Electronic Structure and Energy Transfer in Europium(III

Article pubs.acs.org/JPCA

Electronic Structure and Energy Transfer in Europium(III)− Ciprofloxacin Complexes: A Theoretical Study Tatiana B. Emelina,†,∥ Alexandra Ya. Freidzon,*,‡,§,∥ Alexander A. Bagaturyants,‡,§ and Vladimir E. Karasev† †

Institute of Chemistry, Far East Division, Russian Academy of Sciences, pr.100-let Vladivostoku 159, Vladivostok 690022, Russia Photochemistry Center, Russian Academy of Sciences, ul. Novatorov 7a, Moscow 119421, Russia § Moscow Engineering Physics Institute, National Research Nuclear University, Kashirskoye shosse 31, Moscow 115409, Russia ‡

S Supporting Information *

ABSTRACT: The structure and ligand-localized excited states of [Eu(cfqH) (cfq)(H2O)4]Cl2 (cfqH is ciprofloxacin) are studied by XMCQDPT2/CASSCF with full geometry optimization. The complex includes one anionic and one zwitterionic ligand. Two low-lying triplet states, both localized on the anionic ligand, are found. One of them has sufficient energy to transfer to the 5D1 sublevel of Eu3+, because its T−S0 vertical transition energy is equal (or very close) to the 7F0−5D1 Eu3+ excitation energy. The other triplet state has a very small S0−T1 gap, which favors fast nonradiative relaxation. Two other triplet states are localized on the zwitterionic ligand. One low-lying excited singlet state (S1) is localized on the anionic ligand; the other excited singlet is localized on the zwitterionic one. Spin− orbit coupling constants were calculated for the relaxed geometry of each state (ground state, two low-lying triplets, and one low-lying excited singlet) by spin−orbit configuration interaction (CI) with Pauli−Breit Hamiltonian. Large spin−orbit coupling constants between S1 and both triplets together with small energy gaps are indicative of fast intersystem crossing (ISC) from the excited singlet state to the triplet manifold. This ISC process is followed by energy transfer from the ligand-localized triplet states to the 5D1 sublevel of Eu3+. However, relatively large spin−orbit coupling constants between S0 and one of the triplet states together with the small T−S0 energy gap shows that this state can decay without transferring its energy to Eu3+. This mechanism is expected to be common for other Ln3+−fluoroquinolone complexes.

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INTRODUCTION

sensitivity of luminescence detection and determination of quinolones in the environment and body tissues. Individual Stark structure of the energy levels in some rare earth ions (europium, terbium, samarium, dysprosium, and erbium) in complexes with quinolones opens the ways for their use as visual luminescent labels of various colors making it possible not only to determine low concentrations of the drugs used but also to find the sites of their localization as well (≪fingerprint method≫).9,23−25 A related problem is to develop rational methods for recovery of discontinued, expired, or out-of-use drugs into light-transforming polymer materials concentrating red and near-infrared light for IR lasers widely used in medical practice. Ciprofloxacin−europium(III) complex [Eu(cfqH) (cfq)(H2O)4]Cl2 was studied experimentally in refs 3, 4, and 25. Eu(III) is coordinated to two ciprofloxacinate ligands, one of them protonated in the piperazine ring (zwitterionic form). In the crystal, the ligands form stacked pairs: one pair formed by

Extensive use of synthetic antibacterial drugs presents a severe environmental problem due to their presence in food or drinking water.1,2 Metabolism of these drugs in body tissues is also of interest for therapeutic and diagnostic applications in medicine. Therefore, there is an urgent need for monitoring these drugs in the environment and body tissues.3,4 Quinolones (ciprofloxacin (cfqH) being an example, Figure 1) are a large and constantly expanding group of synthetic antibacterial agents.5−7 The ability of quinolones to form chelate complexes with metal ions, including rare-earth ones, is used to develop sensitive methods of their determination in the environment.8,9 Thus, sensitive procedures were developed for the determination of quinolones in biological samples using the luminescence of its Tb3+ or Eu3+ complexes.10−16 Lanthanide(III)−quinolone complexes are also used as analytical reagents for some analytes of biological importance.17,18 However, lanthanide(III) coordination compounds are widely used as bioprobes in medicine and biology.19−22 Therefore, it is important to understand the mechanisms of energy transfer upon photoexcitation of these complexes to find the best ligand−lanthanide pairs to improve the efficiency and © 2016 American Chemical Society

Received: July 19, 2016 Revised: August 31, 2016 Published: September 7, 2016 7529

DOI: 10.1021/acs.jpca.6b07258 J. Phys. Chem. A 2016, 120, 7529−7537

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The Journal of Physical Chemistry A

