New Soluble Near‐Infrared Dyes Based on Terrylene Diimides with Four Aromatic Heterocycles

Terrylene diimides with four aromatic heterocycles (AHTDIs) were synthesized under Stille Cross‐coupling conditions and fully characterized by NMR and mass spectrometry. The aggregation of the terrylene diimide (TDI) was suppressed by four heterocycles substituents on the bay region, and these AHTDIs exhibited good solubility in common organic solvents. The effects of the substituted groups on the optical and electrochemical properties were also investigated. The introduction of four aromatic heterocycles on the bay of TDI resulted in significant red‐shifts of the absorption peak (100 nm), corresponding to a decrease in the band gap from 1.82 to 1.50 eV. Furthermore, with four rich electron aromatic heterocycles, the AHTDIs showed 280 mV negative‐shifts of first oxidation potentials and a new oxidation wave, corresponding to an increase in the HOMO levels from??5.60 to??5.28 eV.     

Synthesis and Optical Properties of Water‐Soluble Polyglycerol‐Dendronized Rylene Bisimide Dyes

Four new water‐soluble polyglycerol‐dendronized perylene, terrylene, and quaterrylene bisimides have been synthesized and characterized with respect to their optical properties in polar organic solvents and water by using UV/Vis and fluorescence spectroscopy. All of these dyes were highly soluble in water, but the size of the chosen polyglycerol dendron was only sufficient to completely suppress dye aggregation for the core‐unsubstituted perylene derivative. Their high solubility in water and their absorption and emission wavelengths up to the NIR region make the core‐unsubstituted perylene and terrylene bisimides ideal candidates for applications in bioimaging, whilst the lack of fluorescence for quaterrylene bisimide in all polar solvents does not warrant further investigation of this chromophore in fluorescence and imaging applications. Likewise, tuning of the emission of rylene bisimides towards longer wavelengths by employing electron‐donating bay substituents is not a promising strategy, owing to the lower fluorescence quantum yields in polar solvents and, in particular, in water.     

Synthesis and Electrochemical and Photophysical Properties of Azaterrylene Derivatives

A series of terrylene derivatives, such as monoazaterrylene (MATerry), 1,6‐diazaterrylene (DiATerry) and pristine terrylene (Terry), were synthesized by changing the number of nitrogen atoms at the bay region (1 and 6 positions of the Terry core). The electrochemical measurements suggested that the first one‐electron reduction and oxidation potentials became positively shifted with increasing numbers of nitrogen atoms. This agreed with the energies of the corresponding highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states estimated by DFT methods. In contrast, the HOMO–LUMO gaps approximately remained constant. This trend is quite similar to the spectroscopic behaviors observed by absorption and fluorescence spectra. The solvent polarity‐dependent spectroscopic trends of DiATerry suggested the intramolecular charge‐transfer (ICT) characters. The evaluation of the excited‐state dynamics in various solvents indicated the electronic configurational changes of the excited states relative to the ground state via the ICT. This was supported by the Lippert–Mataga plots. Finally, the reversible protonation and deprotonation processes were also observed.     

Thermally-Polymerized Rylene Nanoparticles

Rylene dyes functionalized with varying numbers of phenyl trifluorovinylether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene and terrylene diimide derivatives containing either two or four phenyl TFVE functional groups were synthesized and subjected to thermal emulsion polymerization in tetraglyme. Dynamic light scattering measurements indicated that particles with sizes ranging from 70 - 100 nm were obtained in tetraglyme, depending on monomer concentration. The photophysical properties of individual monomers were preserved in the nanoemulsions and emission colors could be tuned between yellow, orange, red, and deep red. The nanoparticles were found to retain their shape upon dissolution into water and the resulting water suspensions displayed moderate to high fluorescence quantum yield.     

