Macrocyclic Donor Research Articles

Stabilisation of Bromenium Ions in Macrocyclic Halogen Bond Complexes.

Halenium ions (X+) are highly reactive electron deficient species that are prevalent transient intermediates in halogenation reactions. The stabilisation of these species is especially challenging, with the most common approach to sequester reactivity through the formation of bis-pyridine (Py) complexes; [(Py)2X]+. Herein, we present the first example of a macrocyclic stabilisation effect for halenium species. Exploiting a series of bis-pyridine macrocycles, we demonstrate the first example of utilising the macrocyclic ligands to stabilise halenium species via the endotopic complexation of a bromenium cation, impressively facilitating the isolation of a bench stable 'Br+ NO3-' species. Solid state X-ray crystallographic structural comparison of macrocyclic Br(I) complexes with Ag(I) and Au(I) analogues provides insightful information concerning similarities and stark contrasts in halenium/metal cation coordination behaviors. Furthermore, the first chemical ligand exchange reactions of Br(I) complexes are reported between acyclic [(Py)2Br]+ species and a bis-pyridine macrocyclic donor ligand which importantly highlights a macrocycle effect for halenium cation stabilisation in the solution phase.

Stabilisation of Bromenium Ions in Macrocyclic Halogen Bond Complexes

Halenium ions (X+) are highly reactive electron deficient species that are prevalent transient intermediates in halogenation reactions. The stabilisation of these species is especially challenging, with the most common approach to sequester reactivity through the formation of bis‐pyridine (Py) complexes; [(Py)2X]+. Herein, we present the first example of a macrocyclic stabilisation effect for halenium species. Exploiting a series of bis‐pyridine macrocycles, we demonstrate the first example of utilising the macrocyclic ligands to stabilise halenium species via the endotopic complexation of a bromenium cation, impressively facilitating the isolation of a bench stable ‘Br+ NO3‐’ species. Solid state X‐ray crystallographic structural comparison of macrocyclic Br(I) complexes with Ag(I) and Au(I) analogues provides insightful information concerning similarities and stark contrasts in halenium/metal cation coordination behaviors. Furthermore, the first chemical ligand exchange reactions of Br(I) complexes are reported between acyclic [(Py)2Br]+ species and a bis‐pyridine macrocyclic donor ligand which importantly highlights a macrocycle effect for halenium cation stabilisation in the solution phase.

Exploring the Spatial Arrangement of Simple 18-Membered Hexaazatetraamine Macrocyclic Ligands in Their Metal Complexes.

Hexaazamacrocyclic Schiff bases have been extensively combined with lanthanoid (Ln) ions to obtain complexes with a highly axial geometry. However, the use of flexible hexaazatetraamine macrocycles containing two pyridines and acyclic spacers is rather uncommon. Accordingly, we obtained [DyL(OAc)2]OAc·7H2O·EtOH and [DyLMe2(Cl)2]Cl·2H2O, where L and LMe2 are the 18-membered macrocycles 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane and 3,10-dimethyl-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane, respectively, which contain ethylene and methylethylene spacers between their N3 moieties. [DyL(OAc)2]OAc·7H2O·EtOH represents the first crystallographically characterized lanthanoid complex of L, while [DyLMe2(Cl)2]Cl·2H2O contributes to increasing the scarce number of LnIII compounds containing LMe2. Furthermore, the crystal structure of L·12H2O was solved, and it was compared with those of other related macrocycles previously published. Likewise, the crystal structures of the DyIII complexes were compared with those of the lanthanoid and d-metal complexes of other 18-membered N6 donor macrocycles. This comparison showed some effect of the spacers employed, as well as the influence of the size of the ancillary ligands and the metal ion. Additionally, the distinct folding behaviors of these macrocycles influenced their coordination geometries. Moreover, the luminescent properties of [DyL(OAc)2]OAc·7H2O·EtOH and [DyLMe2(Cl)2]Cl·2H2O were also investigated, showing that both complexes are fluorescent, with the emission being sensitized by the ligands.

Engineering the Macrocyclic Donor Structures towards Deep-Blue Thermally Activated Delayed Fluorescence Emitters.

