High-spin Ground State Research Articles

High spin ground state copper(II) and nickel(II) complexes possessing the 3,5-di-tert-butyl-1,2-semiquinonate radical anion

Several high spin ground-state compounds based upon ferromagnetic coupling between a metal ion and the chelating 3,5-di-tert-butyl-1,2-semiquinonate radical anion, [DTBSQ]−, as they possess unpaired electron spins in orthogonal dx2−y2/dz2 and π∗ orbitals, are described. [CuII(DPyA)(DTBSQ)](ClO4) (DPyA=2,2′-dipyridylamine) was reinvestigated and its singlet excited state is 282cm−1 [0.035eV; J/kB=406K (H=−JSa·Sb)] above the triplet ground state. [CuII(bipy)(DBCat)(MeOH)] (bipy=2,2-bipyridine; DBCat=3,5-di-tert-butylcatecholate), [CuII(bipy)(DTBSQ)](BF4), [CuII(DPyA)(DTBSQ)-(THF)2](BF4) and [NiII(DPyA)(DTBSQ)(THF)2](BF4) have been structurally characterized and have high spin ground states whose low spin excited states lie 28cm−1 (0.0034eV), 382cm−1 (0.047eV), 335cm−1 (0.042eV), and 108cm−1 (0.013eV) higher, respectively. The triplet-singlet separation is 18% greater for [CuII(DPyA)(DTBSQ)(THF)2]+ than [CuII(DPyA)(DTBSQ)]+ and is ascribed to greater orthogonality of the CuII dx2−y2/dz2 and [DTBSQ]− π∗ orbitals for octahedral [Cu(DPyA)(DTBSQ)(THF)2]+ with respect to distorted square pyramidal structure of [Cu(DPyA)(DTBSQ)]+. This greater energy of the excited state correlates with the shorter than average M-ODTBSQ distance, i.e. [Cu(bipy)(DTBSQ)]+>[CuII(DPyA)(DTBSQ)(THF)2]+>[Ni(DPyA)(DTBSQ)(THF)2]+. The order of magnitude lower value for [CuII(bipy)(DBCat)(MeOH)] arises from a weak intradimer S=1/2 Cu(II) interaction, not via ferromagnetic coupling between the S=1/2 Cu(II) and [DTBSQ]− sites.

Correction to a New Nitronyl Nitroxide Radical as Building Blocks for a Rare S = 13/2 High Spin Ground State 2p-3d Complex and a 2p-3d-4f Chain

A new nitronyl nitroxide radical L (L = 2-(4-(5-methyl-carbonyl-3-pyriyl)benzoxo)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) containing N–O groups and the pyridyl nitrogen group was designed and synthesized as a multidentate ligand to obtain compounds with interesting structures and magnetic properties from 3d or 3d-4f precursors. The reaction of Cu(hfac)2 and/or Gd(hfac)3·2H2O (hfac = hexafluoroacetylacetonate) with L resulted in a rare S = 13/2 high spin ground state CuII complex [(Cu(hfac)2)7(L)6] (1) and a CuII–GdIII chain complex [Gd(hfac)3Cu(hfac)2(L)2]n·0.5CH2Cl2 (2). Single crystal X-ray diffraction studies indicate that the N–O groups of the L radicals are all axially bound to CuII ions in complex 1, which result in the ferromagnetic exchange between CuII and radicals and an S = 13/2 high spin ground state. While adding Gd(hfac)3 units to the system of Cu(hfac)2 and L radical, a one dimension chain structure is obtained, and there are ferromagnetic GdIII-radical interactions and antiferromagn...

A Synthetically Tunable System To Control MLCT Excited-State Lifetimes and Spin States in Iron(II) Polypyridines.

