Mari Ikeda

Coordination Networks of a Ditopic Macrocycle Exhibiting Anion-Controlled Dimensional Changes and Crystal-to-Crystal Anion Exchange.

A rationally designed NO2S2-donor macrocycle L was synthesized, and anion variation (PF6(-), CF3CO2(-), NO3(-), and CF3SO3(-)) of its silver(I) complexes was employed as a strategy for controlling their coordination modes and network dimensions. The assembly reactions of L with four silver(I) salts afforded the complexes [Ag2L2](PF6)2 (1), [Ag4L2(CF3CO2)4]n (2), [Ag4L2(NO3)4]n (3), and {[Ag3L2(CF3SO3)2]CF3SO3}n (4) that adopt cyclic dimer, 1D, 2D, and pseudo 3D network structures, respectively, with the structure adopted depending on the coordination ability and coordination modes of the anion used. Interestingly, quantitative anion exchange accompanying an irreversible structural conversion from 2, 3, or 4 to 1 was observed in the crystalline state by powder X-ray diffraction (PXRD) and IR spectroscopy. A stepwise mechanistic process from 2 (CF3CO2(-), 1D) to 3 (NO3(-), 2D) by anion exchange was also proposed.

Combination of a new chiroptical probe and theoretical calculations for chirality detection of primary amines.

A method to determine absolute configurations of primary amines by combined use of a chiroptical probe 1 and theoretical calculations is reported. Probe 1 is linked to chiral primary amines yielding 1-amine conjugates, which exhibited exciton coupled circular dichroism in the m-quaterphenyl chromophores. The ratios between the P and M conformers of the 1-amine conjugates, which are calculated with DFT, were correlated highly with the sign and amplitude of the observed CD spectra.

Ligand-Induced Formation of Copper(I) Iodide Clusters: Exocyclic Coordination Polymers with Bis-dithiamacrocycle Isomers

A comparative study on the formation of guest clusters induced by different shapes (or sizes) of exocyclic binding sites embedded in the bis-macrocyclic host isomers is reported. CuI reacts with two regioisomers of a bis-dithiamacrocycle, o-bis-L (W-shaped binding site) and m-bis-L (U-shaped binding site), to yield one-dimensional coordination polymers {[(μ4-Cu4I4)(o-bis-L)]·2CH3CN}n (1a) and [(μ4-Cu2I2)(m-bis-L)]n (2). In 1a, the o-bis-L ligand isomer is linked by a spacious cubane [Cu4I4] cluster, while the m-bis-L ligand in 2 is linked by a smaller rhomboid [Cu2I2] cluster because of the different exocyclic binding sites. The results observed illustrate the possibility for the metal clusters including [CunIn] (n = 2 or 4) to adopt a controlled formation through the binding site alternation or design. Because of the adaptive cluster formations, the products show different photophysical properties. Additionally, sliding of the one-dimensional chains in 1a was observed upon loss of the lattice solvent molecules in ambient condition.

Construction of an M3L2A6 Cage with Small Windows from a Flexible Tripodal Ligand and Cu(hfac)3

An M3L2A6 cage has been prepared with small windows from a tripodal ligand, L, and Cu(hfac)2. Cold spray ionization mass spectrometry of a mixture of L and Cu(hfac)2 revealed the formation of a Cu3L2hfac6 cage in solution. X-ray crystallography showed that the Cu3L2hfac6 cage included neutral molecules such as THF and CHCl3. Furthermore, the six hfac anions have been shown to play an important role in holding neutral guest molecules securely in place.

Hg2+-Sensing System Based on Structures of Complexes

The first example of a new Hg(2+)-sensing system based on the structures of complexes is reported. The system uses a combination of a new chiral bidentate ligand and CD spectroscopy. Significant CD spectral changes are observed when Hg(2+) is added, whereas no CD spectral changes are observed in the cases of Li(+), Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Rb(+), Ag(+), Cd(2+), La(3+), Gd(3+), and Pb(2+).

Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a Benzothiazole-Attached Macrocycle That Correlate with Structural Coordination Modes

We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO2S2-macrocycle L was synthesized, and its mercury(II) selectivity (for perchlorate salt) as a dual-probe channel (UV-vis and fluorescence) chemosensor exhibiting the largest blue shift and the fluorescence turn-off was observed. In the mercury(II) sensing with different anions, except ClO4(-) and NO3(-), no responses for mercury(II) were observed with other anions such as Cl(-), Br(-), I(-), SCN(-), OAc(-), and SO4(2-). A crystallographic approach for the mononuclear mercury(II) perchlorate complex [Hg(L)(ClO4)2]·0.67CH2Cl2 (1) and polymeric mercury(II) iodide complex [Hg(L)I2]n (2) revealed that the observed anion-controlled mercury(II) sensing in the fluorescence mainly stems from the endo- and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg-Ntert bond formation or not. The detailed complexation process with mercury(II) perchlorate associated with the cation sensing was also monitored with the titration methods by UV-vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry.

