Polarization-Modulated Infrared Reflection Absorption Spectroscopic Studies of a Hydrogen-Bonding Network at the Air-Water Interface

Qun Huo, Leila Dziri, Bernard Desbat, K. C. Russell, Roger Leblanc

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

The hydrogen-bonding network formed between a triaminotriazine amphiphile (2C18TAZ, 1) and complementary barbituric acid (BA, 2) at the air-water interface is investigated by polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). The molecular structure and orientation of the 1:1 hydrogen-bonding network at the air-water interface is revealed in this study. Without the addition of BA to the subphase, the NH2 scissoring of 2C18TAZ appeared in the spectrum as a broad negative absorption band between 1660 and 1605 cm-1, indicating its perpendicular orientation to the air-water interface. When BA was added to the subphase, the NH2 scissoring absorption band from the triaminotriazine moiety disappeared due to the complementary hydrogen bonding of BA to the 2C18TAZ monolayer. The formation of the rigid 1:1 hydrogen-bonding network also resulted in the disappearance of one of the ring quadrant stretch absorption bands of the 2C18TAZ molecule. New bands which are attributed to the vibration of BA can be clearly seen. Particularly, the C=0 stretch from BA shows up in the spectra as two negative absorption bands around 1700 cm-1. The negative signature of these two bands suggests that the BA molecules are oriented in the hydrogen-bonding network with the C-2 carbonyl positioned vertically toward the air, and the C-4 and C-6 carbonyls directed into the water subphase. This is consistent with formation of an assembly which optimizes the use of complementary hydrogen bonding between two components. Furthermore, the effect of competitive polar organic solvents in subphase, such as DMSO, on the hydrogen-bonding network has also been observed in this study. Compared to the previous IRRAS studies on the similar monolayers, the sensitivity of PM-IRRAS is obviously improved. PM-IRRAS will likely become a powerful analytical technique for the characterization of molecular structure and orientation of Langmuir monolayers at the air-water interface.

Original languageEnglish
Pages (from-to)2929-2934
Number of pages6
JournalJournal of Physical Chemistry B
Volume103
Issue number15
StatePublished - Apr 15 1999

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infrared reflection
Hydrogen bonds
Polarization
Infrared radiation
Water
air
polarization
hydrogen
Air
Absorption spectra
water
Absorption spectroscopy
absorption spectra
Monolayers
absorption spectroscopy
Molecular orientation
Molecular structure
molecular structure
Amphiphiles
Molecules

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Polarization-Modulated Infrared Reflection Absorption Spectroscopic Studies of a Hydrogen-Bonding Network at the Air-Water Interface. / Huo, Qun; Dziri, Leila; Desbat, Bernard; Russell, K. C.; Leblanc, Roger.

In: Journal of Physical Chemistry B, Vol. 103, No. 15, 15.04.1999, p. 2929-2934.

Research output: Contribution to journalArticle

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