2,2':6',2″-Terpyridyl (tpy) ligands modified by fluorine (dftpy), chlorine (dctpy), or bromine (dbtpy) substitution at the 6- and 6″-positions are used to synthesize a series of bis-homoleptic Fe(II) complexes. Two of these species, [Fe(dctpy)2]2+ and [Fe(dbtpy)2]2+, which incorporate the larger dctpy and dbtpy ligands, assume a high-spin quintet ground state due to substituent-induced intramolecular strain. The smaller fluorine atoms in [Fe(dftpy)2]2+ enable spin crossover with a T1/2 of 220 K and a mixture of low-spin (singlet) and high-spin (quintet) populations at room temperature. Taking advantage of this equilibrium, dynamics originating from either the singlet or quintet manifold can be explored using variable wavelength laser excitation. Pumping at 530 nm leads to ultrafast nonradiative relaxation from the singlet metal-to-ligand charge transfer (1MLCT) excited state into a quintet metal centered state (5MC) as has been observed for prototypical low-spin Fe(II) polypyridine complexes such as [Fe(tpy)2]2+. On the other hand, pumping at 400 nm excites the molecule into the quintet manifold (5MLCT ← 5MC) and leads to the observation of a greatly increased MLCT lifetime of 14.0 ps. Importantly, this measurement enables an exploration of how the lifetime of the 5MLCT (or 7MLCT, in the event of intersystem crossing) responds to the structural modifications of the series as a whole. We find that increasing the amount of steric strain serves to extend the lifetime of the 5,7MLCT from 14.0 ps for [Fe(dftpy)2]2+ to the largest known value at 17.4 ps for [Fe(dbtpy)2]2+. These data support the design hypothesis wherein interligand steric interactions are employed to limit conformational dynamics and/or alter relative state energies, thereby slowing nonradiative loss of charge-transfer energy.

Correction: New tetranuclear manganese clusters with [MnII3MnIII] and [MnII2MnIII2] metallic cores exhibiting low and high spin ground state.

Correction for 'New tetranuclear manganese clusters with [MnII3MnIII] and [MnII2MnIII2] metallic cores exhibiting low and high spin ground state' by M. Sobocińska et al., Dalton Trans., 2016, 45, 7303-7311.

Calix[n]arene-based polyradicals: enhancing ferromagnetism by avoiding edge effects.

Through-bond interacting organic polyradicals, rendered by customizable capacities of the state-of-the-art synthetic routes, are ideal systems to investigate spin topologies. Relying on Rajca and co-workers' synthetic efforts, hereby we investigate the role of borders in the stability of the high-spin ground state in a series of realistic linear and ring-like arylmethyl polyradical derivatives. We show that, compared to their linear counterpart, the absence of borders in a ring-like arrangement of arylmethyl radicals imposes a larger number of spin-alternation rule violations, which strongly stabilizes the high-spin ground state. In addition, the structural flexibility of the investigated compounds translates into the existence of various structural energy minima for which the ferromagnetic ground state is always maintained. In view of the present results we propose these rings as possible candidates for the development of enhanced high spin single molecule toroics.

Investigation of easy-plane magnetic anisotropy in P-ligand square-pyramidal CoII single ion magnets.

In this work we report two pentacoordinated CoII-P4X1 Single Ion Magnets (SIMs) based on P-donor ligands. The tetradentate ligand tris[2-(diphenylphosphino)ethyl]phosphine allows the obtention of the isostructural square pyramidal [Co(PP3)Cl]·ClO4 (1) and [Co(PP3)Br]·ClO4 (2) complexes. Consistent theoretical and experimental studies indicate that these complexes have a high spin (S = 3/2) ground state and suggest that the relaxation dynamics is governed by ground state quantum tunneling, whereas its temperature dependence is directed by optical or acoustic Raman processes.

A new architecture for high spin organics based on Baird's rule of 4n electron triplet aromatics

