research communications
Synthesis and κ2N,N′)gold(III) hexafluoridophosphate
of dichlorido(1,10-phenanthroline-aInstitute of Chemistry, University of Campinas - UNICAMP, Campinas - SP, Brazil
*Correspondence e-mail: ppcorbi@iqm.unicamp.br
A gold(III) salt of composition [AuCl2(C12H8N2)]PF6 was prepared and characterized by elemental and mass spectrometric analysis (ESI(+)–QTOF–MS), 1H nuclear magnetic resonance measurements and by single-crystal X-ray diffraction. The square-planar coordination sphere of AuIII comprises the bidentate 1,10-phenanthroline ligand and two chloride ions, with the AuIII ion only slightly shifted from the least-squares plane of the ligating atoms (r.m.s. = 0.018 Å). In contrast to two other previously reported AuIII-phenantroline structures that are stabilized by interactions involving the chlorido ligands, the packing of the title compound does not present these features. Instead, the hexafluoridophosphate counter-ion gives rise to anion⋯π interactions that are a crucial factor for the crystal packing.
Keywords: gold(III); 1,10-phenanthroline ligand; square-planar coordination; anion-π interactions; crystal structure.
CCDC reference: 1555623
1. Chemical context
AuIII is isoelectronic with PtII and forms compounds with similar coordination modes and structures. Therefore, the synthesis of AuIII-based compounds has attracted much interest in the field of bioinorganic and medicinal chemistry after the successful application of cis-platin [cis-diamminedichloridoplatinum(II)] for cancer treatment (Siddik, 2003). Aromatic N-donors, such as 1,10-phenanthroline, are of interest given their planar structure that synergizes well with the typical square-planar coordination sphere of AuIII, producing potent DNA-intercalating agents (Abbate et al., 2000; Zou et al., 2015). On the other hand, AuIII compounds differ from PtII compounds in terms of their interactions with biomolecules, their stability in biological media or their mechanism of action. A review on cytotoxic properties and mechanisms of AuIII compounds with N-donors has been provided by Zou et al. (2015).
In this context we have prepared the title salt, [AuCl2(C12H8N2)]PF6, that was characterized by elemental and mass spectrometric analysis (ESI(+)–QTOF–MS), 1H nuclear magnetic resonance measurements and by single crystal X-ray diffraction.
2. Structural commentary
All atoms in the title salt are on general positions. The AuIII atom has a square-planar coordination environment, with the chlorido ligands in a cis configuration to each other. The AuIII atom deviates from planarity (as determined based on the four coordinating atoms) by 0.018 Å (r.m.s.). The main bond lengths [Au—N1 = 2.032 (2), Au—N2 = 2.036 (2), Au—Cl1 = 2.251 (1) and Au—Cl2 = 2.255 (1) Å] are in the normal ranges for this kind of complexes (see Database survey). The bite angle of the 1,10-phenanthroline ligand is 81.75 (9)°, while the Cl1—Au—Cl2 angle is 89.28 (3)°. Despite the highly symmetrical nature of the hexafluoridophosphate counter-ion, this unit does not show any disorder. The structures of the molecular entities of the [AuCl2(C12H8N2)]PF6 salt are shown in Fig. 1.
3. Supramolecular features
The molecular packing in the crystal is shown in Fig. 2. Despite the square-planar coordination environment around AuIII and the presence of the highly conjugated and planar 1,10-phenanthroline ligand, π–π interactions have little relevance to the stabilization of the crystal. The shortest π-like interaction between the centroids [Cg1⋯Cg2i; symmetry code: (i) + x, y, − z; Fig. 3] of two neighbouring 1,10-phenanthroline rings are associated with a distance of 4.2521 (15) Å, which is very close to the upper limit of the threshold established by Janiak (2000) for a relevant offset π interaction.
