2-(1-pyridinio)benzimidazolate (SBPa) is a betaine molecule that exhibits solvatochromic shift of the visible absorption spectrum depending on solvent polarity. The maximum of the absorption band of SBPa is located at 358 and 385 nm in aqueous and methanol solutions, while those in trehalose and glucose glasses are at 377 and 369 nm, indicating the polarity of these glasses are in between water and methanol. Two dimensional fluorescence excitation spectra were measured in the saccharide glasses and excitation wavelength dependent shift of the fluorescence maximum (Red-edge effect) was observed. The inclination of the maximum emission frequency versus excitation frequency was almost identical in both glasses (~0.10) indicating similar amount of inhomogeneity. However, the inclination was smaller compared to that observed when a fluorescent molecule, coumarin 153, was utilized as a probe (0.35). [Cryobio Cryotech, 57, 121-124 (2011)] The discrepancy could be reflecting the mobility of the glassy environment surrounding the probe molecules.
