The initial growth behavior of perylene on Cu(100)

Using scanning tunneling microscopy (STM) together with density functional theory (DFT) the growth behavior of perylene on the Cu(100) substrate has been investigated. As revealed by STM images, perylene molecules prefer to adopt lying configuration with their molecular plane parallel to the substrate, and two symmetrically equivalent ordered domains were observed. DFT calculations show that perylene molecule prefers to adsorb on the top site of substrate Cu atoms with its long molecular axis aligning along the [011] or [01-1] azimuth of the substrate which is the most stable adsorption geometry according to its highest binding energy. Consequently, two adsorption structures of c(8×4) and c(8×6), each containing two perylene molecules per unit cell, are proposed based on our STM images. The growth mechanism for ordered perylene domains on Cu(100) can be attributed to the balance between weak adsorbate-adsorbate interaction and comparable adsorbate-substrate interaction.     

银(110)表面苝有序薄膜电子态的研究

运用紫外光电子能谱(UPS)和低能电子衍射(LEED)技术,对银(110)表面上有机分子苝（perylene）的生长进行了研究.有机分子价带的4个特征峰分别位于费米能级以下3.5、4.8、6.4和8.5 eV处.当有机薄膜约为单分子层(厚度为0.3 nm)时, 苝在银(110)表面上形成C(6×2)的有序结构.角分辨紫外光电子能谱(ARUSP)的测量显示:在界面处的苝分子平面平行于衬底.苝在银(110)表面稳定性很高,随着对衬底加热，有机材料发生脱附,在140 ℃以下没有观察到分解现象.     

纳晶的制备及其光谱的尺寸依赖性

用再沉淀法制备了纳米晶体,向体系中加入水溶性高分子聚乙烯醇（PVA）可有效地抑制纳晶的生长,从而制得了稳定的具有不同粒径的纳晶.光谱研究表明,随着纳晶粒径增加,由于纳晶中分子间相互作用的变化,其吸收峰和激发峰位置都发生了红移,同时纳晶中激基缔合物的荧光发射峰强度减弱,荧光寿命有所延长.     

Effect of the Ortho Alkylation of Perylene Bisimides on the Alignment and Self-Assembly Properties

The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non-ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization.     

Self-assembly and characterization of hydrogen-bond-induced nanostructure aggregation.

A supramolecular system of a perylene derivative containing bis(2,6-diacylaminopyridine) units and a perylene bisimide bound through three hydrogen-bonds was synthesized and characterized. 1H NMR spectra confirmed the existence of hydrogen-bonding interactions between the perylene derivative (3) and the perylene bisimide (7). The photocurrent generation of the self-assembled 3.7 film was measured, and a cathodic photocurrent response was obtained. SEM images indicated that well-defined long fibers could be fabricated by self-assembly, by exploiting the hydrogen bonding interactions and pi-pi stacking interactions of perylene rings.     

In situ and ex situ observations of the growth dynamics of single perylene nanocrystals in water

The growth dynamics of fluorescent perylene nanocrystals, which are fabricated by the reprecipitation method, was investigated using in situ and ex situ single-particle fluorescence measurements. A red shift in the emission maxima as the aging time increased was observed by single-particle fluorescence spectral measurements. The number and size of the nanocrystals increased with the increasing aging time in water. It was concluded that the metastable intermediates, such as clusters and initial nanoparticles, are relevant for the early stages of nucleation and growth of the perylene nanocrystals.     

The growth of perylene on Ru(0001)

The structure of perylene adsorbed on Ru(0001) surface has been studied by ultraviolet photoemission spectroscopy (UPS) and low-energy electron diffraction. An ordered p(4x4) structure is observed from a monolayer (about 4 A thickness) of the perylene on Ru(0001) surface. UPS measurements show the molecular features, from the perylene multiplayer, between 2 and 10 eV below the Fermi level. Angle-resolved ultraviolet photoemission spectroscopy measurements suggest that the perylene molecular plane is parallel to the substrate. Temperature dependent UPS measurements show that the perylene multilayer is stable on Ru(0001) surface up to 125 degrees C. The desorption of the multilayer and the decomposition of the monolayer are observed above 125 degrees C.     

