Tautomerism in Athraquinones: II. α-Hydroxy-substituted Anthraquinones

Russian Journal of Organic Chemistry, Vol. 41, No. 5, 2005, pp. 707-714. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005,pp. 722-729.Original Russian Text Copyright Ó 2005 by Fain, Zaitsev, Ryabov.

1070-4280/05/4105-0707Ó2005 Pleiades Publishing, Inc.

Tautomerism in Athraquinones: II.* a-Hydroxy-substitutedAnthraquinones

V.Ya. Fain, B.E. Zaitsev, and M.A. Ryabov

Russian University of Peoples� Friendship, Moscow 127349 Russiae-mail: [email protected]

Received October 2, 2003

Abstract�The fine structure of experimental pl,p*-absorption bands of the a hydroxyanthraquinones originates

from the prototropic anthraquinoid tautomerism. The tautomeric transformations occur both in the ground andexcited states of the molecules; therewith the excited states are more sensitive to the tautomerization than theground ones. The wavelength and intensity of the p

l,p*-bands, the values of all quantum-chemical characteristics

studied for the tautomers of a hydroxyanthraquinones are linearly related to the number of hydroxy groups. Theeffect of the isomerism of di- and trihydroxyanthraquinones on this relationship was considered.

The prototropic tautomerism of a-hydroxyanthra-quinones attract a close attention of researchers [2] mainlybecause of a wide application of these compounds asbiologically active substances and drugs, natural dyes andintermediates for preparation of synthetic colorants,chemicals for conserving and processing information,analytic reagents, indicators etc. [3].

Numerous data indicate that the states with tautomeranthraquinoid structures take part in formation of theelectronic spectra of 9,10 anthraquinones [2]. The com-parison of experimental data on positions of the pl,p*-absorption bands with those calculated by quantum-chemical procedures for various tautomers and applicationof the correlation analysis method [4] made it possible tounderstand the complex character of the spectra belong-ing to 1,4-dihydroxy- and 1,2,4-trihydroxy-9,10-anthra-quinones and their anions [5, 6], of 1,2-dihydroxy-9,10-anthraquinone anions [7], of metal complexes withdihydroxyanthraquinones [8], and to remove the dis-crepancies in the reports of different authors on the di-hydroxyanthraquinones ionization [6]. These data servea base for classification of the pl,p*-absorption bands ofthe anthraquinone derivatives [9, 10] for they permit anunderstanding of the fine structure origin in the pl,p*-ab-sorption bands and of the number of the correspondingcomponents. They show that the tautomer anthraquinoidstructures play a more important part in the anthraquinonechemistry than it has been generally recognized up tillnow.

The goal of the present study was investigation of theeffect of hydroxy groups accumulation on the tauto-

merism of a-hydroxyanthraquinones I�XX (Table 1).Some data on the tautomerism of a mono- and dihydroxy-9,10-anthraquinones were reported in [5, 6, 11]. The tauto-merism of 1,4,5-tri- and 1,4,5,8-tetrahydroxy-9,10-anthra-quinones was still unstudied; six prototropic tautomerswere possible for the former compound: one each of 9,10-XI, 1,4- XII, and 1,5-anthraquinone XVI, and three1,10-anthraquinones XIII�XV; for the second compound4 tautomers were presumable XVII�XX (Table 1).

We carried out quantum-chemical calculations for alltautomers of a-hydroxyanthraquinones within a frame-work of the p electron PPP method applying Dewarversion [12] with the use of approximation of variable b[13]. In Table 1 the wavelengths of the maxima (lmax)

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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 5 2005

708 FAIN et al.

Table 1. Results of quantum-chamical calculations for a-hydroxyanthraquinones I�XX

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�and oscillator force (f) of the pl,p*- absorption band,atomization energy (DH), solvation factor (M), the energyof the highest occupied (EHOMO) and the lowest unoccupi-ed (ELUMO) molecular orbitals, and energy of s- andp-bonds (Es and Ep) are compiled.

The assignment of the experimental bands to the tauto-mer forms is performed by comparison with those cal-culated by the quantum-chemical method. The fidelitycriterion of the assignment is not the closest coincidenceof these values but their linear correlation [4]. At the


709TAUTOMERISM I N ATHRAQUINONES: II. a-HYDROXY-SUBSTITUTED ANTHRAQUINONES

Fig. 1. Correlation of lmax on the spectra of a-hydroxy-anthraquinones in ethanol with lcalc calculated by PPP method:(1) 9,10-, 1,4-, and 1,5-anthraquinones; (2) 1,10-anthraquinones.Here and on the other figures the compounds are numerated asin Table 1.

same time the number of absorption bands in the visibleregion of the experimental spectra of some compoundsexceeded the number of probable tautomers, for instance,in the case of 1,4,5,8-tetrahydroxy-9,10-anthraquinone6 bands were observed in ethanol and 9 bands in heptane(Table 2).

