Supplementary Infromation

S1

Photochemical Behavior of Antibiotics Impacted by Complexation Effects

of Concomitant Metals: A Case for Ciprofloxacin and Cu(II)†

Xiaoxuan Wei,a Jingwen Chen,∗a Qing Xie,a Siyu Zhang,ab Yingjie Li,a Yifei Zhang,a and

Hongbin Xiea

a Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of

Environmental Science and Technology, Dalian University of Technology, Dalian 116024,

China

b Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied

Ecology, Chinese Academy of Science, Shenyang 110016, China

(11 Pages, 3 Texts, 11 Figures, 4 Tables)

Text S1 Determining Kf' for complexation of ciprofloxacin with Cu(II)

The fluorescence spectra of ciprofloxacin (CIP) with different concentrations of

concomitant Cu(II) are shown in Fig. S1(a). The fluorescence intensity at λ = 430 nm was

used to calculate the complex ratio (n) and the conditional stability constant (Kf'):

0f'( )lg lg[Cu(II)] lgF F n K

F−⎡ ⎤ = +⎢ ⎥⎣ ⎦

(S1)

where F0 and F are the fluorescence intensities of CIP and the Cu(II)-CIP mixture,

respectively. As shown in Fig. S1(b), n = 1.05 and lgKf' = 6.09, indicating that Cu(II) and CIP

can form 1:1 complex with a conditional stability constant K'f,Cu(CIP) = 1.23 × 106 in the pH =

7.5 solutions.

† Electronic Supplementary Information (ESI) available: details of the total ion chromatograms and mass spectra of the identified products, the product yields, and the formation and degradation rate constants.

∗ Correspondence to: Jingwen Chen, e-mail: jwchen@dlut.edu.cn; Phone: +86-411-8470 6269

a Dalian University of Technology

b Institute of Applied Ecology, Chinese Academy of Science

Electronic Supplementary Material (ESI) for Environmental Science: Processes & Impacts.This journal is © The Royal Society of Chemistry 2015

Supplementary Infromation

S2

350 400 450 500 5500

25

50

75

100 (a) λex

= 280 nm

10 μmol/L

0 μmol/L

Fluo

resc

ence

Inte

nsity

λ (nm)

[Cu(II)]

-6.0 -5.8 -5.6 -5.4 -5.2 -5.0-0.3

0.0

0.3

0.6

0.9 (b)

lg[(

F 0-F)/F

]

lg[Cu(II)]

y = 1.05x + 6.09r = 0.997p < 0.0001

λex/λem = 280/430 nm

Fig. S1 Effects of Cu(II) on fluorescence intensity of CIP in pH = 7.5 solutions ([CIP] = 0.5

μmol/L, the error bars represent the 95% confidence interval, n = 3)

Text S2 Preparation of Cu(II)-CIP complex

CuCl2 (2.5 mol/L, 20.0 μL) was added to a solution of 1.0 mmol/L CIP (50 mL) with

continuous stirring. pH of the mixed solution was adjusted to 7.5. The formed blue crystals of

the complex were filtered, washed and dried to constant weight. Subsequently, the solid

samples were analyzed by IR, and the results are shown in Fig. S3.

Text S3 DFT calculations of defluorination reactions

The structures of reactants (R), transition states (TS) and products (P) for the C−F bond

cleavage of H2CIP+ at the excited triplet state (T) and [Cu(H2CIP)(H2O)4]3+ at the excited

tripquartet state (4T, where the quartet superscript refers to the total spin of the complex, T

refers to the local multiplicity of H2CIP+) are shown in Fig. S7. Results show that for H2CIP+,

the distance of C12−F was elongated from 1.35 Å in R to 1.48 Å in the TS, and to 3.86 Å in

the P, indicating the rupture of the C−F bond. [Cu(H2CIP)(H2O)4]3+ underwent a similar C−F

bond cleavage process. The distance of C12−F was elongated from 1.34 Å in the R to 1.93 Å

in the TS, and to 3.83 Å in the P. Thus, the Cu(II) complexation has negligible effects on the

C−F bond cleavage process of H2CIP+.