Due to the absence of open subshells (unlike transition metal compounds), stable high spin organic molecules are rare and are mostly limited to states of low multiplicity. As an alternative to high multiplicity polyradicals and polycarbenes, with their small energetic separation of different spin isomers, it is demonstrated that Baird's rule of 4n electron aromaticity in the triplet electronic state allows, in principle, the design of polycyclic high spin organics with high spin multiplicity in the electronic ground state and a large energetic separation for other spin states. Energy spacing between spin isomers is dictated here by the aromaticity or antiaromaticity of individual cycles (taking into account all π electrons), rather than by a spin Hamiltonian alone (accounting only for unpaired spin electrons). As a proof of concept, dyads of the cyclopentadienyl cation (which has been reported to possess a triplet ground state) have been computationally found to possess a quintet electronic ground state with two ferromagnetically coupled Baird aromatic rings (with SCF-GIAO NICS(0) = -4.6 and -4.4, respectively; "NICS" is "nucleus independent chemical shift") at the CASMP2(8,10)/6-311G*//CASSCF(8,10)/6-311G* level, which is 48.3 kcal mol-1 lower in energy than the C2 open shell singlet with two antiaromatic rings (with NICS = +17.4), and 19.7 kcal mol-1 below the triplet which has one aromatic and one antiaromatic ring, with NICS = -4.8 and +45.0, respectively. Triads of the cyclopentadienyl cation in linear and branched topologies are also proposed to be ground states of maximum spin multiplicity by computations at the DFT and CCSD(T)/6-31G//UB3LYP/6-311G* levels.

A New Nitronyl Nitroxide Radical as Building Blocks for a Rare S = 13/2 High Spin Ground State 2p-3d Complex and a 2p-3d-4f Chain

A new nitronyl nitroxide radical L (L = 2-(4-(5-methyl-carbonyl-3-pyriyl)benzoxo)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) containing N–O groups and the pyridyl nitrogen group was designed and synthesized as a multidentate ligand to obtain compounds with interesting structures and magnetic properties from 3d or 3d-4f precursors. The reaction of Cu(hfac)2 and/or Gd(hfac)3·2H2O (hfac = hexafluoroacetylacetonate) with L resulted in a rare S = 13/2 high spin ground state CuII complex [(Cu(hfac)2)7(L)6] (1) and a CuII–GdIII chain complex [Gd(hfac)3Cu(hfac)2(L)2]n·0.5CH2Cl2 (2). Single crystal X-ray diffraction studies indicate that the N–O groups of the L radicals are all axially bound to CuII ions in complex 1, which result in the ferromagnetic exchange between CuII and radicals and an S = 13/2 high spin ground state. While adding Gd(hfac)3 units to the system of Cu(hfac)2 and L radical, a one dimension chain structure is obtained, and there are ferromagnetic GdIII-radical interactions and antiferromagnetic radical–radical coupling in the chain.

Unexpected High Spin Polarization in Cr4 Cluster

Recent X-ray magnetic circular dichroism (XMCD) spectroscopy has demonstrated a total high spin ground state of S = 11/2 in the Cr2+ cluster. The accuracy of these experiments opens the possibility to observe small magnetic particles with greater detail than those obtained in Stern–Gerlach setups. Particularly the chromium clusters, where a high total magnetization can be observed due to their localized d-electrons, are an excellent candidate to be detected in this sophisticated experiments. In this work, the small-sized chromium tetramer has been investigated in detail by means of zero and finite temperature ab initio methods. The dimer and trimer chromium clusters are reported as a benchmark in order to establish a reliable approach. We found the existence of a spin competition between a lower S = 1 and a higher S = 6 spin state in the Cr4 cluster; both spin states are close in geometry, allowing a spin-flip due to an spin–orbit coupling mechanism.

Computational Study of the Stability of Nanotube Fragments.

Extremely short (<1 nm) fragments of zig-zag carbon nanotubes are studied with ab-initio techniques to determine their geometric and electronic structure as well as their magnetic susceptibility. It is found that for lengths of a few carbon-carbon bonds, each fragment can be viewed as composed of crowns, that is, zig-zag rings of carbon atoms along the circumference of the tube. In this case, two kinds of electronic structures are found, depending on whether the number of carbon atoms in each crown is even or odd. Systems comprising three or more crowns either have a high spin ground state or involve a charge transfer across the length of the fragment. Conjugation changes qualitatively when the length of the fragment approaches and surpasses its girth. Indications regarding the predicted chemical stability and electronic response are provided and interpreted in terms of current densities induced within each crown by a magnetic field along the tube axis.

