Synthesis and Properties of a New Type of Terpyridine Cholesterol Derivative Gelator with Applications to Medical Treatments

Abstract

Low molecular mass gelators (LMMGs), as a new type of intelligent soft material, possess good response properties to light, electricity, heat, and ultrasound and have many potential applications in fields such as intelligent sensing, biological materials, and drug release. Additionally, steroid derivatives have been a focus in the study of LMMGs for their desirable properties as well, such as their rigid framework, multichiral center, and strong van der Waals accumulation. Furthermore, the coordination ability of terpyridine has been an emphasis in the study of supramolecular chemistry and coordination chemistry as well. Attempts have been made with terpyridine groups that have special responses, such as terpyridine with steroid derivatives, to build more specialized and functional gelators. In this study, we used 2-acetylpyridine, 2-formaldehyde, and cholesterol to synthesize 6-(2,2:6 ${}^{\prime }$ ,2 ${}^{″}$ -terpyridine-4 ${}^{\prime }$ -carboxamide group) hexanoic acid (with a yield of 64.39%, P1), glycine cholesterol ester (with a yield of 70.36%, P2), and DMTCP (with a yield of 88.92%). Infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, elemental analysis, and gelator performance tests were then conducted to measure the gelation effect of the materials and to explore their gelation mechanisms. Compared to P1 and P2, the DMTCP synthesized by P1 and P2 was able to form gel in more kinds of solvents. In addition, when it contains both terpyridine and cholesterol functional groups, the gelation properties of DMTCP were also significantly improved, and all the gels prepared in the four solvents in which DMTCP can form gels were stimulus responsive.