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A novel pyrrolopyrrole azadipyrrin (Janus-PPAD) with Janus duality was synthesized by a Schiff base-forming reaction of diketopyrrolopyrrole. The orthogonal interactions of the hydrogen-bonding ketopyrrole and metal-coordinating azadipyrrin moieties in Janus-PPAD enabled the metal ions to be arranged at regular intervals: zinc(II) and cobalt(II) coordination provided metal-coordinated Janus-PPAD dimers, which can subsequently form hydrogen-bonded one-dimensional arrays both in solution and in the solid state. The supramolecular assembly of the zinc(II) complex in solution was investigated by 1 H NMR spectroscopy based on the isodesmic model, in which a binding constant for the elongation of assemblies is constant. Owing to the tetrahedral coordination, in the solid state, the cobalt(II) complex exhibited a slow magnetic relaxation due to the negative D value of -27.1 cm-1 with an effective relaxation energy barrier Ueff of 38.0 cm-1 . The effect of magnetic dilution on the relaxation behavior is discussed. The relaxation mechanism at low temperature was analyzed by considering spin lattice interactions and quantum tunneling effects. The easy-axis magnetic anisotropy was confirmed, and the relevant wave functions were obtained by ab initio CASSCF calculations.

Two mononuclear complexes [Ni(dapsc)(H2O)2]Cl(NO3)·H2O (1) and [Ni(dapsc)(NCS)2] (2), and a bimetallic CN-bridged trinuclear molecule [NiII(dapsc)(H2O)]2[WIV(CN)8]·11H2O (3) (dapsc = 2,6-diacetylpyridine-bis(semicarbazone)) were synthesised and characterised in terms of structure and magnetic properties. All three compounds contain Ni(II) ions in a pentagonal bipyramid coordination geometry afforded by the equatorial pentadentate ligand (dapsc) and two O- or N-donating axial ligands. The compounds differ in the relative arrangement of the complexes, intermolecular interactions and distortion from the ideal coordination geometry. The high-field EPR and magnetometric studies show large anisotropy of the Ni(II) centres with the D parameters in the range of −10.5 to −21.2 cm−1 and negligible antiferromagnetic interactions. The easy-axis magnetic anisotropies of 1–3 were reproduced by ab initio CASSCF/NEVPT2 calculations. The ground states consist mainly of the |MS〉 = |±1〉 states, which is consistent with the fact that no out-of-phase signal can be detected in the AC magnetic susceptibility measurements.

A series of the new monophthalocyaninato lanthanide complexes, [Ln(Pc)(cyclen)]Cl (Ln = Y, Tb, Dy, Ho, Er, Tm, and Yb; Pc = phthalocyaninato; cyclen = 1,4,7,10-tetraazacyclododecane) was synthesized and characterized. The crystallographic study of monophthalocyaninato complexes with a capping macrocyclic ligand having no π-conjugation while keeping the 4-fold symmetry is presented for the first time. All the six complexes were crystallized in a tetragonal structure of the I4mm space group. In addition to this, the Tb complex exhibited a triclinic crystal structure of the P1 space group. All of the complexes are isostructural, where both Pc and cyclen are coordinated to an Ln3+ ion giving an eight-coordinate square-antiprismatic geometry. The skew angle between the Pc and cyclen ligands was 45° in the tetragonal crystals and 41.5° in the triclinic crystal. The metal–nitrogen bond lengths were shorter on the Pc ligand side than cyclen side, presumably due to the difference in the charges of the ligands and...

The presence of a new electronic interaction, which couples a 4 f-electronic system with a total angular momentum J and a photoexcited cyclic π-conjugated system with an orbital angular momentum L, in the bis(phthalocyaninato)dysprosium single-molecule magnet ([DyPc2 ]- ) is reported. Two π-π* excited states in the visible spectral region of the [DyPc2 ]- complex, which are denoted here as QL and QH , showed significantly different temperature and field dependences of the magnetic circular dichroism (MCD) A-term intensity. This phenomenon not only indicates the presence of a "J-L" interaction, but also that the interaction generates two different preferred orientations of the J-L pair, either parallel (for the QH band) or antiparallel (for the QL band), depending on the excitation energy. We have constructed a theoretical model that reproduces the temperature and field dependences, and quantitatively evaluated the J-L interaction.

A new type of electronic interaction which couples two angular momenta, i.e. the angular momentum of a localized 4f system (J) and an orbital angular momentum generated in a cyclic π conjugated system by irradiation with a circularly-polarized light, has been identified in a lanthanide single molecule magnet.

Magnetic f-π interactions between localized 4f-electrons and itinerant π-electrons have been observed in a single crystal of bisphthalocyaninato yttrium(iii)/terbium(iii) tetrafluoroborate ([Pc2Y0.95Tb0.05][BF4]) by measuring electrical conductivity of the crystal in the presence of an external magnetic field.

The 4f-electronic structures of the ground multiplet states of a series of lanthanide(iii) monoporphyrinato complexes with a cyclen as the capping ligand [Ln(TPP)(cyclen)]Cl (Ln = Tb, Dy, Ho, Er, Tm, and Yb; TPP = 5,10,15,20-tetraphenylporphyrinato; cyclen = 1,4,7,10-tetraazacyclododecane) have been determined using experimental NMR and magnetic susceptibility data. Magnetic susceptibilities of the microcrystalline samples of [Ln(TPP)(cyclen)]Cl were measured in the range of 1.8-300 K. NMR signals corresponding to the protons on the porphyrin ring show marked paramagnetic shifts (lower = Tb, Dy, Ho, and Yb; higher = Er and Tm) in comparison with the diamagnetic Y congener. A set of ligand-field parameters that simultaneously reproduces the magnetic susceptibilities and the paramagnetic shifts has been determined by using a self-developed multidimensional optimization program. In addition, CASSCF calculations were carried out for further insight into their electronic structures.

