Increase in foreign grad students.
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Biomedical subjects
Publications and source records attributed to Robert M Yeh.
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Supramolecular chiral induction has been observed in five dinuclear triple-stranded helicates composed entirely of achiral components. Three different chiral cations were found to be very effective at inducing high levels of enantiomeric enrichment in racemic mixtures of the helicates. The mechanism of intermolecular chiral induction in one cation-helicate pair, s-nic/K6[Ga2L(1)3], has been elucidated through circular dichroism spectroscopy, X-ray crystallography, and one and two-dimensional NMR spectroscopy (s-nic = N-methyl-s-nicotinium, H4L(1) = 1,4-bis(2',3'-dihydroxybenzamido)phenylene).
As an extension to a rational design for the formation of self-assembled coordination cages, the syntheses for very large M4L4 tetrahedra based on a hexadentate 3-fold symmetric ligand (1,3,5-tris(4'-(2' ',3' '-dihydroxybenzamido)phenyl)benzene (H6L2)) are described. Four tetrahedral M4L2(4) assemblies (M = Al(III), Ga(III), In(III), Ti(IV)), with cavity sizes of around 450 A3, have been characterized by elemental analysis, NMR spectroscopy, and high-resolution electrospray mass spectrometry. Differences in chiral resolution and dynamic behavior of host-guest interactions with previously reported tetrahedral M4L(N)6 and M4L1(4) architectures are highlighted for the ligands 1,5-bis(2',3'-dihydroxybenzamido)naphthalene (H4L(N)) and 1,3,5-tris(2',3'-dihydroxybenzamido)benzene (H6L1). An even larger 3-fold symmetric ligand, 1,3,5-tris(4'-(2' '',3' ''-dihydroxybenzamido)-1',1' '-biphenyl)benzene (H6L3) has been prepared but, due to increased flexibility and deviation from the intended 3-fold symmetry, does not undergo self-assembly to form the M4L3(4) structure.
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