Figure 1. Structural formula (a) and crystal structure (b) of ciprofloxacin−europium(III) complex [Eu(cfqH) (cfq)(H2O)4]2+ (from ref 3).

version from this state (not shown), or go to the nearest triplet state through intersystem crossing (ISC; yellow block arrow), which is facilitated by the presence of a heavy lanthanide ion. For ISC to be efficient, the energy gap between the S1 and the nearest triplet state in the equilibrium geometry of S1 should be sufficiently small. The subsequent fast nonradiative relaxation leads to a local minimum of the lowest triplet state T1. At this particular geometrical configuration, energy is transferred to the nearest excited level of Ln3+ (red block arrow). Finally, the excited complex nonradiatively relaxes to the lowest emissive level (black wavy arrows) and emits a photon (red vertical arrow). Hence, there are two rate-determining steps in the energy transfer process: singlet−triplet conversion of the excited ligand and ligand-to-metal energy transfer. Therefore, the emission of Ln3+ is governed by the relative position of the triplet excited states of the ligands with respect to the resonant levels of the ion and the energy gap between the singlet and triplet states. Hatanaka and Morokuma35 used DFT to explore the reaction coordinate of Tb3+ complexes and find the points where ISC and excitation energy transfer takes place. Previously, we successfully used multireference ab initio methods to describe triplet excited states in mononuclear and dinuclear Ln3+ complexes and to estimate the efficiency of antenna ligands in Ln3+ complexes from level matching in the local minima.36,37 In this paper, we use these methods to study the entire process of ligand-to-Eu3+ energy transfer in

the protonated ligands, and the other one formed by the nonprotonated ones. The luminescence of [Eu(cfqH) (cfq)(H2O)4]2+ is excited by UV irradiation at 340 nm (∼29 400 cm−1), which corresponds to the ligand absorption.4 However, it is known26−28 that the photoexcited ligand cannot directly transfer its energy neither to Eu3+ nor to Tb3+. The energy is transferred from the ligandlocalized triplet state. The triplet energy of cfqH determined from the phosphorescence spectrum of its Gd(III) chelate is 20 500 cm−1.3 The luminescence lifetime for the solid complex was measured to be 920 μs.3 The goal of our paper is to study the mechanism of energy transfer in detail by quantum chemistry using published experimental data as a reference. [Eu(cfqH) (cfq)(H2O)4]2+ complex is a typical representative of Ln3+−fluoroquinolone complexes, and the energy transfer mechanism in such complexes is quite common. Understanding the details of this mechanism will help one to find more efficient ligand− lanthanide pairs for use as luminescent analytical reagents. The general mechanism of photoexcitation and light emission in Ln(III) complexes29−34 is illustrated in Figure 2: upon photoexcitation of a complex (yellow vertical arrow), a singlet exciton is localized on a ligand, which is called antenna. Subsequent fast nonradiative relaxation (blue wavy arrow) leads to a minimum on the potential energy surface of the lowest singlet state S1. Next, the molecule can deactivate through fluorescence, or relax nonradiatively through internal con7530


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tion, the density matrix was averaged over four lowest triplets (SA(4)-CASSCF(12,10)) or three lowest singlets (SA(3)CASSCF(12,10)). After geometry optimization, the vertical triplet and singlet excitation energies were calculated at the optimized geometries by SA-CASSCF with averaging over all target states and corrected by XMCQDPT2. All the calculations were performed using the Firefly software49 partially based on the GAMESS code.50 Spin−orbit coupling constants were calculated for each relaxed state geometry by Spin−Orbit CI implemented in GAMESS50 in the same active space with the two-electron Pauli−Breit Hamiltonian.51−60 The ISC rate kIF ISC from the initial state I to final state F was calculated in the Condon approximation61 as follows, where SO indicates spin orbit. IF kISC =

2π 1 I F ⟨ Ψ 0|HSO|3Ψ 0 ⟩2 |⟨χ0 |χn ⟩|2 ρ ℏ

The Franck−Condon factor ⟨χ0|χn⟩ was taken equal to 1, and ρ = 1/ΔEIF. Using these assumptions, the probability of ISC can be qualitatively estimated.

Figure 2. Energy transfer during photoexcitation of a Eu3+ complex: yellow vertical arrow shows photoexcitation of a complex; blue wavy arrow denotes nonradiative relaxation to the minimum on the potential energy surface of the lowest singlet state; yellow block arrow indicates ISC to the nearest triplet state; red block arrow shows energy transfer to the nearest excited level of Ln3+; black wavy arrows denote nonradiative relaxation of the complex to the lowest emissive level; and red vertical arrow indicates light emission.