Redox Pairs of Diiron and Iron-Cobalt Complexes with High-Spin Ground States.

A series of iron and iron-cobalt bimetallic complexes were isolated: LFe2Cl (1), LFe2 (2), Li(THF)3[LFe2Cl](Li(THF)3[2-Cl]), LFeCoCl (3), and LFeCo (4), where L is a trianionic tris(phosphineamido)amine ligand. As elucidated by single-crystal X-ray diffraction studies and quantum-chemical calculations, the FeIIFeII and FeIICoII complexes, 1 and 3, respectively, have weak metal-metal interactions (the metal-metal distances are 2.63 and 2.59 Å, respectively) with a partial bond order of 0.5. The formally mixed-valent complexes, FeIIFeI (3) and FeIICoI (4), have short metal-metal bonds (2.32 and 2.26 Å, respectively) with a formal bond order of 1.5. On the basis of magnetic susceptibility measurements, complexes 1-4 are all paramagnetic with high-spin ground states, S = 3-4, which are proposed to arise from ferromagnetic coupling of the two metals' spins through a direct exchange mechanism. Zero- and applied-field Mössbauer spectra corroborate the presence of distinct oxidation and spin states for the iron sites. The reduction potentials of 1 and 3 are -1.48 and -1.60 V (vs Fc+/Fc), respectively. Other characterization data are also reported for this series of complexes, electronic absorption spectra and anomalous X-ray scattering data.

Closing the Gap: Preparation and Characterization of the First Half-Open and Open Manganocene Complexes

The first preparations of half-open and open manganocenes were accomplished. Treatment of KPdl′ (Pdl′ = 2,4-(Me3C)2C5H5)) with [{(η5-Cp”)Mn(thf)(μ-I)}2] (Cp″ = 1,2,4-(Me3C)3C5H2) and MnI2(thf)2 resulted in the formation of [(η5-Cp″)Mn(Pdl′)] (2) and [(Pdl′)2Mn] (4), respectively. Both compounds adopt a high-spin (S = 5/2) ground state. Maximum spin states are rather unusual for pentadienyl complexes, since these ligands generally stabilize transition metal complexes in their low-spin state. In addition, the electronic structure of 2 was compared to its closed analogue [(η5-Cp″)Mn(η5-Cp′)] (Cp′ = 1,3-(Me3C)2C5H3), which also adopts the high-spin configuration because of steric hindrance destabilizing the electronically more favorable low-spin state. Reaction of KPdl′ with [(C5H5)2Mn] yields the trimetallic compound [{(η5-Pdl′)Mn(η5-C5H5)]}2Mn] (5) concomitant with the formation of 2,4,7,9-tetra-tert-butyl-1,3,7,9-decatetraene (Pdl′2), indicating reduction of two Mn atoms. Solid-state magnetic susceptibility studies and density functional theory computations suggest that the electronic structure in 5 is best described as two diamagnetic (S = 0) [(η5-Pdl′)Mn(η5-C5H5)]− Mn(I) anions, each being coordinated to a central Mn(II) cation with a high-spin (S = 5/2) configuration.

Development of molecular fragment interaction method for designing organic ferromagnets

The design and preparation of organic ferromagnets are important and challenging from both experimental and theoretical viewpoints. We propose a molecular fragment interaction method for predicting the high-spin stability of conjugated hydrocarbon radicals without quantum chemistry calculations, which comprise three steps: (1) division of the system into fragments and numbering of the carbon atoms, (2) construction of a secular equation, and (3) solving of the secular equation. If there are two or more nonbonding molecular orbitals (NBMOs) and the smallest number of bonds between two carbon atoms with unpaired electrons is an even number, then the conjugated hydrocarbon radical has a high-spin ground state. This method can also be used to compare the high-spin stability between different conjugated hydrocarbon radicals. If a conjugated hydrocarbon radical has a high-spin ground state, then its derivative has a high-spin ground state as long as the degeneracy of the NBMOs is kept. This method is useful for the rapid design of organic ferromagnets.

