A new possibility of generalized two-dimensional correlation spectroscopy: Hybrid two-dimensional correlation spectroscopy

In this paper, we propose a new possibility for generalized two-dimensional (2D) correlation spectroscopy, hybrid 2D correlation spectroscopy. Three types of hybrid 2D correlation spectroscopies are possible. In the first type, 2D correlation spectra are calculated by using two spectral data for the same sample obtained under two kinds of perturbations. In the second type, 2D correlation spectra are constructed by using spectral variations measured under conjunct or related perturbations. The third type treats 2D correlation spectra generated by using two independent spectral data obtained under the same perturbation but different conditions. In all the cases hybrid 2D correlation spectroscopy allows one to discuss directly the con-elation between two independent spectral data sets and, therefore, extract additional information such as that about the comparison of effects of two different perturbations and the comparison of two different systems. In this paper we describe the principle of hybrid 2D correlation spectroscopy and demonstrate one example of type III. Hybrid 2D correlation spectroscopy has been applied to time-dependent infrared (IR) spectra of two kinds of reactions of the hydrogenation of nitrobenzene. One is complete reaction of nitrobenzene, and the other is its catalyst-modified reaction. The sample-sample hybrid 2D correlation spectra reveal clearly the concentration dynamics of the intermediate in the catalyst-modified reaction, and the wavenumber-wavenumber hybrid 2D correlation spectra provide unambiguous band assignments of the intermediate and the product in the IR spectra of the reaction mixture in the 1510-1470 cm(-1) region.