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RESULTS AND DISCUSSION Structure of the Ground and Excited States of [Eu(cfqH) (cfq)(H2O)4]2+. The calculated structures of the ground and excited states of [Eu(cfqH) (cfq)(H2O)4]2+ are shown in Figure 3. Except for the piperazine ring, the geometries of both ligands in the ground state differ only slightly (Figure 3a). The same is true for the charge distribution. However, the lowest singlet state S1 is fully localized on the nonprotonated ligand (Figure 3b). The piperazine ring becomes conjugated with the quinolone π system, and C−F bond comes out of plane. The quinolone moiety becomes nonplanar. Two local minima on the triplet potential energy surface are found, both localized on the nonprotonated ligand: one (called T1a) is shown in Figure 3c, and the other one (called T1b) is shown in Figure 3d. The structure of T1a is typical for so-called twisted intramolecular charge transfer states of aromatic amines and push−pull dyes.62−64 The piperazine ring is perpendicular to the quinolone moiety; the bond lengths in the quinolone fragment are redistributed relative to the ground state. The structure of T1b resembles that of S1. The geometry changes in the excited complexes affect only the fluoroquinolone core of the ligand. Therefore, they should be quite common for other fluoroquinolones, and the energy transfer mechanism should also be general for this class of complexes. Energy Diagram and Energy-Transfer Pathways. The energy diagram of [Eu(cfqH) (cfq)(H2O)4]2+ is shown in Figure 4; the energies of the states in the optimized geometries are given in Table 1. Excitation (vertical arrow) leads to the S1 state, and the excitation energy of 31 980 cm−1 satisfactorily agrees with the experimental value of 29 400 cm−1 determined in ref 4. Two singlet states, S1 and S2, localized on the nonprotonated and protonated ligands, respectively, are quasidegenerate, because protonation of the piperazine moiety has only slight impact on the transition energy of the quinolone fragment. The lowest triplet state, T1, is localized on the nonprotonated ligand, and the next one, T2, is localized on the protonated ligand. These states are also quasi-degenerate. The

[Eu(cfqH) (cfq)(H2O)4]2+, focusing both on the level matching and ISC rates, and compare our calculations with the available experimental data.

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COMPUTATIONAL DETAILS Similarly to our previous papers, 36,37 we used scalar quasirelativistic 4f-in-core pseudopotential ECP52MWB for Eu3+ ion with the associated valence basis set.38,39 For other atoms we used the 6-31G(d,p) basis set (6-31+G(d,p) for F). The states of interest were calculated using the XMCQDPT2/ CASSCF approach.40−43 Unlike DFT-based methods, this approach correctly predicts the localization of excitation and the positions of triplet states relative to the singlet states. The geometries of all singlet and triplet states were optimized. Previously, we used the state-specific version of CASSCF (SS-CASSCF) for geometry optimization. This technique can be applied only to the lowest energy states in the vicinity of the minimum on the corresponding potential energy surface. The SS-CASSCF geometry optimization started with a preoptimized structure obtained by the restricted (open-shell) Hartree−Fock method R(O)HF or configuration interaction singles (CIS) for triplets. After geometry optimization, the state-averaged CASSCF (SA-CASSCF) method was applied at the optimized geometry with averaging over all target states. However, excited singlets cannot be optimized by SSCASSCF because of possible variational collapse. In this paper, we used a recently developed procedure of state-specific optimization by SA-CASSCF.44 Similarly to our previous work,45 we used Grimme’s dispersion correction46−48 adjusted for the Hartree−Fock method, because no dispersion correction is implemented for CASSCF. The active space included three highest occupied and two lowest unoccupied orbitals from each ligand (that is, CASSCF(12,10); see Supporting Information). For geometry optimiza7531


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Figure 3. continued

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Figure 3. Optimized structures of (a) S0, (b) S1, (c) T1a, and (d) T1b states. Bonds shown in red are shorter in the excited state than in the ground state, bonds shown in blue are longer, and bonds shown in green come out of plane. The torsion and out-of-plane angles that change upon excitation are also shown. 7533


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Figure 4. Energy levels of [Eu(cfqH) (cfq)(H2O)4]2+. Vertical arrow shows excitation S0→S1, wavy lines show vibrational relaxation, and red circle denotes S1−T ISC.

