Crystal structure and temperature dependence of the photophysical properties of the [Eu(tta)3(pyphen)] complex

Accepted Manuscript Crystal structure and temperature dependence of photophysical properties of the [Eu(tta)3(pyphen)] complex

the

F.M. Cabral, D.A. Gálico, I.O. Mazali, F.A. Sigoli PII: DOI: Reference:

S1387-7003(18)30441-6 doi:10.1016/j.inoche.2018.09.041 INOCHE 7132

To appear in:

Inorganic Chemistry Communications

Received date: Revised date: Accepted date:

16 May 2018 29 June 2018 28 September 2018

Please cite this article as: F.M. Cabral, D.A. Gálico, I.O. Mazali, F.A. Sigoli , Crystal structure and temperature dependence of the photophysical properties of the [Eu(tta)3(pyphen)] complex. Inoche (2018), doi:10.1016/j.inoche.2018.09.041

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ACCEPTED MANUSCRIPT Crystal structure and temperature dependence of the photophysical properties of the [Eu(tta)3 (pyphen)] complex.

F.M. Cabral1 , D.A. Gálico1 , I.O. Mazali1 , F.A. Sigoli1*

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Laboratory of Functional Materials – Institute of Chemistry - University of Campinas – UNICAMP Campinas, Sao Paulo, Brazil, P.O. Box 6154, 13083-970 e-mail: [email protected]

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RI

*

this

work,

we

synthesized

f][1,10]phenanthroline}europium(III)

the

{tris(thenoyltrifluoroacetone)pyrazino[2,3-

complex

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In

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Abstract

and

studied

its

thermal

emission

quenching. The crystal structure of the [Eu(tta)3 (pyphen)] complex show that the

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europium(III) ion occupies a distorted D4 d symmetry of a square antiprism site. The

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complex shows an absolute emission quantum yield of 31%. The temperature dependence of the photophysical properties of the complex was evaluated and indicates that the complex has potential to be applied as a lifetime based luminescent

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thermometer. The quenching of the luminescence as a function of temperature occurs due the energy back-transfer from the emitter state to the ligand centered triplet state. The temperature induced blue-shift in the

5

D0 →

7

F0 transition band indicates the

presence of the electron-phonon coupling in this complex.

Keywords:

Europium(III)

complex,

Luminescent

thermometer,

Crystal structure,

Electron-phonon coupling.

1

ACCEPTED MANUSCRIPT Trivalent lanthanide ions find applications in areas such as luminescent materials [1-4], molecular

magnetism [5-7]

and

biological [8-10].

Concerning

the luminescent

properties, the lanthanide(III) ions possess particular spectroscopic properties arising from the electron repulsion and the strong spin-orbit coupling and to a lesser extension is the contribution from the crystal field treated as a weak perturbation in the

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spectroscopy terms energies and splitting. This gives rise to the 4f electronic energy

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levels configuration and the well kwon photophysical features such as long emission

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lifetimes, narrow emission bands and large pseudo-Stokes shifts [11, 12]. A potential application for luminescent lanthanide complexes is in the thermometry

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field, where the variation of the emitting state lifetime, the quenching of an emission and/or the ratio between two emission bands are monitored as a function of temperature.

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Luminescent thermometers have the advantages of contactless measurements and large or micro scale image mapping [13, 14].

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The temperature quenching of a lanthanide ion emitting level can occur by three main mechanisms; multiphonon relaxation,

energy transfer to ligand-localized electronic

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states (singlet or triplet) and the crossover from the 4f configuration to a charge-transfer (CT) state [15]. These mechanisms can be modeled a general model developed

In

this

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independently by Mott and Seitz [16, 17]. context,

we

synthesized

and

studied

the

thermal quenching of the

{tris(thenoyltrifluoroacetone)pyrazino[2,3-f][1,10]phenanthroline}europium(III) complex, [Eu(tta)3 (pyphen)]. This complex was synthesized by Sun and coworkers [18] and Li and coworkers [19] and in both cases the complex was studied for applications in electroluminescence devices and the crystalline structure has not been solved up to date. The synthesis of the complex was done by the reaction of the [Ln(tta) 3 (H2 O)2 ], Ln = gadolinium(III)

and

europium(III),

with

an

excess

of

the

pyrazino[2,3-

2

ACCEPTED MANUSCRIPT f][1,10]phenanthroline ligand (3.2 equivalents) in methanol. The resulting solution was refluxed at 60 °C for 4 hours. After this time, the precipitated solid was centrifuged, washed with methanol several times and dried under vacuum. The europium(III) complex was recrystallized by slow evaporation of a diluted methanolic solution of the complex.

