This article was downloaded by: [Memorial University of Newfoundland]On: 02 August 2014, At: 05:07Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Polycyclic Aromatic CompoundsPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/gpol20

AB INITIO AND DFT STUDIES ONCERTAIN η6-ANTHRAQUINONE -Cr(CO) 3 COMPLEXESLemi Türker a & Selçuk Gümüş aa Department of Chemistry , Middle East TechnicalUniversity , Ankara, TurkeyPublished online: 26 Jun 2008.

To cite this article: Lemi Türker & Selçuk Gümüş (2008) AB INITIO AND DFT

STUDIES ON CERTAIN η6-ANTHRAQUINONE -Cr(CO) 3 COMPLEXES, Polycyclic AromaticCompounds, 28:3, 181-192, DOI: 10.1080/10406630802142862

To link to this article: http://dx.doi.org/10.1080/10406630802142862

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

Polycyclic Aromatic Compounds, 28: 181–192, 2008

Copyright c© 2008 Taylor & Francis Group, LLC

ISSN: 1040-6638 print / 1563-5333 online

DOI: 10.1080/10406630802142862

AB INITIO AND DFT STUDIES ON CERTAINη6-ANTHRAQUINONE -Cr(CO)3 COMPLEXES

Lemi Turker and Selcuk GumusDepartment of Chemistry, Middle East TechnicalUniversity, Ankara, Turkey

η6-1,2-, 1,4- and 9, 10-Anthraquinone-Cr (CO)3 complexesare subjected to RHF/6-31 G(d, p), B3LYP/6-31 G(d) andB3LYP/6-31 G(d, p) type quantum chemical treatment. Ineach case the 9, 10-anthraquinone complex has been foundto be more stable than the others. The least stablecomplexes originate from 1, 2-anthraquinone.

Keywords Anthraquinone-Cr(CO)3 complexes, η6-complexes, anthra-quinones, DFT calculations, ab initio calculations

INTRODUCTION

A wide range of η6-arene transition metal complexes are known. Ofthese, the arene-chromium tricarbonyl derivatives are perhaps the moststudied (1–8). In general, the attachment of a metal tricarbonyl unit to anaromatic compound can have several consequences: 1) activation of thearomatic ring to nucleophilic attack; 2) enhancement of aryl-H acidities;3) steric inhibition of attack on functional groups from the same side asthe metal carbonyl group; 4) stabilization of any charge on carbons αand β to the arene-metal moiety (1). The first two effects are the mostimportant. The attachment of Cr(CO)3 groups to an aromatic ring leadsto activation to attack by nucleophiles because the metal group acts as akind of electron sink.

Structural arene-Cr(CO)3 complexes can be either in the eclipsedor staggerred arangement depending on whether Cr-CO bond vectors

Received 18 November 2007; accepted 7 March 2008.Address correspondence to Lemi Turker, Middle East Technical University, Department of

Chemistry, 06531, Ankara, Turkey. E-mail: lturker@metu.edu.tr

181

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

182 L. Turker and S. Gumus

are eclipsed with ring carbon atoms. The staggered arrangement is ob-served for the complexes of benzene, acetophenone, hexamethyl ben-zene, phenanthrene, anthracene and naphthalene (1).

On the other hand, haptotropic migrations, in which metal carbonylmoiety shifts from one arene ring to other, are interesting and quitecommon in arene-tricarbonyl chromium complexes (9–12).

In principle, a haptotropic isomerization may arise from anintramolecular, a bimolecular or a dissociative mechanism (9). An in-tramolecular isomerization of the haptotropic type involves the migra-tion of organometalic moiety along one face of the arene while re-maning coordinated with the π -system of the ligand. A bimolecularprocess results from the transfer of the organometalic fragment ontoa decoordinated arene ligand arising from decomposition prior to theformation of rearranged product. Also, it may arise from a mutual ex-change of the Cr(CO)3 units between two complex molecules. In a dis-sociative process the organometalic fragment is removed from the lig-and and it is attached to a non-coordinated π -ligand. In this process adonor solvent or some additives stabilize the migrating organometalicfragment (9).