Table 1. Energies (cm−1) of States in the Optimized Geometries with Respect to the Ground-State Energy S0

the T1a geometry satisfactorily agrees with the experimental phosphorescence energy of the cfq anion determined in ref 3 as 20 500 cm−1. A deeper minimum on the triplet potential energy surface corresponds, however, to the T1b geometry. In this geometry, both S1 and two lowest triplets are localized on the nonprotonated ligand. On the one hand, the T1−S0 gap in this geometry is only ∼2900 cm−1, which makes this state inefficient for excitation transfer. On the other hand, because of such a small gap, this state can serve as a channel for nonradiative relaxation. The energy that can be transferred from the excited ligand to the Ln3+ is the electronic excitation energy of the ligand, that is, the vertical transition energy in the relaxed geometry of the donor state. Therefore, it is the vertical energy in the relaxed triplet state that should be in resonance with some of the 5Dj levels of Eu3+. Indeed, the vertical T1 energy in the T1a state (19 400 cm−1) is in resonance with the 5D1 state of Eu3+ (19 030 cm−1), as shown in Figure 5. The subsequent fast nonradiative relaxation of the excited ion prevents energy backtransfer and facilitates Eu3+ luminescence. However, the vertical T1 energy in the T1b state (2900 cm−1) is too low, and this state cannot pump Eu3+. Spin−Orbit Coupling. The spin−orbit coupling matrix elements for each optimized geometry are given in Table 2. These values were used to estimate the ISC rate constants. As expected, the highest singlet-to-triplet crossing rates are observed in the S1 geometry for S1−T1 and S1−T2 states. The corresponding lifetimes are as short as 0.8−0.9 ns. This is 2 orders of magnitude shorter than the radiative lifetime of the S1 state in this geometry calculated from the oscillator strength

optimized geometry state energy

S0

S1

T1a

T1b

S0 S1 S2 T1 T2 T3 T4

0 31 979 32 390 28 949 29 558 31 483 32 890

12 320 27 402 37 499 25 531 28 018 37 567 43 127

7268 36 794 38 253 26 680 36 347 37 934 39 089

21 582 31 522 38 229 24 538 34 235 43 692 47 346

next two triplet states, T3 and T4, also lie close to each other and to the singlet states. The vibrational relaxation of the S1 state (blue wavy line) leads to a minimum of the S1 potential energy surface. In this geometry, the two lowest-energy triplet states are quasidegenerate with S1 and localized on the nonprotonated ligand as well as S1 itself. This local minimum is suitable for ISC (shown by the red circle in Figure 4), because the system can reside in this state for a relatively long time (the oscillator strength for the S1→S0 transition is ∼0.09; the radiative lifetime is ∼68 ns). ISC can lead to either T1 or T2 potential energy surface. One state relaxes to the T1a geometry, and the other one relaxes to the T1b. The lowest triplet in the T1a geometry is localized on the nonprotonated ligand, while the next lowest is localized on the protonated one. Two other triplets, T3 and T4, are also localized on the nonprotonated and protonated ligands, respectively. The T1→S0 transition energy of 19 400 cm−1 in 7534


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Figure 5. Energy transfer pathways in [Eu(cfqH) (cfq)(H2O)4]2+ in the T1a and T1b geometries: the T1 level in the T1a geometry is in resonance with 5D1 level of Eu3+, which leads to the emissive state of Eu3+, while the T1 level in the T1b geometry is in resonance with nonemissive 7Fj sublevels of Eu3+.

44 ns. This time appears to be sufficient for the transfer of energy to Eu3+.

Table 2. Intersystem Crossing Rate Constants and Corresponding Lifetimes τ in the Optimized Geometries HSO, cm−1 S0−T1 S0−T2 S0−T3 S0−T4

0.48 0.22 0.58 0.46

S1−T1 S1−T2 S1−T3

1.37 0.76 2.17

S0−T1 S1−T1 T1−T2 T1−T3

3.13 2.28 1.39 1.61

S0−T1 S1−T1 T1−T3

0.61 0.33 0.21

ΔE, cm−1 S0 28 949 29 558 31 483 32 890 S1 1870 616 10 165 T1b 2956 6984 9697 19 154 T1a 19 412 10 114 11 254

kISC, 1 × 106 s−1 9.4 1.9 13.0 7.6

τ, ns

0.84 0.90 1.82

3900 880 240 160

0.25 1.14 4.24 6.24

23.0 13.0 4.6

CONCLUSIONS

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ASSOCIATED CONTENT

Energy transfer in the luminescent ciprofloxacin−europium(III) complex [Eu(cfqH) (cfq)(H2O)4]2+ has been studied by the multireference XMCQDPT2/CASSCF method. The required energy levels have been calculated in the optimized geometries of the ground state and the ligand-localized excited states. It has been found that the T1 state of the nonprotonated ligand in the T1a geometry best corresponds to the 5D1 state of Eu3+. The ISC rates calculated for the optimized geometries show that, as expected, fast ISC from S1 to T1 and T2 occurs in the minimum of the S1 potential energy surface, and this process is responsible for the photoexcitation of Eu3+ through ciprofloxacin antenna. The observed structure changes in the excited ligand indicate that this energy transfer mechanism is quite general in Ln3+−fluoroquinolone complexes.