The interactions between the hexafluoridophosphate counter-ion and the 1,10-phenanthroline ligands constitute the major intermolecular interactions in the crystal and can be divided into two types. The first type corresponds to an anion-donor⋯ π-acceptor interaction (Chifotides & Dunbar, 2013), with the shortest contact being C1⋯F5ii, of 3.096 (4) Å [symmetry code: (ii) x, ½ − y, ½ + z; Fig. 3]. The second and unique type of interaction between the PF6− anion and the π system of the phenanthroline ligand is observed where fluorine atoms point directly to the mid-point of an aromatic C—C bond. The distance between F6ii and the mid-point of C5 and C6 is 2.822 Å. The individual distances are C5⋯F6ii 2.925 (3) and C6⋯F6iii 2.894 (3) Å [symmetry code: (iii) − + x, y, − z].
4. Database survey
A few structures of AuIII-(1,10-phenanthroline) compounds have been reported in the literature with different counter-ions. Abbate et al. (2000) reported the monohydrate chloride structure that crystallizes in the type P21/n, with Au—N distances of 2.033 (8) and 2.056 (8) Å and Au—Cl distances of 2.266 (3) and 2.263 (3) Å, respectively. The N—Au—N angle is 82.0 (3)° and the Cl—Au—Cl angle 89.5 (1)°. Pitteri et al. (2008) determined the structure with a disordered [AuBrCl(CN)2]− unit as a counter-ion in type P. The Au—N distances are 2.05 (1) and 2.05 (1) Å, while the Au—Cl distances are 2.290 (5) and 2.299 (5) Å. The title compound has Au—N distances similar to that of the structure reported by Abbate et al. (2000), but slightly shorter than the one by Pitteri et al. (2008). Regarding the Au—Cl distances, [AuCl2(C12H8N2)]PF6 and the structure reported by Abbate et al. (2000) have shorter ones than that reported by Pitteri et al. (2008). Although the [AuCl2(C12H8N2)]+ cations in the three structures exhibit no significant differences, their crystal packings vary greatly as a consequence of the intermolecular interactions with the different counter-ions. The structure reported by Abbate et al. (2000) has the AuIII-(1,10-phenanthroline) units closer in space, with the shortest centroid-to-centroid distance being 3.820 Å, much closer than 4.2521 (15) Å observed in the title compound. Furthermore, the presence of a water molecule and the chloride counter-ion establish a classical hydrogen-bonding network, which is absent in the structure of the title compound. The structure determined by Pitteri et al. (2008) is the only one with an axial Au⋯L interaction, namely Au⋯Br (3.374 Å).
5. Synthesis and crystallization
[AuCl2(C12H8N2)]PF6 was synthesized by a modification of a literature protocol (Casini et al., 2010): K[AuCl4] (0.25 mmol, 95.0 mg) was dissolved in 3 ml of H2O/CH3CN (1:5, v/v), and 1,10-phenanthroline, (0.25 mmol, 45 mg) dissolved in 0.5 ml of CH3CN was then added to the gold(III)-containing solution. Finally, NH4PF6 (0.75 mmol, 124.6 mg) was added to the solution and the mixture was refluxed for 16 h. The obtained solid was isolated by filtration, washed with cold water and dried in vacuo. Elemental Analysis was performed on an Elemental Analyzer CHNS-O 2400 Perkin Elmer. Anal. Calcd. for C12H8AuCl2F6N2P (593.04 g mol−1): C 24.30%, H 1.36%, N 4.72%. Found: C 24.08%, H 0.70%, N 4.73%. Mass spectra were acquired in a XEVO QTOF–MS instrument (Waters). The sample was dissolved in the smallest possible volume of DMSO and diluted in a 1:1 (v/v) mixture of water and acetonitrile containing 0.1% formic acid. ESI(+)–QTOF–MS (m/z, [AuCl2(C12H8N2)]+, 100% relative abundance): 446. 9707 (calculated 446.9730). Crystals suitable for single crystal X-ray analysis were obtained by recrystallization from acetonitrile solution.
6. Solution stability
The stability of the [Au(1,10-phenanthroline)]3+ moiety is critical for the biological properties of the compound, including cytotoxicity. The [AuCl2(C12H8N2)]PF6 salt was dissolved in deuterated dimethylsulfoxide (DMSO-d6) and the solvent replacement was followed by 1H NMR for 72 h (Fig. 4). 1H NMR spectra were acquired on a Bruker Avance III 400 MHz. The labile chlorido ligands were replaced, as expected, but the [Au(1,10-phenanthroline)]3+ moiety remained stable in the presence of the coordinating solvent (DMSO) throughout the period evaluated.