For the reactions of H2CIP+ at the T state and [Cu(H2CIP)(H2O)4]3+ at the 4T state with OH−

at its ground state (Fig. S8), two transition states (TS1 and TS2), and one intermediate (IM)

were identified, indicating that the OH− addition reactions are stepwise. The reactions are

initiated by the formation of reactant complexes (RCs) between the CIP species and OH− with

different interactions. For H2CIP+, intermolecular hydrogen bonds are formed between O in

Supplementary Infromation

S3

OH− and H42 (connected with N15) in CIP, whereas for [Cu(H2CIP)(H2O)4]3+, intermolecular

hydrogen bonds are formed between O in OH− and H40 (connected with C20) in CIP. The

subsequent reaction processes are similar for the two species, that is, O in OH− gradually

approaches C12 and the distances of C12−O in the IM are reduced to 1.39 Å, falling in the

range of a C−O single bond length. In the following step, the distances of C12−F bonds are

elongated to about 2.00 Å in TS2. Finally, F− and hydroxyl products are formed, with the

C12−O bond length being < 1.35 Å and the C12−F bond length being > 3.54 Å. Thus, the Cu(II)

complexation can alter the OH− addition reaction channels of H2CIP+.

0.0 0.5 1.0 1.5 2.00

20

40

60

80

α C

u(C

IP) (%

)

[Cu2+] (μmol/L)

55.2%

Fig. S2 Effects of equilibrium concentrations of Cu2+ on the fraction of Cu(CIP)

020406080

1800 1700 1600 1500 1400 1300 12000

20406080

υCOO- symυCOO- antisym

υC=O carboxylCIP

υC=O ketone

CIP + Cu(II)

Wavenumber (cm-1)

T (%

)

Fig. S3 IR spectra for CIP and mixture of CIP and Cu(II)

Supplementary Infromation

S4

250 275 300 325 350 3750.00

0.05

0.10

0.15

0.20

[CIP] = 5 μmol/L pH = 7.5

[Cu(II)] = 0 μmol/L [Cu(II)] = 5 μmol/L [Cu(II)] = 10 μmol/L [Cu(II)] = 15 μmol/L [Cu(II)] = 20 μmol/L

Abs

orba

nce

λ (nm) Fig. S4 Variation of UV-vis absorbance spectra of CIP with different [Cu(II)]

HOMO ( )

LUMO ( )

H2CIP+ [Cu(H2CIP)(H2O)4]3+

−−

↓−−↑

LUMO ( )−−

HOMO−1 ( )−↓−↑

HOMO ( )−−↑

Fig. S5 Molecular orbital compositions and structures for the main absorption of H2CIP+ and

[Cu(H2CIP)(H2O)4]3+ (Piperazine ring to the left, carboxylic group and Cu atom to the right of

each molecule. HOMO stands for the highest occupied molecular orbital. HOMO−1 is the

second highest occupied molecular orbital. LUMO stands for the lowest unoccupied

molecular orbital)

Supplementary Infromation

S5

×105

0

4

8 MS2/ESI+ CE 20 eV (m/z = 330)

m/z140 160 180 200 220 240 260 280 300 320 340 360 380 400

312

286 330243

O

N

HO

NHN

O

OH

P330M

M − H2O

M − CO2

M − H2O − CO2

M − CO2 − C2H5N

268

×105

0

1

2

MS2/ESI+ CE 20 eV (m/z = 288)

m/z140 160 180 200 220 240 260 280 300 320 340 360 380 400

270

199 288227

O

NNHNH2

O

OH

P288M

M − H2O

M − H2O − C2H5NM − H2O − C2H5N − CO

×105

0

1

1.5 MS2/ESI+ CE 20 eV (m/z = 306)

m/z140 160 180 200 220 240 260 280 300 320 340 360 380 400

0.5

288

268 306245

O

N

F

NHNH2

O

OH

P306M

M − H2O

M − H2O − HFM − H2O − C2H5N

×105

0

1

2 MS2/ESI+ CE 20 eV (m/z = 263)

m/z140 160 180 200 220 240 260 280 300 320 340 360 380120

245

204 217263

O

N

F

H2N

O

OH

P263M

M − H2O

M − H2O − CO

M − H2O − C3H5

Fig. S6 Mass spectral fragmentation patterns determined by triple quadrupole mass

