Sym-benzvaleno-benzo-benzvalene,a double valence isomer of anthracene

Dilithio-s-indacene ($\text{1}$) on reaction with excess chlorocarbene produces s-benzvaleno-benzo-benzvalene ($\text{3}$). Unlike benzvalene, it does not aromatize on heating but decomposes stepwise to 1,5- and 1,7-bis-methylene-dihydro-indacene ($\text{6}$ and $\text{7}$).     

New 3D metal–organic framework isomer containing trinuclear oxo-centered mixed valence iron

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Integration of nitrogen into coronene bisimides

N-Decorated PBIs and CBIs have been synthesized by the combination of Pictet-Spengler condensation and subsequent oxidative aromatization based on highly electron-deficient amino-PBIs. A detailed analysis of their photophysical properties and molecular crystals has shown that the lateral aryl groups appended on the N-heterocycle have a negligible effect on their optical absorptions and electrochemical potentials, but the subtle modification leads to significant variations on arrangement in the solid state.     

Mössbauer 57Fe isomer shift as a measure of valence in mixed-valence iron sulfides

An empirical formula relating the room-temperature isomer shift δ for high-spin iron in sulfur coordination to the effective iron valence 〈m +〉, of the form δ = A ? B 〈m +〉, has been refined for tetrahedral coordination and modified by an inclusion of orbital degeneracy into the definition of 〈m+〉; it has also been extended to include octahedral coordination by adding 0.17 mm/sec to A. For a given 〈m+〉, the I.S. is shown to be sensitive to nearest-neighbor anion coordination, but much less sensitive than the hyperfine field to the competitive bonding with these anions. However, the sign of the deviation from the empirical line indicates the direction of any net superexchange charge transfer to or from the iron atom. The utility of the relationship is illustrated by application to a wide range of problems.     

New hydrosoluble perylene and coronene derivatives

Several lipophilic perylene and coronene derivatives, employed mainly as liquid crystalline dyes are known and their synthesis has been widely studied. We have applied an analogue strategy using hydrophilic substituents to obtain highly water soluble perylene diimides (4) and a new hydrosoluble coronene derivative (CORON, 6), whose molecular features appear particularly suitable for inducing G-quadruplex DNA structures and inhibiting human telomerase.     

Photochemistry of coronene with water at 10 K: first tentative identification by infrared spectroscopy of oxygen containing coronene products

UV photochemistry of a polycyclic aromatic hydrocarbon model, coronene (C(24)H(12)), has been investigated when it is in interaction with water in argon cryogenic matrices, adsorbed on amorphous water ice films, and embedded in solid water. Photoprocessing, carried out at 10 K and λ > 235 nm by means of a high-pressure Hg arc lamp, results in the oxidation and reduction of coronene. These species have been tentatively identified as being the 1,10-dihydroxycoronene and the 1,10-coroquinone by FTIR spectroscopy with the support of isotopic experiments and DFT calculations. These photochemical products most likely form, after hydrogen bonding between C(24)H(12) and H(2)O, through ionization of the PAH and subsequent reactivity with water upon irradiation. Cations, thus generated, react subsequently with water yielding the production of oxygen containing coronene compounds. Such species are of particular interest as they may form in interstellar and early Solar System ices, and are also of astrobiological significance as they could play an important role in processes taking place in most of the living organisms.     

On the aromatic stabilization of corannulene and coronene

The application of set of homodesmotic reactions allowed us to estimate the aromatic stabilization energy (ASE) of corannulene and coronene. Appropriate reactions have been applied to balance syn/anti mismatches in di-, tetra- and hexamethylene substituted derivatives. Based on many different polycyclic reference structures that compensate the effect of strain in the corannulene moiety the value of ASE comes to 44.5 kcal mol(-1). Planar corannulene is more stabilized by cyclic π-electron delocalization by ca. 10.7 kcal mol(-1), as compared with a bowl-shaped system. A similar approach for coronene leads to an ASE equal to 58.4 kcal mol(-1).     

一种硝基三氮杂蔻化合物的合成及性质研究

通过往蒄中引入氮原子,以氟磺酸为催化剂,通过成环反应合成出目标化合物,并对产物进行了结构表征,对该化合物的性质做了测试,表明该化合物可以作为发光器件分子用于制备电致发光材料。     

Magnetic circular dichroism spectra of triphenylene and coronene

The absorption spectra of triphenylene (I) and coronene (II) are assigned by using the MCD spectra and the results of the SCF screened potential π-MO CI calculations. The calculated Faraday A/D values for the ¹E and ¹E_1u excited states of I and II are in excellent agreement with the experimental values, in contrast to the calculated Faraday B value for the ¹E_1u state of II.     

Prosphorescence and ODMR studies of some coronene compounds

The phosphorescence spectra of 1,2-benzocoronene, naphtho-(2′, 3′; 1,2)-coronene and 1,2;5,6-dibenzocoronene as solutions in n-paraffins were taken at 1.3 K. Basically two strongly radiating sites A and B could be detected. Vibrational analysis yielded a part of the normal modes. ODMR experiments gave different zero-field splittings (ZFS) in sites A and B and the signs of the ZFS parameters. Kinetic rate constants were found to differ too in sites A and B, in particular the out-of-plane rate constants. This seems to indicate a distortion of the molecule which partly removes its planarity. Within one site the out-of-plane kinetic rate constants were found to be much slower than the in-plane rate constants. This difference can be explained within present theoretical models of radiationless processes. From the radiative rate constants in all vibronic bands the radiative mechanisms could be discussed in terms of spin-orbit coupling.     