106.16 516.01 79.08 131.33

1200 1100 550

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44.08 78.47 215.62

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpca.6b07258. Active orbitals of [Eu(cfqH) (cfq)(H2O)4]2+. Bond lengths in the ground and excited states and their change in excited states relative to the ground state. Cartesian coordinates of [Eu(cfqH) (cfq)(H2O)4]2+ in the optimized geometries. (PDF)

(68 ns). Therefore, ISC in the S1 state proceeds faster than fluorescence, in agreement with experimental data. In the T1b geometry, where a small S0−T1 gap is observed, the lifetime of the T1 state is very short, 0.25 ns. Therefore, nonradiative relaxation of the T1 state through ISC in this geometry is rather fast. On the contrary, the T1 state in the T1a geometry is rather stable; its nonradiative relaxation proceeds in 7535


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Presence of the Second Ligand and Micelles of Anionic Surfactants. J. Anal. Chem. 2007, 62 (2), 136−140. (15) Attia, M. S.; Essawy, A. A.; Youssef, A. O. Europium-Sensitized and Simultaneous pH-Assisted Spectrofluorimetric Assessment of Ciprofloxacin, Norfloxacin and Gatifloxacin in Pharmaceutical and Serum Samples. J. Photochem. Photobiol., A 2012, 236, 26−34. (16) Ruiz-Medina, A.; Llorent-Martínez, E. J.; Ortega-Barrales, P.; Fernández-de Córdova, M. L. Lanthanide-Sensitized Luminescence as a Promising Tool in Clinical Analysis. Appl. Spectrosc. Rev. 2011, 46, 561−580. (17) Alam, A.-M.; Kamruzzaman, M.; Lee, S. H.; Kim, Y. H.; Jo, H. J.; Kim, S. H.; Park, S.-R. Sensitive Determination of Adenosine Disodium Triphosphate in Soil, Milk, and Pharmaceutical Formulation by Enoxacin−Europium(III) Fluorescence Complex in Solution. J. Lumin. 2012, 132, 789−794. (18) Alam, A.-M.; Kamruzzaman, M.; Lee, S. H.; Kim, Y. H.; Min, K. Europium-Enoxacin Complex as Fluorescence Probe for the Determination of Folic Acid in Pharmaceutical and Biological Samples. Bull. Korean Chem. Soc. 2012, 33, 3055−3060. (19) Spangler, C.; Schäferling, M. In Lanthanide Luminescence. Photophysical, Analytical and Biological Aspects; Hänninen, P., Härmä, H., Eds.; Springer Series Fluorescence 2011, Springer-Verlag: Berlin, Germany, 2010; Vol. 7, pp 235−262. (20) Bünzli, J.-C. G. Lanthanide Luminescence for Biomedical Analyses and Imaging. Chem. Rev. 2010, 110, 2729−2755. (21) Eliseeva, S. V.; Bünzli, J.-C. G. Lanthanide Luminescence for Functional Materials and Bio-Sciences. Chem. Soc. Rev. 2010, 39, 189− 227. (22) Bünzli, J.-C. G. On the Design of Highly Luminescent Lanthanide Complexes. Coord. Chem. Rev. 2015, 293−294, 19−47. (23) Bakker, B. H.; Goes, M.; Hoebe, N.; van Ramesdonk, H. J.; Verhoeven, J. W.; Werts, M. H. V.; Hofstraat, J. W. Luminescent Materials and Devices: Lanthanide Azatriphenylene Complexes and Electroluminescent Charge Transfer Systems. Coord. Chem. Rev. 2000, 208, 3−16. (24) Su, Y.; Xu, Y.; Yang, L.; Yang, J.; Weng, S.; Yu, Z.; Wu, J. New, Rapid Fluorescence Stain Method for Histologic Sections Using Lanthanide Complexes. Anal. Biochem. 2005, 347, 89−93. (25) Polishchuk, A. V.; Karaseva, E. T.; Medkov, M. A.; Karasev, V. E. Europium(III) Compounds with Cyprofloxacine and Norfloxacine: Spectral and Luminescent Properties and Antibacterial Activity. Russ. J. Coord. Chem. 2004, 30, 828−831. (26) de Sá, G. F.; Malta, O. L.; de Mello Donegá, C.; Simas, A. M.; Longo, R. L.; Santa-Cruz, P. A.; da Silva, E. F. Spectroscopic Properties and Design of Highly Luminescent Lanthanide Coordination Complexes. Coord. Chem. Rev. 2000, 196, 165−195. (27) Gonçalves e Silva, F. R.; Malta, O. L.; Reinhard, C.; Güdel, H.U.; Piguet, C.; Moser, J. E.; Bünzli, J.-C. G. Visible and Near-Infrared Luminescence of Lanthanide-Containing Dimetallic Triple-Stranded Helicates: Energy Transfer Mechanisms in the SmIII and YbIII Molecular Edifices. J. Phys. Chem. A 2002, 106, 1670−1677. (28) Malta, O. L. Ligand-Rare-Earth Ion Energy Transfer in Coordination Compounds. A Theoretical Approach. J. Lumin. 1997, 71, 229−236. (29) Sato, S.; Wada, M. Relation Between Intramolecular Energy Transfer Efficiencies and Triplet State Energies in Rare Earth βDiketone Chelate. Bull. Chem. Soc. Jpn. 1970, 43, 1955−1962. (30) Latva, M.; Takalo, H.; Mukkala, V.-M.; Matachescu, C.; Rodriguez-Ubis, J. C.; Kankare, J. Correlation Between the Lowest Triplet State Energy Level of the Ligand and Lanthanide (III) Luminescence Quantum Yield. J. Lumin. 1997, 75, 149−169. (31) Tobita, S.; Arakawa, M.; Tanaka, I. The Paramagnetic Metal Effect on the Ligand Localized S1-T1 Intersystem Crossing in the Rare-Earth-Metal Complexes with Methyl Salicylate. J. Phys. Chem. 1985, 89, 5649−5654. (32) Whan, R. E.; Crosby, G. A. Luminescence Studies of Rare Earth Complexes: Benzoylacetonate and Dibenzoylmethide Chelates. J. Mol. Spectrosc. 1962, 8, 315−327.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +7(495)9362588. Author Contributions ∥