Raman and infrared spectroscopy of selected vanadates

Raman and infrared spectroscopy has been used to study the structure of selected vanadates including pascoite, huemulite, barnesite, hewettite, metahewettite, hummerite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadates anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands at the higher wavenumbers. The Raman spectra of these minerals are characterised by two intense bands at 991 and 965 cm(-1). Four pascoite Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites. The other minerals namely barnesite, hewettite, metahewettite and hummerite have similar layered structures to the decavanadates but are based upon (V5O14)3- units. Barnesite is characterised by a single Raman band at 1010 cm(-1), whilst hummerite has Raman bands at 999 and 962 cm(-1). The absence of four distinct bands indicates the overlap of the vibrational modes from two of the VO6 sites. Metarossite is characterised by a strong band at 953 cm(-1). These bands are assigned to nu1 symmetric stretching modes of (V6O16)2- units and terminal VO3 units. In the infrared spectra of these minerals, bands are observed in the 837-860 cm(-1) and in the 803-833 cm(-1) region. In some of the Raman spectra bands are observed for pascoite, hummerite and metahewettite in similar positions. These bands are assigned to nu3 antisymmetric stretching of (V10O28)6- units or (V5O14)3- units. Because of the complexity of the spectra in the low wavenumber region assignment of bands is difficult. Bands are observed in the 404-458 cm(-1) region and are assigned to the nu2 bending modes of (V10O28)6- units or (V5O14)3- units. Raman bands are observed in the 530-620 cm(-1) region and are assigned to the nu4 bending modes of (V10O28)6- units or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

Single-molecule spectroscopy of uniaxially oriented terrylene in polyethylene.

Single terrylene molecules doped into linear low-density polyethylene can be oriented by tensile deformation of the matrix. In measurements on ensembles at ambient and on single terrylene molecules at cryogenic temperature, strong orientation along the stretching direction was observed by polarization-resolved confocal microscopy. At cryogenic temperatures narrow and spectrally stable zero-phonon lines were found. The low saturation intensity of 0.07 W cm(-2) is consistent with an uniaxial orientation of terrylene in the sample plane.     

Ferrocene-decorated (phthalocyaninato)(porphyrinato) double- and triple-decker rare earth complexes: synthesis, structure, and electrochemical properties

A series of four mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes (Pc)M[Por(Fc)(2)] [Pc = phthalocyaninate; Por(Fc)(2) = 5,15-di(ferrocenyl)-porphyrinate; M = Eu (1), Y (2), Ho (3), Lu (4)] and their europium(III) triple-decker counterpart (Pc)Eu(Pc)Eu[Por(Fc)(2)] (5), each with two ferrocenyl units at the meso-positions of their porphyrin ligands, have been designed and prepared. The double- and triple-decker complexes 1-5 were characterized by elemental analysis and various spectroscopic methods. The molecular structures of two double-deckers 1 and 4 were also determined by single-crystal X-ray diffraction analysis. Electrochemical studies of these novel sandwich complexes revealed two consecutive ferrocene-based one-electron oxidation waves, suggesting the effective electronic coupling between the two ferrocenyl units. Nevertheless, the separation between the two consecutive ferrocene-based oxidation waves increases from 1 to 4, along with the decrease of rare earth ionic radius, indicating the effect of rare earth size on tuning the coupling between the two ferrocenyl units. Furthermore, the splitting between the two ferrocene-based one-electron oxidations for triple-decker 5 is even smaller than that for 1, showing that the electronic interaction between the two ferrocene centers can also be tuned through changing the linking sandwich framework from double-decker to triple-decker. For further understanding of the electronic coupling between ferrocenyl groups, DFT calculation is carried out to clarify the electronic delocalization and the molecular orbital distribution in these double-decker complexes.     

The mesomorphic and photophysical properties of perylene liquid crystals with different bay-rigid spacers

Three novel perylene derivatives were prepared by introducing two phenyl (biphenyl or naphthyl)-bridging cholesterol units on bay positions and six alkyl chains on imides positions. The influences of different bay-bridging spacers on mesomorphic properties and photophysical properties were investigated. They presented the ordered hexagonal columnar liquid crystalline behaviours, although the large aromatic spacers were bridged on the bay positions. The mesomorphic and photophysical properties could be tuned effectively by the structures of spacers on bay positions. The larger and more rigid aromatic spacer on bay positions resulted in higher phase transition temperatures and stronger fluorescence emission.     

Raman spectroscopic study of pascoite Ca3V10O(28)·17H2O

Raman spectroscopy has been used to study the molecular structure of the vanadate mineral pascoite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadate anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands occurring at higher wavenumbers. The Raman spectrum of pascoite is characterised by two intense bands at 991 and 965 cm(-1). Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites in the mineral structure. In the infrared spectra of pascoite, two wavenumber regions are observed between: (1) 837 and 860, and (2) between 803 and 833 cm(-1). These bands are assigned to ν3 antisymmetric stretching modes of (V10O28)6- or (V5O14)3- units. The spectrum is highly complex in the lower wavenumber region, and therefore the assignment of bands is difficult. Bands observed in the 404 to 458 cm(-1) region are assigned to the ν2 bending modes of (V10O28)6- or (V5O14)3- units. Raman bands observed in the 530-620 cm(-1) region are assigned to the ν4 bending modes of (V10O28)6- or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

