Chihiro Kachi-Terajima

Luminescence tuning of imidazole-based lanthanide(III) complexes [Ln = Sm, Eu, Gd, Tb, Dy]

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me(3)L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(3)L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(2)L). The general formulas are [Ln(Me(3)L)(H(2)O)(2)](NO(3))(3)·3H(2)O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H(3)L)(NO(3))](NO(3))(2)·MeOH (Ln(3+) = Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H(2)L)(NO(3))(2)(MeOH)](NO(3))·MeOH (Ln(3+) = Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me(3)L and H(3)L ligands and 10-coordinate in the complexes with the H(2)L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me(3)L, H(3)L, and H(2)L are 21 000, 22 700, and 23 000 cm(-1), respectively, which were determined from the phosphorescence spectra of their Gd(3+) complexes. The Me(3)L ligand is an effective sensitizer for Sm(3+) and Eu(3+) ions. Efficient luminescence of Sm(3+), Eu(3+), Tb(3+), and Dy(3+) ions was observed in complexes with the H(3)L and H(2)L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions.

Structural and Magnetic Study of O2 Molecules Arranged along a Channel in a Flexible Single-Crystal Host Family

We report the magnetic behaviors of O(2) molecules, which aligned in the channels of four types of single-crystal adsorbents, [M(2)(bza)(4)(pyz)](n) (bza = benzoate; pyz = pyrazine; M = Rh(II) (1a) and Cu(II) (1b)) and [M(2)(bza)(4)(2-mpyz)](n) (2-mpyz = 2-methylpyrazine; M = Rh(II) (2a) and Cu(II) (2b)). The X-ray single-crystal structures at various temperatures from 10 to 298 K were determined for O(2)-included crystals of 1a and 2a. All adsorbed O(2) molecules exhibited abnormal magnetic phases above 4 T in the temperature range around 55-105 K. The magnetic behaviors of adsorbed O(2) molecules between four inclusions were discussed. The existence of the metastable state, which was also suggested by hysteresis on the M-H curves, was revealed by analysis of the time course of the magnetization. Considering that the abnormal magnetic behavior occurred at relatively high temperatures and a low magnetic field, it was suggested that these behaviors were induced because of the changes of magnetic interaction of included O(2) aggregates involving transformation which is supported by the surrounding of the channels of the single-crystal hosts under the applied magnetic field.

Homochiral 1D helical chain based on an achiral Cu(II) complex.

Self-assembly of an achiral [Cu(L)] complex produced a homochiral helical chain [Cu(L)](3)·2H(2)O (1) (L = 2-dimethylaminoethyl(oxamato)). Interestingly, complex 1 obtained in our laboratory exhibits only a left-handed helical chain without any chiral source. Single-crystal X-ray analysis revealed the absolute structure and homochirality of its helical chain structure in the space group of P3(2). Solid-state circular dichroism (CD) spectra confirmed the high enantio excess of the crystals obtained in different synthesis batches. Magnetic susceptibility measurements reveal a relatively strong intrachain antiferromagnetic interaction between Cu(II) centers via an oxamato bridge (J = -74.4 cm(-1)).

Solvent-dependent structures of lanthanide–TCNQ coordination networks and their magnetic properties

Abstract Lanthanide complexes were prepared with 2,6-diacetylpyridinebis(benzoylhydrazone) (DAPBH2) and 7,7,8,8-tetracyano-p-quinodimethanide (TCNQ•−). The complexes adopted one of two structure types depending on the reaction solvent. The complexes were categorized as Type I (i.e. bis{[2,6-diacetylpyridinebis(benzoylhydrazone)] methanollanthanide(III)}bis(µ2- 7,7,8,8-tetracyanoquinodimethanide(1−))bis(7,7,8,8-tetracyanoquinodimethanide(1−))bis(7,7,8,8-tetracyanoquinodimethanide(1−)) methanol disolvate, [Ln2(DAPBH2)2 (µ2-TCNQ•−)2(TCNQ•−)2(MeOH)2](TCNQ•−)2·2MeOH (Ln = Gd, Tb, or Dy) or Type-II (i.e. [Ln2(DAPBH2)2(µ2-TCNQ•−)2(TCNQ•−)2(EtOH)2] (TCNQ•−)2·solvent (Ln = Tb and Dy, solvent =4EtOH for the Tb and 2EtOH·2CH2Cl2 for the Dy complexes). These two complexes exhibit dramatically different molecular structures and packings. In all complexes, the strong intra- and intermolecular stacking interactions of the TCNQ•− radicals lead to the formation of 1D TCNQ chains. Magnetic susceptibility measurements for Type I and Type II complexes reveal that they exhibit paramagnetic behavior and that their magnetic properties originate from the lanthanide ions alone, owing to the diamagnetic nature of the TCNQ•− stacks. GRAPHICAL ABSTRACT

Crystal structures of two isotypic lanthanide(III) complexes: tri­aqua­[2,6-di­acetyl­pyridine bis­(benzoyl­hydrazone)]methano­llanthanide(III) trichloride methanol disolvates (LnIII = Tb and Dy)

Two isotypic complexes of TbIII and DyIII with the ligand 2,6-diacetylpyridine bis(benzoylhydrazone) have been synthesized and structurally characterized.

A new metal–metal bonded diruthenium(II,III) compound bridged by the dianionic tridentate ligand N-(2-pyridyl)-2-oxy-5-chlorobenzylaminate (5-Clsalpy2−)

The ligand-substitution reaction of Ru2(O2CCH3)4Cl with the tridentate ligand N-(2-pyridyl)-2-oxy-5-chlorobenzylaminate dianion (5-Clsalpy2−) led to the unique diruthenium(II,III) compound [{Na(THF)2}{Ru2(O2CCH3)2(5-Clsalpy)2}]·THF (1·THF) which revealed the characteristic 1-D chain structure of the repeating unit [–Na–O–Ru–Ru–O–]∞ and rich redox chemistry.