14- and 17-Membered Macrocycles Containing Amide, Amino, and Carbamate Groups in The Monocyclic Skeleton: An Accidental Byproduct Obtained from a Residue after Separation.

A 14-membered cyclic compound (3) containing amide, amino, and carbamate groups, which was serendipitously obtained in the oily residue after the separation of 4-benzyl-1,4,7,10-tetraazacyldododecane-2,6-dione (2a) and 4,16-dibenzyl-1,4,7,10,13,16,19,22-octaazacyclo-tetracosane-2,6,14,18-tetraone (2b), is reported. The structure of 3 is formally a CO2 insertion between positions 3 and 4 of the 12-membered ring in 2a. The CO2 insertion was confirmed in the synthesis of diethyl 2,2'-(benzylazanediyl)diacetate (1) by the reaction of benzylamine with ethyl bromoacetate using K2CO3 as the base. In addition, the selective synthesis of 3 and ethyl N-benzyl-N-((2-ethoxy-2-oxoethoxy)carbonyl)glycinate (5) and their kinetic behavior are reported. The reaction of 5 with triethylenetetramine afforded a 17-membered macrocycle (7), which was obtained in an 18% yield. Compounds 6 and 8 were prepared from 3 and 7 by introducing benzyl groups to improve their solubility in organic solvents. Titration experiments using 1H NMR showed that both 6 and 8 exhibit Li+ selectivity.

Solvent-Dependent Self-Assembly of a Pillar[5]arene-Based Poly-Pseudo-Rotaxane Linked and Threaded by Silver(I) Trifluoroacetate: A Double Role.

In the supramolecule area, the fabrication of a new concept called polyrotaxanes or poly-pseudo-rotaxanes remains challenging. We herein report the formation of a poly-pseudo-rotaxane in which the same salt-type guest serves both linking and threading in the resulting structure. The combination of A1/A2-thiopyridyl pillar[5]arene (L) and silver(I) trifluoroacetate in CHCl3/CH3OH afforded a one-dimensional (1D) poly-pseudo-rotaxane. In this structure, to our surprise, the AgCF3CO2 guest not only links the di-armed L ligands via an infinite -L-Ag-L-Ag- arrangement but also threads into a pillar[5]arene cavity in a dimer form, (AgCF3CO2)2. In contrast, the same reaction in CH2Cl2/CH3OH yielded a simple 1D coordination polymer because an included CH2Cl2 molecule in the pillar[5]arene cavity prevents the threading of the silver(I) trifluoroacetate guest. Comparative 1H- and 19F-NMR studies support the solvent-dependent poly-pseudo-rotaxane formation at a lower concentration of L.

Organic-inorganic hybrid [NH3(CH2)6NH3]ZnBr4 crystal: structural characterization, phase transitions, thermal properties, and structural dynamics.

Organic-inorganic hybrid [NH3(CH2)6NH3]ZnBr4 crystals were prepared by slow evaporation; the crystals had a monoclinic structure with space group P21/c and lattice constants a = 7.7833 Å, b = 14.5312 Å, c = 13.2396 Å, ß = 90.8650°, and Z = 4. They underwent two phase transitions, at 370 K (T C1) and 430 K (T C2), as confirmed by powder X-ray diffraction patterns at various temperatures; the crystals were stable up to 600 K. The nuclear magnetic resonance spectra, obtained using the magic-angle spinning method, demonstrated changes in the 1H and 13C chemical shifts were observed near T C1, indicating changing structural environments around 1H and 13C. The spin-lattice relaxation time, T 1ρ, increased rapidly near T C1 suggesting very large energy transfer, as indicated by a large thermal displacement around the 13C atoms of the cation. However, the environments of 1H, 14N, and C1 located close to NH3 in the [NH3(CH2)6NH3] cation did not influence it significantly, indicating a minor change in the N-H⋯Br hydrogen bond with the coordination geometry of the ZnBr4 anion. We believe that the information on the physiochemical properties and thermal stability of [NH3(CH2)6NH3]ZnBr4, as discussed in this study, would be key to exploring its application in stable, environment friendly solar cells.