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X-ray single-crystal structural analysis (Figure 1 and Table S1) reveals that the

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europium(III) crystallize in the orthorhombic space group Pna21 . Both complexes are

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isostructural (Figure S1, see supporting information) and consists in a mononuclear complex where the europium(III) or the gadolinium(III) ion is octa-coordinated (O 6 N2

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coordination environment) by six oxygen atoms from the three chelating tta- ligands an two nitrogen atoms from the chelating pyphen ligand. This generates a distorted square

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antiprism geometry in the lanthanide(III) site (distorted D4d symmetry). The Eu–O distance ranges from 2.336(2)–2.400(2) Å range while the Eu–N1 and Eu–N2 distance

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are 2.587(3) and 2.624(3) Å respectively. A π-π stacking interaction occurs between the central ring of the pyphen ligand and the thiofene ring of one of the tta - ligand with the

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distance between the ring centroids of 3.658 Å.

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ACCEPTED MANUSCRIPT

4

ACCEPTED MANUSCRIPT Figure 1: Asymmetric structure (top, left) showing the π-π interaction, coordination polyhedral (top right) and packing diagram (bottom). Hydrogen atoms were omitted for clarity.

The complexes are thermally stable until approximately 190 °C and the final residue of

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the thermal decomposition in air atmosphere is in agreement with the expected for the

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formation of the respective oxide (Figure S2, see supporting information).

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The gadolinium(III) complex was used to the determination of the triplet state energy of the complex. The time-resolved emission spectra is shown in Figure S3 (see supporting

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information) and the spectrum obtained with a delay of 0.1 ms is used for the triplet state energy determination (Figure S4, see supporting information). Two approaches

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were used [4]. The first was by fitting a tangent in the highest energy edge of the emission spectrum and the second was taking the maximum of the highest energy

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vibrational coupled band, the zero-zero phonon, obtained from the deconvolution of the emission spectrum. The value found using the first approach was 20376 cm-1 and by the

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second approach was 19850 cm-1 .

Excitation and emission spectra of [Eu(tta)3 (pyphen)] at 77 and 293 K (black) are

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shown in Fig. 2. Both excitation spectra are dominated by the ligand centered absorptions, differing only in the relative intensity between the components; moreover, it is noted the presence of the europium direct excitation on the 5 D2 ← 7 F0 transition (464 nm). Emission spectra reveal the characteristics intra-4f 6 emissions due to the 5 D0 →

7

F0-4 transitions. The emission spectrum at 77 K reveals the presence of one

component for 5 D0 → 7 F0 transition (peak centroid at 17247 cm-1 ), the 5 D0 → 7 F1,2 Stark splitting in 3 and 5 components, respectively, indicating that the europium(III) ions occupies one chemical environment, with low symmetry and without an inversion

5

ACCEPTED MANUSCRIPT center, as predict by the crystal structure (Figure 1). The low symmetry around Eu(III) ion leads to a higher intensity of the 5 D0 → 7 F2 transition band that the 5 D0 → 7 F1 one (5 D0 → 7 F2 / 5 D0 → 7 F1 integrated intensity ratio is ~ 12.2).

D0 ® 7F2

5

D0 ® 7F1

5

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293 K lem = 612 nm lex = 368 nm

D0 ® 7F0

L6 ¬ F0

575

D0 ® 7F1

580

585

590

605

D0 ® 7F4

D0 ® 7F1

5

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77 K

600

5

D0 ® 7F2

5

595

Wavelength / nm

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Intensity / arb. un.

7

5

lem = 612 nm

2:

Excitation

575

580

585

590

line)

600

595

600

605

Wavelength / nm

D0 ® F4

5

D0 ® 7F1

575

(black

D0 ® 7F0

5

5

ED

400

EP T

300

L6 ¬ 7F0

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lex = 368 nm

5

Figure

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5

5

625

650

675

7

700

Wavelength / nm

and

emission

(red

line)

spectra

for

the

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[Eu(tta)3 (pyphen)] complex obtained at 77 K and 293 K.

