In-Situ Second-Harmonic Generation and Luminescence Measurements for Structural Characterization of Ruthenium−Polypyridine Complex Monolayers with Two and Four Aliphatic Tails at the Air/Water Interface
摘要:
Langmuir monolayer assemblies of ruthenium-polypyridine complexes having two and four aliphatic tails were studied by in-situ optical second-harmonic generation (SHG) and luminescence measurements, together with surface pressure-molecular area (lambda-A) isotherms. As the monolayer was compressed, the four-tailed complex showed a distinct phase transition at a 30-40 mN/m region from phase I (1.3 nm(2) mean molecular area) to phase II (1.1 nm(2)). Excitation with 1064-nm light gave an SHG signal at 532 nm that appeared almost synchronously with the increase of surface pressure, but the p-polarized component of the SHG signal, induced by either p- (parallel to the plane of incidence) or s- (perpendicular to the plane of incidence) polarized fundamental light, showed a different profile upon compression of the monolayer. In the phase II region, the p-polarized component increased steeply, whereas the s-polarized component decreased to almost zero. A significant blue-shift and a longer lifetime of the luminescence signal were also observed in phase II. Thus, a tightly packed structure in which the main hyperpolarizability tensor is directed roughly perpendicular to the water surface is suggested for phase II. For the two-tailed complex, on the other hand, no appreciable phase transitions were observed, only a liquid-expanded phase (0.9 nm(2)). The results are ascribed to differences in the number of long aliphatic tails.
Online Mass Analysis of Reaction Products by Electrospray Ionization. Photosubstitution of Ruthenium(II) Diimine Complexes
摘要:
The first observation of photosubstitution products in electrospray mass spectra is reported. The solvent-coordinated Ru(II) complex ions created by photodissociation of Ru(2,2'-bipyrazine)(3)Cl-2, Ru(2,2'-bipyridine)(3)X(2) (X = Cl- and ClO4-), and the related complexes in acetonitrile solution were directly detected by on-line electrospray mass spectrometry. The mass spectra were well explained in terms of coordinating ability of counterions and solvent. Collision-induced dissociation in the gas phase was an important process particularly for interpretation of photoproducts such as weakly-bound solvent-coordinated complexes. It was found that the electrospray technique, combined with a flowing photoreaction cell, can potentially be used to identify photoproducts or intermediates.
The first observation of photosubstitution products in electrospray mass spectra is reported. The solvent-coordinated Ru(II) complex ions created by photodissociation of Ru(2,2'-bipyrazine)(3)Cl-2, Ru(2,2'-bipyridine)(3)X(2) (X = Cl- and ClO4-), and the related complexes in acetonitrile solution were directly detected by on-line electrospray mass spectrometry. The mass spectra were well explained in terms of coordinating ability of counterions and solvent. Collision-induced dissociation in the gas phase was an important process particularly for interpretation of photoproducts such as weakly-bound solvent-coordinated complexes. It was found that the electrospray technique, combined with a flowing photoreaction cell, can potentially be used to identify photoproducts or intermediates.
In-Situ Second-Harmonic Generation and Luminescence Measurements for Structural Characterization of Ruthenium−Polypyridine Complex Monolayers with Two and Four Aliphatic Tails at the Air/Water Interface
Langmuir monolayer assemblies of ruthenium-polypyridine complexes having two and four aliphatic tails were studied by in-situ optical second-harmonic generation (SHG) and luminescence measurements, together with surface pressure-molecular area (lambda-A) isotherms. As the monolayer was compressed, the four-tailed complex showed a distinct phase transition at a 30-40 mN/m region from phase I (1.3 nm(2) mean molecular area) to phase II (1.1 nm(2)). Excitation with 1064-nm light gave an SHG signal at 532 nm that appeared almost synchronously with the increase of surface pressure, but the p-polarized component of the SHG signal, induced by either p- (parallel to the plane of incidence) or s- (perpendicular to the plane of incidence) polarized fundamental light, showed a different profile upon compression of the monolayer. In the phase II region, the p-polarized component increased steeply, whereas the s-polarized component decreased to almost zero. A significant blue-shift and a longer lifetime of the luminescence signal were also observed in phase II. Thus, a tightly packed structure in which the main hyperpolarizability tensor is directed roughly perpendicular to the water surface is suggested for phase II. For the two-tailed complex, on the other hand, no appreciable phase transitions were observed, only a liquid-expanded phase (0.9 nm(2)). The results are ascribed to differences in the number of long aliphatic tails.