Ga(III) complexes of DOTA and DOTA-monoamide: kinetic and thermodynamic stability.

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1 Supporting Information for Ga(III) complexes of DTA and DTA-monoamide: kinetic and thermodynamic stability. Vojtěch Kubíček, a,b Jana Havlíčková, a Jan Kotek, a Gyula Tircsó, c Petr Hermann, a * Éva Tóth b and Ivan Lukeš a a Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 8, Prague, Czech Republic. b Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, rléans Cedex 2, France. c Department of Analytical and Inorganic Chemistry, University of Debrecen, H-4010, Debrecen, Egyetem tér 1, Hungary. Content : Figure S1: Distribution diagrams for the Ga 3+ -DTA system under equilibrium conditions and for the preformed complex ( non-equilibrium conditions). Page 2 Figure S2: Distribution diagrams for the Ga 3+ -D3AM Bu system under equilibrium conditions and for the preformed complex ( non-equilibrium conditions). Page 3 Figure S3: Pseudo-first-order rate constants k obs of proton-assisted and hydroxide-assisted dissociation of GaDTA and GaDT3AM Bu complexes. Page 4 Figure S4: The crystal packing found in the solid-state structure of [Ga(H 2 dota)](cl 4 ) 0.5HCl 4 5.5H 2. Page 5 Figure S5: Selected 71 Ga NMR spectra recorded during proton-assisted decomplexation (c H+ = 3.0 M, 25 C; [Ga(H 2 ) 6 ] 3+ ~0.0 ppm, [Ga(H) 4 ] 220 ppm in the insert). Page 6 Figure S6: Selected 71 Ga NMR spectra recorded during hydroxide-assisted decomplexation (ph = 10.3 M, 25 C; [Ga(H) 4 ] 220 ppm, [Ga(H 2 ) 6 ] ppm in the insert). Page 7 Table S1: Comparison of geometric parameters reported for crystal structures of Ga 3+ -complexes with DTA and DTA-like ligands, and those of Lu 3+ -DTA complex. Page 8 Table S2: Comparison of stability constants for complexes of some polyaminocarboxylate ligands with trivalent metal ions. Page 10 Table S3: verall stability constants of the studied gallium(iii) complexes determined from out-of-cell titration. Page 11 Table S4: verall protonation constants of the studied gallium(iii) complexes determined from titration of the preformed complexes. Page 11 Table S5: Experimental crystallographic data for [Ga(H 2 dota)](cl 4 ) 0.5HCl 4 5.5H 2. Page 12 Text S1: Suggested correction of the solid-state structure of [Ga(H 2 dota)]cl 5H 2 Page 13 Text S2: Equations describing the dissociation kinetics Page 15 1

2 Figure S1: Distribution diagrams for the Ga 3+ -DTA system under equilibrium conditions (A, c L = c Ga = M) and for the preformed complex ( non-equilibrium conditions; B, c GaL = M); 25 C, I = 0.1 M NMe 4 Cl. A B 2

3 Figure S2: Distribution diagrams for the Ga 3+ -D3AM Bu system under equilibrium conditions (A, c L = c Ga = M) and for the preformed complex ( non-equilibrium conditions; B, c GaL = M); 25 C, I = 0.1 M NMe 4 Cl. A B 3

4 Figure S3: Pseudo-first-order rate constants k obs of proton-assisted dissociation (A, 25 ºC, HN 3 ) and hydroxideassisted dissociation (B, 25 C, 0.2 M CAPS buffer) of GaDTA (u) and GaD3AM Bu ( ) complexes. -4 A log ( H k obs [s 1 ]) [H + ] [mol dm 3 ] B log ( H k obs [s 1 ]) [H ] [x10 3 mol dm 3 ] 4

5 Figure S4: The crystal packing found in the solid-state structure of [Ga(H 2 dota)](cl 4 ) 0.5HCl 4 5.5H 2. Model including disordered solvate water molecules is shown. The H-atoms are omitted for the sake of clarity. View along z axis. 5

6 Figure S5: Selected 71 Ga NMR spectra recorded during proton-assisted decomplexation of GaDTA (c H+ = 3.0 M, 25 C; [Ga(H 2 ) 6 ] 3+ ~0.0 ppm, [Ga(H) 4 ] 220 ppm in the insert). 6

7 Figure S6: Selected 71 Ga NMR spectra recorded during hydroxide-assisted decomplexation of GaDTA (ph = 10.3 M, 25 C; [Ga(H) 4 ] 220 ppm, [Ga(H 2 ) 6 ] ppm in the insert). 7