The 5 D0 emission decay curves were monitored at the 5 D0 → 7 F2 transition band with different excitation energies, Figure S5 and S6 (see supporting information). Both curves can be adjusted by a mono-exponential decay function, indicating the presence of only one lifetime value, in accordance of one chemical environment occupied by Eu(III) as elucidated by the crystal structure (Figure 1). The variation of the 5 D0 emitter state lifetime value with the excitation energy is in agreement with the observed by Ferreira and collaborators for several europium(III) compounds [20]. The authors 6

ACCEPTED MANUSCRIPT predicts an increase in the emission lifetime when the excitation wavelength occurs in the ligand related states, CT states or 5d states, due to the possibility of energy transfer pathways involving states in near-resonance with the emitting level. The temperature dependence of the 5 D0 emitter state was studied with the excitation at 393 nm, near-resonance with the

5

L6 excited state (Figure 3). At the 83-258 K

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temperature range the lifetime of the 5 D0 emitting state shows a weak dependence on

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temperature. Above this temperature (258 K), the thermal quenching is more intense

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and a decrease of the emission lifetime values from 748 μs (258 K) to 518 μs (323 K) is noted. The maximum relative thermal sensitivity calculated by the equation S.1 reach

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1.68 % K -1 at 323 K. The temperature uncertainty (Figure S.7), calculated by the equation S.2, reach values lower than 0.005 K on the temperature range were the

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quenching of the emitter state is more pronounced (283-323 K range), indicating the potential of this complex on the lifetime based thermometry. Three heating/cooling

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cycles confirm the stability and repeatability of the lifetime based thermometry (Figure S.8).

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For the temperature dependence of the quenching of the 5 D0 emitter level, the MottSeitz model [16, 17] involving one non-radiative recombination channels was used

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(Figure 3-d):

𝜏(𝑇) =

𝜏0 −∆ 𝐸 ) 𝑘𝑏𝑇

1+𝛼 𝑒𝑥𝑝 (

eq. (1)

Where τ0 is lifetime value at T = 0 K, α is the (WNR)/(WR) ratios for deactivation process and the activation energies ΔE correspond to the energy gap between the 5 D0 emitting state and de-excitation state. The fit of the data with equation 1 results in a τ0 =

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ACCEPTED MANUSCRIPT 772 ± 4 μs, α = 2616 ± 648 and ΔE = 3495 ± 506 cm-1 , in agreement with the difference of the ligand triplet state and the europium 5 D0 emitter state energies. This indicates that the main mechanism of the thermal quenching of the complex emission is the energy back-transfer mediated by the temperature. These results indicate that the [Eu(tta)3 (pyphen)] complex has potential to be applied as

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a luminescent thermometer based in the 5 D0 emitting state lifetime variation in the 283-

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323 K range. Further studies are being carried out with this complex in polymeric

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matrices for the application in the field of luminescent thermometry. (b)

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323 K

2

3

4

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1

323 K

0

5

1

2

3

4

-50

-25

0

25

750

700

650

(d)

50 1.75

7

8

9

10

400 300

200

100

800

1.50 1.25

750

1.00 0.75

600

0.50

550

0.25

Experimental data Mott-Seitz

700

Lifetime / s

-75

Relative sensitivity / % K

-100

-1

800

Lifetime / s

-125

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-150

6

Temperature / K

Temperature / °C -175

5

Time / ms

Time / ms

(c)

Temperature / K 83 108 133 158 183 208 233 258 283 303 313 323

83 K

ln(Intensity)

83 K

0

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Temperature / K 83 108 133 158 183 208 233 258 283 303 313 323

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Intensity / arb. un.

(a)

(T) = 0 / 1 +  exp(-E/kbT)

650

0 = 772

4 s

 = 2616 448 E = 3496 506 cm-1

600

r2 = 0.988

550

0.00

500 75

100

125

150

175

200

225

Temperature / K

250

275

300

325

500 4

6

8

10

12

-1

1000/T / K

8

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ACCEPTED MANUSCRIPT Figure 3: (a) Emission decay curves of the [Eu(tta)3 (pyphen)] complex at between 83323 K. (b) Linearized curves as a function of temperature. (c) Variation of the 5 D0 emitting state lifetime value with the temperature (black point) and the relative thermal sensitivity obtained (blue point). (d) Comparison between the experimental data and the

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fitted Mott-Seitz model (r2 = 0.988) involving one non-radiative recombination channel.