On the other hand, some theoretical and computational studies werereported on tricarbonyl chromium complexes. Albright et al., considerednaphthalene system and proposed the pathway for the metal-coligandCr(CO)3 migration based on results of the semiempirical calculations atthe level of extended Huckel theory (EHT) (13). Recently, Dotz et al.,reported experimental and some preliminary theoretical results for η6-η6-haptotropic rearrangenent of Cr(CO)3 on substituted phenanthrenesystems (14). Some DFT calculations appeared in the literature veryrecently on Cr(CO)3 complexes of polycyclic hydrocarbons (like naph-thalene, phenanthrene perylene, chrysene) (15, 16).

METHOD

In the present study, after achieving the initial geometry optimiza-tions by using MM2 method, followed by the semi-empirical PM3 self-consistent fields molecular orbital (SCF MO) method (17, 18) at the re-stricted level (19, 20), both ab initio (HF) and Density Functional Theory(DFT-B3LYP) (21, 22) type quantum chemical calculations have beenperformed for the geometry optimizations (restricted level) to obtainenergetically the most favorable structures of the presently consideredspecies. The exchange term of B3LYP consists of hybrid Hartree-Fock

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

Studies on η6-Anthraquinone-Cr(CO)3 Complexes 183

and local spin density (LSD) exchange functions with Becke’s gradientcorrelation to LSD exchange (22, 23). The correlation term of B3LYPconsists of Vosko, Wilk, Nusair (VWN3) local correlation functional(24) and Lee, Yang, Parr (LYP) correlation functional (25).

After preoptimizations (MM2 and PM3 methods) the geometry op-timizations of all the structures have been achieved by the consecutiveapplication of HF/ STO3G, 3-21G and then separately RHF/6-31G(d,p),B3LYP/6-31 G(d), and B3LYP/6-31 G(d,p) methods.

For each set of calculations, vibrational analyses were done (usingthe same basis set employed in the corresponding geometry optimiza-tions). The normal mode analysis for each structure yielded no imaginaryfrequencies for the 3N−6 vibrational degrees of freedom, where N is

FIGURE 1. Geometry optimized structures of the complexes (B3LYP/6-31G(d,p)).

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

184 L. Turker and S. Gumus

FIGURE 1. (Continued)

the number of atoms in the system. This indicates that the structure ofeach molecule corresponds to a local minimum on the potential energysurface. Furthermore, all the bond lengths were thoroughly searched inorder to find out whether any bond cleavage occurred during the geome-try optimization process. All these computations were performed usingthe Spartan 06 package program (26).

RESULTS AND DISCUSSION

In the present study, Cr(CO)3 complexes 1,2-, 1,4- and 9,10-anthraquinone systems are considered. The Cr(CO)3η

6-complexes pos-sess the Cr(CO)3 tripod of 1,2- and 1,4-anthraquinone systems at twodifferent positions in each case which are presently designated as A- andB- type for 1,4-anthraquinone and D- and E- type for 1,2- anthraquinonecomplexes. In the case of 9,10-anthraquinone, the complex is named asC-type. As seen in Figure 1, in A- and D-types, the Cr(CO)3 tripod is onthe ring next to the quinoid ring whereas in B- and D-types it is furtheraway from it.

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

Studies on η6-Anthraquinone-Cr(CO)3 Complexes 185

In the present study, staggered conformations of the complexes ratherthan eclipsed ones are considered because naphthalene, anthracene,phenanthrene are known to form staggered complexes (1). As far aswe know, the complexes shown in Figure 1 have not been synthesizedyet and there exist no molecular orbital calculations on them.

Figure 1 (based on B3LYP/6-31 G(d,p) geometry optimization) alsoshows the bond lengths and direction of the dipole moments. The distancefrom the chromium center to the center of the complexed benzenoidring for A–E type complexes are 1.753, 1.751, 1.726, 1.769, 1.759 A,respectively. The direction of the dipole moments is tilted toward thequinoid ring with exception of C-type complex in which case it inclinesto the Cr(CO)3 tripod. Table 1 shows the dipole moments and pointgroups of the complexes.

The orders of dipole moments are D > E > A > C > B for B3LYP/6-31G(d,p) and RHF/ 6-31 G(d,p) but D > E > A > B > C for B3LYP/6-31G(d) type calculations. Note that metal group and quinone carbonylsattract electron populations from the complexed benzenoid ring causinglarge positive charge development. The combined effect is greater for D-than E- type complex and also greater for A- than B- type complex.