spectrometer for CIP and its photoproducts, where CE stands for collision energy

Supplementary Infromation

S6

0

1

2 MS2/ESI+ CE 30 eV (m/z = 334)

m/z140 160 180 200 220 240 260 280 300 320 340 360 380 400

316217

245 271 298 334

×105

0

1.5

3 MS2/ESI+ CE 20 eV (m/z = 334) 316

334217 245

O

NNH

HN

O

OHF

O P334M

M − H2O

M − 2H2O

M − H2O − CH3NO

M − H2O − C3H5NOM − H2O − C3H5NO − CO

CH3NO = H2N CHO

C3H5NO =HN

O

Continued Fig. S6 Mass spectral fragmentation patterns determined by triple quadrupole

mass spectrometer for CIP and its photoproducts, where CE stands for collision energy

R 12

1.35 Å

qF = −0.33e

\

12

1.34 Å (H2O)

Cu

qF = −0.31e

TS 12

1.48 Å

1.93 Å

12

(H2O)

Cu

P 12

3.86 Å

3.83 Å

12

(H2O)

Cu

H2CIP+ [Cu(H2CIP)(H2O)4]3+

Fig. S7 Optimal structures of the reactants (R), transition states (TS) and products (P) for the

C−F bond cleavage of H2CIP+ at the T state and [Cu(H2CIP)(H2O)4]3+ at the 4T state (Dark

gray: C; Blue: N; Red: O; Light gray: H; Light blue: F; Salmon pink: Cu. qF stands for the

atomic charges on atom F)

Supplementary Infromation

S7

R 10.00 Å

1.35 Å

qC12 = 0.27e

12

10.00 Å

1.34 Å (H2O)

Cu

qC12 = 0.13e

12

RC

2.26 Å2.49 Å

1.36 Å

2.67 Å

2.39 Å

1.35 Å (H2O)

Cu

TS1

2.37 Å

1.35

2.18 Å

1.36 Å

2.15 Å2.37 Å

1.35 Å (H2O)

Cu

IM

1.39 Å

1.47 Å

1.39 Å

1.45 Å(H2O)

Cu

TS2

1.95 Å

1.34 Å 1.33 Å

1.98 Å (H2O)

Cu

P

3.55 Å

1.35 Å

3.54 Å

1.33 Å

(H2O)

Cu

H2CIP+ [Cu(H2CIP)(H2O)4]3+

Fig. S8 Optimal structures of the reactants (R), reactant complexes (RC), transition states

(TS), intermediates (IM) and products (P) for the reactions of H2CIP+ at the T state and

[Cu(H2CIP)(H2O)4]3+ at the 4T state with OH− at its ground state (Dark gray: C; Blue: N; Red:

O; Light gray: H; Light blue: F; Salmon pink: Cu. qC12 stands for the atomic charges on C12)

Supplementary Infromation

S8

2 4.5 7.5 9.5 120.0

0.1

0.2

0.8

1.2

1.6

pH

k (h

-1)

CIP + EDTACIP + Cu(II) + EDTA

CIPCIP + Cu(II)

Fig. S9 Effects of pH, Cu(II) and EDTA on the apparent photolytic rate constants (k) of CIP in

aerated solutions, where [CIP]0 = 5 μmol/L, [Cu(II)] = 10 μmol/L, [EDTA] = 20 μmol/L and

the error bars represent the 95% confidence interval, n = 3

1.0

1.1

1.2

1.3

500502010

CIP + Ca(II)

k

(h-1

)

[Ca(II)] (μmol/L)

0

CIP + EDTA CIP + Ca(II) + EDTA

pH = 7.5

Fig. S10 Effects of Ca(II) and EDTA on the apparent photolytic rate constants (k) of CIP in

aerated solutions ([CIP]0 = 5 μmol/L, [EDTA] = 1 mmol/L. The error bars represent the 95%

confidence interval, n = 3)