These authors contributed equally. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Funding

This work was supported by the Russian Science Foundation (Project No. 14−43−00052). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The calculations were performed using the facilities of the Joint Supercomputer Center of Russian Academy of Sciences and the Supercomputing Center of Lomonosov, Moscow State Univ.65

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REFERENCES

(1) Ayscough, N. J.; Fawell, J.; Franklin, G.; Young, W. Review of Human Pharmaceuticals in the Environment R&D Technical Report P390; Environment Agency: Bristol, U.K, 2000. (2) Botsoglou, N. A.; Fletouris, D. J. Drug Residues in Foods: Pharmacology, Food Safety, and Analysis; CRC Press: Boca Raton, FL, 2001; p 1200. (3) Č urman, D.; Ž ivec, P.; Leban, I.; Turel, I.; Polishchuk, A.; Klika, K. D.; Karaseva, E.; Karasev, V. Spectral Properties of Eu(III) Compound with Antibacterial Agent Ciprofloxacin (cfqH). Crystal Structure of [Eu(cfqH) (cfq)(H2O)4]Cl2•4.55H2O. Polyhedron 2008, 27, 1489−1496. (4) Polishchuk, A. V.; Karaseva, E. T.; Korpela, T.; Karasev, V. E. New Luminophor-Activators Based on (Fluoro)Quinolone Antibacterials. J. Lumin. 2008, 128, 1753−1757. (5) Mitscher, L. A. Bacterial Topoisomerase Inhibitors: Quinolone and Pyridone Antibacterial Agents. Chem. Rev. 2005, 105, 559−592. (6) Brighty, K. E.; Gootz, T. D. in: Andriole, V. T. Chemistry and Mechanism of Action of the Quinolone Antibacterials: The Quinolones; Academic Press: San Diego, 2000. P. 33−97. (7) Sheehan, G.; Chew, N. S. Y. In Fluoroquinolone Antibiotics; Ronald, A. R., Low, D. E., Eds.; Birkhauser: Basel, Switzerland, 2003; p 1. (8) Potamia, M. T.; Calokerinos, A. C. Applications of Sensitized Fluoresce in Chemiluminescence: A Review. Anal. Lett. 2013, 46, 2657−2672. (9) Pandya, S.; Yu, J.; Parker, D. Engineering Emissive Europium and Terbium Complexes for Molecular Imaging and Sensing. Dalton Trans. 2006, 2757−2766. (10) Rieutord, A.; Vazquez, L.; Soursac, M.; Prognon, P.; Blais, J.; Bourget, Ph.; Mahuzier, G. Fluoroquinolones as Sensitizers of Lanthanide Fluorescence: Application to the Liquid Chromatographic Determination of Ciprofloxacin Using Terbium. Anal. Chim. Acta 1994, 290, 215−225. (11) Beltyukova, S.; Teslyuk, O.; Egorova, A.; Tselik, E. Solid-Phase Luminescence Determination of Ciprofloxacin and Norfloxacin in Biological Fluids. J. Fluoresc. 2002, 12, 269−272. (12) Hernández-Arteseros, J. A.; Compañ ó, R.; Prat, M. D. Determination of Ciprofloxacin and Enrofloxacin in Edible Animal Tissues by Terbium-Sensitized Luminescence. Analyst 1998, 123, 2729−2732. (13) Llorent Martínez, E. J. J.; García-Reyes, F.; Ortega-Barrales, P.; Molina-Díaz, A. Terbium-Sensitized Luminescence Optosensor for the Determination of Norfloxacin in Biological Fluids. Anal. Chim. Acta 2005, 532, 159−164. (14) Shtykov, S. N.; Smirnova, T. D.; Bylinkin, Yu. G.; Kalashnikova, N. V.; Zhemerichkin, D. A. Determination of Ciprofloxacin and Enrofloxacin by the Sensitized Fluorescence of Europium in the 7536