7. details
Crystal data, data collection and structure . H atoms were set in calculated positions, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C).
details are summarized in Table 1Supporting information
CCDC reference: 1555623
https://doi.org/10.1107/S2056989017008763/wm5398sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017008763/wm5398Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989017008763/wm5398Isup3.mol
Data collection: APEX2 (Bruker, 2010); cell
SAINT (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2010).[AuCl2(C12H8N2)]PF6 | Dx = 2.558 Mg m−3 |
Mr = 593.04 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pbca | Cell parameters from 119 reflections |
a = 12.9983 (7) Å | θ = 3.4–27.3° |
b = 15.2709 (10) Å | µ = 10.07 mm−1 |
c = 15.5153 (10) Å | T = 150 K |
V = 3079.7 (3) Å3 | Plate, yellow |
Z = 8 | 0.15 × 0.13 × 0.05 mm |
F(000) = 2208 |
Bruker APEX CCD detector diffractometer | 3822 independent reflections |
Radiation source: fine-focus sealed tube | 3192 reflections with I > 2σ(I) |
Detector resolution: 8.3333 pixels mm-1 | Rint = 0.027 |
phi and ω scans | θmax = 28.3°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Bruker, 2010) | h = −17→15 |
Tmin = 0.576, Tmax = 0.746 | k = −20→15 |
15573 measured reflections | l = −15→20 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.019 | H-atom parameters constrained |
wR(F2) = 0.040 | w = 1/[σ2(Fo2) + (0.0194P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max = 0.001 |
3822 reflections | Δρmax = 1.08 e Å−3 |
217 parameters | Δρmin = −0.56 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
Au1 | 0.44227 (2) | 0.09568 (2) | 0.04214 (2) | 0.01802 (4) | |
Cl1 | 0.29239 (6) | 0.03883 (5) | −0.00417 (5) | 0.03186 (17) | |
Cl2 | 0.48300 (6) | 0.12866 (5) | −0.09535 (5) | 0.02952 (17) | |
N1 | 0.57092 (15) | 0.15008 (15) | 0.09387 (16) | 0.0184 (5) | |
N2 | 0.41395 (16) | 0.06735 (15) | 0.16813 (15) | 0.0170 (5) | |
C1 | 0.6465 (2) | 0.1908 (2) | 0.0529 (2) | 0.0254 (7) | |
H1 | 0.6468 | 0.1921 | −0.0083 | 0.030* | |
C2 | 0.7252 (2) | 0.2317 (2) | 0.0982 (2) | 0.0295 (7) | |
H2 | 0.7786 | 0.2608 | 0.0677 | 0.035* | |
C3 | 0.7262 (2) | 0.2303 (2) | 0.1863 (2) | 0.0270 (7) | |
H3 | 0.7794 | 0.2591 | 0.2172 | 0.032* | |
C4 | 0.6474 (2) | 0.18577 (19) | 0.2310 (2) | 0.0221 (6) | |
C5 | 0.57038 (18) | 0.14663 (18) | 0.18156 (19) | 0.0173 (6) | |
