Minoru Takekawa

Synthesis of Hexabenzo[a,cd,f,j,lm,o]perylene

Hexabenzo[a,cd,f,j,lm,o]perylene (HBP), an undecacyclic condensed polycyclic aromatic hydrocarbon with two severely crowded fjord regions, was synthesized by Clars method; the starting material 8H-benzo[fg]-naphthacene-8-one was newly prepared by the glycerol condensation of 5,12-dihydro-naphthacene-5,12-dione. 1H and 13C NMR spectra of HBP were measured and the chemical shifts were completely assigned. Absorption and fluorescence spectra of HBP were also measured and the effects of nonplanarity on its spectroscopic properties was discussed.

Convenient Synthesis of 7H-Naphtho-[1,8-gh]quinolin-7-one

Abstract 7H-Naphtho[1,8-gh]quinolin-7-one was prepared by the glycerol condensation of 3-aminophenalenone in good yields. This method provides a new and convenient synthesis of the compound. NMR spectra of its related compounds were measured, and the rapid interchange between two equivalent α-enone structures was found, which is well known as the phenomenon for the formation of carboxylic acid dimer or hydrogen difluoride ion. GRAPHICAL ABSTRACT

PHOTOCHEMICAL REACTION OF 6H-BENZO[cd]PYREN-6-ONE (NAPHTHANTHRONE)

Fluorescence of naphthanthrone,6H-benzo[cd]pyren-6-one, in degassed organic solution increases on light irradiation, but it stays almost constant in aerated solution. To clarify this phenomenon, the absorption and emission spectra of naphthanthrone were measured in several organic solvents as a function of irradiation time at room temperature and 77 K. The fluorescence enhancement was observed only in solvents containing hydrogen such as ethanol and benzene, but not observed in non-hydrogen-containing solvents. On the basis of the experimental data we proposed the mechanism of the fluorescence enhancement. Naphthanthrone excited to the triplet state on irradiation attracts a near solvent molecule around its carbonyl group to form an association species, which provides strong fluorescence near the wavelength region of the fluorescence of naphthanthrone. The absorption energy and absorptivity calculated for the compound by the ZINDO method were consistent with the experimental results.

CONDENSATION PRODUCTS OF 7H-BENZO[DE]NAPHTHACENE-7-ONE

Condensation reaction of 7H-benzo[de]naphthacene-7-one (1) was conducted in fused salt using zinc dust at 275°C for 2 h. The reaction products were isolated by column chromatography and then purified by recrystallization, yielding crystals of orange-yellow needles as the main product. This compound with an absorption maximum at 450 nm was identified as trinaphtho[2,3-c; 2′,1′,8′-fgh; 2″,1″,8″-uva]-pentaphene by one-dimensional and two-dimensional 1H NMR spectroscopy, which was one of expected condensation products. We are now trying to isolate the other expected condensation products, benzo[vwx]dinaphtho[2,1-a; 8′,1′,2′-cde]hexaphene and benzo[cd]naphtho[2,3-f]anthra[3,2,1-lm]perylene, from the byproducts.

Absorption and Fluorescence Spectra of Nitrobenzanthrones

To identify nitrobenzanthrones (NBAs) such as 3-nitro-7 H -benz[ de ]anthracene-7-one (3-NBA) on the basis of their electronic spectral data, we have synthesized 1-, 2-, 3-, 9-, and 10-NBAs and measured their absorption and emission spectra. The first strong absorption band of the NBAs appeared in the region 350-440 nm; the band of 10-NBA was red-shifted by about 20 nm. The molar absorptivities of 3- and 9-NBA were about two times as large as those of the others. The fluorescence spectra of the NBAs varied more largely with the position of the nitro group compared to the absorption spectra. The quantum yields of fluorescence were very small, ranging from ∼10 m 2 for 2- and 10-NBA to ∼10 m 4 for 1- and 3-NBA. 3-NBA exhibited a characteristic spectrum with two broad bands at 450 and 530 nm. On excitation causing an n ~ * transition in the NBAs, their fluorescence intensities increased by a factor of 10. Phosphorescence was observed at 77 K for all compounds though that of 1-NBA was very weak. These results give the promise of characterizing individual isomers of NBAs on the basis of their spectroscopic data.

Studies of Alkali Fusion of Benzanthrone By-Producing Isoviolanthrone A

The relation between the yields of three isomers of violanthrone--violanthrone A (VOA), violanthrone B (VOB), and isoviolanthrone A (isoVOA)--and the condition of the alkali fusion of benzanthrone have been studied. When the method of alcoholic alkali fusion was applied to benzanthrone at low temperature, the major product was VOB. On the other hand, it was reported by Di Raddo et al. (2) that isoVOA was not obtained as a by-product under proper conditions (alkali fusion at high temperature) of synthesizing VOA. However, the result by the present authors is that 6 ∼ 7 percent of the A compound is isoVOA.

