Hexaazamacrocyclic Complexes Research Articles

Dual visible and near-infrared luminescence in mononuclear macrocyclic erbium(III) complexes via ligand and metal centred excitation.

Considering the structural design of some of the scarce molecular-based Er-centred emitters in the literature, we explored the optical properties of three ErIII hexaazamacrocyclic complexes, namely Er-EDA (1), Er-OPDA(2) and Er-DAP(3). The macrocyclic ligands in these complexes differ in the lateral spacers, and are derived from 2,6-pyridine-dicarbaldehyde and ethylenediamine (EDA), ortho-phenylenediamine (OPDA) or 1,3-diaminopropane (DAP). Upon ligand-centred excitation, the bluish-green and green emissions of the ErIII ion were detected only for the complexes containing macrocycles with aliphatic spacers (1 and 3), which evidenced that these ligands can sensitize the ErIII luminescence. On the other hand, the ligand derived from the aromatic diamine (2) does not sensitize the ErIII luminescence. Energy transfer mechanisms, temperature sensing, CIE coordinates and CCT values were analyzed. Besides the excitation in the ligands, the erbium-centred excitation at 980 nm allowed the detection, in all cases, of bluish-green, green and red up-converted emissions, and also the downshifted NIR emission. The possible mechanisms involved in these transitions were described and analyzed according to the available data.

Sorting Phenomena and Chirality Transfer in Fluoride-Bridged Macrocyclic Rare Earth Complexes.

The reaction of fluoride anions with mononuclear lanthanide(III) and yttrium(III) hexaaza-macrocyclic complexes results in the formation of dinuclear fluoride-bridged complexes. As indicated by X-ray crystal structures, in these complexes two metal ions bound by the macrocycles are linked by two or three bridging fluoride anions, depending on the type of the macrocycle. In the case of the chiral hexaaza-macrocycle L1 derived from trans-1,2-diaminocyclohexane, the formation of these μ2-fluorido dinuclear complexes is accompanied by enantiomeric self-recognition of macrocyclic units. In contrast, this kind of recognition is not observed in the case of complexes of the chiral macrocycle L2 derived from 1,2-diphenylethylenediamine. The reaction of fluoride with a mixture of mononuclear complexes of L1 and L2, containing two different Ln(III) ions, results in narcissistic sorting of macrocyclic units. Conversely, a similar reaction involving mononuclear complexes of L1 and complexes of achiral macrocycle L3 based on ethylenediamine results in sociable sorting of macrocyclic units and preferable formation of heterodinuclear complexes. In addition, formation of these heterodinuclear complexes is accompanied by chirality transfer from the chiral macrocycle L1 to the achiral macrocycle L3 as indicated by CPL and CD spectra.

Syntheses, crystal structures, spectroscopy, and catalytic properties of two nickel-based hexaazamacrocyclic complexes with carboxylate ligands

Two new hexaazamacrocyclic nickel(II) complexes with the formula [NiL1(4-nba)2] (1) and [NiL2(sal)2] (2) (L1=3,10-dioctyl-1,3,5,8,10,12-hexaazacyclotetradecane, L2=3,10-diisobutyl-1,3,5,8,10,12-hexaazacyclotetradecane, 4-nba=p-nitrobenzoate, and sal=salicylate) were synthesized at room temperature. These complexes were characterized by physico-chemical and spectroscopic methods as well as single-crystal X-ray diffraction analysis. The coordination geometry in complexes 1 and 2 exhibit a distorted octahedron around the nickel(II) ion with hexaazamacrocyclic unit in the equatorial positions and two p-nitrobenzoate (or salicylate) anions in the axial positions. The degradation of methyl orange by potassium persulfate (KPS) in the presence of complex 1 (or 2) oxidation system occurred to near completion in 60min compared to only 55% with KPS alone under UV light irradiation. Thus, both complexes in cooperation with KPS could be an attractive choice for degradation of organic pollutants for environmental remediation.

Synthesis, characterization and catalytic studies by zeolite encapsulated hexaazamacrocyclic complexes of nickel(II) and copper(II)

The nickel(II) and copper(II) complexes of the 16-membered 1,3,6,9,11,14-hexaazatricyclo[12.2.1.16,9]octadecane (THA) were synthesized by in situ one-pot template method. The nickel(II)THA and copper(II)THA complexes are represented as NTHA and CTHA respectively. The encapsulation of free complexes (FC) (i.e. NTHA and CTHA) in the cavities of zeolite-Y was achieved by ship-in-bottle method. The zeolite encapsulated metal complexes (ZEMC) are represented as NTHAY and CTHAY. The retention of the free complex with ZEMC was investigated by spectral, thermal, sorption and microscopic techniques (i.e., FTIR, ESI-mass, DRS/UV–visible, XPS, TGA, XRD, nitrogen adsorption isotherm, SEM and TEM). The NTHA, CTHA, NTHAY and CTHAY were employed as catalysts for the oxidation of Reactive Red 198 (RR) and Phenol Red (PR) dyes under UV irradiation. The ZEMC exhibits higher catalytic activity for the degradation of dyes, when compared to that of FC. The reusable photocatalysts show comparable activity to that of the fresh catalysts.