C6 | 0.48791 (19) | 0.10177 (17) | 0.22131 (18) | 0.0166 (5) | |
C7 | 0.4824 (2) | 0.09379 (18) | 0.31033 (19) | 0.0204 (6) | |
C8 | 0.5628 (2) | 0.1336 (2) | 0.3608 (2) | 0.0241 (6) | |
H8 | 0.5611 | 0.1288 | 0.4218 | 0.029* | |
C9 | 0.6403 (2) | 0.1775 (2) | 0.3226 (2) | 0.0260 (7) | |
H9 | 0.6918 | 0.2036 | 0.3576 | 0.031* | |
C10 | 0.3993 (2) | 0.04620 (19) | 0.3444 (2) | 0.0230 (6) | |
H10 | 0.3929 | 0.0386 | 0.4050 | 0.028* | |
C11 | 0.3274 (2) | 0.01083 (19) | 0.29003 (19) | 0.0240 (6) | |
H11 | 0.2715 | −0.0218 | 0.3129 | 0.029* | |
C12 | 0.3362 (2) | 0.02256 (17) | 0.20087 (19) | 0.0210 (6) | |
H12 | 0.2858 | −0.0019 | 0.1636 | 0.025* | |
P1 | 0.40487 (5) | 0.14377 (5) | 0.61776 (5) | 0.01992 (16) | |
F1 | 0.38930 (15) | 0.08895 (13) | 0.70331 (12) | 0.0412 (5) | |
F2 | 0.41427 (15) | 0.05546 (12) | 0.56412 (13) | 0.0362 (5) | |
F3 | 0.52589 (12) | 0.14548 (12) | 0.63152 (14) | 0.0399 (5) | |
F4 | 0.41879 (16) | 0.19932 (14) | 0.53096 (13) | 0.0443 (5) | |
F5 | 0.28305 (12) | 0.14421 (12) | 0.60406 (14) | 0.0410 (5) | |
F6 | 0.39496 (14) | 0.23393 (12) | 0.67051 (14) | 0.0423 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Au1 | 0.02348 (6) | 0.01722 (6) | 0.01336 (6) | 0.00051 (4) | −0.00115 (4) | −0.00098 (4) |
Cl1 | 0.0364 (4) | 0.0344 (4) | 0.0249 (4) | −0.0106 (3) | −0.0115 (3) | 0.0001 (4) |
Cl2 | 0.0419 (4) | 0.0329 (4) | 0.0138 (3) | 0.0045 (3) | 0.0028 (3) | −0.0002 (3) |
N1 | 0.0192 (11) | 0.0202 (12) | 0.0159 (12) | 0.0014 (9) | 0.0006 (9) | −0.0011 (10) |
N2 | 0.0210 (11) | 0.0166 (11) | 0.0134 (12) | 0.0001 (9) | −0.0008 (10) | −0.0012 (10) |
C1 | 0.0246 (14) | 0.0276 (16) | 0.0239 (17) | 0.0031 (12) | 0.0071 (13) | 0.0020 (13) |
C2 | 0.0211 (14) | 0.0331 (18) | 0.0342 (19) | −0.0027 (13) | 0.0067 (13) | 0.0066 (15) |
C3 | 0.0183 (14) | 0.0269 (16) | 0.0359 (19) | 0.0008 (12) | −0.0035 (13) | −0.0017 (14) |
C4 | 0.0189 (13) | 0.0219 (15) | 0.0256 (16) | 0.0023 (11) | −0.0023 (12) | −0.0007 (13) |
C5 | 0.0178 (13) | 0.0168 (13) | 0.0173 (14) | 0.0044 (10) | −0.0005 (11) | −0.0010 (11) |
C6 | 0.0177 (12) | 0.0140 (12) | 0.0182 (14) | 0.0043 (10) | −0.0007 (11) | −0.0005 (12) |
C7 | 0.0236 (13) | 0.0192 (13) | 0.0184 (15) | 0.0051 (11) | −0.0007 (12) | 0.0011 (12) |
C8 | 0.0304 (15) | 0.0259 (15) | 0.0158 (15) | 0.0058 (12) | −0.0056 (13) | −0.0020 (13) |