Deep-blue thermally activated delayed fluorescence (TADF) molecules present promising potential in organic light-emitting diodes (OLEDs), especially for display applications. Here, an efficient molecular engineering approach to modifying the donor or acceptor features of the D-π-A-configured TADF molecules for deep-blue emission is reported. By introducing oxygen and sulfone as a bridge unit onto the macrocyclic donor, two emitters, c-ON-MeTRZ and c-NS-MeTRZ, are synthesized and characterized, respectively. The reduced donor strength of c-ON-MeTRZ and c-NS-MeTRZ as compared to that of the model molecule c-NN-MeTRZ leads to blue-shifted emissions with high photoluminescence quantum yields (PLQYs) and retains TADF characters, while the new emitter c-NN-MePym with the most blue-shifted emission only exhibits a pure fluorescent nature because of the electron-accepting feature of pyrimidine that is insufficient for inducing the TADF property. In the presence of macrocyclic donors, these new emitters show high horizontal dipole ratios (Θ// = 85-89%), which are beneficial for improving the light out-coupling efficiency. Deep-blue TADF OLEDs incorporating c-ON-MeTRZ as an emitter doped in the mCPCN host achieves a high maximum external quantum efficiency (EQEmax) of 30.2% together with 1931 Commission Internationale de I'Eclairage (CIE) coordinates of (0.14, 0.13), while the counter device employing c-NS-MeTRZ as a dopant gives EQEmax of 15.4% and CIE coordinates of (0.14, 0.09). The EQEmax of c-ON-MeTRZ- and c-NS-MeTRZ-based devices can be significantly improved to 34.4 and 29.3%, respectively, with a polar host DPEPO, which stabilizes the charge transfer (CT) S1 state to give lower ΔEST for improving the reverse intersystem crossing process. The efficient TADF character, high PLQYs, and high anisotropic emission dipole ratios work together to render the superior electroluminescence (EL) efficiencies. Based on the detailed characterizations of physical properties, theoretical analyses, and comprehensive study on the corresponding devices, a clear structure-property-performance relationship has been successfully established to verify the effective molecular design strategy of modulating the macrocyclic donor characters for efficient deep-blue TADF emitters.

A benzothiazole-coupled NS4-donor macrocycle and its complexation-based dual-channel sensing for Hg2+: the influence of anions and structure–function relationship

A benzothiazole-coupled NS4-macrocycle as a dual-probe chemosensor was synthesized for the selective detection of Hg2+. The coordination abilities of anions highly influence Hg2+ sensing.

Highly Efficient Blue Thermally Activated Delayed Fluorescence Emitters with a Triphenylamine‐Based Macrocyclic Donor

AbstractThis work reports the incorporation of a triphenylamine‐based macrocyclic donor to design new donor‐π‐acceptor‐configured blue thermally activated delayed fluorescence (TADF) emitters. The X‐ray structure analyses manifest the degree of twisted conformations that can be modulated by methyl substituents of the π‐bridge and macrocyclic donor, leading to well‐separated highest occupied natural transition orbital and lowest unoccupied natural transition orbital frontier orbitals, thus sufficiently small singlet–triplet energy difference (ΔEST) for TADF. The theoretical analyses elucidate the structure–property relationship and reveal the beneficial effect of macrocyclic donor on increasing reverse intersystem crossing (RISC) process that can contribute to improved triplet‐upconversion efficiency. The blue device employing c‐NN‐TRZ as emitter gave a maximum external quantum efficiecny (EQEmax) of 26.3% as compared to that (19.1%) of the device using the model compound DPA‐MeTRZ without the macrocyclic donor, suggesting the contribution of macrocyclic donor to enhance device performance. Benefiting from the combined advantages of macrocyclic donor and methyl substituents, the device incorporating c‐NN‐MeTRZ as emitter achieves an outstanding EQEmax of 32.2%, which is attributed to the more horizontally oriented emission dipoles as well as the significantly accelerated RISC rate constant (kRISC) resulting from reduced ΔEST. This work represents a new strategy of designing twisted TADF emitter incorporating macrocyclic donor to achieve highly efficient blue device.

Macrocyclic Donor–Acceptor Dyads Composed of a Perylene Bisimide Dye Surrounded by Oligothiophene Bridges

AbstractTwo macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) dye have been synthesized via a platinum‐mediated cross‐coupling strategy. The crystal structure of the double bridged PBI reveals allsyn‐arranged thiophene units that completely enclose the planar PBI chromophore via a 12‐membered macrocycle. The target structures were characterized by steady‐state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor–acceptor dyads show ultrafast Förster Resonance Energy Transfer and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent.