Transition Metal Doped Aluminum Clusters: An Account of Spin

The influence of spin on the properties of small sized transition metal doped aluminum clusters are investigated in the framework of density functional theory (DFT). Detailed analysis on minimum spin doped aluminum clusters has shown prominent indication of odd–even oscillation in various calculated properties, supporting the presence of jellium shell structures within them. However, optimized high spin ground state counterparts, on the other hand, show rather smooth trends consistent with the properties of bulk materials. Resemblance to the bulk transition metals is further reflected in the gradual declining trends of heat of adsorption of CO2 molecule on cluster surface by sequentially changing the dopant atom from scandium to zinc. All the observations are also compared and found to be consistent with the earlier theoretical and experimental findings as obtained in the current literature. The similarities in the properties between atomic clusters and the bulk material is of utter importance and indeed ...

Analyzing the enforcement of a high-spin ground state for a metallacrown single-molecule magnet

We have studied element-selective magnetic properties of the hetero- and homometallic metallacrowns $\mathrm{Cu}{(\mathrm{II})}_{2}[12\ensuremath{-}{\mathrm{MC}}_{YN(Shi)}\ensuremath{-}4]$ ($Y=\text{Cu}$, Fe, in short ${\mathrm{CuCu}}_{4}$ and ${\mathrm{CuFe}}_{4}$). These metallacrowns comprise four Fe or Cu ions surrounding a central Cu ion. Using x-ray magnetic circular dichroism we have probed local symmetries, electronic configuration, orbital and spin magnetic moments of the magnetic ions. The ratio between the Cu and Fe moment of $\ensuremath{-}0.11$ is independent of temperature in the range of 15 K to 90 K. The Cu moment shows antiparallel to the Fe moment. For ${\mathrm{CuCu}}_{4}$ we confirm the predicted $S=1/2$ ground state. The comparison of the spectral dependence indicates a localization of the magnetic moment at the central Cu ion. The orbital to spin moment ratio is 0.03 for the Fe ion while a larger ratio of 0.12 was measured for the Cu ion in both compounds. The experimental results are compared to a mean field model and to an isotropic Heisenberg model.

Multiferroic crossover in perovskite oxides

Recently, the perovskite BiCoO$_3$ has been shown experimentally to be isostructural with PbTiO$_3$, while simultaneously the $d^6$ Co$^{3+}$ ion has a high spin ground state with $C$-type antiferromagnetic ordering. Using hybrid density functional calculations, we investigate the atomic, electronic and magnetic structure of BiCoO$_3$ to elucidate the origin of the multiferroic state. To begin with, we perform a qualitative trend sudy of the role of $d$ electrons in affecting the tendency for perovskite materials to exhibit a ferroelectric distortion; this work initially explores a qualitative trend study in artificial cubic and tetragonal LaBO$_3$ perovskites. We choose La as the A-cation so as to remove the effects of Bi $6s$ hybridization. Through first-principles calculations of the LaBO$_3$ series, where B is a $d^0 - d^8$ cation from the $3d$-block, the trend study reveals that increasing the $d$ orbital occupation initially removes the tendency for a polar distortion, as expected. However, for high spin $d^5-d^7$ and $d^8$ cations a strong ferroelectric instability is recovered. We explained this effect in terms of the pseudo Jahn-Teller theory for ferroelectricity. It is shown that, in some cases, unpaired electron spins actually drive ferroelectricity, rather than inhibit it, which represents a shift in the understanding of how ferroelectricity and magnetism interact in perovskite oxides. It follows, that for the case of BiCoO$_3$, the Co$^{3+}$ ion plays a major role in the ferroelectric lattice instability. Importantly, the ferroelectric polarization is greatly enhanced when the Co$^{3+}$ ion is in the high spin state, when compared to the nonmagnetic, low spin state, and a large coupling of the electrical and magnetic polarization is present. Importantly, it is demonstrated that the ground spin state is switched by reducing the internal ferroelectric polarization.

