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Bis(macrocyclic) complexes are investigated as artificial analogues of natural dinuclear metalloenzymes. Two ligands containing two cyclam rings connected through a p‐cresol or 4‐nitrophenol spacer were synthesized and their complexing properties were investigated. CuII complexes were prepared and their properties were studied by a combination of spectral, diffraction and electrochemical methods. The phenolate group is not or only weakly coordinated to the central CuII ion and the two macrocycles behave mostly as two independent complexing units. All the determined solid‐state structures showed cyclam adopting trans‐III geometry, however, solution study indicated the presence of more isomers in the solution whose abundance changes with pH. Electrochemical reduction of the complexes is irreversible and results in the reductive decomplexation to amalgamated Cu metal. The amalgamated metal is re‐oxidized to CuII during the anodic scan of CV and the metal ion is re‐coordinated. The ligand containing the nitro group shows an irreversible four‐electron reduction of the nitro group. The ligands and the complexes undergo also a slow degradation when incubated in the aqueous solutions for a prolonged time. The degradation relies on the "retro‐Mannich" cleavage of the methylene bridge connecting the cyclam ring with the phenol moiety. [ABSTRACT FROM AUTHOR]

Prenylation of peptides is widely observed in the secondary metabolites of diverse organisms, granting peptides unique chemical properties distinct from proteinogenic amino acids. Discovery of prenylated peptide agents has largely relied on isolation or genome mining of naturally occurring molecules. To devise a platform technology for de novo discovery of artificial prenylated peptides targeting a protein of choice, here we have integrated the thioether‐macrocyclic peptide (teMP) library construction/selection technology, so‐called RaPID (Random nonstandard Peptides Integrated Discovery) system, with a Trp‐C3‐prenyltransferase KgpF involved in the biosynthesis of a prenylated natural product. This unique enzyme exhibited remarkably broad substrate tolerance, capable of modifying various Trp‐containing teMPs to install a prenylated residue with tricyclic constrained structure. We constructed a vast library of prenylated teMPs and subjected it to in vitro selection against a phosphoglycerate mutase. This selection platform has led to the identification of a pseudo‐natural prenylated teMP inhibiting the target enzyme with an IC50 of 30 nM. Importantly, the prenylation was essential for the inhibitory activity, enhanced serum stability, and cellular uptake of the peptide, highlighting the benefits of peptide prenylation. This work showcases the de novo discovery platform for pseudo‐natural prenylated peptides, which is readily applicable to other drug targets. [ABSTRACT FROM AUTHOR]

The development of phosphors for warm white light plays a decisive role in the quest for energy-efficient and environmentally friendly lighting technologies. Lanthanide-based phosphors, especially those containing europium ions (Eu3+), offer promising possibilities as they can emit light in the entire visible spectrum. In this study, the luminescence properties of two Eu3+ complexes, specifically [Eucy1a] and [Eu2cy2], synthesized with macrocyclic ligands are presented. The macrocyclic ligands (cy1a)H3 and (cy2)H6 provide a stable coordination environment that allows fine-tuning of photophysical properties, which are crucial for warm white phosphors. Synthesis, molecular modeling using density functional theory (DFT) and spectroscopic characterization of the complexes were performed. Notably, the complexes showed an inefficient energy transfer from the ligands to the Eu3+ ions, resulting in a broad blue emission spectrum corresponding to the ligand emission and the red 4f–4f transitions of Eu3+,which is important for the generation of white light. Photometric evaluation revealed favorable properties, including correlated color temperatures (CCT) indicative of warm white light, high color rendering index (CRI) values and exceptional Luminous Efficacy of Radiation (LER). In addition, the presence of coordinated water molecules influenced the luminescence lifetime and quantum efficiency of the complexes. Overall, the synthesized Eu3+ complexes show promising prospects for applications in solid-state lighting, LED designs and emergency technologies that offer high performance and energy efficiency. [ABSTRACT FROM AUTHOR]

We present a detailed investigation on the coordination chemistry of [nat/203Pb]Pb(II) with chelators H4PYTA and H4CHX‐PYTA. These chelators belong to the family of ligands derived from the 18‐membered macrocyclic backbone PYAN and present varying degrees of rigidity due to the presence of either ethyl or cyclohexyl spacers. A complete study of the stable Pb(II) complexes is carried out via NMR, X‐Ray crystallography, stability constant determination and computational studies. While these studies indicated that Pb(II) complexation is achieved, and the thermodynamic stability of the resulting complexes is very high, a certain degree of fluxionality does exist in both cases. Nevertheless, radiolabeling studies were carried out using SPECT (single photon emission computed tomography) compatible isotope lead‐203 (203Pb, t1/2=51.9 h), and while both chelators complex the radioisotope, the incorporation of carboxylate pendant arms appears to be detrimental towards the stability of the complexes when compared to the previously described amide analogues. Additionally, incorporation of a cyclohexyl spacer does not improve the kinetic inertness of the system. [ABSTRACT FROM AUTHOR]

Lanthanide complexes of DO3A‐derivative ligands bearing a pyridine‐carbamate (L1) or pyridine‐amine (L2) arm have potential interest in the design of enzymatically activated imaging probes. Solid‐state X‐ray structures for CeL1 and YbL2 both demonstrate twisted square antiprismatic geometry, with the metal ion in a nine‐ or an eight‐coordinate environment, respectively. As assessed by pH‐potentiometry, in solution lanthanide ions form more stable complexes with the nonadentate L1 than with the octadentate L2 ligand (logKML=18.7–21.1 vs. 16.7–18.6, respectively), while stability constants are similar for L1 and L2 chelates of Mg2+, Ca2+, Zn2+ or Cu2+. The kinetic inertness of GdL1 is exceptionally high, with an estimated dissociation half‐life of ~108 h at pH 7.4, while LnL2 (Ln=Ce, Gd, Yb) complexes have 3–4 orders of magnitude faster dissociation, related to the presence of the protonatable, non‐coordinating amine function. The water exchange rate determined for the monohydrated GdL2 (kex298=1.3×106 s−1) shows a threefold decrease with respect to GdDOTA, as a consequence of a reduction in the negative charge and in the steric crowding around the water binding site, both important in dissociatively activated water exchange processes. [ABSTRACT FROM AUTHOR]