ESR and theoretical studies of trimer radical cations of coronene

Highly resolved ESR spectra of monomer, dimer and trimer radical cations of coronene (C24H12) were observed at room temperature for a solution of 1,1,1,3,3,3-hexafluoro-2-propan-2-ol (HFP) containing thallium(III) trifluoroacetate as oxidant. The spectra consisting of multiple lines with isotropic 1H-hyperfine splitting (hfs) constants of 0.0766 mT (24H) and 0.013 mT (6H) were attributable to a mixture of the dimer with the trimer radical cations, (C24H12)2+ and (C24H12)3+. For (C24H12)2+, the 1H-hfs constant agreed well with the reported value, 0.077 mT. However, for (C24H12)3+, the values were significantly different from the reported ones, 0.117 mT (12H) and 0.020 mT (24H), by Ohya Nishiguchi et al. [H. Ohya-Nishiguchi, H. Ide, N. Hirota, Chem. Phys. Lett. 66 (1979) 581], but rather similar to those reported by Willigen et al. [H. van Willigen, E. De Boer, J.T. Cooper, W.F. Forbes, J. Chem . Phys. 49 (1968) 1190]. In conflict with Willigen's report, however, no ESR line broadening which has been ascribed to a low stationary concentration of (C24H12)3+ was detected. Based on ab initio MO calculations for benzene as a compact model of C24H12, the structure of (C24H12)3+ was investigated in terms of the observed 1H-hfs constants. A staggered sandwich C(2v) structure was suggested being at the "global" minimum for the benzene trimer cation. In the structure, the unpaired electron spin is predominantly localized to the central ring, which is qualitatively in agreement with the previous ESR results of (C24H12)3+ by Ohya-Nishiguchi et al. In addition, as a "local" minimum, the benzene trimer was indicated to have a slipped sandwich Cs structure, which is less stable by ca. 19 kJ mol(-1) than the "global" minimum. In this structure, the unpaired electron spin was nearly equally distributed on both the central and one of the two side C24H12 molecules. The observed 1H-hfs constants were possibly attributable to the (C24H12)3+ cation with the analogous slipped sandwich Cs structure.     

DFT study of chromium tricarbonyl complexes of coronene and kekulene

A quantum chemical study of the mechanism and determination of the activation barriers of intramolecular η⁶,η⁶-inner-ring haptotropic rearrangements (IHR), consisting in moving a chromium tricarbonyl group Cr(CO)₃ from one six-membered aromatic ring to another, are carried out using the density functional theory (DFT) for the respective η⁶-complexes of coronene I and kekulene II. The stationary states on the potential energy surface, determining the mechanism of η⁶,η⁶-IHR, have a lower hapticity, which is of interest for catalysis because of the possibility of coordinating an additional substrate and reagent around the transition metal during the rearrangement. The processes of η⁶,η⁶-IHR complexes I and II occur with similar energy barriers (ΔG^≠ ≈ 20–25 kcal/mol) that are lower than the barriers (ΔG^≠ ≈ 30 kcal/mol) of similar transformations previously calculated or measured for naphthalene complexes and a number of small polyaromatic hydrocarbons.     

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.     

Spin densities in the trimer cation radical of coronene

The ESR spectrum of the trimer cation radical C^±₃ generated by the partial electro-oxidation of coronene has been observed selectively in a solvent mixture of CH₂Cl₂ and CH₃NO₂ (ratio 3:1) at ?100°C. The spectral analysis has shown that the ratio between the spin densities in the central molecule and those in the side molecule is 6:1. in contrast to the 2:1 ratio predicted by the HMO calculation. This increase of the ratio was rationalized in terms of a McLachlan-type calculation and the stabilization energy of the trimers was estimated to be 0.12 eV. This value agrees with the enthalpy of dissociation obtained experimentally from the temperature of the ESR spectrum.     

Configuration interaction calculations on the dinegative ion of coronene

Configuration interaction calculations using different sets of parameter values were performed to investigate the separation of the ³ A _2g - and ¹ A _1g -levels of the dinegative ions of coronene and annulene. In both cases the separation remains less than 0.1 eV for all four different sets of -values.     

Topological ring-currents and bond-currents in some nonalternant isomers of coronene

The Hückel-London-Pople-McWeeny (HLPM) (topological) approach for calculating π-electron ring-currents and bond-currents in conjugated systems is applied to coronene and the 17 nonalternant isomers of it for which Balaban, Bean, and Fowler recently published ab initio ipso-centric π-electron current-density maps. In a parallel investigation to that conducted by Balaban et al., the key findings of their quantum-mechanical study are confirmed by this topological one: (a) all seven rings in all of the 18 structures studied are found to bear substantial diamagnetic ring-currents, greater than the benzene value; (b) all 18 conjugated systems have a pronounced, overall London diamagnetic-susceptibility, perpendicular to their respective molecular-planes; (c) a substantial diamagnetic current runs around the periphery of each of these structures; and (d) there is general agreement between the two studies as to which structures, of those treated, respect the annulene-within-an-annulene model for conjugated systems of this sort. The same ideas are also tested against ring-current and bond-current intensities recently calculated by Randi? et al. using purely graph-theoretical methods that are based on circuits of conjugation. Considerable qualitative agreement is found, and when there is disagreement, arguments are offered as to why the HLPM topological ring-currents and bond-currents are to be preferred.     

Core-extended perylene tetracarboxdiimides: the homologous series of coronene tetracarboxdiimides

Two novel coronenediimide (CDI) derivatives, CDI 2 and dinaphtho-CDI 4, were synthesized via straightforward synthetic routes completing the homologous series of coronene tetracarboxdiimides, which show remarkable optical properties with absorption wavelengths ranging from 380 to 600 nm, high absorption coefficients, and high fluorescence quantum yields.