Bio-inspired optically controlled ultrafast molecular AND gate.
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Biomedical subjects
Yongyu Zhao
Publications and source records attributed to Yongyu Zhao.
Charge transport in photofunctional nanoparticles self-assembled from zinc 5,10,15,20-tetrakis(perylenediimide)porphyrin building blocks.
Molecules designed to carry out photochemical energy conversion typically employ several sequential electron transfers, as do photosynthetic proteins. Yet, these molecules typically do not achieve the extensive charge transport characteristic of semiconductor devices. We have prepared a large molecule in which four perylene-3,4:9,10-tetracarboxydiimide (PDI) molecules that both collect photons and accept electrons are attached to a central zinc 5,10,15,20-tetraphenylporphyrin (ZnTPP) electron donor. This molecule self-assembles into ordered nanoparticles both in solution and in the solid-state, driven by van der Waals stacking of the PDI molecules. Photoexcitation of the nanoparticles results in quantitative charge separation in 3.2 ps to form ZnTPP(+)PDI(-) radical ion pairs, in which the radical anion rapidly migrates to PDI molecules that are, on average, 21 A away, as evidenced by magnetic field effects on the yield of the PDI triplet state that results from radical ion pair recombination. These nanoparticles exhibit charge transport properties that combine important features from both photosynthetic and semiconductor photoconversion systems.
Journal Article↗
Equilibrium Acidities and Homolytic Bond Dissociation Enthalpies of the Acidic C-H Bonds in As-Substituted Triphenylarsonium and Related Cations(1).
Equilibrium acidities (pK(HA)s) of As-fluorenyltriphenylarsonium, As-phenacyltriphenylarsonium, six As-(para-substituted benzyl)triphenylarsonium [p-GC(6)H(4)CH(2)(+)AsPh(3)] (G = H, Me, CF(3), CO(2)Me, CN, and NO(2)), and six P-(para-substituted benzyl)tri(n-butyl)phosphonium [p-GC(6)H(4)CH(2)(+)P(n-Bu)(3)] (G = H, Me, CF(3), CO(2)Me, CN, and NO(2)) bromide salts, together with the oxidation potentials [E(ox)(A(-))] of their conjugate bases (ylides) have been determined in dimethyl sulfoxide (DMSO) solution. Introduction of an alpha-triphenylarsonium (alpha-Ph(3)As(+)) group was found to increase the adjacent C-H bond acidities by 13-20 pK units (18-27 kcal/mol). The equilibrium acidities for the two series p-GC(6)H(4)CH(2)(+)AsPh(3) and p-GC(6)H(4)CH(2)(+)P(n-Bu)(3) cations were found to be nicely correlated with the Hammett sigma(-) constants of the corresponding para-substituents (G) (Figures 1 and 2). The homolytic bond dissociation enthalpies (BDEs) of the acidic C-H bonds determined by using eq 1 reveal that an alpha-Ph(3)As(+) group increases the BDE value of the adjacent acidic C-H bond by 2-5 kcal/mol, whereas the substituent effects for an alpha-Ph(3)P(+) or alpha-(n-Bu)(3)P(+) group was found to be dependent on the nature of the substituents attached to the alpha-carbon atom. Good linear correlations were obtained for the equilibrium acidities of As-(para-substituted benzyl)triphenylarsonium and P-(para-substituted benzyl)tri(n-butyl)phosphonium cations with the oxidation potentials of their conjugate bases (ylides) as shown in Figures 3 and 4, respectively.
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Bond Dissociation Free Energies (BDFEs) of the Acidic H-A Bonds in HA(*)(-) Radical Anions by Three Different Pathways.
Cleavage of radical anions, HA(*)(-), have been considered to give either H(*) + A(-) (path a) or H(-) + A(*) (path b), and factors determining the preferred mode of cleavage have been discussed. It is conceivable that cleavage to give a proton and a radical dianion, HA(*)(-) right harpoon over left harpoon H(+) + A(*)(2)(-) (path c), might also be feasible. A method, based on a thermodynamic cycle, to estimate the bond dissociation free energy (BDFE) by path c has been devised. Comparison of the BDFEs for cleavage of the radical anions derived from 24 nitroaromatic OH, SH, NH, and CH acids by paths a, b, c has shown that path c is favored thermodynamically.
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