Metal–organic cages (MOCs), which are formed via coordination‐driven assembly, are being extensively developed for various applications owing to the utility of their accessible molecular‐sized cavity. While MOC structures are uniquely and precisely predetermined by the metal coordination number and ligand configuration, tailoring MOCs to further modulate the size, shape, and chemical environment of the cavities has become intensively studied for a more efficient and adaptive molecular binding. Herein, we report self‐expanding MOCs that exhibit remarkable structural variations in cage size and flexibility while maintaining their topology. A cyclic ligand with an oligomeric chain tethering the two benzene rings of stilbene was designed and mixed with RhII ions to obtain the parent MOCs. These MOCs were successfully transformed into expanded MOCs via the selective cleavage of the double bond in stilbene. The expanded MOCs could effectively trap multidentate N‐donor molecules in their enlarged cavity, in contrast to the original MOCs with a narrow cavity. As the direct synthesis of expanded MOCs is impractical because of the entropically disfavored structures, self‐expansion using ring‐openable ligands is a promising approach that allows precision engineering and the production of functional MOCs that would otherwise be inaccessible. [ABSTRACT FROM AUTHOR]

The nature of the interaction between actinide ions and ligands is of great significance in the application of the separation of actinide groups. Therefore, we have been devoted to this aspect in recent years. In this article, the coordination structure, stability and bonding properties of the complexes formed by uranyl and macrocyclic ligands are reviewed. First of all, our study found that the coordination structure of actinyl macrocyclic complexes depends on the size of the macrocyclic ligands; secondly, in the case of “side-on” coordination, uranyl tends to form a 1∶2 complex, while in the case of “insertion” structure, uranyl tends to form a 1∶1 complex; thirdly, it has been found that the ligands with ring size of 18 have excellent coordination ability when combined with uranyl, and ［CHP］4- has the strongest binding ability; finally, this stability is mainly due to the greater covalence of U-N than that of U-O and U-S. These structural rules and bonding characteristics provide important theoretical guidance for the experimental screening of reasonable and efficient ligands for the separation of actinides.

Abstract Background The hypothetical concept of ‘macrocyclic cavity’ is largely employed as useful model to interpret the affinity of metal ions for the macrocyclic chelating ligand 2,2′,2′′,2′′′-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (H4DOTA). It Is hypothesized that a close matching between the size of the macrocyclic cavity and that of the metallic ion is a key parameter to ensure the high-yield formation of stable coordination metal-DOTA complex. This approach has become popular in the design of radiopharmaceuticals containing radiometals and H4DOTA as chelating group. Results Based on X-ray structural data of metallic complexes formed by the ligand H4DOTA upon coordination with a variety of metals, an elementary argument based on Euclidean geometry is presented here that questions the existence of the hypothetical ‘macrocyclic cavity’ within the chelator macrocycle. The geometrical analysis was applied to the complex formed by a Ga3+ ion coordinated to H4DOTA as model compound. Conclusions Application of Euclidean geometry to calculate bond angles in the coordination complex of the ligand H4DOTA with the Ga+3 ion, supposed to incorporate a hypothetical ‘macrocyclic cavity’, revealed that this conceptual entity has no physical reality and, therefore, cannot be considered a meaningful description of a stable structural arrangement for metallic radiopharmaceuticals.

In this study, a novel highly sensitive and selective fluorescent optode membrane aimed at the determination of Pb(II) ion is proposed by incorporating N-(3-(1,4-dioxa-7,13-dithia-10-azacyclopentadecan-10-yl)propyl)-5-(dimethylamino)naphthalene-1-sulfonamide (L) as fluoroionophore in polyvinyl chloride (PVC) containing 2-nitrophenyl octylether (NPOE) as a plasticizer. In addition to high stability and reproducibility, the proposed optosensor showed a unique selectivity toward Pb(II) ion, with a wide linear range of molar concentrations (1.0 × 10−9–1.0 × 10−3 M) and a low detection limit of 7.5 × 10−10 M in solution at pH 5.0. The formation constants of the Pb(II) complexes with the fluoroionophore were evaluated by fitting the fluorescence data with a nonlinear least-squares curve-fitting program, and further information about the structures of the complexes were evaluated based on hybrid-DFT calculations. The optosensor exhibited a fast response time of less than three min, being easily regenerated by exposure to a solution of dithiothreitol. The sensor was applied to the determination of Pb(II) in real samples (canned tuna fish), and it provided satisfactory results comparable to those obtained via atomic absorption spectrometry (AAS). [ABSTRACT FROM AUTHOR]

A combination of NMR studies and quantum chemical calculations were employed to investigate the structure and energetics of Zr4+ chelates of pNO2Bn‐DOTA. We have demonstrated that two discrete regioisomeric chelates are generated during the complex formation. The nitrobenzyl substituent can adopt either an equatorial corner or side position on the macrocyclic ring. These regioisomers are incapable of interconversion and were isolated by HPLC. The corner isomer is more stable than the side, and the SAP conformer of both regioisomers is energetically more favorable than the corresponding TSAP conformer. [ABSTRACT FROM AUTHOR]

Cobalt complexes are extensively studied as bioinspired models for non‐heme oxygenases as they facilitate both the stabilization and characterization of metal‐oxygen intermediates. As an analog to the well‐known Co(cyclam) complex Co{N4} (cyclam=1,4,8,11‐tetraazacyclotetradecane), the CoII complex Co{i‐N4} with the isomeric isocyclam ligand (isocyclam=1,4,7,11‐tetraazacyclotetradecane) was synthesized and characterized. Despite the identical N4 donor set of both complexes, Co{i‐N4} enables the 2e−/2H+ reduction of O2 with a lower overpotential (ηeff of 385 mV vs. 540 mV for Co{N4}), albeit with a diminished turnover frequency. Characterization of the intermediates formed upon O2 activation of Co{i‐N4} reveals a structurally identified stable μ‐peroxo CoIII dimer as the main product. A superoxo CoIII species is also formed as a minor product, as indicated by EPR spectroscopy. In further reactivity studies, the electrophilicity of these in situ generated Co−O2 species was demonstrated by the oxidation of the O−H bond of TEMPO−H (2,2,6,6‐tetramethylpiperidin‐1‐ol) via a H atom abstraction process. Unlike the known Co(cyclam), Co{i‐N4} can be employed in oxygen atom transfer reactions oxidizing triphenylphosphine to the corresponding phosphine oxide highlighting the impact of geometrical modifications of the ligand while preserving the ring size and donor atom set on the reactivity of biomimetic oxygen activating complexes. [ABSTRACT FROM AUTHOR]