Structure-Reactivity Studies by NMR Spectroscopy and Molecular Orbital Calculation: Nitration of Polycyclic Aromatic Ketones

Abstract Complete assignments of NMR spectra were made for benzanthrones, using 2D correlation spectroscopic techniques of homonuclear H-H COSY and NOESY and heteronuclear CH-COSY and COLOC methods. The nitration positions for 6H-benzo[cd] pyren-6-one (1), 13H-dibenzo[a, de]anthracen-13-one (2), 7H-benzo-[hi]chrysen-7-one (3), 7H-dibenzo[a, kl]anthracen-7-one (4), 5H-benzo[fg]naphthacen-5-one (5) and 7H-benzo[de]anthracen-7-one (6) were determined on the basis of the weak or negative NOE cross peaks, which agreed with the results of the absolute values and phase sensitive 2D NOESY experiment. The nitration positions for the benzanthrones were explained by the appearance of negative or weak NOE cross peaks in the 2D NOESY spectra. Molecular orbital calculations also showed that (1), (2), (4) and (6) have the largest electron densities of the highest occupied molecular orbitals at the carbon atoms where nitration takes place. A correlation can be seen between the 2D NOESY spectra and molecular orbital calcu...

Structural Analysis of Hepta-, Nona-, and Undeca-Cyclic Aromatic Hydrocarbons by NMR Spectroscopy

Large condensed polycyclic aromatic hydrocarbons (LCPAHs) generally have distorted structures due to steric repulsion between neighboring hydrogen atoms. The distortion may influence their physicochemical properties such as electric conductivity, photoconductivity, and photochromism. Accordingly we have synthesized LCPAHs and analyzed their structure. In the present study, we synthesized an undecacyclic aromatic compound, dibenzo[a,rst]-dinaphtho[2,1,8-klm:1′,2′-o]pentaphene (DDPP) and determined the structure by use of NMR spectroscopy. To assign the 1H- and 13C-NMR chemical shifts completely, we used the HMQC-TOCSY (Heteronuclear Multiple Quantum Coherence-Total Correlation SpectroscopY) method in which the original proton-carbon correlation is relayed to neighboring protons in the same spin-system. Furthermore, we compared the chemical shifts (δs) of the heptacyclic aromatic hydrocarbon, peropyrene, the nonacyclic, violanthrene B (VEB), and the undecacyclic, DDPP, and investigated correlations between their local structure and δs. For the protons in the bay region, the averaged δs decrease as molecular size increases: 9.23 ppm (hepta-) > 9.07 ppm (nona-) > 8.77 ppm (undeca-). Similar change in the δs is also found for the protons in the cove region: 9.37 ppm (nona-) > 8.81 ppm (undeca-). Thus, it is noted that the averaged δs for the protons in the cove region become downfield than those for the protons in the bay region. The findings are explained in terms of the anisotropic effect of the local magnetic field of benzene rings.

Nitration of Condensed Polycyclic Aromatic Ketones

Abstract Nitration of three isomeric dibenzanthrones, 13H-dibenzo[a,de]-anthracene-13-one(3), 7H-benzo[hi]chrysene-7-one(4), and 7H-dibenzo[a,kl]anthracene-7-one(5), with concentrated nitric acid was studied under various conditions. The nitration of (3) at 15 °C in 1,1,2,2-tetrachloroethane gave the 5-nitro derivative. The nitration of (4) in boiling acetic acid produced the 9-nitro derivative. The nitration of (5) at 70 °C in acetic acid gave the 5-nitro derivative. These nitro compounds are very useful in synthesizing undecacyclic aromatic hydrocarbons.

Syntheses of Dibenzo[h,rst]Naphtho[8,1,2-cde]Pentaphene and Dibenzo[a,lmn]Anthra[1,2,9-hij]perylene

Abstract Dibenzo[h,rst]naphtho[8,1,2-cde]pentaphcne (9) has been synthesized by the condensation of a mixture of 1-phcnalenone (1) and 13H-dibenz[a,de]anthracene-13-one (2) with zinc dust in the presence of ZnCl2 and NaCl. On the other hand, dibenz[a,lmn]anthra[1,2,9-hij]perylene (17) has been synthesized by Ullmann reaction of bromo derivative of benz[a]anthracene-7,12-dione (11).