Molecular Characteristics of a Mixed-Valence Polyoxovanadate {V IV/V 18O 42 } in Solution and at the Liquid-Surface Interface

Transcription

1 Molecular Characteristics of a Mixed-Valence Polyoxovanadate {V IV/V 18O 42 } in Solution and at the Liquid-Surface Interface Oliver Linnenberg, a Marco Moors, b Albert Solé-Daura, c Xavier López, c Christoph Bäumer, b Emmanuel Kentzinger, d Wim Pyckhout-Hintzen, e and Kirill Yu. Monakhov a, * a Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, Aachen, Germany b Peter Grünberg Institute (PGI), JARA-FIT, Forschungszentrum Jülich GmbH, Wilhelm- Johnen-Straße, Jülich, Germany c Departament de Química Física i Inorgànica, Universitat Rovira i Virgili c/marcellí Domingo 1, Tarragona, Spain d Jülich Centre for Neutron Science (JCNS) and Peter Grünberg Institute (PGI), JARA-FIT, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, Jülich, Germany e Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, Jülich, Germany S1

2 Contents: 1. Characterization of compound Elemental analysis 1.2 Powder X-ray diffractogram 1.3 UV/Vis spectra 1.4 IR spectra 1.5 Cyclic voltammograms 2. Additional SAXS data of compound 1 and data evaluation 3. Details of MD calculations of compound 1 4. References S2

3 1. Characterization of compound 1 All starting materials were commercial and used as received. All solvents were degassed with argon. Acetonitrile and DMF were dried over CaH 2 or 4 Å molecular sieves and distilled. Elemental analysis of compound 1 was performed using a Vario EL elemental analyzer. The IR spectrum of compound 1 was recorded on a Nicolet Avatar 360 FTIR spectrometer by using KBr pellets (m KBr 250 mg) in the range v = cm 1 (deviation ± 4 cm 1 ). The powder X-ray diffraction pattern of compound 1 was obtained at room temperature with a STOE Stadi-P diffractometer in transmission geometry [λ(cuk α1 ) = Å, germanium monochromator] by using a flat-plate sample holder; step size 2θ = UV/Vis spectra of compound 1 were recorded on a Jasco V-630 spectrophotometer. The samples were dissolved in the corresponding solvent, homogenized by ultrasonic treatment, diluted, and measured in a quartz cuvette (d = 1 cm). Cyclic voltammetry measurements of compound 1 were performed with a BioLogic SP 50 potentiostat under inert conditions (argon) in a degassed and dry 0.1 M TEAPF 6 -MeCN solution at 25 C. The used electrodes are Ag/AgNO 3 or Ag/AgCl in MeCN (reference electrode), glassy carbon (working electrode, d = 3 mm), and a Pt wire (counter electrode). The redox potentials were measured against the Fc/Fc + redox couple as an external standard. Between each measurement the sample was stirred to attain homogeneity. 1.1 Elemental analysis (NEt 4 ) 5 [V 18 O 42 (I)] (1). Calcd (%) for C 40 H 100 N 5 O 42 V 18 I 1 (M = gmol 1 ): C, 20.30; H, 4.26; N, Found: C, 20.31; H, 4.25; N, Powder X-ray diffractogram Figure S1: The measured powder X-ray diffraction pattern (blue) and the simulated pattern (violet) from single-crystal X-ray data 1 of compound 1, shown for the range 2θ = S3

4 1.3 UV/Vis spectra Figure S2: UV/Vis spectra of compound 1 in a mm HOAc/KOAc aqueous buffer recorded for different ph values. Figure S3: UV/Vis spectrum of compound 1 in MeCN ( mm). S4

5 Figure S4: UV/Vis spectrum of compound 1 in DMF (0.02 mm). 1.4 IR spectra Figure S5: IR spectra of compound 1 in the region ν = cm 1. The value of (V=O) terminal at ca cm 1 is in agreement with the reported 1 one at 995 cm 1. S5

6 1.5 Cyclic voltammograms Figure S6: Cyclic voltammograms (second cycle) of compound 1 (0.3 mm) in a 0.1 M TEAPF 6 - MeCN solution with scan rates of mvs 1 (range: V), referenced to E 1/2 (Fc/Fc + ). Figure S7: (de/dt) 1/2 vs. I (oxidation, de/dt = mvs 1 ) for compound 1 (0.3 mm) in a 0.1 M TEAPF 6 -MeCN solution, referenced to E 1/2 (Fc/Fc + ). S6

7 Figure S8: (de/dt) 1/2 vs. I (reduction, de/dt = mvs 1 ) for compound 1 (0.3 mm) in a 0.1 M TEAPF 6 -MeCN solution, referenced to E 1/2 (Fc/Fc + ). S7