As the complexation site gets away from the quinoid ring, the in-tervening benzenoid ring buffers the electron demand of the electronwithdrawing groups. Hence, the dipole moments of E and B are are lessthan their mate A- and D-types.

Table 2 shows the energies of the complexes in Hartree. The RHF/6-31G(d,p) and B3LYP/6-31 G(d) level of calculations give the same order of

TABLE 1. Dipole Moments (in Debye) and Point Groups for the ComplexesConsidered

A B C D E

B3LYP/6-31G(d,p) 5.07 Cs 3.19 Cs 3.87 C1 8.29 C1 7.17 C1

B3LYP/6-31G(d) 5.08 Cs 4.91 Cs 3.85 C1 8.32 C1 7.17 C1

RHF/6-31G(d,p) 2.26 Cs 1.42 Cs 1.57 Cs 7.59 C1 6.80 C1

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

186 L. Turker and S. Gumus

TABLE 2. Total Energies (in Hartree) of the Complexes

Complex HF/6-31G(d,p) B3LYP/6-31G(d) B3LYP/6-31G(d,p)

A −2065.629892 −2072.986774 −2072.999566B −2065.631298 −2072.989552 −2073.002264C −2065.666895 −2073.019806 −2073.032692D −2065.624372 −2072.983045 −2072.995851E −2065.631296 −2072.989552 −2072.998465

stability; that is C > B ≥ E > A > D, whereas, the results of B3LYP/6-31G(d,p) calculations give rise to stability order of C > B > A≥E > D.In general, all types of calculations predict the parallel results, with theexception of A and E, for the order in the series. Moreover, C appearsto be the most stable of all and the structures in which a benzenoid ringintervenes the complexation site and the quinoid site are more stable thantheir conterparts (B > A and E > D for stability).

As for the thermodynamic properties (H◦, S◦ and G◦) of these isomericcomplexes, the results indicate that there is no parallelism between theresults of different levels of calculations. In the case of B3LYP/6-3 G(d,p)level, C > B > A > E > D order (C being the most negative value) holdsfor H◦ values. Whereas, S◦ follows the order of E > D > C > B > A (Ebeing the most positive value). As for the G◦ values, the order in absolutevalues is C > B > A > D > E (where C has the most negative value). Thecomputer program used assumes that molecules are isolated at a tempera-ture of zero Kelvin and with stationary nuclei. The calculations make useof a set of normal-mode vibrational frequencies and the “normal-mode”approximation. However, as molecules get larger, the approximationbecomes less valid. Because of that relative orders of thermodynamic

TABLE 3. FMO Energies and Interfrontier Energy Gaps of the Complexes

Energies (eV)Method ofcalculation A B C D ERHF/6- LUMO(εL) 0.739932100 0.810369433 1.08533384 0.807879764 0.68106311131G(d,p)

HOMO(εH) −6.02538085 −6.11424558 −6.22007900 −6.24367345 −6.33491957�ε = εL − εH 6.76531295 6.924615013 7.30541284 7.051553214 7.015982681

B3LYP/6- LUMO(εL) −3.44825041 −3.28254487 −3.14263103 −3.29973598 −3.3774313931G(d)

HOMO(εH) −5.67879300 −5.65551286 −6.00140111 −5.91972160 −5.88088444�ε = εL − εH 2.23054259 2.37296799 2.85877008 2.61998562 2.50345305

B3LYP/6- LUMO(εL) −3.45314634 −3.28650753 −3.14904308 −3.30503319 −3.3809396431G(d,p)

HOMO(εH) −5.68233013 −5.65722592 −6.00375387 −5.92044424 −5.88301360�ε = εL − εH 2.22918379 2.37071839 2.85471079 2.61541105 2.50207396

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

Studies on η6-Anthraquinone-Cr(CO)3 Complexes 187

properties are more reliable than the numerical values. Hence, the nu-merical values have not been included in the present treatment.

Table 3 shows the frontier molecular orbital energies of the complexesconsidered. The HF and DFT calculations predict controversial energyvalues for the HOMO and LUMO. The RHF/6-31 G(d,p) results for theLUMO and HOMO energies establish the order of E < A < D < B <C and E < D < C < B < A, respectively. Namely, complex E possesses

FIGURE 2. The frontier orbitals of the complexes (B3LYP/6-31 G(d,p)).

