The esters of 2,5-bis(2-carboxy-phenylthio)terephthalic acid4a-f were prepared by reaction of 2,5-bis(2-carboxy-phenylthio)terephthalic acid2viachloride 3 with alcohols or phenols. These novel glass-forming compounds are of the sulfur ligated “trilling” type. Two structures were established by X-ray analysis as well. The thermal behavior was characterized by DSC. In dependence of the different lateral substituents we found calorimetric glass transition temperatures (Tg) in the range of −50°C to 85°C. The molecular dynamics were investigated by use of dielectric spectroscopy (10-2Hz-109Hz). The temperature time dependence for the α-relaxation, which is associated with the glass transition, is discussed in the fragility concept of liquids.