Supplementary Infromation

S9

0 5 10 15 200.8

1.0

1.2

1.4 CIP + Fe(III)

k

(h-1

)

[Fe(III)] (μmol/L)

CIP + EDTA CIP + Fe(III) + EDTA

pH = 7.5

Fig. S11 Effects of Fe(III) and EDTA on the apparent photolytic rate constants (k) of CIP in

aerated solutions ([CIP]0 = 5 μmol/L, [EDTA] = 20 μmol/L. The error bars represent the 95%

confidence interval, n = 3)

Table S1 Main light absorption wavelength (λ, nm), orbital compositions, and oscillator

strengths of H2CIP+ and [Cu(H2CIP)(H2O)4]3+

λ (nm) Orbital Components* Oscillator Strengths

H2CIP+

322.3 H→L (0.59) 0.118

273.8 H→L+1 (0.66) 0.158

[Cu(H2CIP)(H2O)4]3+

315.5 H−1→H (0.69); H→L (0.68) 0.244

278.6 H−1→L+1 (0.62); H→L+1 (0.63) 0.106

*The main orbital components of the absorptions are given relative to the highest

occupied (H) and lowest unoccupied (L) molecular orbitals and their respective

contributions.

Supplementary Infromation

S10

Table S2 Accurate mass measurements determined by TOF mass spectrometer for CIP and its

photoproducts

Name Proposed formula

[M + H]+

Experimental

mass (m/z)

Calculated

mass (m/z)

Error

(ppm) DBE*

CIP C17H19FN3O3 332.1400 332.1405 1.50 10

P330 C17H20N3O4 330.1441 330.1448 2.23 10

P288 C15H18N3O3 288.1335 288.1343 2.67 9

P306 C15H17FN3O3 306.1243 306.1248 1.79 9

P334 C16H17FN3O4 334.1197 334.1198 0.18 10

P263 C13H12FN2O3 263.0825 263.0826 0.56 9

* DBE stands for double bond equivalents.

Table S3 Computed Gibbs free energy changes (ΔG, kcal/mol), enthalpy changes (ΔH,

kcal/mol) and activation free energies (ΔG‡, kcal/mol) for the defluorination reactions of

H2CIP+ and [Cu(H2CIP)(H2O)4]3+

ΔG

(kcal/mol)

ΔH

(kcal/mol)

ΔG‡

(kcal/mol)

Cleavage of the C−F Bonds

H2CIP+ −4.8 −2.8 27.3

[Cu(H2CIP)(H2O)4]3+ −1.4 −0.6 32.8

Defluorination caused by OH− Addition

H2CIP+ −68.8 −71.9 0.8, 6.0 *

[Cu(H2CIP)(H2O)4]3+ −51.0 −52.6 4.5, 10.8 *

* OH− addition reactions are stepwise. The two ΔG‡ values correspond to the process of OH−

attack and cleavage of C−F bond, respectively. Cleavage of C−F bond is a rate-limiting step.

Supplementary Infromation

S11

Table S4 Optimized geometries and Mulliken atomic charges of H2CIP+ and

[Cu(H2CIP)(H2O)4]3+ at ground state (Dark gray: C; Blue: N; Red: O; Light gray: H; Light

blue: F; Salmon pink: Cu)

Atom

Atomic Charges

1215

18

109

22

43

521

1411

H2CIP+

(H2O)

12

1518

Cu

109

22

4

32114

5

11

[Cu(H2CIP)(H2O)4]3+

C3 −0.24e 0.43e

C4 −0.33e −0.31e

N5 0.06e 0.12e

C9 −0.34e 0.20e

C10 1.06e 0.30e

C11 −0.04e −0.32e

C12 0.07e 0.08e

C14 −0.10e 0.08e

N15 −0.63e −0.68e

N18 −0.61e −0.59e

C21 −0.50e −0.25e

C22 −0.02e −0.40e