Phthalocyanine-Based Single-Component Molecular Conductor [Mn Ⅲ (Pc)(CN)] 2 O Mitsuo Ikeda, Hiroshi Murakawa, Masaki Matsuda, and Noriaki Hanasaki *, Department of Physics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan E-mail:hanasaki@phys.sci.osaka-u.ac.jp Table of contents Experimental Methods. Table S1. Crystal data for [Mn(Pc)(CN)] 2 O. Structural disorder of [Mn(Pc)(CN)] 2 O. Figure S1. Molecular structure of [Mn(Pc)(CN)] 2 O. Figure S2. Infrared absorption spectra of [Mn(Pc)(CN)] 2 O. Figure S3. Isotropic magnetoresistance of [Mn(Pc)(CN)] 2 O. Magnetic moment due to thermal activation of π and d electrons. Scanning electron microscope / Energy dispersive x-ray spectroscopy. Experimental Methods X-ray Crystal Structural Analysis. An x-ray structural analysis was performed using a Rigaku VariMax Rapid FR-E diffractometer with Mo-Kα radiation. The crystal data are summarized in Table S1. The structure was solved by direct method (SHELX-97), and the hydrogen atoms were placed at the calculated ideal positions. A full-matrix least-squares technique with anisotropic thermal parameters for non-hydrogen atoms and isotropic ones for hydrogen atoms was employed for the structural refinement. The crystallographic data (CCDC 1459332) can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Infrared Absorption Spectroscopy. The infrared absorption spectra were measured by the potassium bromide disk method using a JASCO FT/IR-6100 FT-IR spectrometer in the temperature range of 5-400 K. Electrical Resistivity. Electrical resistivity measurements of single crystals were performed in the temperature range of 70-320 K in static magnetic fields of up to 9 T. In the high temperature range (T 200 K), the electrical resistivity in the ab plane was measured by the conventional four-probe method using the Quantum Design PPMS resistivity measurement system. The resistivity measurements below 220 K in the ab plane, and in all temperature ranges along the c axis were performed by a two-probe method using a KEITHLEY 6517 electrometer. The contacts between the gold wires and the sample were made of gold paste. Magnetic Susceptibility. Magnetic susceptibility measurement of polycrystalline samples was performed using a Quantum Design MPMS SQUID magnetometer. The magnetic susceptibility was measured in the temperature range of 2-300 K in static field of 1 T. Scanning electron microscope / Energy dispersive x-ray spectroscopy. Energy dispersive x-ray spectroscopy (EDS) was performed using a JEOL JSM-7600F scanning electron microscope (SEM). The sample crystal was attached to a brass sample holder with a carbon tape. We set the accelerating voltage to 15 kv in order to detect the characteristic x-ray signal attributed to the manganese atom (E Mn(K) = 5.894 kev).
Table S1 Crystal data for [Mn(Pc)(CN)] 2 O Chemical formula C 66 H 32 N 18 OMn 2 Molecular weight 1202.98 Crystal system Tetragonal Space group P4/nnc a (Å) 13.7022(14) c (Å) 13.5358(10) V (Å 3 ) 2541.4(4) Z 2 µ(mo-kα) (cm -1 ) 5.67 Temperature of data collection (K) 296 No. of reflections measured 1469 No. of independent reflections 945 [I > 2σ(I)] observed R 0.0726 R w 0.1874 Structural disorder of [Mn(Pc)(CN)] 2 O. The Bragg points in x-ray diffraction of [Mn(Pc)(CN)] 2 O have the P4/nnc symmetry without any superlattice reflection. However, in the refinement with isotropic thermal parameters, two positions were suggested as the sites occupied by single atoms. These results indicated that two species of the atomic distribution exist without ordered structure. Thus, we performed the refinement with the two sets of coordinates having a half-occupancy for each atom except the oxygen atom, and found that this refinement was consistent with the diffraction data. The results of this refinement are shown in Fig. S1(a). We divided the disordered atoms into two groups by the distance to the oxygen atom. In the figure, the black and grey atoms belong to the same group as the Mn1 and Mn2 atom, respectively. Here, Mn1 denotes the manganese atom that has a longer distance to the oxygen atom than Mn2. The distances from the manganese atom to the oxygen atom and carbon atom of the CN ligand are shown in Fig. S1(b).
