Supporting Information. for. Angew. Chem. Int. Ed Wiley-VCH 2004

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1 Supporting Information for Angew. Chem. Int. Ed Wiley-VCH Weinheim, Germany

2 1 Challenges in Engineering Spin Crossover. Structures and Magnetic Properties of six Alcohol Solvates of Iron(II) tris(2-picolylamine) Dichloride Marc Hostettler, Karl W. Törnroos, Dmitry Chernyshov, Brita Vangdal and Hans-Beat Bürgi* Syntheses and crystallization of the iron(ii) tris(2-picolylamine) dichloride solvates were based on a literature method. [1] FeCl 2 4H 2 O p.a. (FLUKA) and 2-picolylamine purum (FLUKA) were used as purchased. All solvents were dried and degassed prior to use. Reactants and final products were handled in a nitrogen atmosphere glove box and reactions carried out under a nitrogen using a standard Schlenk set-up. The iron salt (typically.25 g, 1.45 mmol) was dissolved in a minimum amount of the alcohol at ~6 ºC under stirring. The ligand was added drop-wise in typically equivalents and the solution left stirring at the same temperature for ~2h. The solution was then left to cool slowly without stirring. After removal of excess solvent the yellowish precipitate was washed repeatedly with cold acetone. The final product was dried in vacuo for.5-1 h. The precipitate typically contained micro-crystals as well as single crystal suitable for X-ray analysis. Magnetic susceptibility measurements between 2 and 298 K were performed with a SQUID MPMS-XL5 (Quantum Design) instrument on freshly made micro-crystalline samples (weight 13.3 mg (ethanol), 1.62 mg (allyl alcohol), 21.3 mg (2-propanol), 12 mg (1-propanol), 33 mg (tert-butanol)) in field-cooling mode (field 1 Oe). The measured susceptibilities were corrected for diamagnetic contributions of the sample holder, normalized to one mole of sample and then corrected for the diamagnetic contribution of the sample itself. Paramagnetic susceptibilities χ(t) of compounds without spin crossover obey the Curie law. For the other compounds the HS fraction as a function of temperature γ HS (T) was calculated from the susceptibilities χ HT (T) and χ LT (T) according to χ (T) = γ HS (T) χ HT (T) + χ LT (T). X-ray data of the allyl alcohol, 1-propanol and 2-propanol solvates were collected with a SMART 1K CCD diffractometer,.3º ω-scans, MoΚα radiation, λ =.7173 Å, using SMART and SAINT at 2 K. [27] The x-ray data of the methanol solvate were collected at 2 and 3 K with a SMART 2K CCD diffractometer,.3º ω-scans, MoКα radiation, λ =.7173 Å, using SMART and SAINT. [2] The x-ray data of the tert-butanol solvate were collected at 2 K on the SNBL beamline BM1A at the ESRF synchrotron in Grenoble (France) with a MAR345 image-plate area detector using λ =.7(1) Å, ϕ-