Article


(53) Koseki, S.; Gordon, M. S.; Schmidt, M. W.; Matsunaga, N. Main Group Effective Nuclear Charges for Spin-Orbit Calculations. J. Phys. Chem. 1995, 99, 12764−12772. (54) Matsunaga, N.; Koseki, S.; Gordon, M. S. Relativistic Potential Energy Surfaces of XH2 (X = C, Si, Ge, Sn, and Pb) Molecules: Coupling of 1A1 and 3B1 states. J. Chem. Phys. 1996, 104, 7988−7996. (55) Koseki, S.; Schmidt, M. W.; Gordon, M. S. Effective Nuclear Charges for the First- through Third-Row Transition Metal Elements in Spin−Orbit Calculations. J. Phys. Chem. A 1998, 102, 10430−10435. (56) Koseki, S.; Fedorov, D. G.; Schmidt, M. W.; Gordon, M. S. Spin−Orbit Splittings in the Third-Row Transition Elements: Comparison of Effective Nuclear Charge and Full Breit−Pauli Calculations. J. Phys. Chem. A 2001, 105, 8262−8268. (57) Koseki, S.; Matsushita, T.; Gordon, M. S. Dissociation Potential Curves of Low-Lying States in Transition Metal Hydrides. 3. Hydrides of Groups 6 and 7. J. Phys. Chem. A 2006, 110, 2560−2570. (58) Furlani, T. R.; King, H. F. Theory of Spin-Orbit Coupling. Application to Singlet−Triplet Interaction in the Trimethylene Biradical. J. Chem. Phys. 1985, 82, 5577−5583. (59) King, H. F.; Furlani, T. R. Computation of One and Two Electron Spin-Orbit Integrals. J. Comput. Chem. 1988, 9, 771−778. (60) Fedorov, D. G.; Gordon, M. S. A Study of the Relative Importance of One and Two-Electron Contributions to Spin−Orbit Coupling. J. Chem. Phys. 2000, 112, 5611−5623. (61) Marian, C. M. Spin−Orbit Coupling and Intersystem Crossing in Molecules. WIREs Comput. Mol. Sci. 2012, 2, 187−203. (62) Freidzon, A. Y.; Safonov, A. A.; Bagaturyants, A. A.; Alfimov, M. V. Solvatofluorochromism and Twisted Intramolecular Charge-Transfer State of the Nile Red Dye. Int. J. Quantum Chem. 2012, 112, 3059− 3067. (63) Rotkiewicz, K.; Grellmann, K. H.; Grabowski, Z. R. Reinterpretation of the Anomalous Fluorescense of p-N,N-Dimethylamino-Benzonitrile. Chem. Phys. Lett. 1973, 19, 315−318. (64) Rettig, W. Charge Separation in Excited States of Decoupled SystemsTICT Compounds and Implications Regarding the Development of New Laser Dyes and the Primary Process of Vision and Photosynthesis. Angew. Chem., Int. Ed. Engl. 1986, 25, 971−988. (65) Voevodin, Vl. V.; Zhumatiy, S. A.; Sobolev, S. I.; Antonov, A. S.; Bryzgalov, P. A.; Nikitenko, D. A.; Stefanov, K. S.; Voevodin, V. V. Practice of “Lomonosov” Supercomputer. Open Systems J. 2012; Vol. 7, pp 36−39. http://www.osp.ru/os/2012/07/13017641/ (in Russian, accessed June 27, 2016).