8 Table S1: Comparison of geometric parameters reported for crystal structures of Ga 3+ -complexes with DTA and DTA-like ligands, and those of Lu 3+ -DTA complex. CCDC coden devhiw hodcae niyxid tirhae ur structure Formula C 2 H C 2 H C 2 C 2 C 2 N 4 N 4 N 4 N 4 N 4 N 1 Ga N 7 N 1 Ga N 7 N 1 Ga N 7 N 1 Ga N 7 N 1 Ga N N 10 C N N 10 C N N 10 C 2 H 311 HN PPh 3 + NH 2 Distances (Å) Ga1 N (4) Ga1 N (3) Ga1 N (4) Ga1 N (3) (N10 N4 # ) Ga (3) Ga (3) Angles ( ) N1-Ga1-N (1) N1-Ga1-N (2) N1-Ga1-N (1) (N10 N4 # ) N1-Ga (2) N1-Ga (2) N4-Ga1-N (1) N4-Ga1-N (2) (N10 N4 # ) N4-Ga (1) N4-Ga (1) N7-Ga1-N (1) (N10 N4 # ) N7-Ga (2) N7-Ga (2) N10-Ga (1) (N10 N4 # ) N10-Ga (1) (N10 N4 # ) 111-Ga (1) Torsion angles ( ) N1-C2-C3-N N4-C5-C6-N N7-C8-C9-N (C8,C9,N10 C6 #,C5 #,N4 # ) N10-C11-C12-N (N10,C11,C12 N4 #,C3 #,C2 # ) 8

9 Table S1: Continuation CCDC coden nojyiu jaytim Formula N N 1 N 7 N 1 Lu N Ga N Distances (Å) M1 N M1 N M1 N M1 N M M M M M1-w N Angles ( ) N1-Ga1-N N4-Ga1-N N7-Ga1-N Ga Ga Ga N1-Ga N4-Ga N7-Ga N1-Ga N4-Ga N7-Ga N1-Ga N4-Ga N7-Ga Torsion angles ( ) N1-C2-C3-N N4-C5-C6-N N7-C8-C9-N1(10) N10-C11-C12-N

10 Table S2: Comparison of stability constants, logk(ml), for complexes of some polyaminocarboxylate ligands with some trivalent metal ions (taken form Martell, A. E.; Smith, R. M. Critical Stability Constants, Plenum Press, New York, , Vols. 1 6 and NIST Standard Reference Database 46 (Critically Selected Stability Constants of Metal Complexes), Version 7.0, 2003). metal ion H 4 edta H 5 dtpa H 4 dota In(III) Ga(III) Al(III) Fe(III) La(III) Gd(III)

11 Table S3: verall stability constants (β) a of the studied gallium(iii) complexes determined from out-of-cell titration. Standard deviations in parentheses are given directly by the fitting program. Equilibrium b Equilibrium constant (logβ) Species b Ga 3+ -DTA Ga 3+ -D3AM Bu H 2 + Ga + L [Ga(H)(L)] + H H 1 GaL 15.83(12) Ga + L [Ga(L)] GaL 26.05(3) 24.64(4) H + Ga + L [Ga(HL)] HGaL 29.69(6) 27.76(8) 2H + Ga + L [Ga(H 2 L)] H 2 GaL 32.12(5) 30.02(7) 3H + Ga + L [Ga(H 3 L)] H 3 GaL 33.96(7) a β = [H h GaL]/[H] h [Ga] [L]. b Charges are omitted. Table S4: verall protonation constants (β) a of the studied gallium(iii) complexes determined from titration of the preformed complexes. Standard deviations in parentheses are given directly by the fitting program. Equilibrium b Species b Equilibrium constant (logβ) GaDTA GaD3AM Bu H + [Ga(L)] [Ga(HL)] HGaL 3.52(2) 3.24(2) 2H + [Ga(L)] [Ga(H 2 L)] H 2 GaL 5.96(2) 4.78(2) 3H + [Ga(L)] [Ga(H 3 L)] H 3 GaL 7.50(3) a β = [H h GaL]/[H] h [GaL]. b Charges are omitted. 11

12 Table S5: Experimental crystallographic data for [Ga(H 2 dota)](cl 4 ) 0.5HCl 4 5.5H 2. Parameters [Ga(H 2 dota)](cl 4 ) 0.5HCl 4 5.5H 2 Formula C 16 H 37.5 Cl 1.5 GaN M r Colour Colorless Habit Plate Crystal size (mm) Crystal system rthorhombic Space group I bam (No. 72) a (Å) (3) b (Å) (3) c (Å) (6) U (Å 3 ) (2) Z 8 D calc (g cm 3 ) µ (mm 1 ) F(000) 2992 θ range ( ) Abs. correction multi-scan Max., min. scale factors 0.917, GF on F Total refl bsd. refl. [I>2σ(I)] 2758 Parameters 196 Restraints 0 R R [I>2σ(I)] wr wr [I>2σ(I)] Largest diff. peak/hole (Å 3 ) 1.080, CCDC ref. number CCDC

