Biomedical subjects
Publications and source records attributed to James H R Tucker.
The dynamics of pyramidal nitrogen inversion can be controlled by reversible redox switching in trans-2,3-diphenylaziridines bearing a suitable 1,4-naphthaquinone substituent. In the reduced form, an intramolecular H-bond significantly raises the inversion barrier slowing this molecular motion by >50-fold. The experimental findings are further supported by DFT calculations.
A novel anthracene-tagged oligonucleotide can discriminate between a fully-matched DNA target sequence and one with a single mismatching base-pair through a remarkable difference in fluorescence emission intensity upon duplex formation.
The ground- and excited-state properties of a series of photochromic barbiturate receptors (N,N'-bis{6-[omega-(anthracen-9-yloxy)alkanoylamino]pyridin-2-yl}-5-t-butyl-isophthalamide, Tn), in which anthracene chromophores are tethered via (CH2)n (n = 1, 3-6) polymethylene linkers to the H-bond receptor moiety, are described. In these systems, the thermally reversible [4pi + 4pi] photodimerization of the anthracenes yields macrocyclic receptors (TnC) that possess significantly reduced affinity toward barbital as compared to their acyclic counterparts. The length of the tether not only determines the overall binding ability of the cyclized receptor but also has a profound influence on the photochemical and photophysical properties of the anthracene chromophores. The reduced mobility experienced by the covalently bound anthracenes controls the reactivity of a fluorescent excimer that is proposed to be an intermediate in the photocyclization process.
Ferrocene-containing amidopyridine receptors bind carboxylic acids and the amino acid phenylalanine in acetonitrile via a novel proton transfer process that enables guests to be electrochemically sensed by positive shifts in the ferrocene-centred redox potentials.
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A heterodifunctionalised ferrocene, containing a carboxylic acid and an amidopyridine unit, self-assembles in organic solvents through complementary hydrogen bonds.
A ferrocene-based ditopic receptor containing a urea and a benzocrown ether unit shows a remarkable colour switching (ON-and-OFF) function induced by anion and cation recognition.
A new strategy for the asymmetric synthesis of chiral primary alpha-ferrocenylalkylamines has been utilized to generate homochiral redox-active receptors that bind chiral carboxylate anions with moderate enantioselectivity and undergo a redox response to complexation. [structure: see text]
Aza-crown ethers 2 and 3 with anthracene-containing pendant arms have been synthesised and characterised. Both compounds bind Group 1 metal cations in solution, forming complexes of 1:1 stoichiometry. The properties of compound 2 and its complexes have been studied by a range of techniques, including NMR, UV and fluorescence spectroscopy and X-ray crystallography. The pendant arms can adopt either a cis or a trans geometry, the cis geometry favoured with larger cations. The geometry of the complex affects the fluorescence properties of the system, with larger cations giving higher excimer/monomer ratios. Upon irradiation at lambda>300 nm, coronand 2 forms the cryptand 5 through a reversible intramolecular [4pi+4pi] cycloaddition reaction. The rates of the forward and reverse reactions of this photochromic process are cation dependent; in particular the rate of the thermal reverse reaction is decreased by smaller cations and increased by larger cations, especially Rb(+). The metal binding constants in methanol for 2 and 5 have been determined, revealing that the cryptand 5 binds Na(+) and Rb(+) more weakly than crown ether 2 by over two orders of magnitude.
This review summarizes and puts into context recent advances in the field of redox-switched binding processes, with particular reference to the interaction between redox-active compounds and organic compounds, both charged and neutral. Simple homogeneous, two-component systems are discussed at first as a precursor to sections on more advanced systems (e.g. multi-component and multi-pole) and binding processes involving components attached to a surface.