As seen from Fig. 1, the points corresponding totautomeric anthraquinones are located on two straightlines: From the common line 1 separated line 2 for 1,10-anthraquinones. These straight lines are described byequations (1) and (2) respectively (Table 3).

lmax (ethanol) = (0.954 ± 0.025)lcalc + (24 ± 11), nm

Number of points N 9, correlation factor r 0.998,standard deviation s 4.5.

lmax (ethanol) = (1.779 ± 0.093)lcalc � (413 ± 47), nm

N 6, r 0.995, s 6.3.

In hydrocarbon solvents the analogous relations arevalid with r 0.989 and 0.996 respectively.

Angular coefficient of equation (2) is 1.779 : 0.954 »1.9 times greater than that of equation (1). The valueindicates that the PPP method simulated the position ofthe pl,p*-bands of the 1,10-tautomers nearly twice lessaccurately than for the other tautomers.

The accuracy of the assignments presented inTable 2 is additionally proved by several mutuallyindependent correlations. For instance, a proportionalresponse of the experimental lmax values of variousa-hydroxyanthraquinones to the tautomerism was observ-ed fitting, e.g., to equation (3) (Table 3).

lmax(exp) = k lmax(1,4,5,8) + l0, nm

Here lmax (exp) correspond to the spectra of 1,4-,1,8-dihydroxy-, 1,4,5-trihydroxy-, and 1,4,5,8-tetra-

Table 3. Correlation parameters of equations (3)

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hydroxyanthraquinones measured in different solvents,lmax (1,4,5,8) are wavelengths of pl,p*-bands of tautomers1,4,5,8-tetrahydroxyanthraquinone in heptane, k is theangular coefficient, l0 = lmax (exp) at lmax (1,4,5,8) = 0.

Linearly related to each other are lmax(exp) belong-ing to bands 5 and 7 (Table 2) (N 4, r 1.00000), 9 and10 (N 5, r 0.99990) with the assumption that the maximumat 544 nm in the spectrum of 1,4,5,8-tetra-hydroxy-anthraquinone taken in ethanol belongs to the band 9 andnot to the band 7. Therewith the validity of this bandassignment to 1,10- and not to 1,4-tautomer is confirmed.Correlations with the calculated values permittedassignment of band 6 to 9,10- but not to 1,4-tautomer.The existence of all these correlations and also poorcorrelations with the wavelengths of p,p*-bands that wecalculated using the INDO/S [22] method confirm thepl,p*-character of the bands under consideration [2].

The above data support the assignment of bands 4, 5,and 6 to 9,10- and bands 9 and 10 to 1,10-anthraquinones.Due to insufficient data the bands 1�3 may only tentativelybe regarded as the components of the vibronic structureof the pl,p*-bands of 9,10-anthraquinones, and band 8as those of 1,10-anthraquinones.

Hence the presence in the visible region of the experi-mental spectra of a-hydroxyanthraquinones of morebands than predicted by the quantum-chemical calcula-tions is due to the appearance of vibronic structure onthe pl,p*-bands of 9,10- and 1,10-tautomers, especiallydeveloped in the spectra measured in nonpolar hydro-

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710 FAIN et al.

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carbons. These facts are consistent with findingspreviously obtained [5] for 1,4-dihydroxyanthraquinone.

It was remarked in [11] that the position of the short-wave pl,p*-band at 403.5 nm of compound I was in

agreement with that calculated by PPP method (404 nm)whereas the lmax of the long-wave band at 423 nm wasconsiderably different from the value calculated forcompound II (471 nm). On these grounds it was concluded


a Numbers of compounds are given not consistent with this relationship.



that in the spectrum a band corresponding to the absorp-tion of 1,10-anthraquinoid tautomer was lacking, and theband at 423 nm was redarded as n,p*-band. Howeverthe point II corresponding to the band at 423 nm is locatedon the straight line 2 (Fig. 1) proving that it belongs to thepl,p*-absorption of the 1,10-tautomer. This is a clearexample of rectifying the error in band assignment withthe help of correlation analysis.

