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Titolo:
ORIENTATION CHANGE OF PORPHYRIN IN LANGMUIR-BLODGETT-FILMS CAUSED BY A TRIGGER MOLECULE
Autore:
AZUMI R; MATSUMOTO M; KAWABATA Y; KURODA S; SUGI M; KING LG; CROSSLEY MJ;
Indirizzi:
NATL INST MAT & CHEM RES TSUKUBA IBARAKI 305 JAPAN ELECTROTECH LAB TSUKUBA IBARAKI 305 JAPAN CSIRO,DIV FOOD SCI & TECHNOL N RYDE NSW 2113 AUSTRALIA UNIV SYDNEY,SCH CHEM SYDNEY NSW 2006 AUSTRALIA
Titolo Testata:
Journal of physical chemistry
fascicolo: 49, volume: 97, anno: 1993,
pagine: 12862 - 12869
SICI:
0022-3654(1993)97:49<12862:OCOPIL>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-SPIN-RESONANCE; COPPER PHTHALOCYANINE; MONOLAYER ASSEMBLIES; MEROCYANINE DYE; MIXED SYSTEM; LB FILMS; MULTILAYERS; ESR; CONDUCTIVITY; SPECTROSCOPY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
53
Recensione:
Indirizzi per estratti:
Citazione:
R. Azumi et al., "ORIENTATION CHANGE OF PORPHYRIN IN LANGMUIR-BLODGETT-FILMS CAUSED BY A TRIGGER MOLECULE", Journal of physical chemistry, 97(49), 1993, pp. 12862-12869

Abstract

The orientation of the functional molecule PM, etrakis(3,5-di-t-butylphenyl)porphinatocopper(II), was controlled by adding a small amount of the trigger molecule, n-hexatriacontane (CH3(CH2)34CH3) in the mixedLangmuir--Blodgett (LB) films with cadmium icosanoate. The orientation of PM was investigated by using the electron spin resonance (ESR) and UV/vis absorption spectroscopies for mixed LB films with the molar mixing ratio PM/cadmium icosanoate/n-hexatriacontane = 1.5/10/x in the range 0 less-than-or-equal-to x less-than-or-equal-to 5. The ESR spectra showed that there were two PM components, having different orientation, in each of the LB films. Without n-hexatriacontane, the major component had an orientation tilted with the most probable angle theta0 =58-degrees between the plane normal of the molecule and the film surface, while the macrocycle plane of the major component was oriented almost vertically (theta0 = 80-degrees) with respect to the film surfacefor the LB film with the mixing ratio x = 0.5 of n-hexatriacontane. This mixing ratio means that the number of n-hexatriacontane molecules can be as small as one-third the number of PM molecules to control theorientation of PM. Polarized UV/vis absorption spectra indicated thatdoubly degenerated transition dipole moments of the Soret band of theporphyrin give rise to the two absorption bands due to the aggregation of molecules. They are J-like and H-like bands resulting from the interaction between the in-plane (parallel to the film surface) and out-of-plane (tilted with respect to the film surface) components of transition dipole moments, respectively. The dichroic ratio A(s)/A(p) of each band obtained by using UV/vis polarized light at the incident angle45-degrees is well explained by taking in to account the molecular orientation determined with the ESR measurements. Study of the dependence of the mixing ratio x of n-hexatriacontane showed that there is a transition in the orientation of PM from the theta0 = 58-degrees to the theta0 = 80-degrees state in such a manner that the population of the former species decreases with increasing x and becomes indiscernible at x = 0.5. The X-ray diffraction analyses and IR absorption spectroscopy showed that the orientation of cadmium icosanoate is not affected significantly by the presence of n-hexatriacontane, suggesting that theorientation of PM is controlled through the molecular interaction with n-hexatriacontane. At x = 2, the orientation of PM is slightly different from the one at x = 0.5 probably due to the change in the structure of the LB film caused by the introduction of an excess amount of the nonamphiphilic molecule, n-hexatriacontane.

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Documento generato il 26/09/20 alle ore 14:37:20