Metal complexes inspired by carbonic anhydrase (CA), which is a metalloenzyme containing Zn(II), have been investigated as alternatives for CO2 fixation systems operating under ambient temperature and pressure conditions. In this study, we designed a trinuclear Zn(II) cryptate complex (Zn3L) and demonstrated rapid CO2 fixation with carbonation of CO2 using Zn3L. The CO2 fixation performance of Zn3L surpassed that of a standard CO2 absorbent, KOH(aq) solution, under conditions of the same solute concentration. In addition, the reaction achieved operation without support addition of base, which has been often required in systems of CA‐inspired complexes. Fixed CO2 was released by protonating polyazacryptate ligand (L) and breaking the complex structure, and deprotonation of L induced the reconstruction of Zn3L, allowing it to refix CO2. This reaction mechanism was proposed based on the analysis of operando extended X‐ray absorption fine structure spectroscopy. Zn3L also demonstrated the ability to capture dilute CO2 from air, and the volume of CO2 captured by Zn3L was approximately 2.6 times that captured by the KOH(aq) solution. Our Zn3L exhibited three valuable properties: rapid CO2 fixation without a base, reversibility, and ability to capture dilute CO2; thus Zn3L is a promising candidate as CO2 fixatives. [ABSTRACT FROM AUTHOR]

Fluorene‐based tripyrrane has been used as a fused precursor to synthesize three novel examples of nonaromatic meso‐fused thia and selenabenzihomoporphyrin(2.1.1.1)s by condensing it with appropriate 2,5‐bis(hydroxymethyl)aryl thiophene or selenophene under acid catalyzed conditions. The meso‐fused heterobenzihomoporphyrins contain one fluorene unit, two pyrrole rings and one thiophene/selenophene ring connected via five meso‐carbons in the macrocyclic framework. The macrocycles were thoroughly characterized by HR‐MS, 1D and 2D NMR, absorption, cyclic voltammetry and DFT/TD‐DFT studies. NMR, absorption, and DFT studies indicated the nonaromatic nature of meso‐fused heterobenzihomoporphyrins. The macrocycles displayed one intense band at ∼380 nm along with a shoulder band at 450 nm and a broad band in the region of 590–850 nm which were bathochromically shifted in the monoprotonated derivatives and absorbed prominently in the NIR region with the peak maxima at ∼1035 nm. The electrochemical studies revealed that the macrocycles showed three well‐defined oxidations and reductions, and TD‐DFT studies corroborated experimental observations. [ABSTRACT FROM AUTHOR]

A new series of 16–18 membered cobalt (II) macrocyclic complexes derived by 3,4-diaminobenzophenone have been synthesized. The elemental analysis, FT-IR, 1H NMR, 13C NMR, mass spectrometry, UV–visible, ESR, thermogravimetric analysis, PXRD, SEM studies and DFT analysis were used to characterize these synthesized tetraamide macrocyclic ligands and their cobalt (II) complexes. DFT (density functional theory) calculations were used to calculate quantum chemical parameters. The octahedral geometry of all the complexes has been proposed by DFT and experimental evidences. The synthesized ligands and their cobalt (II) complexes were tested for their in vitro antimicrobial and scavenging activities. Antibacterial activity of synthesized compounds was tested against S. Marcescence, E. coli and S. aureus. The A. Flavus, G. Candidum, F. oxysporum were tested for antifungal properties. The DPPH method was used to further screen the tetraamide macrocyclic ligands and their Co(II) macrocyclic complexes for their in vitro antioxidant properties. Moreover, the complexes are highly active against E. coli bacteria and A. flavus fungi than other microorganisms. The results are well corroborated with molecular docking studies. Furthermore, the purpose of the molecular docking studies was to better understand how these compounds interact with biomolecules. [ABSTRACT FROM AUTHOR]

Many distinct amino acid and aromatic amine-derived transition metal complexes are used as physiologically active compounds. A few Cobalt (II) complexes have been synthesized by reacting cobalt (II) chloride with 1, 8-diaminonapthalene-based tetraamide macrocyclic ligands in an ethanolic media. These synthesized ligands (TAML1-3) and associated Co(II) complexes were fully characterized with various spectroscopic techniques, such as IR, NMR, CHN analysis, EPR, molar conductance, and magnetic susceptibility measurements, TGA, UV–visible spectra, powder X-ray diffraction and DFT analysis. The IR spectra reveal interactions between the core metal atom and ligands through N of 1, 8-diaminonapthalene. The distorted octahedral geometry of synthesized Co(II) macrocyclic complexes were confirmed by ESR, UV–Vis and DFT studies. The synthesized ligands (TAML1-TAML3) and their Co(II) complexes were tested for antimicrobial activity against A. niger, C. albicans, and F. oxysporum in addition to bacteria like S. aureus, B. subtilis, and Gram-negative bacteria like E. coli. The ligand TAML1 and complex [Co(TAML1)Cl2] showed an excellent antibacterial activity. The minimum inhibitory concentration of TAML1 and [Co(TAML1)Cl2] against S. aureus were found to be 7 mm and 10 mm zone of inhibition at 500 ppm, respectively, compared to drug ampicillin (3 mm). Additionally, each molecule exhibited notable antioxidant activity. The biological significance of the synthesized compounds was then evaluated by molecular docking experiments with the active site of the receptor protein such as Sars-Cov-2, C. Albicans, X. campestris and E. coli. The molecular docking assisted data strongly correlated to the experimental approach of antimicrobial activity. [ABSTRACT FROM AUTHOR]

In previous reports, it has been demonstrated that cyclometalated iron(II/III) complexes can be prepared by reacting iron(0) precursors and mercurated or brominated derivatives. However, in this report, the reaction between [Fe3(CO)12] and mercurated 6‐phenyl‐2,2′‐bipyridine or brominated 2,6‐diphenyl‐pyridine pincer derivatives led to compounds in which C(sp2)−C(sp2) bonds have been formed between two ligands. A 16‐electron iron(II) complex (1Cl) bearing a tetradentate ligand originating from the dimerization of 6‐phenyl‐2,2′‐bipyridine was isolated, while a protonated 14‐membered macrocycle with [FeBr4]− as counterion (2) was obtained from 2,6‐diphenyl‐pyridine. Studies by X‐ray diffraction crystallography, NMR, UV‐vis and cyclic voltammetry confirmed the structures. Additionally, the cytotoxicity of the new compounds toward gastric cancer cell lines was evaluated, and it was established that the presence of the iron(II) center was crucial for an elevated activity. [ABSTRACT FROM AUTHOR]

Background: The hypothetical concept of 'macrocyclic cavity' is largely employed as useful model to interpret the affinity of metal ions for the macrocyclic chelating ligand 2,2′,2′′,2′′′-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (H4DOTA). It Is hypothesized that a close matching between the size of the macrocyclic cavity and that of the metallic ion is a key parameter to ensure the high-yield formation of stable coordination metal-DOTA complex. This approach has become popular in the design of radiopharmaceuticals containing radiometals and H4DOTA as chelating group. Results: Based on X-ray structural data of metallic complexes formed by the ligand H4DOTA upon coordination with a variety of metals, an elementary argument based on Euclidean geometry is presented here that questions the existence of the hypothetical 'macrocyclic cavity' within the chelator macrocycle. The geometrical analysis was applied to the complex formed by a Ga3+ ion coordinated to H4DOTA as model compound. Conclusions: Application of Euclidean geometry to calculate bond angles in the coordination complex of the ligand H4DOTA with the Ga+3 ion, supposed to incorporate a hypothetical 'macrocyclic cavity', revealed that this conceptual entity has no physical reality and, therefore, cannot be considered a meaningful description of a stable structural arrangement for metallic radiopharmaceuticals. [ABSTRACT FROM AUTHOR]