Synthesis and spectral studies of lanthanide metal tetraaza macrocyclic complexes

Intrinsic kinetic stability is one of the reasons to grab the attraction of lanthanide macrocyclic ligands. Lanthanide coordination chemistry and derivatives were extensively studied. 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DO 3 A) ligands were widely studied. Aza-macrocycles like [12]aneN 4 (cyclen) were developed significantly with consider to lanthanide coordination chemistry and derivatives like DO 3 A have been briefly studied. Diacids and Diamino ligands are interesting because they offer donor sets of seven or eight atoms that can recapitulate lanthanide ions, which prefer eight or nine coordination geometry in traditional manner. The alleviate with which cyclen can be functionalized has also led to the development of ligands that not only prevent the approach of solvent molecules, but also include aromatic chromophores thus overcoming the naturally low molar absorbtivities of lanthanide ions. The present study is aimed to synthesize few biologically significant (NNNN) donor macrocycles and their transition metal complexes in alcoholic media using microwave protocol. Macrocyclic ligands were synthesized by incorporating of 3,5-Diaminbenzoicacid, phthalic acid and 3,4-Dimamin pyridine in 1:1:1 M ratio. The synthesized ligands and their macrocyclic metal complexes have been analyzed by elemental analysis, conductance measurement, magnetic measurement, and their structure configuration has been confirmed by various spectroscopic (FT-IR, EPR, UV − Vis, VSM and TGA) techniques. The spectral studies confirm the binding sites the nitrogen atom of the macrocycles and octahedral geometry has been assigned to the metal complexes.

Structural and Luminescence Properties of Heteronuclear Gold(I)/Thallium(I) Complexes Featuring Metallophilic Interactions Tuned by Quinoline Pendant Arm Derivatives of Mixed Donor Macrocycles.

Reaction of the heterometallic complex [{Au(C6F5)2}Tl]n with the quinoline pendant arm derivatives L1 and L2 of the mixed donor macrocycles [12]aneNS2O and PhenNS2 affords the new Au(I)/Tl(I) complexes [{Au(C6F5)2}Tl(L1)] (1), [{Au(C6F5)2}Tl(L2)] (2), [{Au(C6F5)2Tl}{Au(C6F5)2Tl(L1)}]2 (3), and [{Au(C6F5)2Tl}{Au(C6F5)2Tl(L2)}]n (4) depending on the reaction molar ratios used. These complexes present different optical properties strictly related to their structural features and to the presence of Au(I)···Tl(I) metallophilic interactions, which are finely tuned by the coordinating quinoline moiety and have been studied experimentally and theoretically via TD-DFT calculations.

Reversible Self-Assembly of Supramolecular Vesicles and Nanofibers Driven by Chalcogen-Bonding Interactions.

Chalcogen-bonding interactions have been viewed as new non-covalent forces in supramolecular chemistry. However, harnessing chalcogen bonds to drive molecular self-assembly processes is still unexplored. Here we report for the first time a novel class of supra-amphiphiles formed by Te···O or Se···O chalcogen-bonding interactions, and their self-assembly into supramolecular vesicles and nanofibers. A quasi-calix[4]chalcogenadiazole (C4Ch) as macrocyclic donor and a tailed pyridine N-oxide surfactant as molecular acceptor are designed to construct the donor-acceptor complex via chalcogen-chalcogen connection between the chalcogenadiazole moieties and oxide anion. The affinity of such chalcogen-bonding can dictate the geometry of supra-amphiphiles, driving diverse self-assembled nanostructures. Furthermore, the reversible disassembly of these structures can be promoted by introducing competing halide ions or by decreasing systemic pH.

DFT Analysis of Spin Crossover in Mn(III) Complexes: Is a Two-Electron S = 2 to S = 0 Spin Transition Feasible?

Six-coordinate, rigorously octahedral d4 Mn(III) spin crossover (SCO) complexes are limited by symmetry to an S = 1 (intermediate spin, IS) to S = 2 (high spin, HS) transition. In order to realize the potential S = 0 to S = 2 transition, a lower symmetry and/or change in coordination number is needed, which we explore here computationally. First, a number of complexes are analyzed to develop a reliable and relatively fast DFT protocol for reproducing known Mn(III) spin state energetics. The hybrid meta-GGA functional TPSSh with a modest split valence plus polarization basis set and an empirical dispersion correction is found to predict correctly the ground spin state of Mn(III) complexes, including true low-spin (LS) S = 0 systems, with a range of donor sets including the hexadentate [N4O2] Schiff base ligands. The electronic structure design criteria necessary for realizing a ΔS = 2 SCO transition are described, and a number of model complexes are screened for potential SCO behavior. Five-coordinate trigonal-bipyramidal symmetry fails to yield any suitable systems. Seven-coordinate, approximately pentagonal bipyramidal symmetry is more favorable, and when a known pentadentate macrocyclic donor is combined with π-acceptor axial ligands, a novel Mn(III) complex, [Mn(PABODP)(PF3)2]3+ (PABODP = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene), is predicted to have the right spin state energetics for an S = 0 to S = 2 transition. Successful synthesis of such a complex could provide the first example of a ΔS = 2 SCO transition for d4 Mn(III). However, the combination of a rigid macrocycle and a high coordination number dilutes the stereochemical activity of the d electrons, leading to relatively small structural changes between HS and LS systems. It may therefore remain a challenge to realize strong cooperative effects in Mn(III) systems.

