugated heterocycles, and therefore makes it a worse candidate for its adsorption (particularly via π-π interactions) onto the DWNTs when compared to FITC that has a planar geometry.…”