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Compared to pure organic amphiphiles, metalloamphiphiles display distinctive features, including luminescence, magnetism and catalytic properties. However, the self-organization of metalloamphiphiles is commonly driven by solvophobic effects. Alkyl chains and oligomeric ethylene glycol moieties are thus the most frequently used aggregation units to drive the self-assembly of metalloamphiphiles. We expect novel metallo-supramolecular structures with exciting functions to be created if additional noncovalent interaction modes are incorporated. In this work, a new type of metalloamphiphile, consisting of a Tb(III) complex head and a cholesteryl unit (TbL 3+ (I)), was designed and synthesized. TbL 3+ (I) spontaneously self-assembles into helical nanofibers (d = 6 nm) in water. This synthetic multivalent nanoscale binding array displays powerful capability for the recognition of DNA conformations through a turn-on luminescence sensing mechanism. ssDNA-kit1 triggered a 26-fold increase in the luminescence intensity of TbL 3+ (I). Its corresponding G-quadruplex structure (G-quadruplex-kit1), however, induced a 6.6-fold enhancement under the same conditions. Consequently, TbL 3+ (I) nanofibers can monitor DNA folding. In contrast, neither ssDNA-kit1 nor G-quadruplex-kit1 markedly promoted the luminescence of molecularly dispersed TbL 3+ (II), illustrating that the multivalent electrostatic interactions between the phosphate groups on the backbone of DNA and TbL 3+ (I) self-assembled into nanofibers could greatly improve the efficiency of the energy transfer between the guanine units and the organized TbL 3+ (I). The TbL 3+ (I) nanofibers could bind and distinguish not only the kit1-ssDNA/G-quadruplex but also the conformations of other G-rich DNA, such as spb1, htelo, and intermolec-htelo. The self-assembly of luminescent metalloamphiphiles thus provides a general and convenient strategy for the efficient recognition and conversion of molecular information.

A novel low-molecular-mass gelator containing a redox-active ferrocenyl group, cholesteryl glycinate ferrocenoylamide (CGF), was intentionally designed and prepared. It was demonstrated that the gelator gels 13 out of the 45 solvents tested. Scanning electron microscopy (SEM) measurements revealed that the gelator self-assembled into different supramolecular network structures in different gels. Chemical oxidation of the ferrocenyl residue resulted in phase transition of the gel from gel state to solution state. FTIR and (1)H NMR spectroscopy studies revealed that hydrogen bonding between the gelator molecules in the gel was one of the main driving forces for the formation of the gels.

Abstract: Ferrocene (Fc) as a pendant structure has been intentionally introduced into three dicholesteryl derivatives of a LS2 type structure, where L denotes a linker and S stands for a steroidal unit. The compounds as designed are denoted as 1, 2 and 3 according to the number of hydrogen-bonding sites in the linkers. Gelation tests revealed that 1 gelates none of the 34 solvents tested, 2 gelates some of the alkanes, and 3 gelates only cyclohexane and DMSO. Importantly, the gel system of 2/n-decane exhibits a sol–gel phase transition upon thermal, ultrasonic, mechanical or even chemical treatments. FTIR, temperature- and concentration-dependent 1H NMR spectroscopy measurements revealed that intermolecular hydrogen-bonding is one of the driving forces for gel formation. XRD analysis demonstrated that 2 exists in a stretched conformation and aggregates into layered structure in its n-decane and cyclohexane gels. Far from that expected, introduction of Fc unit does not bring the redox responsive properties to the gel systems. [Copyright &y& Elsevier]