Ji Liu

Peripherally dimethyl isophthalate-functionalized poly(benzyl ether) dendrons: a new kind of unprecedented highly efficient organogelators.

A series of poly(benzyl ether) dendrons, up to the fourth generation, decorated in their periphery with dimethyl esters were divergently synthesized and fully characterized. These dendrons were found to be unprecedented highly efficient organogelators toward various aromatic and polar organic solvents with the critical gelator concentration (CGC) approaching 2.2 mg/mL. The gelation ability was found to be highly dependent on the nature of the peripheral groups, dendron generation, and the dendritic architecture. The large monodisperse dendron G(4) with a globular shape could also form stable gels in several aromatic solvents with relatively high CGCs. A number of experiments (SEM, TEM and AFM imaging, X-ray crystal structure analysis, concentration- and temperature-dependent (1)H NMR spectroscopy, fluorescence spectroscopy, and powder X-ray diffraction) confirmed the self-aggregation of these dendrons, despite the lack of any conventional gelating motifs such as amides, long alkyl side chains, and steroidal groups. The multiple strong pi-pi stacking interactions due to the peripheral dimethyl isophthalate rings and the internal benzyl rings are found to be the key contributor in forming the self-assembled gel.

N-Boc-Protected 1,2-Diphenylethylenediamine-Based Dendritic Organogels with Multiple-Stimulus-Responsive Properties

A new class of poly(benzyl ether) dendrimers, decorated in their cores with N-Boc-protected 1,2-diphenylethylenediamine groups, were synthesized and fully characterized. It was found that the gelation capability of these dendrimers was highly dependent on dendrimer generation, and the second-generation dendrimer (R,R)-G(2)DPENBoc proved to be a highly efficient organogelator. A number of experiments (SEM, TEM, FTIR spectroscopy, (1)H NMR spectroscopy, rheological measurements, UV/Vis absorption spectroscopy, CD, and XRD) revealed that these dendritic molecules self-assembled into elastically interpenetrating one-dimensional nanostructures in organogels. The hydrogen bonding, π-π, and solvophobic interactions were found to be the main driving forces for formation of the gels. Most interestingly, these dendritic organogels exhibited smart multiple-stimulus-responsive behavior upon exposure to environmental stimuli such as temperature, anions, and mechanical stress.

Highly Enantioselective Hydrogenation of 2,4‐Diaryl‐1,5‐Benzodiazepines Catalyzed by Dendritic Phosphinooxazoline Iridium Complexes

A PHOX with arms: A series of dendrimers with Ir phosphinooxazoline (PHOX) cores were designed and synthesized and found to be highly effective and recoverable catalysts for asymmetric hydrogenation of 2,4-diaryl-1,5-benzodiazepines. An obvious positive dendritic effect on reactivity was observed, leading to chiral nitrogen-containing heterocycles with excellent enantioselectivities.

Janus dendritic phosphines: synthesis and application in Suzuki coupling reactions

A new kind of codendrimer consisting of a Frechet-type dendron and a Tomalia-type PAMAM dendron has been synthesized via a liquid-phase approach, which could easily be purified using a simple precipitation method without the need for chromatographic separation. Functionalization at the periphery of a PAMAM dendron with bis(diphenylphosphinomethyl)amino groups led to a novel class of Janus dendritic phosphines. Their use as a recyclable homogeneous catalyst has been demonstrated with the Pd-catalyzed Suzuki coupling reaction.