C9 | 0.0252 (15) | 0.0277 (16) | 0.0250 (17) | 0.0017 (12) | −0.0082 (13) | −0.0068 (14) |
C10 | 0.0266 (14) | 0.0237 (15) | 0.0187 (15) | 0.0048 (12) | 0.0022 (13) | 0.0040 (13) |
C11 | 0.0261 (14) | 0.0233 (14) | 0.0227 (16) | −0.0014 (12) | 0.0034 (13) | 0.0020 (13) |
C12 | 0.0208 (13) | 0.0178 (13) | 0.0244 (16) | −0.0014 (11) | −0.0016 (12) | −0.0007 (12) |
P1 | 0.0199 (3) | 0.0183 (4) | 0.0216 (4) | −0.0015 (3) | 0.0008 (3) | −0.0005 (3) |
F1 | 0.0531 (12) | 0.0476 (12) | 0.0228 (11) | −0.0131 (10) | −0.0014 (9) | 0.0103 (9) |
F2 | 0.0484 (11) | 0.0258 (10) | 0.0345 (12) | 0.0000 (9) | −0.0003 (9) | −0.0105 (9) |
F3 | 0.0205 (8) | 0.0374 (11) | 0.0619 (15) | −0.0024 (8) | −0.0029 (9) | −0.0005 (11) |
F4 | 0.0583 (12) | 0.0407 (12) | 0.0340 (13) | −0.0018 (10) | 0.0028 (9) | 0.0167 (10) |
F5 | 0.0221 (8) | 0.0325 (11) | 0.0683 (15) | −0.0025 (8) | −0.0081 (9) | 0.0000 (10) |
F6 | 0.0387 (10) | 0.0321 (11) | 0.0560 (14) | −0.0106 (8) | 0.0194 (10) | −0.0224 (10) |
Au1—N1 | 2.032 (2) | C6—C7 | 1.388 (4) |
Au1—N2 | 2.036 (2) | C7—C10 | 1.406 (4) |
Au1—Cl1 | 2.2506 (7) | C7—C8 | 1.440 (4) |
Au1—Cl2 | 2.2549 (8) | C8—C9 | 1.348 (4) |
N1—C1 | 1.325 (3) | C8—H8 | 0.9500 |
N1—C5 | 1.362 (4) | C9—H9 | 0.9500 |
N2—C12 | 1.322 (3) | C10—C11 | 1.370 (4) |
N2—C6 | 1.372 (3) | C10—H10 | 0.9500 |
C1—C2 | 1.389 (4) | C11—C12 | 1.400 (4) |
C1—H1 | 0.9500 | C11—H11 | 0.9500 |
C2—C3 | 1.368 (4) | C12—H12 | 0.9500 |
C2—H2 | 0.9500 | P1—F1 | 1.582 (2) |
C3—C4 | 1.411 (4) | P1—F3 | 1.5877 (17) |
C3—H3 | 0.9500 | P1—F2 | 1.589 (2) |
C4—C5 | 1.396 (4) | P1—F5 | 1.5976 (18) |
C4—C9 | 1.430 (4) | P1—F4 | 1.602 (2) |
C5—C6 | 1.414 (4) | P1—F6 | 1.6070 (19) |
N1—Au1—N2 | 81.75 (9) | C10—C7—C8 | 124.8 (3) |
N1—Au1—Cl1 | 174.84 (7) | C9—C8—C7 | 120.9 (3) |
N2—Au1—Cl1 | 93.90 (6) | C9—C8—H8 | 119.5 |
N1—Au1—Cl2 | 95.11 (7) | C7—C8—H8 | 119.5 |
N2—Au1—Cl2 | 176.74 (6) | C8—C9—C4 | 122.0 (3) |
Cl1—Au1—Cl2 | 89.28 (3) | C8—C9—H9 | 119.0 |
C1—N1—C5 | 120.1 (2) | C4—C9—H9 | 119.0 |
C1—N1—Au1 | 127.8 (2) | C11—C10—C7 | 119.7 (3) |
C5—N1—Au1 | 112.00 (17) | C11—C10—H10 | 120.1 |
C12—N2—C6 | 120.2 (2) | C7—C10—H10 | 120.1 |
C12—N2—Au1 | 128.12 (19) | C10—C11—C12 | 120.2 (3) |
C6—N2—Au1 | 111.69 (18) | C10—C11—H11 | 119.9 |
N1—C1—C2 | 121.0 (3) | C12—C11—H11 | 119.9 |
N1—C1—H1 | 119.5 | N2—C12—C11 | 120.5 (3) |
C2—C1—H1 | 119.5 | N2—C12—H12 | 119.7 |
C3—C2—C1 | 120.4 (3) | C11—C12—H12 | 119.7 |