Argentivorous molecules with chromophores: dependence of their fluorescence intensities on the distance between a donor and an acceptor.

We have prepared new argentivorous molecules (L2 and L3) having different linker lengths between cyclen and anthracene units. The structures of Ag+ complexes with the new ligands were investigated in solution and solid states. The silver(I) ion-induced 1H NMR and UV-vis spectral changes of L2 and L3 showed the presence of 1 : 1 complexes. The solid-state structures of the Ag+ complexes with L2 and L3 are stable 1 : 1 complexes because four aromatic side-arms wrap the Ag+ incorporated in the cyclen unit. A photo-induced electron transfer (PET) effect that depends on the length of the linker connecting the nitrogen atoms of cyclen to the chromophore is also investigated. The result indicates a linear (log) correlation between the donor-chromophore average distances of the optimized structures calculated by DFT calculations and fluorescence intensities (log I), and the PET effect becomes ineffective at about 12 Å in this system.

Phase transition, thermal stability, and molecular dynamics of organic-inorganic hybrid perovskite [NH3(CH2)6NH3]CuCl4 crystals.

Organic-inorganic hybrid perovskites have various potential applications in fuel cells and solar cells. In this regard, the physicochemical properties of an organic-inorganic [NH3(CH2)6NH3]CuCl4 crystal was conducted. The crystals had a monoclinic structure with space group P21/n and lattice constants a = 7.2224 Å, b = 7.6112 Å, c = 23.3315 Å, ß = 91.930°, and Z = 4 at 300 K, and the phase transition temperature (T C) was determined to be 363 K by X-ray diffraction and differential scanning calorimetry experiments. From the nuclear magnetic resonance experimental results, the changes in the 1H chemical shifts in NH3 and the influence of C1 located close to NH3 in the [NH3(CH2)6NH3] cation near T C are determined to be large, which implies that the structural change of CuCl4 linked to N-H⋯Cl is large. The 1H spin-lattice relaxation time (T 1ρ) in NH3 is shorter than that of CH2, and the 13C T 1ρ values for C1 close to NH3 are shorter than those of C2 and C3 due to the influence of the paramagnetic Cu2+ ion in square planar geometry CuCl4. The structural mechanism for the phase transition was the change in the N-H⋯Cl hydrogen bond and was associated with the structural dynamics of the CuCl4 anion.

Bis-Argentivorous Molecules Bridged by Phenyl and 4,4'-Biphenyl Groups: Structural and Dynamic Behavior of Silver Complexes.

Bis-argentivorous molecules (La and Lb), which have phenyl and 4,4'-biphenyl groups as linkers, have been prepared. The structures of Ag+ complexes with the new ligands (La and Lb) were investigated in solution and the solid state. The CSI-MS and 1H NMR titration of La and Lb with Ag+ show 1:1 and 1:2 complexes depending on the [Ag+]:[L] ratios. In the solid-state structures, single crystals of La and Lb with 2 equiv of Ag+ were prepared. X-ray crystallography of the silver(I) complexes with La and Lb showed that an intramolecular racemic structure (Δ(δδδδ)Λ(λλλλ) form) and a racemic mixture of Δ(δδδδ)Δ(δδδδ) and Λ(λλλλ)Λ(λλλλ) forms were formed, respectively. The dynamic 1H NMR studies suggest the following: (i) the activation entropies (ΔS⧧) of the side arm rotations in the Ag+ complex with La were all negative, indicating restricted rotation of the side arms due to their shortness, and (ii) the ΔS⧧ values of the Ag+ complexes with Lb were negative only when the side arms of both cyclens rotated simultaneously, and the ΔS⧧ values for the 1:1 and 1:2 complexes were positive when one cyclen side arm was rotated. These values of ΔS⧧ indicate that the biphenyl side arms between the two cyclens are not long enough to rotate the ring freely.

Influence of the Reaction Sequence on the Complexation of an NS4-Macrocycle with CdII and CuI Salts Leading to the Formation of Supramolecular Isomers and an Endo/Exocyclic CuI Complex.

