Biomedical subjects
Publications and source records attributed to K Travis Holman.
The well-known hexameric capsules sustained by self-assembly of resorcin[4]arenes 1 with water molecules (1(6).(H2O)8) are shown to assemble similarly with (+/-)-2-ethylhexanol (2EH) as an achiral 1(6).(2EH)6.(H2O)2 species which further encapsulates 2EH.
Metalation of the exterior arene faces of the molecular capsule (+/-)-cryptophane-E with [Cp*Ru]+ moieties results in a pi-acidic cavity capable of encapsulating anions. The [CF3SO3]- and [SbF6]- salts have been crystallographically characterized and demonstrate the encapsulation of these anions by the metalated cryptophane. 1H and 19F NMR spectroscopy establish the binding of anions in NO2CD3 solution and reveal the relative affinity of the cavity for different anions (KX-/KOTf-): [BF4]- approximately 0, [PF6]- = 1.18, [CF3SO3]- identical with 1, [SbF6]- = 0.30. Variable temperature rate studies reveal the activation barrier for triflate encapsulation to be DeltaG298K = 18.0(8) kcal.mol-1 (DeltaH = 17.5(4) kcal.mol-1 and DeltaS = 2(1) cal.mol-1.K-1).
The iodine(III) reagent, PhI[double bond, length as m-dash]NTs, acts as a source of the nitrene fragment NTs, which undergoes facile insertion into the metal-sulfur bonds of a range of dithiocarbamate complexes. Addition of two equivalents of PhI=NTs to [M(S(2)CNR2)2] affords sulfido-amido complexes [M{SC(NR2)SNTs}2](M=Ni, Cu), which insert two further nitrene fragments to afford zwitterionic tetraamido complexes [M{TsNSC(NR2)SNTs}2](M=Co, Ni, Cu). Crystallographic studies have been carried out on both types of complex allowing possible resonance hydrids of the new ligand types to be assessed.
Explore the source record for details and available documents.
Technetium-99 (beta-, t(1/2) = 2.15 x 10(5) years) is produced in a 6% fission yield from fission reactors. Technetium-99 continues to be of major concern at various nuclear sites because of its mobility in its most common chemical form during the reprocessing cycle and in the environment. Under these oxic aqueous environments the chemical form of Tc is typically Tc(VII)O4-, which is difficult to remove. Methods for pertechnetate removal to date have mixed results and pose further environmental concerns. Utilization of new cyclotriveratrylene host materials for the extraction of pertechnetate from 0.9% saline into nitromethane has shown high selectivity and efficiency. A deep-cavity host, tris[cyclopentadienyliron(II) arene]cyclotriguiasylene (2), has shown >95% extraction of pertechnetate and perrhenate into nitromethane from saline in the presence of competing anions, outperforming previously reported materials.