Experimental values of lmax and especially those ofthe molar extinction coefficients åmax significantly dependon the purity of compounds. Therefore the investigationof the tautomerism effect on the wavelength and intensityof the pl,p*-band is more convenient to perform on thecalculated values of lcalc and f free of the solvent influenceand of the experimental errors. We reported in [1] on thespecific features of the proportional response of thesevalues to the tautomerism of 1,2,4-trihydroxy-9,10-anthraquinone. A similar relation is observed also for theother hydroxyanthraquinones. For instance, with the1,4,5-trihydroxyanthraquinone it was revealed in the formof two intersecting lines (Fig. 2).

The values of quantum-chemical characteristics Y ofa-hydroxyanthraquinones are linearly related to thenumber of the hydroxy groups n [equation (4), Table 4].

Y = kn + Y0

This dependence appears separately for each seriesof tautomeric anthraquinones. Due to the existence ofisomeric di- and trihydroxyanthraquinones the relationshipis rather peculiar. The values M, Es, and Ep of dihydroxy-9,10-anthraquinones differ insignificantly, and equation (4)is valid for all six 9,10-anthraquinones. To the lines (4) fitELUMO values of two dihydroxyanthraquinones, f and DHof one, and the lcalc and EHOMO of all the three dihydroxy-9,10-anthraquinones deviate from these lines, but theirarithmetic means fit to the lines (Table 4).

In the case of 1,10-anthraquinones only parametersDH and Es of all 8 compounds are in agreement with aunique equation (4). For lcalc and EHOMO this relationappears in the form of three straight lines, and a pointcorresponding to one of the dihydroxyanthraquinone isoutside of all the three (Fig. 3, Table 4). The remainingcharacteristics are described by two straight lines (e.g.,Fig. 4, Table 4). For 1,4- and 1,5-anthraquinones all pos-sible compounds are in agreement with this relationship.

The values of factors k of equations (4) (Table 4)show that as a rule the characteristics of 9,10-anthra-quinones are the most sensitive to the accumulation of

the hydroxy groups, and those of 1,4 anthraquinones arethe least sensitive.

The atomization energy DH characterizes the com-pound stability in the vapor state, and solvation factorsM correspond to the stability in solution. It follows fromthe DH values (Table 1) that the anthraquinoid tautomerin keeping with their stability in pairs form a series:9,10 > 1,10 > 1,4 > 1,5. The M values show that thestability in solution is described by a nearly oppositesequence: 1,5 > 1,10 > 1,4 > 9,10. The k values ofequations (4) demonstrate an essentially differentinfluence of the tautomerism on the sensitivity of thesecharacteristics to the hydroxy groups accumulation:Whereas for DH this effect is insignificant (the alterationdoes not exceed 5%), they are twice larger for M. These

Fig. 2. Proportional response of lcalc and f of 1,4,5-trihydroxy-

9,10-anthraquinone to tautomerism.

(4)

Fig. 3. Wavelengths of p l,p*-bands of hydroxy-1,10-

anthraquinones as a function of the hydroxy groups number.

1, 2: 9-hydroxyanthraquinones; 3: 5-hydroxyanthraquinones.


712 FAIN et al.

data suggest that the solvation of a-hydroxyanthra-quinone molecules significantly facilitates the tautomerictransformations.

The tautomerism affects the energy of p-bonds toa notably greater extent then the energy of s-bonds (upto 4% against 0.9%) (Table 1). These changes arequalitatively dissimilar: the Ep and Es values for the sametautomers do not correlate with each other. For everytautomeric anthraquinone the Ep and Es values growlinearly with the growing number of the hydroxy groups,and the Es values are thrice as sensitive to the hydroxy



groups accumulation as the Ep values (Table 4). Thesefinding show that the tautomerism occurs due to changesin the energy of both p- and s bonds, but the contributionof the former prevails.

A proportional response of lcalc values to tautomeriza-tion is characteristic of various a-hydroxyanthraquinone[equation (5), Table 5].

lcalc = kl(1,4,5) + l0, nm

Here lcalc corresponds to 1,4- and 1,5-di- and 1,4,5,8-tetrahydroxyanthraquinones, and l(1,4,5) = lcalc of 1,4,5-trihydroxyanthraquinone.

The k factors of equation (5) evidence that with theaccumulation of hydroxy groups (1,4 � 1,4,5 � 1,4,5,8)the sensitivity of lcalc to the tautomerism decreases.A similar relation was observed in the other char-acteristics, for instance, for the 1,4,5-trihydroxy- and1,4,5,8-tetra-hydroxyanthraquinones [equation (6), Table6]. This relation is usually valid only for the anthraquinonescontain-ing a carbonyl group in position 1, whereas thepoints belonging to the 9,10-tautomers as a rule deviatefrom the straight lines. The exception forms only the linefor EHOMO where the deviating point belongs to 1,5-anthra-quinones.