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From the emission spectrum at 293 K, the photophysical parameters of the

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[Eu(tta)3 (pyphen)] complex was determined by the equation widely described in the literature [21-23]. As expected, the elimination of the O-H oscillators of the inner

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coordination sphere of the complex, results in an increase in the 5 D0 state lifetime value in relation to the diaqua complex [24] and consequently an increase in the radiative

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emission rate in relation to the non-radiative one (Table S2, see supporting information). The quantum efficiency has a large increase, from 27 % in the

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[Eu(tta)3 (H2 O)2 ] complex to 61 % in the [Eu(tta)3 (pyphen)] complex. Besides that, the absolute emission quantum yield increases from 15 % for the [Eu(tta)3 (H2 O)2 ] complex

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to 31.30 ± 0.24 % for the [Eu(tta)3 (pyphen)] complex. The temperature dependence of the emission spectra intensities of [Eu(tta)3 (pyphen)]

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shows a small quenching with the temperature increase (Figure S9, see supporting information). For instance, between 83-303 K temperature range, the integrated area of the 5 D0 → 7 F2 transition band is only 62.7 % quenched (Figure S10, see supporting information). For comparison, in the case of the [Eu(bzac)3 (H2 O)2 ] complex [4] this quenching reaches 97.3 % in the same temperature range. The maximum relative thermal sensitivity (calculated by the equation S.1) for the [Eu(tta)3 (pyphen)] complex on the intensity based measurements reach 1.98 % K -1 at 323 K. The temperature uncertainty (Figure S.11), calculated by the equation S.2, reach values lower than 0.015

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ACCEPTED MANUSCRIPT K on the temperature range were the quenching of the emitter state is more pronounced (283-323 K range). This value is relatively low when compared with others systems were only one emission is monitored as for example [Eu(bzac)3 (H2 O)2 ] complex [4] that reach a maximum relative sensitivity of 5.25 % K -1 at 303 K, the [Tb(hfa)3 (tppo)2 ] complex [25] that reach a maximum relative sensitivity of 5.45 % K -1 at 323 K and the

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[Eu(tta)3 (H2 O)2 ] complex embedded on a PMMA matrix [26] that reach a maximum

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relative sensitivity of 4.40 % K -1 at 333 K. Three heating/cooling cycles were realized

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and confirms the photostability and repeatability of the intensity based thermometry (Figure S.12).

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Besides that, the emission lifetime based measurement have the advantage of overcome some disadvantages of the single emission approach as the influence of optoelectronic

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oscillations of the excitation source and detectors and the material inhomogeneities [13, 14]. Therefore, for the [Eu(tta)3 (pyphen)] complex the use of lifetime parameter is more

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suitable for the thermometry purpose. Although the intensity based measurement have a slightly higher value of the maximum relative sensitivity, the advantages of the lifetime

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based measurement make this approach more suitable. Besides that, the analysis of the temperature dependence 5 D0 → 7 F0 transition band

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(Figure 4) revels that with the temperature increase, this band is blue-shifted. The variation of the peak centroid follow an almost linear behavior. This linear blue-shift in the 5 D0 → 7 F0 transition band is an indicative of a dynamical interaction between the f electrons due to the presence of the electron-phonon coupling in the complex. Hill and Hufner firstly described this behavior in europium(III) salts [27] and recently, this behavior was demonstrated for europium(III) complexes [4, 28]. Between 83-283 K the transition energy shift 8.3 cm-1 in the [Eu(tta)3 (pyphen)]. The value is comparable with

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ACCEPTED MANUSCRIPT the observed in the [Eu(bzac)3 (H2 O)2 ] and [Eu(keto)3 (H2 O)2 ] complexes in the same temperature range, 10.7 [4] and 11.3 cm-1 [28], respectively. Temperature / °C

(b)

(a)

-175

-125

-100

-75

-50

-25

0

25

50

200

225

250

275

300

325

17256

PT

17254

17252

17250

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Peak centroid / cm-1

323 K

Normalized intensity

83 K

-150

17258

Temperature / K 83 108 133 158 183 208 233 258 283 303 323

17220 17230 17240 17250 17260 17270 17280 17290 17300

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17248

17246

75

-1

100

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Wavenumber / cm

125

150

175

Temperature / K

Figure 4: (a) Temperature dependence of the 5 D0 → 7 F0 transition band and (b) the

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peak centroid for this transition in the [Eu(tta)3 (pyphen)] complex.