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

188 L. Turker and S. Gumus

FIGURE 2. (Continued)

the lowest LUMO and HOMO energies. On the orher hand, the resultsof both of the DFT calculations predict the same order of energies, thatis A < E < D < B < C for the LUMO and C < D < E > A < B for theHOMO. In other words, A and C have the lowest LUMO and HOMOenergies, respectively.

On the other hand, interfrontier molecular orbital energy gaps (�ε =εL − εH) follow the same order irrespective of the type of calculations.The order is A < B < E < D < C. Thus, complex C has the largest and Apossesses the smallest gap (see Table 3). Hence, the spectral (UV-VIS)characteristics of these complexes arise in such a way that A absorbs ata longer whereas C at a shorter wavelenght.

Figure 2 shows the HOMO and LUMO of the complexes obtainedwithin the framework of B3LYP/6-31 G(d,p) level of calculations. Asseen there, in all cases, the HOMO is mainly constructed by contributionof atomic orbitals around the complexation site. whereas, the LUMO isgenerated by atomic orbitals of the quinoid part (thus, the quinoid part ofthe complexes is still the main site of nucleophilic attact). The same trendexists for the next HOMO (NHOMO) but the next LUMO (NLUMO)spreads over a larger part of these complexes.

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

Studies on η6-Anthraquinone-Cr(CO)3 Complexes 189

Figure 3 shows the IR spectra of the complexes. Generally, they re-semble each other, except with some intensity differences. The bandintensity around 1350 cm−1 is greater for C than the others, whereas,the band around 1750 cm−1(quinoid carbonyl streching but higher thanexpected) is more intense for D and E type complexes. The intense bandsat 2000–2100 cm−1 ( Cr(CO)3 strechings (27)) have almost equal inten-sity for A–C but the band at lower vawenumber has less intensity for Dand E types.

FIGURE 3. IR spectra of the complexes (B3LYP/6-31 G(d,p)).

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

190 L. Turker and S. Gumus

FIGURE 3. (Continued)

CONCLUSION

The calculations reveal that between the same type of anthraquinonecomplexes (1,2- and 1,4-anthraquinones) B is more stable than A and Emore stable than D. However, the energy differences are not great. Hence,as long as the transition energies are favorable then A↔B and D↔E typehaptotropic conversions may occur. The present treatment also revealsthat the quinoid part of the complexes is still the main site of a nucle-ophilic attack. On the other hand, η-complexes of aromatic compoundsgreatly affect the chemical properties of the parent system and can beused as intermediary compounds for certain chemical conversions.

REFERENCES

1. Pearson, A. J. 1985. Metallo-Organic Chemistry. New York: Wiley.2. Kogen, H., K. Tomioka, S.-I. Hashimoto, and K. Koga. 1981. Diastereoselective

and enantioselective synthesis of 1,2-disubstituted cycloalkanecarboxaldehydes.Tetrahedron 37:3956.

3. Semmelhack, M. F., and A. Yamashita. 1980. Arene-metal complexes in organicsynthesis: synthesis of acorenone and acorenone B. J. Am. Chem. Soc. 102:5924.

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

Studies on η6-Anthraquinone-Cr(CO)3 Complexes 191

4. Maity, B. C., V. M. Swamy, and A. Sarkar. 2001. Assembling monocyclic, spiro-cyclic and fused carbocycles by ring-closing metathesis on an arene–chromiumtemplate. Tetrahedron Letters 42:4373.

5. Bolm, C., and K. 1999. Muniz. Planar chiral arene chromium(0) complexes: Po-tential ligands for asymmetric catalysis. Chem. Soc. Rev. 28:51.

6. Solladie-Cavallo, A., G. Solladie, and E. Tsamo. 1979. Chiral (arene)tricarbonyl-chromium complexes: Resolution of aldehydes. J. Org. Chem. 44:4189.

7. Sur, S., S. Ganesh, D. Pal, V. G. Puranik, P. Chakrabarti, and A. Sarkar. 1996.Stereodivergent C C bond formation on arene-chromium template: endo-selectiveallylation by hosomi-sakurai reaction. J. Org. Chem. 61:8362.