8 2. Additional SAXS data of compound 1 and data evaluation The scattering intensity is proportional to the product of the form factor P(Q) and the structure factor S(Q). The former describes the intraparticle correlation and is a function of the particle shape, while the latter considers long-range interactions between the scattering centers. P(Q) and S(Q) are form and structure factors, respectively. P(q) for monodisperse spheres is given by the following equation:, = 9 sin and P(Q=0) is normalized to 1. The structure factor for the PY-type hard sphere interaction potential is described by:,, = ,, with A = 2QR HS. R HS represents the effective or apparent hard sphere interaction radius and η is the volume fraction occupied by such hard spheres. The observed peak in all samples roughly occurs at 2pi/2R H. = where α, β, and γ are: = = = As an example, the scattering data of a highly water containing DMF solution (10 % H 2 O) are decomposed into its constituents, taking into account the diffuse background. The hard-sphere structure factor (red) oscillates around 1 (labelled S), the form factor labelled P (in black) reduces to a simple monotonic Guinier-like contribution due to its small size and the product of both leads to the green intensity line, labelled PS. The Guinier fit is independent of the shape of the particle and leads to I(Q)=I(0)exp( (QR) 2 /5). S8

9 Figure S9: Decomposition of a highly water containing DMF solution (10 % H 2 O) SAXS spectra into structure and form factors by the Guinier fit. The calculated scattering length density for the vanadium-oxo cluster is Å 2. For the MeCN, DMF, and H 2 O solvents the values are Å 2, Å 2, and Å 2, respectively. For the TEA cation shell we estimate Å 2. S9

10 3. Details of MD calculations of compound 1 DFT-optimized Cartesian coordinates (in Å) of the [V 18 O 42 (I)] 5 structure (V 18 ) used in the Molecular Dynamics calculations. V V V V V V V V V V V V V V V V V V O O O O O O O O O O O O O O O O O O O O O O O O O O O S10

11 O O O O O O O O O O O O O O O I S11

12 Figure S10: V 18 TEA RDF between the respective centers of mass (black curves) obtained from Molecular Dynamics simulations in different pure solvents. Red lines correspond to the integration of the RDF, namely the coordination number N(r). Figure S11: Left: V 18 V 18 RDF between centers of mass (black curves) in DMF. The red line corresponds to the integration of the RDF, namely the coordination number N(r). Right: a typical snapshot of the simulations showing the lack of agglomeration. S12

13 Figure S12: A) and B) compile the analysis of MD trajectories in wet MeCN containing 1% and 5% of water, respectively. Black curves are the RDFs, g(r), and red lines are the number of particles found, on average, at a given distance. In both cases, the distance is measured between the centers of mass of both molecules. Integration of the red line at the end of the RDF peak corresponds to the number of V 18 (respectively, TEA or H 2 O) molecules coordinating the reference molecule. Top: V 18 V 18 RDF (left) accompanied by a typical snapshot of one dimer (right). Water molecules are colored in green and TEA countercations are represented as sticks for the sake of clarity. Bottom: V 18 TEA (left) and V 18 H 2 O (right) RDFs. Figure S13: Superposition of snapshots taken every 10 ps, representing the position of three different random water molecules (one in each different simulation box) throughout 5 representative ns. Water molecules are colored as function of the time (from white at t = 0 ns to red at t = 5 ns). View of the simulation boxes along the z axis. S13

14 Figure S14: Left: a typical snapshot of a cation- and water-mediated V 18 V 18 dimer obtained from the simulations in wet MeCN (5 % H 2 O). Water molecules surrounding the POVs but not participating in the formation of the dimer are omitted for clarity. Right: V 18 (H 2 O) 2 V 18 pattern, where red dotted lines represent H-bonds linking two V 18 polyoxoanions. Distances are given in Å. Table S1: Detailed information of the calculated RDFs for all the simulated systems. The characteristics of the peaks include the distance corresponding to the maximum value of the peak (given in Å), the coordination number obtained by integration of the peak (in bold), and the integration distance (given in Å) between parentheses. System V 18 V 18 V 18 in water (12.49) V 18 in MeCN (16.57) RDF V 18 TEA (10.81) (11.05) V 18 in DMF (10.33) V 18 in wet MeCN (1 % H 2 O) (16.33) V 18 in wet MeCN (5 % H 2 O) (16.57) (10.57) (11.05) S14

15 4. References (1) Müller, A.; Sessoli, R.; Krickemeyer, E.; Bögge, H.; Meyer, J.; Gatteschi, D.; Pardi, L.; Westphal, J.; Hovemeier, K.; Rohlfing, R.; Döring, J.; Hellweg, F.; Beugholt, C.; Schmidtmann, M. Polyoxovanadates: High-Nuclearity Spin Clusters with Interesting Host Guest Systems and Different Electron Populations. Synthesis, Spin Organization, Magnetochemistry, and Spectroscopic Studies. Inorg. Chem. 1997, 36, S15