Regioselectivity and stereoselectivity of dioxygenase catalysed cis-dihydroxylation of mono- and tri-cyclic azaarene substrates

cis-Dihydrodiol metabolites were obtained from dioxygenase-catalysed asymmetric dihydroxylations of five monocyclic (azabiphenyl) and four tricyclic (azaphenanthrene) azaarene substrates. Enantiopurity values and absolute configuration assignments were determined using a combination of stereochemical correlation, X-ray crystallography and spectroscopy methods. The degree of regioselectivity found during cis-dihydroxylation of monocyclic azaarenes (2,3 bond > 3,4 bond) and of tricyclic azaarenes (bay region > non-bay region bonds) was dependent on the type of dioxygenase used. The cis-dihydrodiol metabolite from an azaarene (3-phenylpyridine) was utilised in the chemoenzymatic synthesis of the corresponding trans-dihydrodiol.     

Transition from a nonbonding to a bonding interaction in a tetranuclear [Mo2]2(mu-OR)4 cluster

Tetranuclear Mo4 clusters with two quadruply bonded Mo2(4+) units, [Mo2(cis-DAniF)2] (DAniF = N,N'-di-p-anisylformamidinate), linked by alkoxides (OCH3 for 1 and OC2H5 for 4) have been prepared. The nonbonding separation between the midpoints of the quadruply bonded units, ca. 3.24 A, is the shortest among compounds having two linked Mo2(4+) units. Electrochemical measurements show two redox waves for each compound with large DeltaE(1/2) values (554 and 587 mV for 1 and 4, respectively) that correspond to K(C) values on the order of 10(9). The large electronic communication is attributed to the short separation between dinuclear units that favor direct delta-to-delta orbital interactions between the two dimetal centers. Compound 1 was chemically oxidized using stoichiometric amounts of ferrocenium salts to a one-electron oxidation product 2 (in which the counteranion is PF6-) and a two-electron oxidation product 3 (which contains two BF4- anions). Upon oxidation there are significant decreases in the distance between the two [Mo2] units to 3.100 A and then to 2.945 A. The mixed-valence species 2 shows two broad absorption bands at 5900 and 7900 cm(-1) in the NIR region which are assigned to the HOMO-1 --> SOMO and HOMO-2 --> SOMO transitions. Compound 3 is fluxional in solution, as shown by variable-temperature 1H NMR spectra. The sharp signals in the NMR spectrum at -50 degrees C and the lack of an EPR signal suggest that this species is diamagnetic and that a four-center, two-electron bond is formed in the cyclometallic Mo4 cluster. To a first-order approximation, an average bond order of 0.25 is assigned to the bonding interaction between the two Mo atoms along the long edges of the rectangle defined by the four Mo atoms.     

Structural and electrochemical studies of novel bis(mu-methoxo)diiron complexes: observation of Fe(III)Fe(IV) and Fe(IV)Fe(IV) states resonating with phenoxyl radicals

Novel diiron complexes with an Fe2(mu-OMe)2 core were studied as models of the active site of nonheme iron-containing enzymes. X-ray crystal structures of the complexes showed the existence of two types of ligand folding-parallel and twisted-both of which have four virtually equivalent phenolato groups sticking out from the Fe2O2 rhombic plane. Cyclic voltammetry measurements revealed two or more distinct redox waves in a region of relatively high potential, in addition to known Fe(II)/Fe(III) redox waves in a region of lower potential. These new peaks were assigned to the high-valence state of iron atoms, that is, Fe(III)Fe(IV) and Fe(IV)Fe(IV), resonating with the phenoxyl radical(s). The split width of the redox waves ranged from 0.14 to 0.20 eV, which may be a measure of the electronic interaction of the phenolate groups through the Fe2(mu-OMe)2 core.     