8. Mandal, S. K., and A. Sarkar. 1999. Engineering endo-selectivity in arene-chromiumfunctionalizations: out-of-plane coordination of TiCl4 to ketones leads to stereodi-vergence. J. Org. Chem. 64:2454.

9. Dotz, K. H., and H. C. Jahr. 2004. Tunable haptotropic metal migration in fusedarenes: towards organometallic switches. The Chemical Record 4:61.

10. Kirss, R. U., and P. M. Treichel, Jr. 1986. Haptotropic rearrangements in naph-thalenechromium tricarbonyl complexes. J. Am. Chem. Soc. 108:853.

11. Treichel, Jr., P. M., and R. U. Kirss. 1987. Metalation of the fused polycyclicaromatic ligand in (arene)chromium tricarbonyl complexes: Kinetic and thermody-namic site preferences. Organometallics 6:249.

12. Deubzer, B., H. P. Fritz, C. G. Kreiter, and K. Ofele. 1967. Spektroskopische un-tersuchungen an metallorganischen verbindungen XLV. 1H-NMR-spektren vonnaphthalinchrom(0)-tricarbonyl und seinen derivaten, Journal of OrganometallicChemistry 7:289.

13. Albright, T. A., P. Hofmann, R. Hoffmann, C. P. Lillya, and P. A. Dobosh. 1983.Haptotropic rearrangements of polyene-MLn complexes. 2. Bicyclic polyene-MCp,M(CO)3 systems. J. Am. Chem. Soc. 105:3396.

14. Dotz, K. H., J. Stendel, Jr., S. Muller, M. Nieger, S. Ketrat, and M. Dolg. 2005.Haptotropic metal migration in densely substituted hydroquinoid phenanthreneCr(CO)3 complexes, Organometallics 24:3219.

15. Arrais, A., E. Diana, G. Gervasio, R. Gobetto, D. Marabello, and P. L. Stanghellini.2004. Synthesis, structural and spectroscopic characterization of four [(η6-PAH)-Cr(CO)3] complexes (PAH = pyrene, perylene, chrysene, 1,2-benzanthracene).Eur. J. Inorg. Chem. 2004 (7):1505.

16. Ketrat, S., S. Muller, and M. Dolg. 2007. A Quantum chemical study of the hap-totropic rearrangements of Cr(CO)3 on naphthalene and phenanthrene systems.Phys. Chem. A. 111:6094.

17. Stewart, J. J. P. 1989. Optimization of parameters for semiempirical methods.Method. J. Comput. Chem. 10:209.

18. Stewart, J. J. P. 1989. Optimization of parameters for semiempirical methods. Ap-plication. J. Comput. Chem. 10:221.

19. Leach, A. R. 1997. Molecular Modeling; Essex: Longman.20. Fletcher, P. 1990. Practical Methods of Optimization. New York: Wiley.21. Kohn, W., and L. J. Sham. 1965. Self-consistent equations including exchange and

correlation effects. Phys. Rev. 140:A1133.

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014

192 L. Turker and S. Gumus

22. Parr, R. G., and W. Yang. 1989. Density Functional Theory of Atoms and Molecules.London: Oxford University Press.

23. Becke, A. D. 1988. Density-functional exchange-energy approximation with correctasymptotic behavior. Phys. Rev. A 38:3098.

24. Vosko, S. H., L. Vilk, and M. Nusair. 1980. Accurate spin-dependent electron liquidcorrelation energies for local spin density calculations: a critical analysis. Can. J.Phys. 58:1200.

25. Lee, C., W. Yang, and R. G. Parr. 1988. Development of the Colle–Salvetti correla-tion energy formula into a functional of the electron density, Phys. Rev. B 37:785.

26. Spartan 06 program. Irvine, CA: Wavefunction Inc.27. Andrews, L., M. Zhou, G. L. Gutsev, and X. Wang. 2003. Reactions of laser-ablated

chromium atoms, cations and electrons with CO in excess argon and neon: In-frared spectra and density functional calculations on neutral and charged unsatıratedchromium carbonyls. J.Phys. Chem. A 167:561.

Dow

nloa

ded

by [

Mem

oria

l Uni

vers

ity o

f N

ewfo

undl

and]

at 0

5:07

02

Aug

ust 2

014