Annellation effects in the perylene and coronene series

Naphtho(2′:3′, 2:3)perylene (VIII), dinaphtho(2′:3′, 2:3); (2″:3″, 8:9)perylene (VII), anthraceno(1′:4′, 1:12)perylene(IV), 1:12-benzonaphtho(2″:3″, 2:3)perylene(II), 1:12-benzonaphtho (2″:3″, 4:5)perylene (III) and 1:12-benzodinaphtho(2″:3″, 2:3); (2″“:3″”,8:9)perylene (XV) were synthesized. There are two different annellation effects in passing from 1:12-benzoperylene (I) to II or III resp., the one in naphthocoronene (V) lies in between these two effects. The annellation effect in the perylene series cannot be related to the molecular axes but is easily explained by the strict application of Robinsons aromatic sextet.     

Characterization of organic overlayers on well-defined substrates

Proceeding from some remarks on the importance of organic/inorganic interfaces and of the controlled growth of thin organic films for both, basic research and present or future applications it is shown that surface sensitive methods like NEXAFS, XPS, ARUPS, and TPD can nicely be applied for studying various model systems. These systems range from perylene single crystals, over perylene and PTCDA layers on Si(111), PTCDA on Ag(111), HCOOH on Ni(111) to adsorption and polymerization of thiophene on a Ag(111) surface. Selected data are shown, and some results are briefly discussed.     

Light-harvesting metallosupramolecular squares composed of perylene bisimide walls and fluorescent antenna dyes

The fluorescent dye 4-dimethylamino-1,8-naphthalimide was incorporated at the bay area of N,N'-bispyridyl perylene bisimide to afford a fourfold-functionalized perylene bisimide ligand. Through self-assembly directed by metal-ion coordination, a multichromophore supramolecular entity composed of sixteen dimethylaminonaphthalimide antennas and a perylene bisimide-walled square core was subsequently constructed from this linear ditopic ligand and 90 degrees metal corner [Pd(dppp)](OTf)2 (dppp=1,3-bis(diphenylphosphino)propane; OTf=trifluoromethanesulfonate) in good yield. The isolated metallosupramolecular square was characterized by elemental analysis and 1H, 13C, and 31P{1H} NMR and UV/Vis spectroscopy. Furthermore, by means of 1H NMR diffusion-ordered spectroscopy (DOSY) the dimension of this assembly was evaluated by employing a previously reported perylene bisimide ligand and its square assembly as references. The results obtained confirm the square framework of the current assembly. The optical properties of this multichromophore dye assembly were investigated by UV/Vis and steady-state and time-resolved fluorescence spectroscopy. It was revealed that light captured by dimethylaminonaphthalimide antennas could be efficiently transported to the perylene bisimide core by a fluorescence resonance mechanism (energy-transfer efficiency E=95%), and this resulted in almost exclusive detection of intense perylene bisimide emission, irrespective of the excitation wavelength applied. The present square scaffold containing aminonaphthalimide antenna dyes exhibits more than seven times higher fluorescence quantum yield (Phifl=0.37) than a previously reported pyrene-bearing perylene bisimide-walled square (Phifl=0.05). Thus, this multichromophore square assembly with aminonaphthalimide antenna dyes is an artificial model for the cyclic light-harvesting complexes in purple bacteria.     

Colloid chemical reaction route to the preparation of nearly monodispersed perylene nanoparticles: size-tunable synthesis and three-dimensional self-organization

By employing a colloid chemical reaction method we demonstrate the preparation of organic nanoparticles composed of perylene molecules (PeNPs) based on the reduction of perylene perchlorate by Br- anions in the presence of cetyl trimethyl ammonium bromide (CTA+Br-) in acetonitrile. A discrete nucleation event, followed by a slower controlled growth on the existing particles, is identified during formation of PeNPs. By changing the growth parameters, such as the monomer concentration and the method of injection, quasi-spherical PeNPs with controllable sizes from 25 to 90 nm could be obtained. The homogeneous solution phase of this method makes it capable of large-scale synthesis of PeNPs with a size distribution (<10%) that is improved by formation of a protective layer of CTA+ around the PeNPs. The three-dimensional, hierarchical self-organization of 25-nm PeNPs building blocks is observed to form nanobelts and square nanorods, possibly templated by the CTA+ lamellar micelle structures in acetonitrile. Spectroscopic results reveal two kinds of trends in the development of the optical properties of perylene as they evolve from the molecular to the bulk phase in the nanometer range. The so-called size dependence is evidenced by a switch from Y-type to E-type excimers as the size of the PeNPs increased from 25 to 90 nm. As the 25-nm PeNPs organize into nanobelts or square nanorods the oscillator strength of the Y-type excimers is relatively enhanced. That is, collective phenomena develop as the proximal particles interact in the glassy solids. Our very recent results indicate that this colloid chemical reaction method can also be applied to other organic compounds.     