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In conclusion, the crystal structure of the [Eu(tta)3 (pyphen)] complex was determined; the europium(III) ion occupies a O 6 N2 coordination environment related to a distorted

5

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square antiprismatic geometry (D4d). The temperature dependence of the lifetime of the D0 emitting state was studied and the complex have potential to be applied as a lifetime

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based luminescent probe in the 283-323 K range. The 5 D0 → 7 F0 transition band is linearly blue-shifted with the increase of the temperature, being an indication of the presence of an electron-phonon coupling in this complex.

Acknowledgements FMC and DAG are indebted to CNPq for the PhD. Fellowship. IOM and FAS are indebted to INOMAT (FAPESP: 2014/50906-9), CNPq, CAPES and FAPESP (2013/22127-2) for financial support. All authors would like to thank the Multiuser Laboratory of Advanced Optical Spectroscopy – Institute of Chemistry – UNICAMP 11

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References

[1] J.-C.G. Bünzli. Lanthanide luminescence for biomedical analyses and imaging.

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Chem. Rev. 110 (2010) 2729.

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[2] J.C.G. Bünzli. Rising stars in science and technology: Luminescent lanthanide

SC

materials. Eur. J. Inorg. Chem. 44 (2017) 5058.

[3] E.M. Rodrigues, D.A. Gálico, I.O. Mazali, F.A. Sigoli. Temperature probing and color

tuning

by

morphology

and

size

control of upconverting

β-

NU

emission

NaYb0.67 Gd0.30 F4 :Tm0.015 :Ho0.015 nanoparticles. Methods Appl. Fluoresc. 5 (2017)

MA

024012.

[4] D.A Gálico, I.O. Mazali, F.A. Sigoli. Nanothermometer based on intensity variation

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and emission lifetime of europium(III) benzoylacetonate complex. J. Lumin. 192 (2017) 224.

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[5] J. Long, Y. Guari, R.A.S. Ferreira, L.D. Carlos, J. Larionova. Recent advances in

57.

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luminescent lanthanide based Single-Molecule Magnets. Coord. Chem. Rev. 363 (2018)

[6] T. Lacelle, G. Brunet, A. Pialat, R.J. Holmberg, Y. Lan, B. Gabidullin, I. Korobkov, W. Wernsdorfer, M. Murugesu. Single-molecule magnet behaviour in a tetranuclear DyIII complex formed from a novel tetrazine-centered hydrazone Schiff base ligand. Dalton Trans. 46 (2017) 2471. [7] K.P. Carter, K.E. Thomas, S.J.A. Pope, R.J. Holmberg, R.J. Butcher, M. Murugesu, C.L.

Cahill.

Supramolecular assembly of molecular rare-earth–3,5-dichlorobenzoic

12

ACCEPTED MANUSCRIPT acid–2,2′:6′,2″-terpyridine

materials: Structural systematics,

luminescence properties

and magnetic behavior. Inorg. Chem. 55 (2016) 6902. [8] H.M. Aly, R.H. Taha, N.M. El-deeb, A. Alshehri. Efficient procedure with new fused pyrimidinone derivatives, Schiff base ligand and its La and Gd complexes by green chemistry. Inorg. Chem. Front. 5 (2018) 454.

PT

[9] D.A. Gálico, T.F.C. Fraga-Silva, J. Venturini, G. Bannach. Thermal, spectroscopic

RI

and in vitro biological studies of the lanthanum complex of naproxen. Thermochim.

SC

Acta. 644 (2016) 43.

[10] J.H.S.K. Monteiro, D. Machado, L.M. de Hollanda, M. Lancellotti, F.A. Sigoli, A.

NU

de Bettencourt-Dias. Selective cytotoxicity and luminescence imaging of cancer cells with a dipicolinato-based EuIII complex. Chem. Comm. 53 (2017) 11818.

MA

[11] K. Binnemans. Interpretation of europium(III) spectra. Coord. Chem. Rev. 295 (2015) 1.

Chem. Rev. 293 (2015) 19.

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[12] J.-C.G. Bünzli. On the design of highly luminescent lanthanide complexes. Coord.

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[13] C.D.S. Brites, P.P. Lima, N.J.O. Silva, A. Millán, V.S. Amaral, F. Palacio, L.D. Carlos. Thermometry at the nanoscale. Nanoscale. 4 (2012) 4799.