Synthesis, photophysical, electrochemical, and electrogenerated chemiluminescence studies. Multiple sequential electron transfers in BODIPY monomers, dimers, trimers, and polymer

Synthesis of the C(8) BODIPY monomers, dimers, and trimers, a C(8) polymer, and N(8) aza-BODIPY monomer and dimer was carried out. Methyl and mesityl C(8)-substituted monomers, dimers, and trimers were used. Dimers, trimers, and polymer were formed chemically through the β-β (2/6) positions by oxidative coupling using FeCl(3). A red shift of the absorbance and fluorescence is observed with addition of monomer units from monomer to polymer for C(8) dyes. The aza-BODIPY dye shows red-shifted absorbance and fluorescence compared with the C(8) analogue. Cyclic voltammetry shows one, two, and three one-electron waves on both reduction and oxidation for the monomer, dimer, and trimer, respectively, for the C(8) BODIPYs. The separation for the reduction peaks for the C(8) dimers is 0.12 V compared with 0.22 V for the oxidation, while the trimers show separations of 0.09 V between reduction peaks and 0.13 V for oxidation peaks. The larger separations between the second and third peaks, 0.25 V for the oxidation and 0.2 V for the reduction, are consistent with a larger energy to remove or add a third electron compared with the second one. The BODIPY polymer shows the presence of many sequential one-electron waves with a small separation. These results provide evidence for significant electronic interactions between different monomer units. The aza-BODIPY dye shows a reduction peak 0.8 V more positive compared to the C(8) compound. Aza-BODIPY dimer shows the appearance of four waves in dichloromethane. The separation between two consecutive waves is around 0.12 V for reduction compared with 0.2 V for oxidation, which is comparable with the results for the C(8) dyes. Electrogenerated chemiluminescence (ECL) of the different species was obtained, including weak ECL of the polymer.     

1,6- And 1,7-Regioisomers of Perylene Tetracarboxylic Dianhydride and Diimide: The Effects of Neutral Bay Substituents on the Electrochemical and Structural Properties

Abstract

The electrochemical and structural properties of a series of 1,6- and 1,7-regioisomers of different sized bay-appended perylene diimides (PDIs) and perylene tetracarboxylic dianhydrides (PTCDs) were assessed. Steric effects by large bay substituents triphenylsilylacetylene and tritylacetylene play a major role in the geometry of the solid and solution states. New triphenylsilylacetyene and 1-pentynyl derivatives were prepared and characterized. Suitable crystals for X-ray analysis of tritylacetylene and n-hexyl compounds illustrated the structural alterations in the bay region. The bulky tritylacetylene appended PDI assumed a nearly planar π-configuration, equivalent to an unsubstituted PDI. In contrast, a slender and less bulky hexyl chain incorporated PDI underwent a significant twisting of the central core of PDI. Neutral and conjugated groups at the bay region of PDI enhanced its reductive capability. In contrast, incorporation of neutral and nonconjugated groups at the bay region slightly diminished the reductive capability of resulting PDI derivative. PTCDs consisting of both bulky and slender groups were reduced significantly more readily in relation to the respective PDIs. Electrochemical reductive properties of selected PDIs and PTCDs were obtained along with optical properties of 1,6- and 1,7-PDIs.     

Fluorescence studies of terrylene in a supersonic jet: indication of a dark electronic state below the allowed transition

Jet-cooled terrylene has been studied in helium buffer gas using a pulsed nozzle by means of laser-induced fluorescence. Fluorescence excitation and two-color depletion experiments (resulting in hole burning spectra) are presented. Analysis of the spectra leads to the conclusion that another excited electronic state is present in the vicinity of the allowed 1B1u state. Assuming (according to previous literature suggestions Karabunarliev, S.; Baumgarten, M.; Müllen, K. J. Phys. Chem. A 1998, 102, 7029) that this dark state is the 21Ag state, we discuss the vibrational structure of the fluorescence excitation spectrum in terms of two manifolds of vibronic states belonging to Sd(21Ag) and S1(1B1u) states. The anomalous shift between excitation and dispersed fluorescence spectra observed earlier for terrylene in a neon matrix is discussed as a consequence of terrylene electronic relaxation to the low-energy dark state.     

The impact of vertical π-extension on redox mechanisms of aromatic diimide dyes

Aromatic diimide dyes are an attractive class of redox-active organic molecules for lithium-ion batteries, whose battery performances (stabilities, conductivities and cyclicities) are strongly dependent on the sizes of their π-systems. However, due to the different Clar’s structures possessed, three vertically π-extended aromatic diimides, namely, naphthalene diimide (two one-electron reductions), perylene diimide and terrylene diimide (two one-electron reductions), exhibit different electronic redox mechanisms when served as cathode materials in organic lithium-ion batteries. Herein, we have studied carefully the different electrochemical characteristics of the three aromatic diimides through experimental and theoretical calculations. Their battery present different shape of charge/discharge curves resulting from stability of their reduction state during charge/discharge process. Terrylene diimide shows better cycle and rate capacities than those of naphthalene diimide and perylene diimide, which could be attributed to the more energies released during terrylene diimide combining with lithium ions than those of other two diimides.     