Y(1,4,5,8) = kY(1,4,5) + Y0

The k factors of equation (6) evidence that the intro-duction of the fourth hydroxy group into the moleculeambiguously affects the sensitivity of the quantum-chemical characteristics toward the tautomerism: the mostof them decrease to various extent, but f slightly in-creases. Thus the change in a single parameter is notsufficient for any conclusions on the effect of structuralalterations on the sensitivity of a given compound to thetautomeric transformations..

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Fig. 5. Correlation between lcalc of hydroxy-9,10-anthra-

quinones with EHOMO (1, 2) and ELUMO (3, 4).

The EHOMO characterizes the ground state of themolecules, and ELUMO corresponds to the exited state.In every tautomeric anthraquinone the accumulation ofhydroxy groups results in the mutually proportionalchanges in these characteristics along equation (7)(Table 7).

ELUMO = kEHOMO + E0, eV

The peculiar feature of this relation consists in thefollowing: In event of 9,10-anthraquinone the pointsbelong-ing to the isomeric dihydroxyanthraquinones donot fit to the line 1 but form a seoarate straight line 2,and from the unique line for 1,10-anthraquinones deviatesthe point corresponding to compound VII. The values ofk factors of equation (7) show that the relative sensitivityof the main and excited states of the tautomericanthraquinones to the hydroxy groups accumulation growsin the series 1,4 < 9,10 < 1,10 < 1,5.

The comparison of various characteristics with EHOMOand ELUMO values made in [1] revealed that the tauto-merisation of purpurin and its anions occurred both in theground and in the excited states of molecules; the ac-companying changes in the quantum-chemical char-acteristics were qualitatively different for both statses,and therewith the excited states were more sensitive tothe tautomeric transformations that the ground states.The same trends were observed in the case of a-hy-droxyanthraquinones. Let as consider as an example thechanges in the lcalc values. Correlations described byequation (8) are characteristic of different tautomers, buteach series of 9,10- and 1,10-anthraquinones separatesin two parts (Fig. 5, Table 8).

Here E = EHOMO or ELUMO.

The k factors of equation (8) evidence that the lcalcvalues are very sensitive to the changes both in EHOMOand ELUMO and the relationship is qualitatively differentfor unlike tautomers. The mentioned sensitivity is higherin the excited than in the ground state: for 9,10-tautomers1791:12.44 » 19 times, for 1,4-tautomers 256.25:77.66 »3 times, for 1,10- and 1,5-tautomers 145.7:63.82 »153.58:70.64 » 2 times.

The k values from equation (8) may be used forquantitative estimation of the sensitivity of the groundand excited states of molecules to the displacements ofthe p l,p*-bands resulting from the tautomerictransformations. For instance, the ratios kHOMO(1,10)/

(7)



714 FAIN et al.

kHOMO(9,10) = 63.82:12.44=5.1 and kLUMO(9,10)/kLUMO(1,10) = 1791:145.7= 12.3 indicate that the excitedstate is 12.3:5.1 = 2.4 times more sensitive to 9,10-1,10-anthraquinoid rearrangement that the ground state;therewith the sensitivity of lcalc to the energy change ofthe molecular orbital is greater in the ground state anddecreases in the exceited state.

Hence the values of the quantum-chemical character-istics of a-hydroxyanthraquinones are governed by theknown correlation dependences [4]: the proportionalresponse of various parameters in one series ofcompounds or of a single parameter from two series ofcompounds to versatile structural alterations: introductionsof substituent, changes in its position, and tautomerism.The most of these dependences occurs with very high,often with the limiting correlation factors presenting anunassailable proof of their certainty irrespective of thesmall and even minimum objectively possible number ofpoints.

Therewith our data show that the relationship betweenthe structure and characteristics are not alwaysunambiguous and predictable. This is confirmed, forinstance, by unlike participation of isomeric dihydroxy-anthraquinones in the linear dependences of variousparameters on the number of hydroxy groups (Table 4).This is also supported by the absence of the proportionalresponse of Ep and Es to the tautomerism in 1,4,5-tri-hydroxy- and 1,4,5,8-tetrahydroxyanthraquinones incontrast to that shown by purpurin [1]. The relativelylow (less than 0.990) r values of some correlations forthe 1,4-anthraquinones (Tables 4 and 7) probably alsoindicate the more complicated character of theserelations.