Thirty tin (II) metal complexes of the type [SnX2L1-10] (where X= Cl or Br or I; L= macrocyclic ligands (L1 to L10) derived from thiodiglycolic acid and different aliphatic diamines were created and characterized using elemental analysis, X-ray photoelectron (XPS), Infrared, and molar conductivity spectra. An octahedral geometry was found for these compounds. Frontier molecular orbitals (FMO) analysis has been done to obtain the HOMO-LUMO gap. [ABSTRACT FROM AUTHOR]

The extraction ability and selectivity of nonmacrocyclic (8-quinolinol and 2,3-dihydroxynaphthelene) and macrocyclic (sulfur-containing calixarene derivatives) ligands toward rare earth and transplutonium elements in carbonate media was studied. Both macrocyclic and nonmacrocyclic derivatives showed moderate selectivity to americium in the Am/Eu pair (separation factor SF from 1.6 to 14 at pH > 12), and sulfur-containing calixarenes showed also high selectivity to Am in the Am/Cm pair (SF 3–8 at pH > 13). The compounds studied show promise as extractants for group recovery and separation of actinides, and also for separation of rare earth and transplutonium elements in carbonate media. [ABSTRACT FROM AUTHOR]

The effect of different pendant arms on the structural chemistry of the 1,4,7-trithia-10-aza-cyclododecane ([12]aneNS3) macrocycle is discussed in relation to the coordination chemistry of all known functionalized derivatives of [12]aneNS3, which have been structurally characterized. [ABSTRACT FROM AUTHOR]

A flexible macrocyclic ligand with two tridentate {CNC} compartments can host two Cu ions in reversibly interconvertible states, CuICuI (1) and mixed‐valent Cu1.5Cu1.5 (2). They were characterized by XRD and multiple spectroscopic methods, including EPR, UV/Vis absorption and MCD, in combination with TD‐DFT and CASSCF calculations. 2 features a short Cu⋅⋅⋅Cu distance (≈2.5 Å; compared to ≈4.0 Å in 1) and a very high delocalization energy of 13 000 cm−1, comparable to the mixed‐valent state of the biological CuA site. Electron self‐exchange between 1 and 2 is rapid despite large structural reorganization, and is proposed to proceed via a sequential mechanism involving an active conformer of 1, viz. 1′; the latter has been characterized by XRD. Such electron transfer (ET) process is reminiscent of the conformationally gated ET proposed for biological systems. This redox couple is a unique pair of flexible dicopper complexes, achieving fast electron self‐exchange closely related to the function of the CuA site. [ABSTRACT FROM AUTHOR]

In many metalloenzymes, sulfur‐containing ligands participate in catalytic processes, mainly via the involvement in electron transfer reactions. In a biomimetic approach, we now demonstrate the implication of S‐ligation in cobalt mediated oxygen reduction reactions (ORR). A comparative study between the catalytic ORR capabilities of the four‐nitrogen bound [Co(cyclam)]2+ (1; cyclam=1,5,8,11‐tetraaza‐cyclotetradecane) and the S‐containing analog [Co(S2N2‐cyclam)]2+ (2; S2N2‐cyclam=1,8‐dithia‐5,11‐diaza‐cyclotetradecane) reveals improved catalytic performance once the chalcogen is introduced in the Co coordination sphere. Trapping and characterization of the intermediates formed upon dioxygen activation at the CoII centers in 1 and 2 point to the involvement of sulfur in the O2 reduction process as the key for the improved catalytic ORR capabilities of 2. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Efficient synthesis of polyester polyols with tunable molecular weight and microstructures from cyclic anhydride/epoxide mixtures by taking advantage of chain transfer reaction remains a great challenge, because most of the catalysts exhibit poor tolerance to chain transfer agent (CTA). In this contribution, we demonstrated that potassium acetate (KOAc) and 18‐crown‐6 (18‐C‐6) combination has great potential in the synthesis of diverse polyester polyols with controllable molecular weight and high‐end group fidelity. Compared with KOAc, KOAc/18‐C‐6 pair could induce a much faster chain transfer between the active and dormant chains, and thus produce polyester polyols with narrow and monomodal distribution. In addition, polyester polyols could be efficiently prepared in laboratory by using commercially available cyclic anhydride without further purification (containing about 2% diacid residual as CTA) with an extremely low catalyst loading ([catalyst pair] : [anhydride] : [epoxide] = 1 : 50000 : 250000, [catalyst pair] = 0.0004 mol%). KOAc/18‐C‐6 could also promote the self‐switchable copolymerization of cyclic anhydride/epoxide/cyclic ester mixtures. Ring‐ opening copolymerization of cyclic ester was initiated automatically after the full conversion of cyclic anhydride, finally producing polyester polyols with ABA‐type block structure. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Efficient synthesis of polyester polyols with tunable molecular weight and microstructures from cyclic anhydride/epoxide mixtures by taking advantage of chain transfer reaction remains a great challenge, because most of the catalysts exhibit poor tolerance to chain transfer agent (CTA). In this contribution, we demonstrated that potassium acetate (KOAc) and 18‐crown‐6 (18‐C‐6) combination has great potential in the synthesis of diverse polyester polyols with controllable molecular weight and high‐end group fidelity. Compared with KOAc, KOAc/18‐C‐6 pair could induce a much faster chain transfer between the active and dormant chains, and thus produce polyester polyols with narrow and monomodal distribution. In addition, polyester polyols could be efficiently prepared in laboratory by using commercially available cyclic anhydride without further purification (containing about 2% diacid residual as CTA) with an extremely low catalyst loading ([catalyst pair] : [anhydride] : [epoxide] = 1 : 50000 : 250000, [catalyst pair] = 0.0004 mol%). KOAc/18‐C‐6 could also promote the self‐switchable copolymerization of cyclic anhydride/epoxide/cyclic ester mixtures. Ring‐ opening copolymerization of cyclic ester was initiated automatically after the full conversion of cyclic anhydride, finally producing polyester polyols with ABA‐type block structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystal structures and properties of coordination polymers with unsubstituted exo -coordinated macrocyclic ligands were summarized. • The relationship of designable macrocyclic ligand features was correlated to the structure and motifs of coordination polymers. • The guidance for preparing specific coordination polymers with unsubstituted macrocyclic ligands was provided. • Current application and future perspectives of unsubstituted exo -coordinated macrocyclic CPs were discussed. This article overviews the structures and properties of coordination polymers (CPs) with unsubstituted exo -macrocyclic ligands formed by coordinating inner macrocyclic ring donor atom(s) to the metal cation. The unique properties and applications of CPs are not solely dependent on their chemical composition, which includes metal ions, ligands, and anions. They are also influenced by dimensionality and motifs that can be creatively crafted to a certain extent. Due to the cyclic nature, designing macrocyclic ligands to bind specific metal cations, anions, or neutral species is possible if endo -cyclic coordination occurs. The exo -coordination of inner macrocyclic ring donor atoms to a metal ion(s) is a less common coordination mode that favors the formation of polymeric species. The primary focus of this article pertains to the correlation between designable macrocycle characteristics and the structural attributes of emerged CPs. A comprehensive review of crystal structures and structural motifs was done to set specific guidelines for designing macrocyclic ligands that tend to form exo -coordinated CPs. The coordination properties of ligands were analyzed concerning the donor atom set, cavity size, linkers between donor atoms, and anion influence to discuss and set applicable guidelines for designing macrocyclic CPs. The application of the investigated CPs as optical materials and biologically active substances was mentioned, and unfortunately, the broader application of these compounds is scarce. Therefore, future perspectives on these materials, such as gas sorption, conductivity, catalysis, and energetic materials, were conferred. [ABSTRACT FROM AUTHOR]