Selective Retention of Methanol over Ethanol by a Cyclen-Based Cryptand/Copper(II) Complex

A cyclen-based cryptand (2) was prepared in a two-step synthesis from dioxocyclen. When a Cu(CF3SO3)2 complex with 2 was prepared in methanol, the 2/Cu(CF3SO3)2 complex incorporated one methanol in the cavity formed by the diethyleneoxy unit and the NH group of the cyclen. When prepared in ethanol, the 2/Cu(CF3SO3)2 complex similarly incorporated one ethanol. Cold electrospray ionization mass spectrometry (CSI-MS) of the 2/Cu(CF3SO3)2/alcohol complexes selectively retains methanol over ethanol under CSI-MS conditions.

Anion-Controlled Circular Dichroism Spectral Changes in Hg2+ Complexes with a Chiral Bidentate Ligand

Anion-controlled circular dichroism (CD) spectral changes in Hg(2+) complexes with a chiral bidentate ligand are reported. Although the Hg(CF(3)SO(3))(2) and Hg(CF(3)CO(2))(2) complexes with (R)-(-)-1-(naphthalen-1-yl)-N,N-bis(pyridin-4-ylmethyl)ethanamine, (R)-(-)-1, show significant CD spectral changes, no CD spectral changes were observed in the HgCl(2), HgBr(2), Hg(CN)(2), or Hg(CH(3)CO(2))(2) complexes. X-ray analysis indicates that both the (R)-(-)-1-Hg(CF(3)SO(3))(2) and (R)-(-)-1-HgCl(2) complexes form a coordination polymer and a discrete 2:3 [=(R)-(-)-1/HgCl(2)] complex with a figure-eight structure. X-ray crystallography revealed that (i) the Hg-Hg distances bridged by anions vary depending on the anions used and (ii) a coordination polymer cannot be formed when the Hg-Hg distances are too short. Therefore, the formation of a coordination polymer is required to give the observed significant CD spectral changes.

Guest-triggered assembly of zinc(II) supramolecular isomers with accompanying dimensional change and reversible single-crystal-to-single-crystal transformation

Solvent-directed assembly of two-dimensional (2D) and 3D supramolecular isomers as well as guest-exchange induced transformation of the 2D isomer accompanied by photoluminescence switching are reported. Solvothermal reaction of Zn(NO3)2·4H2O, 1,4-bis(4-pyridyl)piperazine (bpp), and benzene-1,3-dicarboxylic acid (H2bdc) in dimethylformamide (DMF) afforded a self-penetrated 3D coordination polymer, {[Zn2(bpp)2(bdc)2]·4DMF·4H2O}n (1), adopting a firewood-like stacking structure. When the above synthetic procedure was repeated employing dimethylacetamide (DMA) as a solvent, a 2D coordination polymer, {[Zn2(bpp)2(bdc)2]·4DMA·6H2O}n (2), was obtained, whose structure shows a crinkled square (4,4) grid type, as a supramolecular isomer of 1. The dimensional difference between isomers 1 and 2 stems mainly from the directional arrangement and the conformation of the bpp ligand. In the guest-exchange experiment, isomer 2 with the crinkled square grid structure not only represents a reversible spreading–folding conversion due to the conformational change of the bpp ligand but also displays a photoluminescence switching behaviour.

Tetra-armed cyclen bearing two benzo-15-crown-5 ethers in the side arms.

A tetra-armed cyclen bearing two benzo-15-crown-5 ethers in the side arms (1) is reported. When 1 equiv of Ag(+) is added to 1, the aromatic side arms cover the Ag(+) incorporated in the cyclen. Upon the addition of more than 1 equiv of Ag(+) to 1, the cyclen moiety binds Ag(+) first, before the crown ether in the side arms subsequently binds Ag(+). The log K11, log K12, and log K13 values for the 1:1, 1:2, and 1:3 (= 1/Ag(+)) complexes were estimated to be 9.4, 5.8, and 4.0, respectively. We found that the tetra-armed cyclen possessing crown ethers in the side arms behaves like an argentivorous molecule even though the crown ether arms bind metal cations.