13 Text S1: Suggested correction of the solid-state structure of [Ga(H 2 dota)]cl 5H 2 ( = [Ga(Hdota)] HCl 5H 2 ; refcode NIYXID, CCDC ): A. Heppeler, J. P. André, I. Buschmann, X. Wang, J.-C. Reubi, M. Hennig, T. A. Kaden, H. R. Maecke Chem. Eur. J. 2008, 14, Citation from the Experimental of the original work: [Ga III (H 2 dota)] + Cl : [Ga III (H 2 dota)] + Cl was obtained by treating DTA (78.73 mg, mmol) with Ga(N 3 ) 3 9H 2 (91 mg, mmol) in aqueous solution (5 ml, ph 4, 80 C, 30 min). After cooling to room temperature, the ph was adjusted to 8 with 0.1M aqueous NaH. Excess Ga III (in the form of hydroxide) was removed by filtration and the final ph was adjusted to 7 with 0.1M HCl. Slow evaporation of water afforded colourless crystals suitable for X-ray diffraction. 1 H NMR: (400 MHz, 27 C, D 2 ): δ = 3.40 (br s, 16H, N-CH 2 - CH 2 -N), 3.68 ppm (br s, 8H; N-CH 2 -CD); 13 C NMR: (101 MHz, 27 C, D 2, pd = 6.9): δ = (N-CH 2 - CH 2 -N), (N-CH 2 -CGa), ppm (CGa); IR (KBr): ν = 3570, 3492, 2956, 2705, 2650, 2590, 1746, 1710, 1699, 1620, 1496, 1475, 1384, 1339, 1316, 1287, 1240, 1212, 1083, 1047, 925 cm 1 ; MS (ESI): C16H25GaN48 (M = g mol 1 ): m/z (%): 471.1, (6:4) (100) [M+H] + ; elemental analysis calcd. (%) for C 16 H 25 N 4 8 Ga HN 3 2H 2 (M = g mol 1 ): C 33.71, H 5.30, N 12.29, 36.47; found: C 33.57, H 5.10, N 12.25, Following the Experimental above and a treatment of data from the deposited CIF file, we can have doubts on the atom assignment in the reported structure. First, the elemental analysis reported for the bulk material is not corresponding to the formula assigned from the single-crystal analysis (elemental analysis is reported for [Ga(Hdota)] HN 3 2H 2 ); although, it is common that the few crystals suitable for X-ray analysis are not representing the stoichiometry of the bulk material. However, the formula [Ga(Hdota)] HCl 5H 2 implies protonation of the complex to give the [Ga(H 2 dota)] + cation or a presence of an oxonium cation as HCl is a very strong acid. Such complex protonation has to occur on the non-coordinated carboxylate arm(s). Nevertheless, such material cannot be isolated from solutions having ph ~7 (as described in the Experimental) as the pk A value of the [Ga(H 2 dota)] + species is 2.4 from our potentiometric data. In addition, according to the distribution diagram, the GaDTA complex is present exclusively in the form of the fully deprotonated [Ga(dota)] species at ph ~7 (as pk A value of [Ga(Hdota)] species is 3.6). Furthermore, the hydrogen atoms corresponding to the protonated complex species were not located in the electronic difference density map, and C bond distances found in the structure do not support the hypothesis of their protonation (the distances are and Å for one and and Å for the other uncoordinated carboxylate moiety, respectively). In addition, the hydrogen bond system suggested in the original report (following the Cl distances) point to a definitely wrong assignment of the chlorine atom, as it results in six (!) non-realistically short Cl distances in a range of Å (!), forming distorted octahedron around the suggested chloride anion. As the X-ray diffraction power of Cl is similar to that of the K + cation, it can be suggested that a correct formula of the reported crystal structure should be K[Ga(dota)] 5H 2. In such case, the range of the K distances corresponds 13

14 to the length of common coordination bonds and a reliable crystal packing is obtained, i.e. the complex molecules are connected through K + cations into a polymeric coordination chain (see Figure below). 14