Synthesis and characterization of 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole functionalized tetraaryloxy perylene bisimide and metal-directed self-assembly

[structure: see text] New perylene bisimide dyes bearing 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole receptor units with different spacers have been synthesized and characterized. The fluorescence and electronic properties of these compounds have been studied. MALDI-TOF, UV-vis, and fluorescence titration experiments proved that monotopic perylene bisimide ligands could be assembled into dimmers by Fe(III) coordination. The coordination properties of the ditopic perylene bisimide ligands have also been studied preliminarily. Furthermore, the SEM images indicated that well-defined nanoscale structures could be fabricated by self-assembly due to metal ion coordination and pi-pi stacking interactions of perylene rings with the help of a proper spacer.     

Energy transfer in calixarene-based cofacial-positioned perylene bisimide arrays

The synthesis of multichromophoric perylene bisimide-calix[4]arene arrays with up to five perylene units (containing orange, violet, and green perylene bisimide chromophores) and of monochromophoric model compounds was achieved by subsequent imidization of mono-Boc functionalized calix[4]arene linkers with three different types of perylene bisimide dye units. The optical properties of all compounds were studied with UV/vis absorption and steady state and time-resolved fluorescence spectroscopy. Upon excitation of the inner orange dye at 490 nm of array 3, strong fluorescence emission of the outer green perylene bisimide (PBI) chromophore at 744 nm is observed. The fluorescence excitation spectra of compounds 3 and 4 (lambdadet = 850 nm) show all absorption bands of the parent chromophores (e.g., all perylene units contribute to the emission from S1 state of the green PBI). Thus, the fluorescence emission and excitation spectra as well as time-resolved data of fluorescence lifetimes in the absence (tauD = 5.1 ns) and in the presence of an acceptor (tauDA = 0.8 ns) suggest efficient energy transfer processes between the perylene bisimide dye units. For the bichromophoric array 4, the energy transfer rate is calculated to a value of 1.05 x 109 s-1. These results demonstrate highly efficient energy transfer in cofacially assembled dye arrays.     

Comparison of the electronic structure of different perylene‐based dye‐aggregates

Aggregates of functionalized polycyclic aromatic molecules like perylene derivatives differ in important optoelectronic properties such as absorption and emission spectra or exciton diffusion lengths. Although those differences are well known, it is not fully understood if they are caused by variations in the geometrical orientation of the molecules within the aggregates, variations in the electronic structures of the dye aggregates or interplay of both. As this knowledge is of interest for the development of materials with optimized functionalities, we investigate this question by comparing the electronic structures of dimer systems of representative perylene‐based chromophores. The study comprises dimers of perylene, 3,4,9,10‐perylene tetracarboxylic acid bisimide (PBI), 3,4,9,10‐perylene tetracarboxylic acid dianhydride (PTCDA), and diindeno perylene (DIP). Potential energy curves (PECs) and characters of those electronic states are investigated which determine the optoelectronic properties. The computations use the spin‐component‐scaled approximate coupled‐cluster second‐order method (SCS‐CC2), which describes electronic states of predominately neutral excited (NE) and charge transfer (CT) character equally well. Our results show that the characters of the excited states change significantly with the intermolecular orientation and often represent significant mixtures of NE and CT characters. However, PECs and electronic structures of the investigated perylene derivatives are almost independent of the substitution patterns of the perylene core indicating that the observed differences in the optoelectronic properties mainly result from the geometrical structure of the dye aggregate. It also hints at the fact that optical properties can be computed from less‐substituted model compounds if a proper aggregate geometry is chosen. © 2012 Wiley Periodicals, Inc.     

Evolution of absorption, fluorescence, laser and chemical properties in the series of compounds perylene, benzo(ghi)perylene and coronene.

Absorption. fluorescence and laser properties of perylene, benzo(ghi)perylene and coronene are studied experimentally (under the same conditions) and quantum chemically at room (293 K) and at low (77 and 4 K) temperatures and direct comparison is made between the results for each molecule. All the main absorption and fluorescence parameters such as oscillator strength, fe, quantum yield, gamma, decay time, tauf, fluorescence rate constant, kf (Einstein coefficient, A) and intersystem crossing rate constant, kST, are measured or calculated. The systems of singlet and triplet levels for these compounds are simulated and analyzed. Triplet states mixing with the lowest singlet S1 state are determined. The low values of kST found are explained. The possible vibronic coupling in the molecule coronene is discussed. The nature of the three fluorescence bands of coronene observed is interpreted. The change in the arrangement of the singlet and triplet levels of the studied compounds is interpreted quantum-chemically. It is found that at room temperature (293 K), only perylene shows laser action, while all three compounds show good laser oscillation at low temperature (< 100 K). The differences in the laser properties of these compounds are explained by the inversion of the Sp(1La) and Sinfinity(1Lb) levels which occurs in the transition from perylene to benzo(ghi)perylene. Chemical properties of the compounds studied are outlined. Linear and quasi-linear fluorescence spectra of perylene and benzo(ghi)perylene, obtained at 77 and 4 K. can be used in the identification of these compounds.     

