Photophysics and electrochemistry of a platinum-acetylide disubstituted perylenediimide.

The synthesis and photophysical study of a perylene diimide (PDI) functionalised with platinum acetylide units of the type, trans{-C≡C-Pt(PBu3)2-C≡C-Ph} and comparison with a phenylacetylide substituted model compound are reported. The model compound demonstrates typical perylene absorption and photoluminescence spectra characteristic of singlet excited state formation and decay. The Pt-substitution, however, appears to induce spin-orbit coupling into the chromophore and giving rise to a triplet excited state which was confirmed by transient absorption measurements. This excited state is quenched by oxygen, leading to the formation of singlet oxygen in dichloromethane, recorded by time-resolved near-infrared luminescence measurements.

Solubilized derivatives of perylenetetracarboxylic dianhydride (PTCDA) adsorbed on highly oriented pyrolytic graphite.

The effect on 2D molecular crystallization caused by the addition of propylthioether side groups to the 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecule is investigated using scanning tunneling microscopy (STM). The molecule was deposited from 1-phenyloctane onto highly oriented pyrolytic graphite (HOPG) and imaged at the liquid-solid interface. We observe a different structure to previously reported arrangements of PTCDA due to the presence of the propylthioether side groups which inhibits the formation of the herringbone phase. A model, supported by calculations based on density functional theory, is proposed in which molecules form rows stabilized by hydrogen bonding.

Building multistate redox-active architectures using metal-complex functionalized perylene bis-imides.

A series of multistate redox-active architectures has been synthesized, structurally characterized, and their optical and redox properties investigated. Specifically, two redox-active ferrocene or cobalt-dithiolene moieties have been introduced to the "bay" region of perylene-bisimides. Three of these disubstituted perylene-bisimide species have been structurally characterized by single crystal X-ray diffraction, confirming the twisted nature of the central perylene core. The first isomeric pair of disubstituted perylene-bisimide isomers, N,N'-di-(n-butyl)-1,7-diferrocenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide (2) and N,N'-di-(n-butyl)-1,6-diferrocenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide (3), structurally characterized by single crystal X-ray diffraction are reported and compared. Structural characterization of the cobalt-dithiolene substituted perylene-bisimide, N,N'-di-(n-butyl)-1,7-dicyclopentadienyl-cobalt(II)-dithiolenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide (4), reveals the expected twisting of the perylene core and confirms the ene-dithiolate geometry of the cobalt dithiolene moiety. Cyclic voltammetry measurements, coupled with spectroelectrochemcial and electron paramagnetic resonance studies, of 1-4, where 1 is N,N'-di-(n-butyl)-1,7-diethynylferrocenyl-perylene-3,4:9,10-tetracarboxylic acid bisimide, reveal the two anticipated perylene-bisimide based reductions. In addition, for the ferrocene substituted compounds, 1-3, a single reversible two-electron oxidation is seen with only a small degree of communication between the ferrocene groups observed in the 1,6-isomer where the two ferrocene groups are attached to the same naphthyl moiety. In the case of 4, two reversible reductions associated with the cobalt-dithiolene moieties are observed, confirming communication across the reduced perylene core.

Self-assembly of a pyridine-terminated thiol monolayer on Au(111).

Self-assembled monolayers (SAMs) of 3-(4-pyridine-4-yl-phenyl)-propane-1-thiol (PyP3) on Au(111)/mica have been studied by scanning tunneling microscopy (STM), polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), high-resolution X-ray photoemission spectroscopy (HRXPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The quality of the SAM is found to be strongly dependent on the solvent. Substantial gold corrosion is observed if pure ethanol is used. In contrast, highly ordered and densely packed SAMs are formed from acetonitrile or a KOH/ethanol mixture. The structure is described by a 2 radical3 x radical3 unit cell with the aromatic moiety oriented nearly perpendicular to the surface. The PyP3 films form with the pyridine moiety deprotonated. Variation of pH allows reversible protonation without measurable damage of the SAM.

Bis-morpholine-substituted perylene bisimides: impact of isomeric arrangement on electrochemical and spectroelectrochemical properties.

The synthesis and separation of the 1,6- and 1,7- isomers of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide are reported. Investigations of the electrochemical and spectroscopic, in particular, spectroelectrochemical, properties of the two isomers reveal a sequence of electrochemically and chemically reversible redox processes for both isomers. Importantly, the 1,7-isomer of N,N'-bis(n-butyl)dimorpholino-3,4:9,10-perylenetetracarboxylic acid bisimide was observed to undergo a two-electron oxidation process, which contrasts with the behavior of both the corresponding 1,6-isomer and other related amino-substituted perylene bis-imide species.

Functionalized supramolecular nanoporous arrays for surface templating.

Controlled self-assembly and chemical tailoring of bimolecular networks on surfaces is demonstrated using structural derivatives of 3,4:9,10-perylenetetracarboxylic diimide (PTCDI) combined with melamine (1,3,5-triazine-2,4,6-triamine). Two functionalised PTCDI derivatives have been synthesised, Br(2)-PTCDI and di(propylthio)-PTCDI, through attachment of chemical side groups to the perylene core. Self-assembled structures formed by these molecules on a Ag-Si(111)sqrt3 x sqrt3R30 degrees surface were studied with a room-temperature scanning tunneling microscope under ultrahigh vacuum conditions. It is shown that the introduction of side groups can have a significant effect upon both the structures formed, notably in the case of di(propylthio)-PTCDI which forms a previously unreported unimolecular hexagonal arrangement, and their entrapment behaviour. These results demonstrate a new route of functionalisation for network pores, opening up the possibility of designing nanostructured surface structures with chemical selectivity and applications in nanostructure templating.