15 Text S2: Equations describing the dissociation kinetics In the following text, charges of individual species are omitted for reasons of clarity. The decomplexation rate is given by Equation 1 where [GaL] t is the total concentration of the Ga(III) complex. d[gal] t = kobs[gal] t (1) dt Proton-assisted dissociation The total decomplexation rate is given by the sum of the contributions given by the dissociation of the species in different degree of protonation (Equation 2), where k Hi is the dissociation rate constant and β Hi is the overall proton protonation constant of the [H i GaL] species that is given by consecutive protonation constants as follows: β Hi = K H1 K H2 K Hi ). d[gal] t i = khi[higal] = k0[gal] + khiβ Hi[GaL][H] (2) dt So, taking into account that the maximal protonation state of the Ga(III)-complexes is four, k obs can be expressed as in Equation 3. H1 H2 2 k H0 + kh1βh1[h] + k H2β H2[H] + kh3β H3[H] + kh4β H4[H] k obs = (3) β [H] + β [H] + β [H] + β [H] H3 3 H4 4 Both complexes undergo several protonation steps that were observed by potentiometry, all occurring above the ph region of the kinetic measurements. According to the distribution diagram (Figures S1 and S2), we can assume that both complexes exist predominantly in one degree of protonation; thus, [GaL] t = [H 3 GaL] in the GaDTA system and [GaL] t = [H 2 GaL] in the GaD3AM Bu system, respectively, and the less protonated complexes do not show a significant abundance along the ph region of the kinetic measurements. This assumption gives that terms β H3 [H] 3 and β H2 [H] 2 are the dominant ones in the denominator for the GaDTA and the GaD3AM Bu systems, respectively, and other terms can be neglected. The less protonated forms of the complexes are generally less reactive and, therefore, their contribution to the dissociation rate is negligible and the corresponding terms in the numerator can be neglected. Thus, only the terms corresponding to the reactivity of the dominantly present species (i.e. [H 3 GaL] for GaDTA and [H 2 GaL] for GaD3AM Bu ) and those in higher degree of protonation (i.e. [H 4 GaL] for GaDTA and [H 3 GaL] and [H 4 GaL] for GaD3AM Bu ) can be taken into account in the nominator. Then, the rate law can be simplified and k obs can be expressed as in Equations 4 and 5 for GaDTA and GaD3AM Bu systems, respectively. For the GaDTA system: H k = k + k [H] (4) obs H0 H1 15

16 where k H0 = k H3 and k H1 = K H4 k H4 For the GaD3AM Bu system: H obs H0 H1 H2 2 k = k + k [ H] + k [H] (5) where k H0 = k H2, k H1 = K H3 k H3 and k H2 = K H3 K H4 k H4 Hydroxide-assisted dissociation The decomplexation rate given by Equation 1 can be rewritten as the sum of the contributions originating from the dissociation of the hydroxido-species (Equation 6), where k Hi is the dissociation rate constant and β Hi is the overall hydroxide-dissociation constant of the species [GaL(H) i ] that is given by consecutive protonation constants as follows: β Hi = K H1 K H2 K Hi ). d[gal] t i = khi[gal(h) i ] = k0[gal] + khiβ Hi[GaL][H] (6) dt Assuming the formation of maximum dihydroxido species, k obs can be expressed by Equation 7. kh0 + kh1βh1[h] + kh2 βh2[h] k obs = (7) 2 1+ β [H] + β [H] H1 H2 2 n the basis of potentiometry, we can assume that the coordination of the hydroxide anion in the [GaDTAM Bu (H)] complex is fully finished at ph below the lower limit of the range studied in the kinetic measurements and this species is dominant in the ph region used in the kinetic study. For the GaDTA system, no hydroxido species was found by potentiometry. So, for the rate law, we can assume both complexes present in only one dominant form, i.e. [GaL] t = [GaL] in the GaDTA system and [GaL] t = [GaL(H)] in the GaD3AM Bu system, respectively. In the GaDTAM Bu system, it can be assumed that the [GaL] species has a very low reactivity (and also negligible abundance along the ph region of kinetic measurements) and, thus, its contribution to the dissociation rate can be neglected. nly the terms corresponding to the reactivity of the dominantly present species (i.e. [GaL] for GaDTA and [GaL(H)] for GaD3AM Bu ) and those with more hydroxido ligands (i.e. [GaL(H)] and [GaL(H) 2 ] for GaDTA and [GaL(H) 2 ] for GaD3AM Bu ) can be taken into account in the nominator. Thus, the rate law can be simplified and k obs can be expressed as in Equations 8 and 9. For the GaDTA system: H obs H0 H1 H2 2 k = k + k [ H] + k [H] (8) where k H0 = k H0, k H1 = K H1 k H1 and k H2 = K H1 K H2 k H2 For the GaD3AM Bu system: H k = k + k [H] (9) obs H0 H1 where k H0 = k H1 and k H1 = K H2 k H2 16