Spin modulation and electrochemical behavior of a five-coordinate cobalt(III) salen complex

We report the synthesis of a Co(III) complex with the five-coordinate salen-type ligand (N,N′-bis(3,5-di-tert-butyl-2-hydroxybenzyliden)-1,7-diamino-4-methyl-4-azaheptane). This complex is stable in air with a trigonal bipyramidal geometry and we show spectroscopically and computationally that a high-spin triplet ground state is preferred. This spin state is readily modulated by introduction of an exogenous ligand (pyridine, acetonitrile) to yield a six-coordinate complex with low-spin ground state. The five-coordinate complex exhibits solvent- and ligand-dependent electrochemical behavior in solution for the CoII/III transition and undergoes a one-electron ligand oxidation to generate a phenoxyl radical species that is relatively stable in the absence of oxygen. We show that this phenoxyl radical species is a Class I mixed-valence compound that can undergo photoinduced inner-sphere charge transfer with the neighboring phenoxide. This process is mediated by the Co(III) center which acts as a bridge. Understanding this behavior will lead to a better understanding of a dicobalt bis-salen analog previously reported by our group as a proton reduction catalyst.

Reversible CO Scavenging via Adsorbate-Dependent Spin State Transitions in an Iron(II)-Triazolate Metal-Organic Framework.

A new metal-organic framework, Fe-BTTri (Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH, H3BTTri =1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene)), is found to be highly selective in the adsorption of CO over a variety of other gas molecules, making it extremely effective, for example, in the removal of trace CO from mixtures with H2, N2, and CH4. This framework not only displays significant CO adsorption capacity at very low pressures (1.45 mmol/g at just 100 μbar), but, importantly, also exhibits readily reversible CO binding. Fe-BTTri utilizes a unique spin state change mechanism to bind CO in which the coordinatively unsaturated, high-spin Fe(II) centers of the framework convert to octahedral, low-spin Fe(II) centers upon CO coordination. Desorption of CO converts the Fe(II) sites back to a high-spin ground state, enabling the facile regeneration and recyclability of the material. This spin state change is supported by characterization via infrared spectroscopy, single crystal X-ray analysis, Mössbauer spectroscopy, and magnetic susceptibility measurements. Importantly, the spin state change is selective for CO and is not observed in the presence of other gases, such as H2, N2, CO2, CH4, or other hydrocarbons, resulting in unprecedentedly high selectivities for CO adsorption for use in CO/H2, CO/N2, and CO/CH4 separations and in preferential CO adsorption over typical strongly adsorbing gases like CO2 and ethylene. While adsorbate-induced spin state transitions are well-known in molecular chemistry, particularly for CO, to our knowledge this is the first time such behavior has been observed in a porous material suitable for use in a gas separation process. Potentially, this effect can be extended to selective separations involving other π-acids.

High-Spin Chains and Crowns from Double-Exchange Mechanism

This article addresses the question of the possibility of obtaining high-spin chains and crowns of magnetic units s = 1 from doped (by a hole) antiferromagnetic architectures. It aims at determining the range of values of the double-exchange model interactions for which these molecules exhibit a high-spin ground state. Several chains and crowns of sizes varying between three to seven magnetic sites have been studied using a refined double-exchange model. It is shown that, for physical values of the parameters, linear chains of three, four and five sites are likely to adopt the highest spin state. For chains of six sites, small values of magnetic couplings are needed to get the highest spin, but it would be easy to get an S = 3/2 ground state. For systems of seven (or slightly more) sites, the highest spin state becomes non accessible but S = 5/2 states are likely to be obtained. Surprisingly, the physics of crowns is substantially different. The same trends are observed for even-number systems but with a larger double-exchange regime. At variance, odd-number systems do not exhibit a double-exchange mechanism for low values of the magnetic couplings. These observations are rationalized from an analysis of the computed spectra and wave functions.