In the construction of metallosupramolecules, the reaction sequence in a three-reactant system (one ligand plus two metal ions) could be one of the controlling factors influencing the outcome of the reaction. In this work, the formation of supramolecular isomers (1 and 2) and an endo/exocyclic Cu+ complex (4) of the NS4-macrocycle (L) via different sequential metal addition protocols (routes I-III) is reported. In one-pot reactions of L with Cu(CH3CN)4PF6 in the absence (route I) and presence (route II) of CdI2, a cyclic dimer CuI complex, [Cu2(L)2](PF6)2 (1), and a one-dimensional coordination polymer, [Cu2(L)2]n·n[CdI4] (2), were obtained, respectively. Interestingly, the complex cations in 1 and 2 are supramolecular isomers formed via cyclization and polymerization upon complexation, respectively, probably due to different geometric and electronic complementarities, via the C-H···X- hydrogen bonds, between L and the counterion. In the two-step reaction (route III), an endocyclic Cd2+ complex, [Cd(L)I2] (3), obtained in the first step was utilized in the following reaction with Cu(CH3CN)4PF6, giving rise to an endo/exocyclic tetranuclear Cu+ complex, [Cu4(L)2(CH3CN)6](PF6)4 (4), via Cd2+ → 2Cu+ substitution, which is not accessible by conventional procedures. Solution studies by comparative NMR and electrospray ionization mass spectroscopy also support metal substitution by showing the stronger binding affinity of Cu+ over Cd2+. These results demonstrate that the metal substitution protocol could be useful for reaching novel metallosupramolecules difficult to obtain by other methods.

Argentivorous Molecules with Oxyethylene Chains in Side-Arms: Silver Ion-Induced Selectivity Changes toward Alkali Metal Ions.

Argentivorous molecules with mono, di, tri, tetra, and penta-oxyethylene chains in aromatic side-arms were prepared (L1-L5). Titration experiments using proton nuclear magnetic resonance and cold electrospray ionization (cold-spray ionization, CSI) mass spectrometry showed that silver ions were trapped in the cyclen moiety and the arranged oxyethylene chains of the side-arms when two equivalents of silver ions were added. The silver complexes formed by adding one equivalent of silver ion to L2-L5 bind alkali metal ions using the oxyethylene chains; alkali metal ion-induced CSI mass spectral changes of L2-L5 were measured in the absence and presence of silver ions to compare the binding properties of the ligand for Li+, Na+, and K+ ions. As a result, the intensity ratios of [L + H + M]2+/[L + H]+ in L1-L3 were almost zero or very low. L4 and L5, which have tetra(oxyethylene) and penta(oxyethylene) chains, respectively, bind a larger size of alkali metal ions. On the other hand, in the presence of silver ions, the ratio for [L + Ag + M]2+/[L + H]+ (M = Li, Na, K) in L2-L5 was increased. The highest [L + Ag + M]2+/[L + H]+ ratios for K+ were observed in L4 and L5, while selectivity for Na+ was observed in the case of L2 and L3. These results indicate that the increased binding ability and selectivity by L2-L5 are due to the arrangement of oxyethylene chains by the conformational change of the aromatic side-arms. The Ag+-induced carbon-13 nuclear magnetic resonance spectral changes suggested that the second and third oxyethylene units, close to the benzene, are involved in the coordination of the second metal ion.

Argentivorous Molecules with Chromophores in Side Arms: Silver Ion-Induced Turn On and Turn Off of Fluorescence.

The synthesis of argentivorous molecules (L1 and L2) having two chromophores (4-(anthracen-9-yl)benzyl or 4-(pyren-1-yl)benzyl groups) and two benzyl groups and the fluorescence properties of their silver complexes in a solution and the solid state are reported. A crystallographic approach for the Ag+ complexes with L1 and L2 revealed that the observed fluorescence changes stem from the excimer formation and extinction of fluorescent. Furthermore, binding stabilities of L1 and L2 toward Ag+ ions were estimated by the Ag+-induced UV-vis and PL spectral changes.

