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 (<b>1</b>) is reported. When 1 equiv of Ag⁺ is added to <b>1</b>, the aromatic side arms cover the Ag⁺ incorporated in the cyclen. Upon the addition of more than 1 equiv of Ag⁺ to <b>1</b>, the cyclen moiety binds Ag⁺ first, before the crown ether in the side arms subsequently binds Ag⁺. The log <i>K</i>₁₁, log <i>K</i>₁₂, and log <i>K</i>₁₃ values for the 1:1, 1:2, and 1:3 (= <b>1</b>/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

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 (<b>1</b>) is reported. When 1 equiv of Ag⁺ is added to <b>1</b>, the aromatic side arms cover the Ag⁺ incorporated in the cyclen. Upon the addition of more than 1 equiv of Ag⁺ to <b>1</b>, the cyclen moiety binds Ag⁺ first, before the crown ether in the side arms subsequently binds Ag⁺. The log <i>K</i>₁₁, log <i>K</i>₁₂, and log <i>K</i>₁₃ values for the 1:1, 1:2, and 1:3 (= <b>1</b>/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

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

Anion-controlled circular dichroism (CD) spectral changes in Hg²⁺ complexes with a chiral bidentate ligand are reported. Although the Hg­(CF₃SO₃)₂ and Hg­(CF₃CO₂)₂ complexes with (<i>R</i>)-(−)-<b>1</b>-(naphthalen-1-yl)-<i>N</i>,<i>N</i>-bis­(pyridin-4-ylmethyl)­ethanamine, (<i>R</i>)-(−)-<b>1</b>, show significant CD spectral changes, no CD spectral changes were observed in the HgCl₂, HgBr₂, Hg­(CN)₂, or Hg­(CH₃CO₂)₂ complexes. X-ray analysis indicates that both the (<i>R</i>)-(−)-<b>1</b>-Hg­(CF₃SO₃)₂ and (<i>R</i>)-(−)-<b>1</b>-HgCl₂ complexes form a coordination polymer and a discrete 2:3 [=(<i>R</i>)-(−)-<b>1</b>/HgCl₂] 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

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 <b>1</b> and theoretical calculations is reported. Probe <b>1</b> is linked to chiral primary amines yielding <b>1</b>–amine conjugates, which exhibited exciton coupled circular dichroism in the <i>m</i>-quaterphenyl chromophores. The ratios between the <i>P</i> and <i>M</i> conformers of the <b>1</b>–amine conjugates, which are calculated with DFT, were correlated highly with the sign and amplitude of the observed CD spectra

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

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

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

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

Hg²⁺-Sensing System Based on Structures of Complexes

The first example of a new Hg²⁺-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 Hg²⁺ is added, whereas no CD spectral changes are observed in the cases of Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Rb⁺, Ag⁺, Cd²⁺, La³⁺, Gd³⁺, and Pb²⁺

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

An M₃<b>L</b>₂A₆ cage has been prepared with small windows from a tripodal ligand, <b>L</b>, and Cu­(hfac)₂. Cold spray ionization mass spectrometry of a mixture of <b>L</b> and Cu­(hfac)₂ revealed the formation of a Cu₃<b>L</b>₂hfac₆ cage in solution. X-ray crystallography showed that the Cu₃<b>L</b>₂hfac₆ 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

Double-armed and tetra-armed cyclen-based cryptands

<p>Double-armed and tetra-armed cyclen-based cryptands (<b>1a</b>–<b>1d</b> and <b>2</b>) that bridge two aromatic rings by diethyleneoxy and triethyleneoxy units were prepared. The CSI-MS of 1:1 mixtures ([Ag⁺]/[ligand]) indicated that these new cryptands form 1:1 complexes with Ag⁺. The log <i>K</i> values for the interaction between Ag⁺ and <b>2</b> was greater than those of <b>1a</b>–<b>1d</b>, double-armed cyclens (<b>3a</b>–<b>3c</b> and <b>4</b>), and tetra-armed cyclen (<b>5</b>). The Ag⁺-ion-induced ¹H NMR spectral changes suggest that the Ag⁺–<i>π</i> interactions of the Ag⁺ complexes with the cryptands (<b>1a</b>–<b>1d</b> and <b>2</b>) are stronger than those in Ag⁺/double-armed and tetra-armed cyclens. To visualise the Ag⁺−<i>π</i> interactions, the isosurfaces of the LUMO and HOMOs of the Ag⁺ complexes were calculated at the B3LYP/3–21G(*) theoretical level. The LUMO of the Ag⁺ ion is distorted by interaction with the HOMOs of the aromatic side arms. The calculations reveal Ag⁺−<i>π</i> interactions between the Ag⁺ ion and the aromatic side arms, and these are shown graphically.</p

A Ditopic O₄S₂ Macrocycle and Its Hard, Soft, and Hard/Soft Metal Complexes Exhibiting Endo‑, Exo‑, or Endo/Exocyclic Coordination: Synthesis, Crystal Structures, NMR Titration, and Physical Properties

A 20-membered O₄S₂ macrocycle (<b>L</b>^<b>2</b>) was synthesized as a ditopic ligating system toward hard and soft metal ions simultaneously. Five complexes (<b>3</b>–<b>7</b>) of <b>L</b>^<b>2</b> with different structures and coordination modes, including discrete to infinite forms, mono- to heteronuclear, and endo- to exo- and endo/exocoordination, were prepared and structurally characterized. First, the reaction of <b>L</b>^<b>2</b> with Pb­(ClO₄)₂·3H₂O afforded a typical endocyclic mononuclear perchlorato complex [Pb­(<b>L</b>^<b>2</b>)­(ClO₄)₂] (<b>3</b>) in which one lead­(II) is surrounded by the macrocycle adopting a “tight and bent” conformation. Meanwhile, the reaction with a softer metal salt AgNO₃ resulted in the formation of the dinuclear bis­(macrocycle) complex [Ag₂(<b>L</b>^<b>2</b>)₂(NO₃)₂] (<b>4</b>) in which two exocyclic silver­(I) ions are doubly linked by two nitrate ions. The treatment of <b>L</b>^<b>2</b> with CuI gave a mixture of the exocyclic monomer complex [Cu­(<b>L</b>^<b>2</b>)­I] (<b>5</b>) and the exocyclic dimer complex [(Cu₂I₂)­(<b>L</b>^<b>2</b>)₂] (<b>6</b>), which were separated manually because of their brick and rhomboid shapes of the crystals, respectively. Furthermore, the reaction of <b>L</b>^<b>2</b> with a mixture of CuI and NaI afforded a photoluminescent heteronuclear complex [Na₂(Cu₆I₈)­(<b>L</b>^<b>2</b>)₂­(CH₃CN)₄]_<i>n</i> (<b>7</b>) in the endo/exocyclic coordination mode. In this case, the endocyclic sodium­(I) complex units are linked by the double-open cubanes-type cluster Cu₆I₈, yielding a two-dimensional network. The structural and binding properties of the complex of <b>L</b>^<b>2</b> with silver­(I) nitrate in solution were monitored by the NMR titration. Photophysical and thermal properties for complex <b>7</b> were also investigated and discussed