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[14] X. Wang, O.S. Wolfbeis, R.J. Meier. Luminescent probes and sensors for temperature. Chem. Soc. Rev. 42 (2013) 7834. [15] M.T. Berry, P.S. May, H. Xu. Temperature dependence of the Eu3+ 5 D0 lifetime in europium tris(2,2,6,6-tetramethyl-3,5-heptanedionato). J. Phys. Chem. 100 (1996) 9216. [16] N.F. Mott. On the absorption of light by crystals. Proc. R. Soc. 167 (1938) 0384. [17] F. Seitz. An interpretation of crystal luminescence. Trans. Faraday Soc. 35 (1939) 0074.

13

ACCEPTED MANUSCRIPT [18] P.P. Sun, J.P. Duan, J.J. Lih, C.H. Cheng. Synthesis of new europium complexes and their application in electroluminescent devices. Adv. Func. Mat. 13 (2003) 683. [19] X.-N. Li, Z.-J. Wu, Z.-J. Si, L. Zhou, X.-J. Liu, H.-J. Zhang. Effect of secondary ligands size on energy transfer and electroluminescent efficiencies for a series of europium(III) complexes, a density functional theory study. Phys. Chem. Chem. Phys.

PT

11 (208) 9687.

RI

[20] R.A.S. Ferreira, M. Nolasco, A.C. Roma, R.L. Longo, O.L. Malta, L.D. Carlos. Dependence of the lifetime upon the excitation energy and intramolecular energy

SC

transfer rates: The 5 D0 EuIII emission case. Chem. Eur. J. 18 (2012) 12130.

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[21] G.F. de Sá, O.L. Malta, C. de Mello Donegá, A.M. Simas, R.L. Longo, P.A. Santa Cruz, E.F. da Silva Jr. Spectroscopic properties and design of highly luminescent

MA

lanthanide coordination complexes. Coord. Chem. Rev. 196 (2000) 165. [22] B.R. Judd. Optical absorption intensities of rare-earth ions. Phys. Rev. 127 (1962)

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750.

(1962) 511.

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[23] G.S. Ofelt. Intensities of crystal spectra of rare‐ earth ions. J. Chem. Phys. 37

[24] E.R. Souza, J.H.S.K. Monteiro, I.O. Mazali, F.A. Sigoli. Photophysical studies of

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highly luminescent europium(III) and terbium(III) complexes functionalized with amino and mercapto groups. J. Lumin. 170 (2016) 520. [25] S. Katagiri, Y. Hasegawa, Y. Wada, S. Yanagida. Thermo-sensitive luminescence based on the back energy transfer in terbium(III) complexes. Chem. Lett. 33 (2004) 1438. [26] K. Oyama, M. Takabayashi, Y. Takei, S. Arai, S. Takeoka, S. Ishiwata, M. Suzuki. Walking nanothermometers: Spatiotemporal temperature measurement of transported acidic organelles in single living cells. Lab. Chip. 12 (2012) 1591.

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ACCEPTED MANUSCRIPT [27] P. Hill, S. Hufner. Lineshift and linewidth in optical spectra of europium salts. Z. Phys. 240 (1970) 168. [28] M.G. Lahoud, R.C.G. Frem, D.A. Gálico, G. Bannach, M.M. Nolasco, R.A.S. Ferreira, L.D. Carlos. Intriguing light-emission features of ketoprofen-based Eu(III)

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ED

MA

NU

SC

RI

PT

adduct due to a strong electron–phonon coupling. J. Lumin. 170 (2016) 357.

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Graphical abstract

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ACCEPTED MANUSCRIPT Crystal structure and temperature dependence of the photophysical properties of the [Eu(tta)3 (pyphen)] complex.

F.M. Cabral1 , D.A. Gálico1 , I.O. Mazali1 , F.A. Sigoli1*

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Laboratory of Functional Materials – Institute of Chemistry - University of Campinas – UNICAMP Campinas, Sao Paulo, Brazil, P.O. Box 6154, 13083-970 e-mail: [email protected]

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Highlights

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*

Europium(III) complex showing absolute emission quantum yield of 31%.

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Temperature dependence of emission lifetime.

Luminescent molecular temperature-probe in the 283-323 K range.

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The complex showing electron-phonon coupling .

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