(33) Crosby, G. A.; Whan, R. E.; Freeman, J. J. Spectroscopic Studies of Rare Earth Chelates. J. Phys. Chem. 1962, 66, 2493−2499. (34) Faustino, W. M.; Malta, O. L.; Teotonio, E. E. S.; Brito, H. F.; Simas, A. M.; de Sá, G. F. J. Photoluminescence of Europium(III) Dithiocarbamate Complexes: Electronic Structure, Charge Transfer and Energy Transfer. J. Phys. Chem. A 2006, 110, 2510−2516. (35) Hatanaka, M.; Morokuma, K. Exploring the Reaction Coordinates for f−f Emission and Quenching of Lanthanide Complexes − Thermosensitivity of Terbium(III) Luminescence. J. Chem. Theory Comput. 2014, 10 (10), 4184−4188. (36) Freidzon, A. Ya.; Scherbinin, A. V.; Bagaturyants, A. A.; Alfimov, M. V. Ab Initio Study of Phosphorescent Emitters Based on RareEarth Complexes with Organic Ligands for Organic Electroluminescent Devices. J. Phys. Chem. A 2011, 115, 4565−4573. (37) Romanova, K. A.; Freidzon, A.; Bagaturyants, A. A.; Galyametdinov, Y. G. Ab Initio Study of Energy Transfer Pathways in Dinuclear Lanthanide Complex of Europium(III) and Terbium(III) Ions. J. Phys. Chem. A 2014, 118, 11244−11252. (38) Dolg, M.; Stoll, H.; Savin, A.; Preuss, H. Energy-Adjusted Pseudopotentials for Rare Earth Elements. Theor. Chim. Acta. 1989, 75, 173−194. (39) Dolg, M.; Stoll, H.; Preuss, H. A Combination of Quasirelativistic Pseudopotential and Ligand Field Calculations for Lanthanoid Compounds. Theor. Chim. Acta. 1993, 85, 441−450. (40) Roos, B. O. Multiconfigurational Quantum Chemistry for Ground and Excited States. Challenges and Advances in Computational Chemistry and Physics 2008, 5, 125−156. (41) Schmidt, M. W.; Gordon, M. S. The Construction and Interpretation of MCSCF Wavefunctions. Annu. Rev. Phys. Chem. 1998, 49, 233−66. (42) Nakano, H. Quasidegenerate Perturbation Theory with Multiconfigurational Self-Consistent-Field Reference Functions. J. Chem. Phys. 1993, 99, 7983−7992. (43) Granovsky, A. A. Extended Multi-Configuration QuasiDegenerate Perturbation Theory: The New Approach to Multi-State Multi-Reference Perturbation Theory. J. Chem. Phys. 2011, 134, 214113. (44) Granovsky, A. A. An Efficient Approach to Compute StateSpecific Nuclear Gradients for a Generic State-Averaged MultiConfiguration Self Consistent Field Wavefunction. J. Chem. Phys. 2015, 143, 231101. (45) Freidzon, A. Ya.; Safonov, A. A.; Bagaturyants, A. A. Theoretical Study of the Spectral and Charge-Transport Parameters of an Electron-Transporting Material Bis(10-hydroxybenzo[h]qinolinato) beryllium (Bebq2). J. Phys. Chem. C 2015, 119, 26817−26827. (46) Grimme, S. Accurate Description of Van der Waals Complexes by Density Functional Theory Including Empirical Corrections. J. Comput. Chem. 2004, 25, 1463−1473. (47) Grimme, S.; Ehrlich, S.; Goerigk, L. Effect of the Damping Function in Dispersion Corrected Density Functional Theory. J. Comput. Chem. 2011, 32, 1456−1465. (48) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A. Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu. J. Chem. Phys. 2010, 132, 154104. (49) Granovsky, A. A. Firef ly, version 8.1.1. Firefly Project: Moscow, Russia, 2015. http://classic.chem.msu.su/gran/firefly/index.html (accessed June 27, 2016). (50) Schmidt, M. W.; Baldridge, K. K.; Boatz, J. A.; Elbert, S. T.; Gordon, M. S.; Jensen, J. H.; Koseki, S.; Matsunaga, N.; Nguyen, K. A.; Su, S.; et al. General Atomic and Molecular Electronic Structure System. J. Comput. Chem. 1993, 14, 1347−1363. (51) Fedorov, D. G.; Koseki, S.; Schmidt, M. W.; Gordon, M. S. Spin-Orbit Coupling in Molecules: Chemistry beyond the Adiabatic Approximation. Int. Rev. Phys. Chem. 2003, 22, 551−592. (52) Koseki, S.; Schmidt, M. W.; Gordon, M. S. MCSCF/6-31G(d,p) Calculations of One-Electron Spin-Orbit Coupling Constants in Diatomic Molecules. J. Phys. Chem. 1992, 96, 10768−10772. 7537


Electronic Structure and Energy Transfer in Europium(III

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