Cosmosen: Octa-Armed 24-Membered Cyclic Octaamine Synthesized from a Byproduct in the Preparation of 4-Benzyl-2,6-dioxocyclen.

The synthesis of an octa-armed 24-membered cyclic octaamine (1) is reported. When 4-benzyl-1,4,7,10-tetraazacyclododecane-2,6-dione (3a) was prepared by the reaction of diethylenetriamine with diethyl N-benzyliminodiacetate (2), a dimeric macrocycle (3b) was obtained as a byproduct in a 5% yield. An octa-armed 24-membered cyclic octaamine (1), named Cosmosen, was prepared via the reductive amination and reduction of 3b. The binding constants for the 1:1 and 2:1 (Ag+/1) complexation of 1 were estimated to be ca. 7.9 and 13.9, respectively, by titration experiments using UV-vis spectrometry in methanol and chloroform (v/v, 9:1) solutions at 298 K.

Construction of 2D Interdigitated Polyrotaxane Layers and their Transformation to a 3D Polyrotaxane by a Photocycloaddition Reaction between Wheels.

Following the pioneering work of Sauvage and Stoddart on rotaxanes, construction of higher dimensional polyrotaxanes in metal-organic frameworks (MOFs) via a modified protocol is challenging. We present the formation of a two-dimensional (2D) polyrotaxane and its conversion to a three-dimensional (3D) polyrotaxane MOF via a photoreaction between interdigitated "olefin wheels". For this purpose, a 2-fold entangled 2D MOF [Pb2(bpp)(sdc)2] (1), showing a 2D + 2D → 2D polyrotaxane motif, has been synthesized from the solvothermal reaction of lead(II) nitrate, 3,3'-stilbenedicarboxylic acid (H2sdc) containing an olefin group, and 1,4-bis(4-pyridyl)piperazine (bpp). The single-crystal X-ray diffraction analysis of 1 revealed that the adjacent entangled 2D layers are interdigitated, with the separation of 3.72 Šbetween C═C bond pairs in adjacent layers satisfying Schmidt's criteria for the occurrence of a [2 + 2] photocycloaddition reaction. Irradiation of the single crystals of 1 under UV light resulted in formation of a 3D polyrotaxane, [Pb2(bpp)(rctt-tccb)]n (2), due to a [2 + 2] photocycloaddition reaction between two wheels via a single-crystal to single-crystal transformation. The photocycloaddition and partial thermal cleavage reaction between 1 and 2 were confirmed by 1H NMR and powder X-ray diffraction (PXRD) in solution and the solid state, respectively. The present approach could contribute to the understanding of the construction of higher dimensional polyrotaxanes which are not accessible by the traditional routes.

Mole-Ratio-Dependent Reversible Transformation between 2:2 and Cyclic 3:6 Silver(I) Complexes with an Argentivorous Molecule.

A tetra-armed cyclen (L) with two substituted 3,5-difluorobenzyl and two substituted pyridine-4-yl methyl groups at the 1,4- and 7,10-positions of the cyclen ring as side arms was synthesized. When L was reacted with 1 equiv of the silver(I), dimetallo[3.3]paracyclophane-like 2:2 cyclic dimer, [Ag2(L)2](PF6)2, was obtained. The reaction of L with 2 equiv of silver(I) gave a 3:6 cyclic trimer, [Ag6(L)3(CH3CN)3](OTf)6·3CH3CN. Furthermore, reversible complexation between the 2:2 cyclic dimer and 3:6 cyclic trimer was confirmed by 1H NMR and the CSI mass in the addition of silver(I) or the [2.2.2]cryptand.

Pentacyclic Nano-Trefoil.

Tetra-armed cyclen (1) bearing two 4-(4'-pyridyl)benzyl and two 3,5-difluorobenzyl groups and its Ag+ complexes were prepared and structurally characterized. The complexes formed between 1 and Ag+ undergoes a reversible structural transformation between a 2:2 dimeric complex and a 3:5 pentacyclic trefoil complex with changes in the Ag+ /1 molar ratio. It was also revealed that the 3:5 trefoil complex could encapsulate benzene and [D6 ]benzene selectively in solid-state. The benzene-included structures are stabilized by C-H⋅⋅⋅F-C interactions between the benzene molecule and the ligand molecule.