The impact of vertical π-extension on redox mechanisms of aromatic diimide dyes

The impact of vertical π-extension on redox mechanisms of aromatic diimides in the organic lithium-ion batteries have been carefully studied by a combined experiment and theoretical analyses.     

Cyclophanes of perylene tetracarboxylic diimide with different substituents at bay positions

Cyclophanes of perylene tetracarboxylic diimides (PDIs) with different substituents at the bay positions, namely four phenoxy groups at the 1,7-positions (1), four piperidinyl groups at the 1,7-positions (2), and eight phenoxy groups at the 1,6,7,12-positions (3) of the two PDI rings, have been synthesized by the condensation of perylene dianhydride with amine in a dilute solution. These novel cyclophanes were characterized by (1)H NMR spectroscopy, MALDI-TOF mass spectrometry, electronic absorption spectroscopy, and elemental analysis. The conformational isomers of cyclophanes substituted with four piperidinyl groups at the 1,7-positions (2 a and 2 b) were successfully separated by preparative TLC. The main absorption band of the cyclophanes shifts significantly to the higher energy side in comparison with their monomeric counterparts, which indicates significant pi-pi interaction between the PDI units in the cyclophanes. Nevertheless, both the electronic absorption and fluorescence spectra of the cyclophanes were found to change along with the number and nature of the side groups at the bay positions of the PDI ring. Time-dependent DFT calculations on the conformational isomers 2 a and 2 b reproduce well their experimental electronic absorption spectra. Electrochemical studies reveal that the first oxidation and reduction potentials of the PDI ring in the cyclophanes increase significantly compared with those of the corresponding monomeric counterparts, in line with the change in the energy of the HOMO and LUMO according to the theoretical calculations.     

Terrylene in hexadecane revisited: a hole burning study

Holes burnt into the absorption spectrum of terrylene in hexadecane have quite unusual features: spectral diffusion behavior under thermal cycles shows a narrowing regime at very low temperatures (2-5 K) followed by a plateau region (up to about 13 K) and a broadening regime (T>13 K). Thermal line broadening (quasihomogeneous linewidth) shows a nonmonotonous behavior as a function of temperature: at around 4 K there is a maximum followed by a flat minimum and the onset of strong broadening at higher temperatures. Finally, the central hole shows one-sided narrowly spaced side features. This behavior is interpreted within the frame of a two-site model. One of the two sites can be well described by a standard two level system; the other, however, shows characteristic features of a multilevel system. The two sites are characterized by strongly different optical linewidths, phototransformation yields, and thermal stabilities.     

New metal-organic polygons involving MM quadruple bonds: M8(O2CtBu)4(mu-SC4H2-3,4-{CO2}2)6 (M=Mo, W)

The reactions between M2(O2CtBu)4, where M=Mo or W, and thienyl-3,4-dicarboxylic acid (0.5-1.5 equiv) in toluene proceed via a series of detectable intermediates to the compounds M8(O2CtBu)4(mu-SC4H2-3,4-{CO2}2)6, which are isolated as air-sensitive yellow (M=Mo) or red (M=W) powders and show parent molecular ions in their mass spectra (MALDI). The structure of the molybdenum complex was determined by single-crystal X-ray crystallography and shown to contain an unusual M8 polygon involving four Mo2 quadruply bonded units linked via the agency of the six 3,4-thienylcarboxylate groups. The structure has crystallographically imposed S4 symmetry and may be described in terms of a highly distorted tetrahedron of Mo2 units or a bisphenoid in which two Mo2 units are linked by a thienyldicarboxylate such that intramolecular Mo2...O bonding is present, while the other thienylcarboxylate bridges merely serve to link these two [Mo2]...[Mo2] units together. The color of the compounds arises from intense M2 delta-to-thienyl pi transitions and, in THF, the complexes are redox-active and show four successive quasi-reversible oxidation waves. The [M8]+ radical cations, generated by one-electron oxidation with AgPF6, are shown to be valence-trapped (class II) by UV-vis-near-IR and electron paramagnetic resonance spectroscopy. These results are supported by the electronic structure calculations on model compounds M8(O2CH)4(mu-SC4H2-3,4-{CO}2)6 employing density functional theory that reveal only a small splitting of the M2 delta manifold via mixing with the 3,4-thienylcarboxylate pi system.