Synthesis, spectral and extended spectrum beta-lactamase studies of transition metal tetraaza macrocyclic complexes.

Urinary tract infections commonly occur in humans due to microbial pathogens invading the urinary tract, which can bring about a range of clinical symptoms and potentially fatal sequelae. The present study is aimed at addressing the development of a new antimicrobial agent against extended spectrum beta lactamase (ESBL) producing E. coli bacteria. We have synthesised some biologically potent (NNNN) donor macrocycles (L 1 =dibenzo[f,n]dipyrido[3,4-b:4',3'-j][1,4,9,12]tetraazacyclohexadecine-6,11,18,23(5H,12H, 7H, 24H)-tetraone, and L 2 =6,12,19,25-tetraoxo-4,6,11,12,16,18,23,24-octahydrotetrabenzo [b,g,k,p][1,5,10,14]tetra azacyclooctadecine-2,13-dicarboxylic acid) and their Ti and Zr metal complexes in alcoholic media using microwave protocol. Macrocyclic ligands were synthesised by incorporating of 3,5-diaminobenzoic acid, phthalic acid and 3,4-diaminopyridine in 1:1:1 molar ratio. The macrocyclic ligands and their metal complexes have been characterised by elemental analysis, conductance measurement, magnetic measurement and their structure configurations have been determined by various spectroscopic (FTIR, 1H/13C NMR, UV-Vis, LC-MS mass, XRD and TGA) techniques. [ZrL2Cl2]Cl2 metal complex shows excellent antibacterial activity against ESBLs. A zone of inhibition and minimum inhibitory concentration was determined by McFarland and the dilution method, respectively. The spectral studies confirm the binding sites of the nitrogen atom of the macrocycles. An octahedral geometry has been assigned to the metal complexes based on the findings.

A double decker type complex: copper(i) iodide complexation with mixed donor macrocycles via [1 : 1] and [2 : 2] cyclisations.

19-membered and a 38-membered macrocycles obtained as a mixture via respective [1 : 1] and [2 : 2] cyclisations were separated and their coordination behaviours with copper(i) iodide were investigated. One of the notable products isolated is a tetranuclear bis(macrocycle) complex with the larger macrocycle adopting a double decker type structure. Furthermore, removal of the lattice solvent molecules in the above complex in air motivates the displacement of the double decker units along the a-axis by sliding in a single-crystal-to-single-crystal manner.

Syntheses and Crystal Structures of a Novel 20‐Membered N3O2‐Donor Macrocycle and Its Disilver(I) Bis(Macrocycle) and Monocadmium(II) Complexes

Syntheses and Crystal Structures of a Novel 20‐Membered <scp>N₃O₂</scp>‐Donor Macrocycle and Its Disilver(I) Bis(Macrocycle) and Monocadmium(<scp>II</scp>) Complexes

Synthesis and characterization of metal-free phthalocyanine containing 16-membered N2S2-donor macrocycles linked to a 2-pyridinyl methyl moiety

A metal-free phthalocyanine ( H 2 Pc ) containing 16-membered N 2 S 2 -donor macrocycles linked to a 2-pyridinyl methyl moiety has been prepared via cyclotetramerization of a phthalonitrile. A metal-free phthalocyanine ( H 2 Pc ) containing four diazadithiamacrocycles a with 2-pyridinyl methyl groups attached was synthesized via cyclotetramerization of 4,5- bis {2-[13(2-pyridinylmethyl)-1,9-dithia-5,13-diazacyclohexadecanyl-5]ethyl} thiophthalonitrile in the presence of DBU as a strong organic base. New compounds were characterized by a combination of elemental analysis, 1 H NMR, 13 C NMR, IR, UV/vis, and MS spectral data.