1H NMR Study of a Chiral Argentivorous Molecule/Ag+ Complex: Assignment of Proton Signals of Four Aromatic Rings with Slightly Different Environments.

The proton signals at the 2'- and 6'-positions of the aromatic side arms of a silver(I) complex with a chiral tetra-armed cyclen ((S)-L2) are assigned by comparison with 1H NMR spectra and X-ray structure of Ag+ complexes with three analogues of (S)-L2: (S)-L23D having one benzyl group and three deuterium-substituted benzyl groups, (S)-L22D having two benzyl groups and two deuterium-substituted benzyl groups, and (S)-L2F having three benzyl groups and one 4'-fluorobenzyl group. An interaction factor is defined by using the X-ray structures. The chemical shift values of the proton signals in the aromatic side arms can be explained by using the interaction factors that are defined by the dihedral angles, the angles between two mean planes, and the CH···π distances from the X-ray data of the (S)-L2/Ag+ complex.

Argentivorous Molecules Exhibiting Highly Selective Silver(I) Chiral Enhancement.

We report the synthesis of chiral tetra-armed cyclens, having an asymmetric center at one side-arm, that show selective chiral enhancement with silver(I). When the chiral ligand forms a silver(I) complex, the side-arms cover the silver(I) incorporated into the cyclen. The asymmetric center controls the conformation of the side-arms in one direction, increasing the molar ellipticity of the CD spectrum. Chiral cyclens substituted with biphenyl groups exhibit large molar ellipticity values with strong exciton coupling effects.

Influence of the Molar Ratio and Solvent on the Coordination Modes of 1,7-Dibenzyl-4,10-bis(pyridin-4-ylmethyl)cyclen.

The synthesis of a tetra-armed cyclen (L) with two benzyl groups at the 1- and 7-positions and two pyridin-4-ylmethyl groups at the 4- and 10-positions as side arms and the solvent- and/or molar-ratio-dependent coordination modes in the formation of silver(I) complexes are reported. 1H NMR and cold-spray-ionization mass spectrometry studies suggest that a silver(I) complex with L gives different species depending on the molar ratio of silver ions used as the reactant. Furthermore, the conformation of cyclen in the one-dimensional (1D) coordination polymers, obtained using 2 equiv of silver(I), changes depending on the presence or absence of acetonitrile. When L was reacted with 1 and 2 equiv of silver(I) triflate in a mixed solvent system (CH2Cl2/CH3OH/CH3CN), a dimetallo[3.3]paracyclophane-like discrete cyclic dimer, [Ag2L2](OTf)2 (1), and a 1D coordination polymer, [Ag2L(OTf)2(CH3CN)]n (2), respectively, were obtained as single crystals. In the absence of acetonitrile, a zigzag 1D coordination polymer, {[Ag2L(OTf)]OTf·3CH2Cl2}n (3), was obtained when 2 equiv of silver(I) was used. Molar-ratio-dependent structural changes were not observed when L was reacted with AgBF4 or AgPF6 in the CH2Cl2/CH3OH/CH3CN mixed-solvent system. The solvent effect on the coordination modes can be explained by the coordination ability of the solvents toward the metal cation affecting the conformation of the cyclen.

Silver ion-induced chiral enhancement by argentivorous molecules.

Optically active tetra-armed cyclens with an asymmetric chiral centre in the cyclen moiety were synthesized and were shown to enhance chirality and control of enantiomers on complexation with Ag+. Binding studies of the Ag+ complex demonstrated that Ag+ preferentially interacts with electron-rich substituents over other aromatic substituents.

Inclusion of alkyl nitriles by tetra-armed cyclens with styrylmethyl groups.