3 2 scans of 1.2º and a readout pixel resolution of 15 µm. Intensities were integrated with CrysAlis, [3] reflections shadowed by the cryostats were removed from the data by means of locally written software. All samples were cooled with Oxford Cryostream series 6 N 2 cryostats. Empirical absorption correction was made with SADABS, [4] structure refinement with SHELXL97. [5] Contrary to ref [9] in the main text, only average structures of the complex molecules were refined. All non-h atoms except for the minor disorder components of the solvent molecules were refined anisotropically. Methanol was modeled by distributing the molecule over three different sites. All atoms of the allyl alcohol and 1- propanol molecules are disordered over two positions. Molecules of 2-propanol were modeled with two positions for the oxygen atom. The tert-butanol derivative shows two solvent molecules in the asymmetric unit, one of them fully ordered, the other with all atoms disordered over two positions. Hydrogen atoms were input as riding atoms and their isotropic displacement parameters fixed at 1.2 U eq (CH, CH 2 ) and 1.5 U eq (CH 3, OH) of their respective parent atoms. The data for the ethanol derivative were taken from ref. [1] in the main text. Crystal data for the methanol derivative at 2 K: refl. integrated = 66964, θ min/max = , unique refl. refined = 5723, R int =.268, R 1 =.356, wr2 =.769, S = 1.155, max./min. residual density =.32/.27 e Å 3, populations of the disorder components =.375(15),.317(4) and.38(15). Crystal data for the methanol derivative at 3 K: refl. integrated = 65914, θ min/max = , unique refl. refined = 586, R int =.296, R 1 =.49, wr2 =.852, S = 1.19, max./min. residual density =.29/.28 e Å 3, populations of the disorder components =.422(3),.32(6) and.276(6). Crystal data for the allyl alcohol derivative at 2 K: refl. integrated = 4639, θmin/max = , unique refl. refined = 3179, R int =.546, R1 =.758, wr2 =.145, S = 1.22, max./min. residual density =.49/.33 e Å3, population of the minor disorder component =.334(1). Crystal data for the 1-propanol derivative at 2 K: refl. integrated = 14212, θ min/max = , unique refl. refined = 5582, R int =.649, R 1 =.555, wr2 =.113, S =.989, max./min. residual density =.48/.44 e Å 3, population of the minor disorder component =.282(9). Crystal data for the 2-propanol derivative at 2 K: refl. integrated = 28153, θ min/max = , unique refl. refined = 5856, R int =.52, R 1 =.561, wr2 =.1254, S = 1.33, max./min. residual density =.66/.5 e Å 3, population of the minor disorder component =.151(9). Crystal data for the tert-butanol derivative at 2 K: twinned crystal modeled with [ 1 1 1] as twinning symmetry operation, refl. integrated = 6895, θ min/max = o, unique refl. refined = 1858, R int =.43, R 1 =.538, wr2 =.1273, S = 1.76, max./min. residual density =.49/.78 e Å 3, population of the minor disorder component =.487(7). CCDC contain the supplementary crystallographic data for this paper. These can be obtained free of charge via (or from the Cambridge

4 3 Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ, UK; fax (+44) ; or The susceptibility χ(t) was measured in field-cooling mode (field 1 Oe), corrected for the diamagnetic contributions of the sample mount, normalized to one mole of sample and then corrected for the diamagnetic contribution of the sample itself (ethanol 13.3 mg, allyl alcohol 1.62 mg, 2-propanol 21.3 mg, 1-propanol 12. mg, tert-butanol 33. mg). The paramagnetic susceptibilities χ HT (T) and χ LT (T) at high (23-3 K, HT) and low (2-3 K, LT) temperatures were fitted to a Curie-Weiss law. The nonzero magnetic response at low temperatures χ LT (T) is probably due to the presence of an unknown amount of some paramagnetic impurity, most likely Fe(III) [R. Boča et al., Inorg. Chem. 21, 4, 325]. The paramagnetic impurities affect the absolute values of paramagnetic susceptibilities but do not affect the calculated transition curves. Fig. S1. Molar susceptibilities and their inverses as a function of temperature. Yellow lines represent χ HT (T), red ones χ LT (T). The curves for the 1-propanol and tert-butanol solvates, which show no spin transition, are given in black.

5 2-propanol solvate SQUID data χ LT χ HT LT 1 5 HT Allyl alcohol.25.2 SQUID data χ HT χ LT

6 5 8 LT LT tert-butanol propanol [1] M. Sorai, J. Ensling, P. Gütlich, Chem. Phys. 1976, 18, 199. [2] SMART, Version 5.59 & SAINT, Version 6.2a Bruker AXS Inc., Madison, Wisconsin, USA, 21.

7 6 [3] CrysAlis Software System, Version 1.169, Oxford-diffraction Ltd. Oxford, England, 21. [4] G. M. Sheldrick, SADABS, Version 2.6, Empirical Absorption Correction Program, University of Göttingen, Germany, 22. [5] G. M. Sheldrick, SHELXS97 & SHELXL97, University of Göttingen, Germany, 1997.