Fluorescence Quenching and Size Selective Heterodimerization of a Porphyrin Adsorbed to Gold and Embedded in Rigid Membrane Gaps

Abstract

Octaanionic meso-tetra(3,5-dicarboxylatophenyl) porphyrin 1 was adsorbed to gold electrodes at pH 12 and stayed there after repeated washing with 10-2 M KOH. The fluorescence on sputtered gold surfaces amounted to 10% of the intensity observed on an organic subphase. Addition of 10-6 M aqueous solutions of the manganese(III) complexes of an isomer mixture of tetracationic β-tetraethyl-β‘-tetrakis(1-methyl-4-pyridinium)- and meso-4-(1-methyl-4-pyridinium)phenyl porphyrins 2 and 4 at pH 12 quenched the fluorescence quantitatively. Visible spectroscopy proved that the amount of porphyrin 1 on the gold surface had not changed. The octaanionic porphyrin 1 was then embedded in a membrane by self-assembly of a bolaamphiphile containing two secondary amide groups. Two hydrogen bond chains rigidify such a monolayer. The emission of porphyrin 1 remained after the self-assembly process. 1 was now localized on the bottom of a rigid membrane gap. Its fluorescence was again quantitatively quenched by the tetracationic manganese(III) porphyrinate 2, which fit in with the membrane gap. A larger manganese(III) porphyrin with a phenyl spacer between the porphyrin and methyl pyridinium rings could not enter, and no quenching was observed. The same experiment with a more fluid membrane made of octadecanethiol showed no such discriminating effect. The entrapment of 1,2-trans-cyclohexanediol within the “immobile” water volume of the membrane gap is also reported. Water-soluble compounds have thus been separated within a 2 nm3 water volume from bulk water. So far, the membrane pores with a porphyrin bottom resemble natural enzyme clefts.

Dendron-protected Au nanoparticles—Effect of dendritic structure on chemical stability

“…They proposed that a 'vertex effect' [23] accounted for the difference in decomposition rate. They argued that when amide groups were present, they formed strong hydrogen bonds with one another along the flatter parts of the nanoparticle surface, leaving gaps at the vertices, which could be exploited by cyanide ions to decompose the gold core.…”

Efficient Charge Injection from the S2 Photoexcited State of Special‐Pair Mimic Porphyrin Assemblies Anchored on a Titanium‐Modified ITO Anode

“…Subsequent oxidation of 3,5-triethoxycarbonylbenzyl alcohol with PCC (pyridinium chlorochromate) in dry chloroform afforded 3,5-diethoxycarbonylbenzaldehyde. In the literature procedure, [48] oxidation to the aldehyde was achieved with CAN (cerium(IV) ammonium nitrate) as the oxidant. In our trial, we found it difficult to prevent over-oxidation to the corresponding carboxylic acid with CAN.…”

Nano/Micro Patterning of Inorganic Thin Films

“…Besides a general trend toward miniaturization, nanosized ceramic oxide materials, such as semiconductor nanoparticles, [3][4][5][6][7][8][9][10] nanowires, [11][12][13] nanotubes, 14 and various types of artificial supramolecular entities. 15 along with integration materials including inorganic/organic hybrid materials 16,17 and thin films 18 are interesting because of the size-/ thickness-dependent properties of materials and because of their potential for a broad range of applications. Functional ceramic thin films exhibit unique properties in electronics, coatings, displays, sensors, optical equipment, and numerous other technologies, and suit the need for scaling devices to small sizes, and are therefore attractive both in theory and practice.…”