In this study, a novel highly sensitive and selective fluorescent optode membrane aimed at the determination of Pb(II) ion is proposed by incorporating N-(3-(1,4-dioxa-7,13-dithia-10-azacyclopentadecan-10-yl)propyl)-5-(dimethylamino)naphthalene-1-sulfonamide (L) as fluoroionophore in polyvinyl chloride (PVC) containing 2-nitrophenyl octylether (NPOE) as a plasticizer. In addition to high stability and reproducibility, the proposed optosensor showed a unique selectivity toward Pb(II) ion, with a wide linear range of molar concentrations (1.0 × 10−9–1.0 × 10−3 M) and a low detection limit of 7.5 × 10−10 M in solution at pH 5.0. The formation constants of the Pb(II) complexes with the fluoroionophore were evaluated by fitting the fluorescence data with a nonlinear least-squares curve-fitting program, and further information about the structures of the complexes were evaluated based on hybrid-DFT calculations. The optosensor exhibited a fast response time of less than three min, being easily regenerated by exposure to a solution of dithiothreitol. The sensor was applied to the determination of Pb(II) in real samples (canned tuna fish), and it provided satisfactory results comparable to those obtained via atomic absorption spectrometry (AAS).

Spectroscopic and computational examination of a homologous series of rhodium(I) pybox carbonyl complexes has revealed a correlation between the conformation of the flanking aryl‐substituted oxazoline donors and the carbonyl stretching frequency. This relationship is also observed experimentally for octahedral rhodium(III) and ruthenium(II) variants and cannot be explained through the classical, Dewar–Chatt–Duncanson, interpretation of metal‐carbonyl bonding. Instead, these findings are reconciled by local changes in the magnitude of the electric field that is projected along the metal‐carbonyl vector: the internal Stark effect. [ABSTRACT FROM AUTHOR]

In current research, we determined the stability constants and kinetic properties of Bi3+ complexes with the benzoazacrown ligand H4BATA along with the H4DOTA ligand. Correct determination of the stability constants is possible when equilibrium with the free forms of the cation is observed. Unlike potentiometric titration, it is possible to apply the free‐ion selective radiotracer extraction (FISRE) method with highly stable complexes at low pH values, where the true equilibrium with the free cation forms in the solution is achieved. FISRE clarified the stability constants of Bi3+ complexes with H4BATA towards higher values. According to the UV spectroscopy data, the H4BATA ligand binds Bi3+ at room temperature within a few minutes at pH 1. We also defined the acid‐assisted mechanism of complex dissociation, where monoprotonated and deprotonated forms of the complex were found to be inert. In summary, the H4BATA ligand is highly suitable for use as a component of bismuth‐based radiopharmaceuticals. [ABSTRACT FROM AUTHOR]

The coordination and redox chemistry of aqueous CeIV/III macrocyclic compounds were studied by using the ligands DOTA and DOTP (1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrayl)tetraacetic acid and 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetra(methylene phosphonic acid), respectively). The hydrolysis tendency of the tetravalent cation in the presence of DOTA is shown to result in the formation of a highly ordered, fluorite‐like [CeIV6(O)4(OH)4(H2O)8(DOTAH)4] oxo‐hydroxo structure both in solution and in the solid state. The lifetime of the analogous species formed in the presence of DOTP was found to be much shorter. Spectroscopic measurements of the latter suggest its similarity to the former. Its gradual decomposition in solution leads to the accumulation of the in‐cage complexes [CeIVDOTP] and [CeIIIDOTP(H2O)], which were crystallographically characterized in this study. The redox energetics and spectroscopic characteristics for the transition between these two in‐cage complexes in aqueous solutions were studied as well. Together with the crystallographic structures of the above‐mentioned species, the in‐cage [CeIVDOTA(H2O)] complex structure is presented herein for the first time. An elaborative analysis of the X‐ray crystallographic structural data obtained for the in‐cage complexes studied herein and similar structures published previously suggests that hard‐bonding cyclen‐derived ligands are, counter‐intuitively, better suited for encapsulating, and perhaps kinetically stabilize softer cations than harder ones with DOTP, marked as a possible adequate chelator for the study of the aqueous properties of LnII and AcIII cations. [ABSTRACT FROM AUTHOR]

Four triazamacrocyclic and two tetraazamacrocyclic ligands carrying two and three coordinating donor groups, respectively, and a carbostyril light‐harvesting antenna were synthesized. The antenna was linked to a macrocycle either via secondary or tertiary amide. Complexation with europium (Eu), gadolinium (Gd), terbium (Tb), and ytterbium (Yb) yielded overall +1 or +2 charged species. Paramagnetic 1H NMR, and steady‐state and time‐resolved luminescence spectroscopies showed that the complexes had 1–3 inner‐sphere water molecules and displayed a variety of coordination geometries in solution. The antennae sensitized Eu(III) and Tb(III) emission with quantum yields of 0.3–4.3 % and 9.9–24.5 %, respectively. The addition of excess fluoride or cyanide to buffered Eu(III) complex solutions resulted in anion‐dependent changes. Fluoride addition increased the Eu(III) luminescence intensity by displacing all inner‐sphere water molecules and stabilizing the +3 oxidation state of Eu. Eu(III) luminescence increased up to 25‐fold for one emitter. Cyanide quenched Eu(III) luminescence in all cases despite partial water ligand displacement. [ABSTRACT FROM AUTHOR]