(Invited) Switching of Single Molecule Magnetism and Conductance in Porphyrin-Based Terbium Double-Decker Complexes

Organic functional materials are utilized in commonly used electronic products such as organic light emitting diodes and liquid crystals in cellular phones and televisions. Currently, materials are used in mass and most of their characteristic properties arise from the cooperative interaction of a number of molecules or atoms. As the result, many physical properties disappear when the size of the material becomes smaller than a certain size. For example, ferromagnetism is observed in larger samples than ca. 15 nm in diameter because collaboration of many spins in the sample is required for the property. As the result, the density of memory size in hard disk is limited to ca. 3 TB/in2 with ordinal magnetic materials. If the single molecules can work as magnets, the density can increase to 600 TB/in2 theoretically. Molecules which can work as magnets in single molecule are called single molecule magnet, and first found as a Mn12 cluster by Sessoli et al., in 1993.1 During the last two decades, polymetallic transition-metal complexes with strong intramolecular exchange coupling have been typical research targets because their high-spin ground state and large anisotropy may impart a higher energy barrier than that of single–metal-ion complexes. Since Ishikawa reported SMMs based on single lanthanide ions in 2003,2 many mononuclear complexes with slow magnetic relaxation have been reported. In particular, phthalocyanine (Pc) Tb double-decker compounds display a higher blocking temperature, below which magnetic relaxation is slow. Moreover, the magnetic relaxation behavior of double-decker complexes is sensitive to their coordination mode, which can be easily tuned through their flexible structure. This variation in the coordination modes makes it possible to control their magnetic properties via external stimuli such as a redox reaction or pulse current from an STM chip, resulting in unique switching properties. A tetraphenylporphyrin (TPP) Tb double-decker complex was synthesized, and the crystal structures of both the protonated and deprotonated forms have been determined. The structure analysis demonstrated for the first time in tetrapyrrole-based double-decker complexes that a proton is localized on the pyrrole ring nitrogen for charge balance. The AC magnetic susceptibility measurements revealed that the protonated form does not show SMM behavior although the anionic form does act as an SMM. The SMM behavior of the double-decker complex can be reversibly switched through only a single proton.3,4 We studied the synthesis and study of octaethylporphyrin (OEP) Tb double-decker complexes with different electronic structures comprising protonated, anionic, and radical forms. Magnetic susceptibility measurements revealed that only the anionic and radical forms of the OEP Tb double-decker complexes exhibited SMM properties. Scanning tunneling microscopy (STM) investigations revealed that these OEP Tb complexes form well-ordered monolayers upon simple dropcasting from dilute dichloromethane solutions. All three complexes form an isomorphic pseudo-hexagonal 2D pattern, regardless of the differences in the electronic structures of their porphyrin-Tb cores. This finding is of interest for SMM technology since chemical transformations in ultrathin films of these materials will not require any detrimental reorganization.5 Further, we effect sub-molecular scale patterning to create an ordered assembly of SMMs by using (OEP)-Tb double-decker complex, Tb(OEPH)(OEP)), which exhibits non-SMM properties but changes into the SMM molecule Tb(OEP)2 by discharging a hydrogen atom. We locally formed an SMM molecule Tb(OEP)2 by injecting tunneling electrons using scanning tunneling spectroscopy (STS) on the ordered film of Tb(OEPH)(OEP), where the spin of the converted Tb (OEP)2 molecule was detected by a Fano dip of Kondo resonance in scanning tunneling spectroscopy. Single molecular conductance of Tb(TPP)2 and Tb(TPP)(Phthalocyanine) complexes were also studied using break-junction methods to show that in the later complex the conductance changed greatly by deprotonation. REFERENCES. (1) Sessoli, R.; Gatteschi, D.; Caneschi, A.; Novak, M. A. Nature 1993, 365, 141. (2) Ishikawa, N.; Sugita, M.; Ishikawa, T.; Koshihara, S.; Kaizu, Y. J. Am. Chem. Soc. 2003, 125, 8694. (3) Tanaka, D.; Inose, T.; Tanaka, H.; Ishikawa, N.; Ogawa, T. Chem. Commun. 2012, 7796. (4) Inose, T.; Tanaka, D.; Ogawa, T. Heterocycles 2012, 86, 1549. (5) Inose, T.; Tanaka, D.; Tanaka, H.; Ivasenko, O.; Nagata, T.; Ohta, Y.; De Feyter, S.; Ishikawa, N.; Ogawa, T. Chem. Eur. J. 2014, 20, 11362.