Pteridine derivatives: novel low-molecular-weight organogelators and their piezofluorochromism†
Here, π-conjugated compounds based on pteridine derivatives were synthesized and their self-assembling behaviors in a variety of organic solvents were studied. Although there were no conventional gelation groups, such as alkyl groups, amide bonds, or hydrogen bond units, the synthesized pteridines substituted with phenyl, p-chlorophenyl and p-fluorophenyl exhibited different self-assembling abilities, and the p-chlorophenyl-substituted pteridine derivative CCP showed excellent gelation ability with a minimum gelation concentration (MGC) of 2 mg mL−1 in isopropanol, n-butanol and amylene alcohol. In addition, the fluorescence response to mechanical forces for the 4-amino- or hydroxyl-substituted pteridine derivatives, namely, PYP, PIP, DBP, BNP and OHP was obtained. Interestingly, the pyrrolidine- and dibutyl amino-substituted compounds PYP and DBP showed a blue-shift in emission after grinding, while the piperidine-, benzyl amino- and hydroxyl-substituted compounds PIP, BNP and OHP showed a red-shift in emission after grinding. The single-crystal structures of PYP and PIP excluded that the distance corresponding to the π–π interactions led to the differences in MFC properties.