The tetradentate organotelluroether (C9H6NTe)2CH2 ligand has been synthesized and its coordination behaviour with a stoichiometric amount of copper(II) and silver(I) perchlorate and triflate salts has been experimentally investigated. The isolated ligand and metal complexes are characterized by multinuclear (1H, 13C, 125Te) NMR spectroscopy, single crystal X‐ray diffraction, and DFT calculations. The X‐ray analysis revealed the formation of self‐assembled bimetallic complexes with the molecular formula of 2[M(C9H6NTe)2CH2]+ X− [M+=Cu, Ag; X−=ClO4, CF3SO3]. Further, it has been noticed that the metal ions act as a bridging unit to form cationic 8‐membered metallamacrocycles in the chair conformation. The atoms in molecule (AIM) and non‐covalent interactions (NCI) analysis display a weak intramolecular Te⋅⋅⋅Te interaction. Natural bond orbital (NBO) calculations suggest that the tellurium has a rich electron donating ability toward metal ions than the quinoline nitrogen in the complexes. [ABSTRACT FROM AUTHOR]

Enhancement of axial magnetic anisotropy is the central objective to push forward the performance of Single‐Molecule Magnet (SMM) complexes. In the case of mononuclear lanthanide complexes, the chemical environment around the paramagnetic ion must be tuned to place strongly interacting ligands along either the axial positions or the equatorial plane, depending on the oblate or prolate preference of the selected lanthanide. One classical strategy to achieve a precise chemical environment for a metal centre is using highly structured, chelating ligands. A natural approach for axial‐equatorial control is the employment of macrocycles acting in a belt conformation, providing the equatorial coordination environment, and leaving room for axial ligands. In this review, we present a survey of SMMs based on the macrocycle belt motif. Literature systems are divided in three families (crown ether, Schiff‐base and metallacrown) and their general properties in terms of structural stability and SMM performance are briefly discussed. [ABSTRACT FROM AUTHOR]

The synthesis of the unsymmetric macrocyclic tetrakismidazolium salts H4‐4(PF6)4 and H4‐5(PF6)4 featuring a 2,6‐pyridinylene‐ and a 2‐bromo‐1,3‐xylylene‐bridged bisimidazolium unit is described. Reaction of macrocycle H4‐4(PF6)4 with Ag2O yields the tetranuclear complex [6](PF6)4 composed of four AgI ions sandwiched in between two tetra‐NHC ligands. The 2,6‐pyridinylene‐bridged bisimidazolium moiety of the macrocycles can be site‐selectively deprotonated and metallated with RuII or RhI to give the pincer complexes [8](PF6)3‐[11](PF6)3. Introduction of a second metal in these complexes by deprotonation/metallation and oxidative addition to the 2‐bromo‐1,3‐xylylene‐bridged bisimidazolium moiety of the macrocycles proved not possible. [ABSTRACT FROM AUTHOR]

Two close structurally related isomers of nonaromatic meso‐fused dicarbahexaphyrins were synthesized by condensing one equivalent of fluorene based tripyrrane with one equivalent of pentafluorobenzaldehyde in CH2Cl2 under BF3.OEt2 catalyzed conditions. The cis and trans isomers of meso‐fused dicarbahexaphyrins were separated by preparative thin‐layer chromatography and isolated pure macrocycles as green solids in 6–7% yields. NMR spectra of cis and trans isomers are quite distinct from each other and trans isomer was very symmetric and showed fewer resonances than cis isomer in NMR. The NMR study supported the nonaromatic nature of both cis and trans isomers of meso‐fused dicarbahexaphyrins. DFT optimized structures revealed that the cis isomer adopted a singly twisted puckered conformation whereas the trans isomer displayed a saddle like conformation. Both cis and trans isomers almost showed similar nonaromatic absorption features with slight differences in their peak maxima. However, the protonated derivative of cis isomer showed absorption bands in visible‐NIR region with bands extended upto 1000 nm whereas the trans isomer showed strong bands in the visible region. Both cis and trans macrocycles were easier to oxidize and reduce and TD‐DFT studies corroborated with the experimental findings. [ABSTRACT FROM AUTHOR]

NOTA monoamides are commonly and widely used chelators for the complexation of copper radioisotopes applied in molecular imaging and targeted nuclear therapy. However, information about their coordination behavior remains scarce. In this study, two NOTA‐monoamides, N‐ethyl (H2L1) and N,N‐diethyl (H2L2), were synthesized as model ligands and tested to probe differences in their coordination behavior between the secondary and tertiary amide pendant arms for potential applications as copper radioisotope carriers. Our results demonstrated that the solid [Cu(L1)] and [Cu(L2)] complex have a distorted octahedral arrangement, similar to structure of the [Cu(Hnota)] complex. As shown by equilibrium data, the ligands have a slightly lower basicity, and thus complexes with divalent metal ions and LiI have slightly lower stability constants than those of the parent ligand, H3nota. The dissociation constants of the CuII, ZnII and NiII complexes with H2L1 also indicate deprotonation and N‐coordination of the secondary amide group at pH>9. Complexation of CuII ions with the title ligands is slower than that with H3nota but still very fast (quantitative binding in <1 s, pH 2, millimolar concentrations), and CuII complexes of both monoamide ligands are more resistant to acid‐assisted decomplexation than the CuII‐H3nota complex. Therefore, our coordination data highlight that NOTA‐monoamides are suitable chelators for molecular imaging and nuclear medicine. [ABSTRACT FROM AUTHOR]

Incorporation of redox‐inactive metals into redox‐active complexes and catalysts attracts attention for engendering new reactivity modes, but this strategy has not been extensively investigated beyond the first‐row of the transition metals. Here, the isolation and characterization of the first series of heterobimetallic complexes of palladium with mono‐, di‐, and tri‐valent redox‐inactive metal ions are reported. A Reinhoudt‐type heteroditopic ligand with a salen‐derived [N2,O2] binding site for Pd and a crown‐ether‐derived [O6] site has been used to prepare isolable adducts of the Lewis acidic redox‐inactive metal ions (Mn+). Comprehensive data from single‐crystal X‐ray diffraction analysis reveal distinctive trends in the structural properties of the heterobimetallic species, including an uncommon dependence of the Pd⋅⋅⋅M distance on Lewis acidity. The reorganization energy associated with reduction of the heterobimetallic species is strongly modulated by Lewis acidity, with the slowest heterogeneous electron transfer kinetics associated with the strongest incorporated Lewis acids. This hitherto unexplored reorganization energy penalty for electron transfer contrasts with prior thermodynamic studies, revealing that kinetic parameters should be considered in studies of reactivity involving heterobimetallic species. [ABSTRACT FROM AUTHOR]

The dinuclear nickel(II) complex [Ni2LmClO4] + , where Lm represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, reacts with 5-(4-pyridyl)tetrazole (PyrCN4H) to give the dinuclear complex [Ni2Lm(PyrCN4)]+ . The new complex was both isolated as perchlorate or tetraphenylborate salts and characterised by elemental analysis and IR spectroscopy. The structure of [Ni2Lm(PyrCN4)]BPh4 ⋅ MeCN was determined by single crystal X-ray diffraction, showing that tetrazolate units are in a N2,N3-bridging mode to generate dioctahedral N3Ni(µ-S)2(µ-N4CPyr)NiN3 core.