Synthesis of tetra-armed cyclens (2a-2e), with substituted styrylmethyl groups as side-arms, and their Ag+ complexes is reported. The Ag+ complex with a tetra styrylmethyl-armed cyclen (2a) incorporates alkyl nitriles in a pseudo-cavity formed by the four styrylmethyl side-arms. This prompted us to apply this system to the determination of the absolute configurations of chiral nitriles with low [α]D and low circular dichroism (CD) intensity. In the CD spectra of the 2a/Ag+ complex, (S)- and (R)-G1 did not show a specific Cotton effect, while when chiral nitriles were added to the 2a/Ag+ complex, drastic spectral changes were observed. The (S)-G1@2a/Ag+ system exhibited first a negative and then a positive Cotton effect, whereas the (R)-G1@2a/Ag+ system showed the mirror image of the Cotton effect of (S)-G1@2a/Ag+. We have, therefore, demonstrated a new technique for determining the absolute configurations of weak optical rotation molecules using the Ag+ complex with 2a.

Mechanistic insights into heavy metal ion sensing by NOS2-macrocyclic fluorosensors via the structure-function relationship: influences of fluorophores, solvents and anions.

To obtain a mechanistic understanding of the effects derived from fluorophores, solvents and anions on heavy metal sensing, two NOS2-macrocycle-based fluorosensors with different fluorophores (L1: 9-methylanthracene, L2: benzothiazolyl) were synthesised. In this regard, particular attention was given to monitoring the cation-ligand, cation-anion and cation-solvent interactions from the detailed complexation processes in both the solution and solid states while considering the structure-function relationship. L1 showed turn-on type silver(i) selectivity over other metal ions, including mercury(ii), in ethanol. According to the complexation results obtained by titration (UV-vis, fluorescence and NMR), cold-spray ionization mass spectrometry and X-ray crystallography, the observed silver(i) sensing by L1 is mainly due to its 1 : 1 complexation with silver(i) via the Ag-Ntert bond and the strong solvation of mercury(ii). Thus, the turn-on sensing for silver(i) can be explained by the CHEF effect, in which the coordination of silver(i) to the receptor unit effectively prevents PET quenching. As a dual-probe (UV-vis and fluorescence) chemosensor, L2 showed fluorescence turn-off type selectivity for both silver(i) and mercury(ii) in ethanol. In acetonitrile, L2 showed improved fluorescence turn-off type selectivity for mercury(ii) with ClO4- and NO3-; however, no such responses were observed with other anions, such as Cl-, Br-, I-, SCN-, OAc- and SO42-. Together with the complexation results by titration, the crystal structures of an endocyclic mercury(ii) perchlorate complex and an exocyclic mercury(ii) iodide complex revealed that the anion-controlled mercury(ii) sensing by L2 arises from the endo- and exo-coordination modes depending on the anion coordinating ability, which induces either metal-receptor/fluorophore binding (Hg-Ntert and Hg-Nfl) or no binding. Taken collectively, the photophysical, thermodynamic and structural results of the complexations herein suggest that the sensing properties of heavy metal ions by macrocycle-based fluorosensors are very sensitive not only to the cation-receptor and cation-fluorophore interactions but also to the cation-anion (endo/exo-coordination modes) and/or cation-solvent interactions.

Formation of a four-bladed waterwheel-type chloro-bridged dicopper(ii) complex with dithiamacrocycle via double exo-coordination.

A combination of O3S2-macrocycles incorporating different sulfur-to-sulfur separations (S-(CH2)n-S, L1: n = 2, L2: n = 3) and copper(ii) nitrate afforded new types of both monocopper(ii) and dicopper(ii) complexes, respectively. L1 gave a 1D coordination polymer [Cu2(L1)2(NO3)4]n (1) based on a convergent exo-coordination mode while L2 resulted in the formation of a divergent exo/exo-coordinated dicopper(ii) complex, [Cu2(L2ox)4(µ-Cl)](NO3)4 (2), whose shape resembles a four-bladed waterwheel in which in situ oxidized macrocycles (L2ox) act as the blades and a CuII-(µ-Cl)-CuII entity corresponds to the axle shaft. The chloro-bridging ligand is derived from the dichloromethane solvent and its arrangement is held together by C-HCl- H-bonds. Compound 2 shows a weak antiferromagnetic property via the CuII-(µ-Cl)-CuII entity.