C3—C2—H2 | 119.8 | F1—P1—F3 | 91.30 (11) |
C1—C2—H2 | 119.8 | F1—P1—F2 | 90.01 (11) |
C2—C3—C4 | 119.5 (3) | F3—P1—F2 | 90.47 (10) |
C2—C3—H3 | 120.3 | F1—P1—F5 | 89.25 (11) |
C4—C3—H3 | 120.3 | F3—P1—F5 | 178.81 (11) |
C5—C4—C3 | 117.2 (3) | F2—P1—F5 | 90.58 (11) |
C5—C4—C9 | 117.5 (3) | F1—P1—F4 | 179.13 (12) |
C3—C4—C9 | 125.3 (3) | F3—P1—F4 | 89.57 (11) |
N1—C5—C4 | 121.9 (3) | F2—P1—F4 | 90.02 (11) |
N1—C5—C6 | 117.3 (2) | F5—P1—F4 | 89.88 (11) |
C4—C5—C6 | 120.8 (3) | F1—P1—F6 | 90.90 (11) |
N2—C6—C7 | 121.9 (3) | F3—P1—F6 | 89.82 (10) |
N2—C6—C5 | 117.0 (3) | F2—P1—F6 | 179.04 (12) |
C7—C6—C5 | 121.0 (3) | F5—P1—F6 | 89.13 (10) |
C6—C7—C10 | 117.4 (3) | F4—P1—F6 | 89.06 (12) |
C6—C7—C8 | 117.8 (3) | ||
C5—N1—C1—C2 | −1.0 (4) | C4—C5—C6—N2 | 178.2 (2) |
Au1—N1—C1—C2 | 174.1 (2) | N1—C5—C6—C7 | 178.8 (2) |
N1—C1—C2—C3 | 0.2 (5) | C4—C5—C6—C7 | −1.4 (4) |
C1—C2—C3—C4 | 1.0 (5) | N2—C6—C7—C10 | 2.1 (4) |
C2—C3—C4—C5 | −1.4 (4) | C5—C6—C7—C10 | −178.4 (2) |
C2—C3—C4—C9 | 178.5 (3) | N2—C6—C7—C8 | −178.9 (2) |
C1—N1—C5—C4 | 0.6 (4) | C5—C6—C7—C8 | 0.7 (4) |
Au1—N1—C5—C4 | −175.2 (2) | C6—C7—C8—C9 | 0.4 (4) |
C1—N1—C5—C6 | −179.7 (2) | C10—C7—C8—C9 | 179.4 (3) |
Au1—N1—C5—C6 | 4.5 (3) | C7—C8—C9—C4 | −0.8 (4) |
C3—C4—C5—N1 | 0.6 (4) | C5—C4—C9—C8 | 0.1 (4) |
C9—C4—C5—N1 | −179.3 (3) | C3—C4—C9—C8 | −179.8 (3) |
C3—C4—C5—C6 | −179.1 (2) | C6—C7—C10—C11 | −0.7 (4) |
C9—C4—C5—C6 | 1.0 (4) | C8—C7—C10—C11 | −179.7 (3) |
C12—N2—C6—C7 | −2.3 (4) | C7—C10—C11—C12 | −0.5 (4) |
Au1—N2—C6—C7 | 177.4 (2) | C6—N2—C12—C11 | 1.0 (4) |
C12—N2—C6—C5 | 178.2 (2) | Au1—N2—C12—C11 | −178.6 (2) |
Au1—N2—C6—C5 | −2.2 (3) | C10—C11—C12—N2 | 0.4 (4) |
N1—C5—C6—N2 | −1.6 (3) |
Footnotes
‡Additional correspondence author, e-mail: raphael.enoque@gmail.com.
Acknowledgements
The authors are grateful to Dr Déborah de Alencar Simoni, technician of the Institutional Single Crystal XRD facility – UNICAMP, Brazil, for the data collection and preliminary data refinements.
Funding information
Funding for this research was provided by: Fundação de Amparo à Pesquisa do Estado de São Paulo (grant No. 2015/25114-4 to Pedro Paulo Corbi; grant No. 2015/20882-3 to Douglas Hideki Nakahata); Conselho Nacional de Desenvolvimento Científico e Tecnológico (grant No. 140466/2014-2 to Raphael Enoque Ferraz de Paiva).
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