Presented herein is a study of the acid-induced demetalation of two sterically hindered copper corroles, Cu β-octabromo-meso-triphenylcorrole (Cu[Br8TPC]) and β-octakis(trifluoromethyl)-meso-tris(p-methoxyphenyl)corrole (Cu[(CF3)8TpOMePC]). Unlike reductive demetalation, which affords the free-base β-octabromocorrole, demetalation of Cu[Br8TPC] under non- reductive conditions (CHCl3/H2SO4) resulted in moderate yields of free-base 5- and 10-hydroxy isocorroles. The isomeric free bases could be complexed to CoII and NiII, affording stable complexes. Only reductive demetalation was found to work for Cu[(CF3)8TpOMePC], affording a highly saddled, hydrated corrole, H3[5-OH,10-H-(CF3)8TpOMePC], where the elements of water had added across C5 and C10. Interaction of this novel free base with CoII resulted in Co[iso-10-H-[CF3)8TpOMePC], a CoII 10-hydro isocorrole. The new metal complexes were all characterized by single-crystal X-ray diffraction analysis and, despite their sterically hindered nature, were found to exhibit almost perfectly planar isocorrole cores.

Abstract The great potential of subphthalocyanines (SubPcs) to stabilize boron peroxides has been demonstrated. In particular, a subphthalocyanato boron (III) peroxide has been prepared in good yield via boron triflate. This derivative is remarkably stable under ambient conditions and can be fully characterized. The impact of the peroxide group on the structural and optoelectronic properties of SubPc was examined by NMR and UV/Vis spectroscopies, as well as single-crystal X-ray diffraction analysis. Moreover, density functional theory calculations were performed to explain the experimental results. The reactivity of this peculiar boron peroxide as an oxidant and a Lewis base was also studied.

The effect of different pendant arms on the structural chemistry of the 1,4,7-trithia-10-aza-cyclododecane ([12]aneNS3) macrocycle is discussed in relation to the coordination chemistry of all known functionalized derivatives of [12]aneNS3, which have been structurally characterized.

A radical anion −NO2.− is formed upon an electrochemically reversible one‐electron reduction of the square‐planar NiII complex of N‐nitrobenzylcyclam. The −NO2.− group goes to occupy an axial position of the metal ion, thus establishing a significant electronic interaction with the metal center. In particular, the ESR spectrum supports the occurrence of an electron transfer from −NO2.− to the metal, which therefore presents a significant NiI character. On re‐oxidation, the nitrobenzyl side chain detaches and the NiII complex is restored, providing an example of a fully reversible redox driven intramolecular motion. [ABSTRACT FROM AUTHOR]

Protonolysis of [Cp*M] (M=Ga, In, Tl) with [(Me4TACD)H][BAr4Me] (Me4TACD=N,N′,N′′,N′′′‐tetramethyl‐1,4,7,10‐tetraazacyclododecane; [BAr4Me]−=[B{C6H3‐3,5‐(CH3)2}4]−) provided monovalent salts [(Me4TACD)M][BAr4Me], whereas [Cp*Al]4 yielded trivalent [(Me4TACD)AlH][BAr4Me]2. Protonation of [(Me4TACD)Ga][BAr4Me] with [Et3NH][BAr4Me] gave an unusually acidic (pKa(CH3CN)=24.5) gallium(III) hydride dication [(Me4TACD)GaH][BAr4Me]2. Deprotonation with IMe4 (1,3,4,5‐tetramethyl‐imidazol‐ylidene) returned [(Me4TACD)Ga][BAr4Me]. These reversible processes occur with formal two‐electron oxidation and reduction of gallium. DFT calculations suggest that gallium(I) protonation is facilitated by strong coordination of the tetradentate ligand, which raises the HOMO energy. High nuclear charge of [(Me4TACD)GaH]2+ facilitates hydride‐to‐metal charge transfer during deprotonation. Attempts to prepare a gallium(III) dihydride cation resulted in spontaneous dehydrogenation to [(Me4TACD)Ga]+. [ABSTRACT FROM AUTHOR]

Protonolysis of [Cp*M] (M=Ga, In, Tl) with [(Me4TACD)H][BAr4Me] (Me4TACD=N,N′,N′′,N′′′‐tetramethyl‐1,4,7,10‐tetraazacyclododecane; [BAr4Me]−=[B{C6H3‐3,5‐(CH3)2}4]−) provided monovalent salts [(Me4TACD)M][BAr4Me], whereas [Cp*Al]4 yielded trivalent [(Me4TACD)AlH][BAr4Me]2. Protonation of [(Me4TACD)Ga][BAr4Me] with [Et3NH][BAr4Me] gave an unusually acidic (pKa(CH3CN)=24.5) gallium(III) hydride dication [(Me4TACD)GaH][BAr4Me]2. Deprotonation with IMe4 (1,3,4,5‐tetramethyl‐imidazol‐ylidene) returned [(Me4TACD)Ga][BAr4Me]. These reversible processes occur with formal two‐electron oxidation and reduction of gallium. DFT calculations suggest that gallium(I) protonation is facilitated by strong coordination of the tetradentate ligand, which raises the HOMO energy. High nuclear charge of [(Me4TACD)GaH]2+ facilitates hydride‐to‐metal charge transfer during deprotonation. Attempts to prepare a gallium(III) dihydride cation resulted in spontaneous dehydrogenation to [(Me4TACD)Ga]+. [ABSTRACT FROM AUTHOR]

The synthesis of mixed-ligand complexes of the type [M2L(μ-L')]+, where L represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, L' is an azobenzene carboxylate co-ligand, and M = Cd(II), Ni(II) or Zn(II), is reported. A series of new complexes were synthesized, namely [M2L(μ-L')]+ (L' = azo-H, M = Cd (1), Ni (2); L' = azo-OH, M = Zn (3), Ni (4); L' = azo-NMe2, M = Zn (5), Cd (6), Ni (7); L' = azo-CO2Me, M = Cd (8), Ni (9)), and characterized by elemental analysis, electrospray ionization mass spectrometry (ESIMS), IR, UV–vis and NMR spectroscopy (for diamagnetic Zn and Cd complexes) and X-ray single crystal structure analysis. The crystal structures of 3' and 5–8 display an isostructural series of compounds with bridging azobenzene carboxylates in the trans form. The paramagnetic Ni complexes 2, 4 and 7 reveal a weak ferromagnetic exchange interaction with magnetic exchange coupling constant values between 21 and 23 cm−1 (H = −2JS1S2). Irradiation of 1 with λ = 365 nm reveals a photoisomerization of the co-ligand from the trans to the cis form.