Syntheses of a novel pseudotetrahedral four-coordinate mononuclear Co(II) complex that has two halved phthalocyanine moieties as the ligands, [Co(half-Pc)2] (1), and its magnetic properties as a single molecule magnet (SMM) are reported. A one pot reaction of phthalonitrile and lithium methoxide followed by the coordination to a Co(II) ion gave 1 as an orange solid in a moderate yield. X-ray crystallography on 1 reveals tetragonally distorted coordination geometry around the Co(II) ion. The M- HT-1 plots suggest that 1 has large axial magnetic anisotropy. The ac magnetic susceptibility data of the magnetically diluted 1 (dil.1) clearly show that the complex acts as an SMM even in the absence of the external static magnetic field ( Hdc). The influence of intermolecular and intramolecular interactions for the magnetic relaxation behaviors has been discussed by comparison of the magnetic data of 1 and dil.1. The Orbach process is suggested as the predominant mechanism of magnetic relaxations in the high-temperature range, and the Arrhenius plots provide the effective relaxation energy barrier and pre-exponential factor of Ueff = 54.0 cm-1 and τ0 = 3.17 × 10-10 s, respectively. The direct estimation of the axial anisotropic parameter of 1 was successfully performed by high-field, multifrequency ESR measurements up to 55 T and 2.5 THz. The evaluated axial zero-field splitting (ZFS) energy of 57.0 cm-1 is comparable to the Ueff energy, confirming that the magnetic relaxations are initiated by the thermal excitation from the ground | M S⟩ = |±3/2⟩ states to the |±1/2⟩ states in the high-temperature range. The results of the ab initio calculations based on the CAS(7,5) SCF wave functions indicate that the ground states of 1 consist mainly of | M S⟩ = |±3/2⟩ states, while the first excited states are the mixture of | M S⟩ = |+1/2⟩ and |-1/2⟩.

Interactions of three different types of electronic angular momenta, namely, spin, orbital, and total angular momenta from different origins in a photoexcited neutral bis(phthalocyaninato)terbium single-molecule magnet (Pc2Tb, where Pc2- denotes a phthalocyaninato anion) have been studied. We have conducted varied-temperature and varied-magnetic-field magnetic circular dichroism (MCD) measurements on the highest occupied molecular orbital-lowest unoccupied molecular orbital electronic transition in the ligand side of the neutral Pc2Tb to reveal the quantum nature of the system composed of a π-radical with a spin angular momentum S, the 4f system with a total angular momentum J, and the cyclic π conjugate system with a photoinduced orbital angular momentum L. We have constructed a new theoretical model that gives a quantitative agreement to the temperature and magnetic field dependence of MCD. The theoretical analysis revealed that the system takes eight quantum states that can be expressed as | J z S z L z⟩ = |±±±⟩, where the three angular momenta are quantized along the fourfold symmetry axis. Thus, we have identified the existence of the magnetic interactions among the three angular momenta and quantitatively determined their magnitudes for the first time.

A series of heavy lanthanide(III) and yttrium(III) monoporphyrinato complexes formulated in [Ln(TPP)(cyclen)]Cl (Ln = Tb, Dy, Ho, Er, Tm, Yb, and Y; TPP = 5,10,15,20-tetraphenylporphyrinato), with cyclen, 1,4,7,10-tetraazacyclododecane, as a capping ligand, have been prepared in mild conditions and studied using single-crystal X-ray diffraction crystallography. The complexes exhibit an electronic absorption band (B(0,0)) in the range of 421–423 nm, showing a bathochromic shift associated with the increase of the ionic radii of the lanthanide, as well as two peaks of Q(1,0) and Q(0,0) bands between 548–586 nm. All of the complexes are isostructural, where both TPP and cyclen are coordinated to a lanthanide(III) or yttrium(III) ion giving an eight-coordinate square-antiprismatic (SAP) geometry (average skew angles are in the range of 43.01°–43.67°). The mean plane of the four nitrogen atoms of TPP (N4t) and that of the cyclen (N4c) are virtually parallel with a dihedral angle of less than 1°. The lanthanide...

The synthesis, and spectroscopic and magnetic properties of quadruple-decker phthalocyanines (Pcs) have been reviewed. While the presence of stacked mercury Pc oligomers was proposed as early as 1992, the isolation of a quadruple-decker Pc was first achieved in 2010. Herein, we review how the synthetic strategy for quadruple-decker Pcs has come to be conceived from the recent development of cadmium Pc oligomers, which will be followed by illustration of unique physicochemical properties originating from the structure of the quadruple-decker frameworks. In the spectroscopy section, the electronic structures of the quadruple-decker Pc are discussed based on the theoretical and experimental results. A simple molecular orbital (MO) method predicts that energy gaps among the occupied frontier MOs of the quadruple-decker Pc become smaller than those of double- or triple-decker Pcs, leading to the observation of exceptionally low-lying electronic transitions for the oxidized quadruple-decker Pcs. It has been confirmed that the corresponding lowest π–π* electronic transitions reach the infrared region for the one-electron oxidized quadruple-decker Pcs. In the magnetic property section, a clear evidence of the long-range magnetic dipole–dipole f–f interactions between two f-electronic centers of diterbium quadruple-decker Pc is provided, and its magnetic relaxation phenomena arising mainly from quantum tunneling magnetizations (QTMs) will be discussed by using the alternate current (ac) magnetic susceptibility data, and the numerically calculated Zeeman diagram of the f-electronic centers in the quadruple-decker Pc.