Temperature and H/D Isotopic Effects in the IR Spectra of the Hydrogen Bond in Solid-State 2-Furanacetic Acid and 2-Furanacrylic Acid

Figure 14

The theoretically derived 𝜈_O−H band contours calculated in terms of the “strong-coupling” theory in the limits of the two different vibrational exciton coupling mechanisms involving the cyclic dimer hydrogen bonds, that is, “side-to-side” (SS) and “tail-to-head” (TH). (a) The SS coupling mechanism. (b) The TH coupling mechanism. (I) The “minus” band. (II) The “plus” band (III) Superposition of the I and II spectra, each taken with its appropriate individual statistical weight parameter, 𝐹⁻ and 𝐹⁺. In both mechanism cases, the same coupling parameter value system was used for calculations: 𝑏_𝐻 = 1.4, 𝐶₀ = 1.5, 𝐶₁ = −0.2, F⁺ = 1.0, 𝐹⁻ = 0.2, Ω_O⋯O = 100 cm⁻¹. The transition frequencies are in the ω _O⋯O vibrational quantum units, and the transition frequencies are expressed with respect to the gravity center of the hypothetical spectrum of a monomeric hydrogen bond in the cyclic hydrogen bond dimer. Transition intensities are in arbitrary units.

(a)

(b)