A bicyclic ligand, 1,4,7‐triazacyclononane 1,4‐bridged with methylene‐bis(phosphinate) and bearing benzyl substituent on the remaining amino group, was synthesized from N‐benzyl‐tacn and CH2(PO2H2)2 by two sequential Mannich‐type reactions in a high yield. Basicity of the macrocycle is high (pK1=12.25). Complexes with CuII and NiII ions show dimeric structures in the solid state. The structures exhibit distorted octahedral environment with two ring amino groups from one molecule and two oxygen atoms of chelating bis(phosphinate) anion from the other molecule in the equatorial plane, and with the apical positions occupied by the remaining macrocycle amino group and by one of the phosphinate oxygen atoms. The metal ions in the dimers are additionally bridged by one phosphinate group. Stability of the CuII complex is more than ten orders of magnitude lower than that of the [Cu(nota)]− complex due to a different number and different nature of the pendant arms, and inappropriate arrangement of donor atoms in the ligand bicyclic structure. Rigidity of the short P−C−P chain of the geminal methylene‐bis(phosphinate) does not allow simultaneous coordination of both phosphinate groups and the ring amines to the same metal ion. The low solubility of NiII and ZnII complexes disabled determination of their stability constants. [ABSTRACT FROM AUTHOR]

The compound named 4-[10-(4-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)butanamido)decyl]-11-[10-(β, d -glucopyranos-1-yl)-1-oxodecyl]-1,4,8,11-tetraazacyclotetradecane-1,8-diacetic acid is a newly synthesised molecule capable of binding in vivo to albumin to form a bioconjugate. This compound was given the name, GluCAB(glucose-chelator-albumin-binder)-maleimide- 1. Radiolabelled GluCAB-maleimide- 1 and subsequent bioconjugate is proposed for prospective oncological applications and works on the theoretical dual-targeting principle of tumour localization through the "enhanced permeability and retention (EPR) effect" and glucose metabolism. The precursor, GluCAB-amine- 2 , and subsequent GluCAB-maleimide- 1 was synthesised via sequential regioselective, distal N-functionalisation of a cyclam template with a tether containing a synthetically-derived β-glucoside followed by a second linker to incorporate a maleimide moiety for albumin-binding. GluCAB-amine- 2 was radiolabelled with [64Cu]CuCl 2 in 0.1 M NH 4 OAc (pH 3.5, 90 °C, 30 min), purified and converted post-labeling in 0.01 M PBS to [64Cu]Cu-GluCAB-maleimide- 1. Serum stability and protein binding studies were completed according to described methods. Healthy BALB/c ice (three groups of n = 5) were injected intravenously with [64Cu]Cu-TETA, [64Cu]Cu-GluCAB-amine- 2 or [64Cu]Cu-GluCAB-maleimide- 1 and imaged using microPET/CT at 1, 2, 4, 8 and 24 h post-injection. Biodistribution of the compounds were determined ex vivo after 24 h using gamma counting. GluCAB-maleimide- 1 was synthesised in five consecutive steps with an overall yield of 11%. [64Cu]Cu-GluCAB-amine- 2 (97% labelling efficiency) was converted to [64Cu]Cu-GluCAB-maleimide- 1 (93% conversion; 90% radiochemical purity). Biodistribution analysis indicated that the control compounds were rapidly and almost completely excreted as compared to [64Cu]Cu-GluCAB-maleimide- 1 that exhibited a prolonged biological half-life (6–8 h). Both, [64Cu]Cu-GluCAB-maleimide- 1 and -amine- 2 were excreted through the hepatobiliary system but a higher hepatic presence of the albumin-bound compound was noted. This initial evaluation paves the way for further investigation into the tumour targeting potential of [64Cu]Cu-GluCAB-maleimide- 1. An efficient targeted radioligand will allow for further development of a prospective theranostic agent for more personalized patient treatment which potentially improves overall patient prognosis, outcome and health care. GluCAB is a newly synthesised radioligand designed to bind in vivo to albumin (HSA) for the purpose of development as a potential dual-targeting oncological theranostic agent. Subsequent to its synthesis and 64Cu-radiolabelling, this radioligand has shown a prolonged circulation time in healthy mice but with appropriate systemic clearance within 24 h. This radioligand met the criteria to be further investigated for tumour targeting and uptake. [Display omitted] [ABSTRACT FROM AUTHOR]

A number of novel tetracyano‐substituted dihydrotetraaza[14]annulene (DH‐TAA) analogues were obtained in a simple and convenient way by one‐pot synthesis. The ligands, as well as their complexes with nickel(II), copper(II) and palladium(II) ions were characterised, including X ray structures for seven compounds. The X‐ray analysis shows relatively short distances between tetraazamacrocyclic rings (3.0–3.3 Å), resulting from the presence of strong π‐π interactions. Moreover, some of synthesised compounds can easily be modified in order to attach commonly used reactive groups, which makes them very promising as future components of π‐interaction based supramolecular systems [ABSTRACT FROM AUTHOR]

Host–guest binding behavior of macrocyclic hosts is significantly influenced by the shapes and sizes of the hosts. In particular, closing/opening the apertures of the hosts controls the guest uptake/release. A post‐metalation modification method was used to achieve the open/close conversions. The starting open complex, [LCo2(pip)4](OTf)2, was efficiently converted to the closed complex, [LCo2(hda)2](OTf)2, which has a doubly bridged structure. The conversion of this closed complex to the open complex [LCo2(hda)2(OAc)]+ was too slow to be completed, but this gate‐opening was dramatically accelerated by the addition of Na+. The Na+ binding was also significantly enhanced by the gate‐opening, that is, conversion of [LCo2(hda)2]2+ to [LCo2(hda)2(OAc)]+. [ABSTRACT FROM AUTHOR]

The formation of a macrocyclic hexanuclear silver complex with a giant cavity (diameter ∼16.5 Å) is reported. Six silver centers are sandwiched by two molecules of a macrocyclic ligand possessing six pap (2‐[(pyridin‐2‐ylmethylene)amino]phenol) chelating units, and the metals are arranged on the wall of the internal cavity. Various analytical techniques revealed that each pap binds to the silver as an NN bidentate ligand. [ABSTRACT FROM AUTHOR]