Figure S1. (a) Atomic distributions of [Mn(Pc)(CN)] 2 O. The black and grey spheres represent the atoms of the same group as the Mn1 and Mn2, respectively. The red sphere is an oxygen atom. (b) Bond lengths between the manganese atoms and the axial ligands in each group.
Figure S2. Infrared absorption spectra of [Mn(Pc)(CN)] 2 O. Figure S3. Magnetic-field dependence of the normalized resistivity ρ(b)/ρ(0 T) in the magnetic fields perpendicular to the electric current direction (a) and parallel to the electric current direction (b). Magnetic moment due to thermal activation of π and d electrons. As to why the effective magnetic moment increases with temperature, we propose two possibilities. The first is the thermally activated magnetic moment of the π electron with strong antiferromagnetic interaction. It was reported in a previous report on x-form Li(Pc) [S1] that strong antiferromagnetic interaction works between π electrons, and that magnetic susceptibility contains the contribution of thermally activated paramagnetic term, as given in eq. (1).
χ π T = C π exp( - E T π k B T) (1) Here, C π and E π are constant and activation energy, respectively. We expect that the magnetic moment of π electrons contributes to the magnetic susceptibility in [Mn(Pc)(CN)] 2 O the same way, since [Mn(Pc)(CN)] 2 O has similar stacking and distance between Pc rings to x-form Li(Pc). The second possibility is the d-electron configuration. Kotani reported that the general formula for the magnetic susceptibility is expressed by eq. (2) [S2]. χ d T = N (1) 2 (2) (0) n,m E nm kb T-2E nm exp(-en k B T) (0) n exp(-e n k B T) (2) (x) Here, E nm is defined by the relation of eq. (3) with the energy of the n-th level having magnetic quantum number m E nm and magnetic field H. E nm = E (0) nm + E (1) nm H + E (2) nm H 2 + (3) In the case of [Mn(Pc)(CN)] 2 O, the effective magnetic moment excluding the contribution of thermally activated magnetic moment implies that the d-electron configuration in the ground state of Mn1 and Mn2 is (d yz ) 2 (d zx ) 2 and (d xy ) 2 (d yz ) 1 (d zx ) 1, respectively. Taking into account the crystal field on manganese sites, (d xy ) 1 (d yz ) 2 (d zx ) 1 and (d xy ) 1 (d yz ) 1 (d zx ) 2 configurations are considered to be the 1st excited states of Mn1 and Mn2. Therefore, it is predicted by eqs. (2) and (3) that the effective magnetic moment increases with temperature, since the magnetic moment in the 1st excited state (S = L = 1) is larger than that in the ground state of Mn1 (S = L = 0). We can qualitatively explain the origin of the increase of effective magnetic moment by the above scenario. However, a quantitative analysis of the experimental results could not be given owing to the difficulty of the calculation including several magnetic interactions with very complicated temperature dependence, since the magnetic moments of π electrons interact with those of d electrons through the strong π-d interaction, as indicated by the magnetoresistance measurement. References (S1) Brinkmann, M.; Turek, P.; Andre, J. J. J. Mater. Chem. 1998, 8, 675-685. (S2) Kotani, M. J. Phys. Soc. Jpn. 1949, 4, 293-297. Scanning electron microscope / Energy dispersive x-ray spectroscopy. We performed SEM / EDS (Scanning electron microscope / Energy dispersive x-ray spectroscopy) analysis to confirm the elements contained in [Mn(Pc)(CN)] 2 O. The EDS spectrum of [Mn(Pc)(CN)] 2 O is shown in Fig. S4. Above 1 kev, we could observe only one peak attributed to a manganese atom (E Mn(K) = 5.89 kev). On the other hand, four peaks exist in the energy region below 1 kev (inset of Fig. S4). These four peaks originate from carbon (E C = 0.277 kev), nitrogen (E N = 0.392 kev), oxygen (E O = 0.525 kev), and manganese atom (E Mn(L) = 0.637 kev).
This result is consistent with the constituent elements determined by the x-ray structural analysis. Figure S4. EDS spectrum of [Mn(Pc)(CN)] 2 O below 10 kev. The peak observed just below 6 kev is attributed to the manganese atom. Inset: EDS spectrum below 1 kev.