Effects of bay substituents on the racemization barriers of perylene bisimides: resolution of atropo-enantiomers

The activation parameters for the interconversion of atropisomers (P- and M-enantiomer) of core-twisted perylene bisimides have been determined by dynamic NMR spectroscopy (DNMR) and time- and temperature-dependent CD spectroscopy. By comparing the activation parameters of a series of perylene bisimides containing halogen or aryloxy substituents in the bay area (1,6,7,12-positions), a clear structure-property relationship has been found that demonstrates that the kinetic and thermodynamic parameters for the inversion of enantiomers are dependent on the apparent overlap parameter Sigmar* of the bay substituents. This study reveals a high stability (DeltaG(368 K) = 118 kJ/mol) for the atropo-enantiomers of tetrabromo-substituted perylene bisimide in solution. Accordingly, the enantiomers of this derivative could be resolved by HPLC on a chiral column. These enantiomers do not racemize in solution at room temperature and, thus, represent the first examples of enantiomerically pure core-twisted perylene bisimides.     

Hydrogen-bonded oligo(p-phenylenevinylene) functionalized with perylene bisimide: self-assembly and energy transfer

We describe the synthesis, supramolecular ordering on surfaces and in solution, and photophysical characterization of OPV4UT-PERY, an oligo(p-phenylenevinylene) (OPV) with a covalently attached perylene bisimide moiety. In chloroform, the molecule forms dimers through quadruple hydrogen bonding of the ureido-s-triazine array. This is supported by scanning tunneling microscopy (STM) studies, which reveal dimer formation at the liquid (1,2,4-trichlorobenzene)/solid (graphite) interface. Moreover, contrast reversal in bias-dependent STM imaging provides information on the ordering and different electronic properties of the oligo(p-phenylenevinylene) and perylene bisimide moieties. In dodecane, the molecule self-assembles into H-type aggregates that are still soluble as a result of the hydrophobic shell formed by the dodecyloxy wedges. The donor-acceptor molecule is characterized by efficient energy transfer from the photoexcited OPV to the perylene bisimide. Mixed assemblies with analogous OPVs lacking the perylene bisimide unit have been prepared in dodecane solution and energy transfer to the incorporated perylene bisimides has been studied by fluorescence spectroscopy.     

Investigation of the two-photon absorption cross-section in perylene tetracarboxylic derivatives: nonlinear spectra and molecular structure

We investigated the 2PA absorption spectrum of a family of perylene tetracarboxylic derivatives (PTCDs): bis(benzimidazo)perylene (AzoPTCD), bis(benzimidazo)thioperylene (Monothio BZP), n-pentylimidobenzimidazoperylene (PazoPTCD), and bis(n-butylimido)perylene (BuPTCD). These compounds present extremely high two-photon absorption, which makes them attractive for applications in photonics devices. The two-photon absorption cross-section spectra of perylene derivatives obtained via Z-scan technique were fitted by means of a sum-over-states (SOS) model, which described with accuracy the different regions of the 2PA cross-section spectra. Frontier molecular orbital calculations show that all molecules present similar features, indicating that nonlinear optical properties in PTCDs are mainly determined by the central portion of the molecule, with minimal effect from the lateral side groups. In general, our results pointed out that the differences in the 2PA cross-sections among the compounds are mainly due to the nonlinearity resonance enhancement.     

Studies on the electrochemical growth of (Per)2[Au(mnt)2

The first stages of the electrocrystallization of (Per)(2)[Au(mnt)(2)] salt from dichloromethane on gold, platinum, and highly orientated pyrolytic graphite (HOPG) were investigated by cyclic voltammetry, atomic force microscopy, and X-ray photoelectron spectroscopy in order to understand the determinant factors for nucleation and crystal growth. The crystal growth occurs from adsorbed films of dithiolate on gold or platinum and of perylene on HOPG, after homogeneous nucleation, and it is controlled by the low diffusion of the species toward the growing surface.