Template synthesis and spectral studies on mononuclear complexes of chromium(III) and manganese(II) with tetradentate N4 donor macrocycles

The present article deals with the synthesis, spectral characterization and antimicrobial activity of a series of new complexes of chromium(III) and manganese(II)of general formula [Cr(Macn)Cl2]·Cl and [Mn(Macn)Cl2] respectively. These complexes were prepared via template reaction by mixing methanolic solution of diacetyldihydrazone, diacids (oxalic acid, succinic acid, glutaric acid and adipic acid) with CrCl3·6H2O and MnCl2·4H2O in 2:2:1M ratios respectively. The newly synthesized complexes were characterized on the basis of chemical analysis and spectral studies like IR, UV, ESR and X-ray diffraction. An octahedral structure has been proposed for the chromium(III) and manganese(II)macrocyclic complexes. The synthesized complexes were further tested in vitro against fungi and bacteria in order to assess their antibacterial and antifungal activities. The studies demonstrate that the complexes possess antimicrobial properties.

Synthesis and characterization of NiII, CuII and ZnII complexes of N,O-mixed donor macrocycles derived from a-diketones and 1,13-diamino-4, 7,1 0-trioxatridecane

Synthesis and characterization of NiII, CuII and ZnII complexes of N,O-mixed donor macrocycles derived from a-diketones and 1,13-diamino-4, 7,1 0-trioxatridecane

Synthesis, structural elucidation and antimicrobial effectiveness of coordination entities of cobalt (II) and nickel (II) derived from 9,17-diaza-2,6,11,15-tetrathia-1,7,10,16-(1,2)-tetrabenzenacyclooctadecaphan-8,17-diene

9,17-Diaza-2,6,11,15-tetrathia-1,7,10,16-(1,2)-tetrabenzenacyclooctadecaphan-8,17-diene, macrocycle was synthesized, thereafter formulation and designing strategies applied for the preparation of coordination entities of Co(II) and Ni(II). Coordination behaviour of N 2 S 4 donor macrocycle towards metal ion(s) was assessed by physiochemical measurements and spectral investigations viz . elemental analysis, molar conductance, magnetic susceptibility measurements, infrared, UV-Vis, 1 H and 13 C NMR, mass spectroscopy, electron paramagnetic resonance (EPR), cyclic voltammetry and molecular modeling. Side-by-side comparison of the spectral findings exposed different geometrical aspects of macrocycle and coordination entities. Cyclic voltammogram showed fully oxidized and reduced species in one unified experiment. Macrocycle and coordination entities were screened for antimicrobial effectiveness (antifungal properties against Aspergillus-niger ).

Spectral, structural elucidation and coordination abilities of Co(II) and Mn(II) coordination entities of 2,6,11,15-tetraoxa-9,17-diaza-1,7,10,16-(1,2)-tetrabenzenacyclooctadecaphan-8,17-diene

Designing tactics were tailored and followed by synthetic and formulation methodologies to prepare 2,6,11,15-tetraoxa-9,17-diaza-1,7,10,16-(1,2)-tetrabenzenacyclooctadecaphan-8,17-diene. Spectral techniques (MS, infrared, 1H NMR, 13C NMR, electronic and EPR), physiochemical measurements (elemental analysis, molar conductance and magnetic susceptibility), electrochemistry (cyclic voltammetry) and classical mechanics (molecular modeling) were employed for structural elucidation of Co(II) and Mn(II) coordination entities having N 2O 4 chromophore. Comparative spectral analysis revealed legating nature of N 2O 4 donor macrocycle and confirmed host/guest connectivity between ligand and metal(s). Mass spectrometry (MS) determined 1:1 stoichiometry in CEs. Further electrochemical study confirmed change in oxidation and reduction patterns of CEs. Inhibiting potential (antifungal screened against Aspergillus flavus) showed enhanced antimicrobial properties of CEs as compared to ligand. Molecular modeling was employed to find out different molecular features along with their stabilization energies.

Selective transport of Ag (I) ion across a bulk liquid and polymer membranes incorporated with di- N-benzylated O 3N 2 donor macrocycles

The selective bulk liquid membrane and polymer membrane transports of Ag (I) from an aqueous solution containing seven metal cations, Co (II), Ni (II), Cu (II), Zn (II), Ag (I), Cd (II) and Pb (II), was studied. The source phases contained equimolar concentrations of the above-mentioned cations, with the source and receiving phases being buffered at pH 5.0 and 3.0, respectively. Ag (I) ion transport occurred with a good efficiency from the aqueous source phases across the bulk liquid membrane and polymer membrane (derived from cellulose triacetate) containing ligand 1 as the ionophores, into the aqueous receiving phases. Clear transport selectivity for Ag (I) was observed using ligand 1. There was no selectivity for the cations using ligand 2 in the both bulk liquid membrane and polymer membrane transports.