REFERENCES

1. Fain, V.Ya., Zaitsev, B.E., Ryabov, M.A., Zh. Org. Khim., 2005,vol. 41, 43.

2. Fain, V.Ya., Elektronnye spektry pogloshcheniya i stroenie9,10-antrakhinonov. I. 9,10-Antrakhinon i ego mono-zameshchennye antrakinony (Electron Absorption Spectraand Structure of 9,10-Anthraquinones. I. 9,10-Anthra-quinones and Their Monosubstituted Anthraquinones),Moscow: Kompaniya Sputnik+, 2003, 231 p.; Elektronnyespektry pogloshcheniya i stroenie 9,10-antrakhinonov. II.Dizameshchennye 9,10-antrakhinony (Electron AbsorptionSpectra and Structure of 9,10-Anthraquinones. IIDisubstituted 9,10-Anthraquinones), Moscow: KompaniyaSputnik+, 2003, 288 p.

3. Fain, V.Ya., 9,10-Antrakhinony i ikh primenenie (9,10-Anthraquinones and Its Application), Moscow: Tsentr

Fotokhimii Rissian Acad. Nauk, 1999, 92 p.4. Fain, V.Ya., Korrelyatsionnyi analiz elektronnykh spektrov

pogloshcheniya (Correlation Analysis of Electron Absorp-tion Spectra), Moscow: Kompaniya Sputnik+, 2002, p. 29.

5. Fain, V.Ya., Zaitsev, B.E., and Ryabov, M.A., Zh. Obshch.Khim., 2003, vol. 73, p. 1688.


7. Fain, V.Ya., Zaitsev, B.E., and Ryabov, M.A., Zh. Obshch.Khim., 2004, vol. 74, vol. 1681.

8. Fain, V.Ya., Zaitsev, B.E., and Ryabov, M.A., Koord. Khim.,2003, vol. 29, p. 395; 2004, vol 30, pp. 385, 390.

9. Fain, V.Ya., Tablitsy elektronnykh spektrov poglo-shcheniya antrakhinona i ego proizvodnykh (Tables ofElectron Absorption Spectra of Anthraquinone and ItsDerivatives), Leningrad: Khimiya, 1970, vol. 31, pp. 95, 103.

10. Fain, V.Ja., Ait, A.O., Churbanov, V.A., Avakyan, V.G.,Voronezheva, N.I., Svyatoslavskaya, T.A., and Petrov, A.N.,Abstracts of Papers, ICP XX International conference onphotochemistry, Moscow, 2001, p. 235.


12. Dewar, M. J. S., The Molecular Orbital Theory of OrganicChemistry, New York: McGraw-Hill, 1969; D�yuar, M.,Metod molekulyarnykh orbitalei v organicheskoi khimii,Moscow: Mir, 1972, 590 p.

13. Nishimoto, K. and Forster, L.S., Theor. Chim. Acta, 1966,vol. 4, p. 155.

14. Morton, R.A., Biochemical Spectroscopy, Adam Hilger,1975, vol. 2, p. 499.

15. Gornostaev, L.M. and Lavrikova, T.I., Zh. Org. Khim., 1984,vol. 20, p. 2208; Amer, M.M., El-Tarras, M.F., Abd, El, Fat-tah, S., and Metwally, F.H., Egypt J. Pharm. Sci., 1989,vol. 30, p. 271.

16. Tucker, K.B.E., Sawyer, R., and Stockwell, P.B., Analyst.,1970, vol. 95, p. 730.

17. Atlas spektrov aromaticheskikh i geterotsiklicheskikhsoedinenii (Atlas of Spectra of Aromatic and HeterocyclicCompounds), Koptyug, V.A. Ed., Novosibirsk: Inst. Org.Khimii, SO Akad. Nauk SSSR, 1978, vol. 16, p. 162.

18. Brockmann, H. and Niemeyer, J., Chem. Ber., 1968, vol. 101,p. 1341.

19. Brockmann, H., Boldt, P., and Niemeyer, J., Chem. Ber., 1963,vol. 96, p. 1356; Brockmann, H. and Brockmann, H., Jr.,Chem. Ber., 1963, vol. 96, p. 1771.

20. Anoshin, A.N., Val�kova, G.A., Gastilovich, E.A., Klimen-ko, V.G., Kopteva, T.S., Nurmukhametov, R.N., Rodio-nov, A.N., and Shcheglova, N.A., Elektronno-koleba-tel�nye spektry aromaticheskikh soedinenii s getero-atomami (Vibronic Spectra of Aromatic Compounds withHeteroatoms), Moscow: Nauka, 1984, p. 82.

21. Brockmann, H. and Boldt, P., Chem. Ber., 1961, vol. 94,p. 2174.

22. Pople, J.A., Beveridge, D.L., and Dobosh, P.A., J. Chem.Phys., 1967, vol. 47, p. 2026.

Tautomerism in Athraquinones: II. α-Hydroxy-substituted Anthraquinones

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