Syntheses and characterization of various supramolecular compounds from the self-assembly of nickel(II) hexaaza macrocyclic complex with carboxylic acid derivatives

The supramolecular compounds [Ni(C16H38N6)(2,7-NDC)] (1), [Ni(C16H38N6)(H2O)2] [Ni(C16H38N6)(1,3,5-BTC)2] (2), and [Ni(C16H38N6)(nicotinate)2] (3) were prepared via self-assembly of a nickel(II) azamacrocyclic complex containing butyl pendant groups, [Ni(C16H38N6)(ClO4)2], with 2,7-naphthalenedicarboxylic acid (2,7-NDC), 1,3,5-benzenetricarboxylic acid (1,3,5-BTC), and nicotinic acid, respectively. These compounds were characterized by elemental analysis, infrared spectroscopy, magnetic measurement and single crystal X-ray diffraction. In 1, the nickel(II) azamacrocyclic complex links two 2,7-NDC2− ligand at the axial position and each 2,7-NDC2− ligand binds two adjacent nickel(II) azamacrocylic units with syn–syn and syn–anti orientations to form a zigzag 1-D chain structure. The zigzag 1-D chain tends to interact via offset face-to-face π–π interactions with adjacent 1-D chains, which leads to a 2-D supramolecular network. Compound 1 exhibits very weak antiferromagnetic interactions through the bridged 2,7-NDC2− ligand within the 1-D zigzag chains (g=2.11 and J/κB=−0.29cm−1). Compound 2 consists of two nickel(II) azamacrocyclic cation units and one nickel(II) azamacrocylic anion unit. Each nickel(II) ion in the cation and anion units is coordinated with four nitrogen atoms of the azamacrocyclic ligand in the equatorial plane, and two oxygen atoms from the water molecules or BTC3− ligands at the axial positions, to display a distorted octahedral geometry. The cation and anion units form intermolecular hydrogen bonds, giving rise to a 3-D supramolecular structure. In 3, the coordination environment around the nickel(II) ion has a distorted octahedral geometry via coordination with four nitrogen atoms of the azamacrocyclic ligand in the equatorial plane, and two nicotinate anions at the axial positions and intramolecular hydrogen bonding interactions between the amine groups and nicotinate anions stabilize the molecular structure.

Aromatic Lateral Substituents Influence the Excitation Energies of Hexaaza Lanthanide Macrocyclic Complexes: A Wave Function Theory and Density Functional Study.

The high interest in lanthanide chemistry, and particularly in their luminescence, has been encouraged by the need of understanding the lanthanide chemical coordination and how the design of new luminescent materials can be affected by this. This work is focused on the understanding of the electronic structure, bonding nature, and optical properties of a set of lanthanide hexaaza macrocyclic complexes, which can lead to potential optical applications. Here we found that the DFT ground state of the open-shell complexes are mainly characterized by the manifold of low lying f states, having small HOMO-LUMO energy gaps. The results obtained from the wave function theory calculations (SO-RASSI) put on evidence the multiconfigurational character of their ground state and it is observed that the large spin-orbit coupling and the weak crystal field produce a strong mix of the ground and the excited states. The electron localization function (ELF) and the energy decomposition analysis (EDA) support the idea of a dative interaction between the macrocyclic ligand and the lanthanide center for all the studied systems; noting that, this interaction has a covalent character, where the d-orbital participation is evidenced from NBO analysis, leaving the f shell completely noninteracting in the chemical bonding. From the optical part we observed in all cases the characteristic intraligand (IL) (π-π*) and ligand to metal charge-transfer (LMCT) bands that are present in the ultraviolet and visible regions, and for the open-shell complexes we found the inherent f-f electronic transitions on the visible and near-infrared region.

Synthesis, crystal structure, and properties of an azido-bridged 1D nickel hexaazamacrocyclic complex

A new complex of [Ni(C15H32N6)(N3)]ClO4 · H2O was obtained by the reaction of macrocyclic precursor complex [Ni(C15H32N6)]ClO4 with sodium azide in water solution, and characterized by EA, IR, PXRD and single-crystal X-ray diffraction (CIF file CCDC no. 930570). Single X-ray diffraction analysis reveals that the central nickel(II) ion displays six-coordinate octahedral coordination geometry by coordination with four nitrogen atoms of N3− macrocyclic ligand and two nitrogen atoms of ligand. In this complex, each μ1,3-N3− binds two nickel(II) ions, resulting a 1D chain. Magnetic measurements have been performed on the complex, showing strong antiferromagnetic coupling interaction within the metal center.

Synthesis and Characterization of New Polyaza Non-macrocyclic and Macrocyclic Nickel(II) Complexes Containing One 1,3-Diazacyclohexane Ring

A new nickel(II) complex ( = 1-(2-aminoethyl)-3-(N-{2-aminoethyl}aminomethyl-1,3-diazacyclohexane) containing one 1,3-diazacyclohexane ring has been prepared selectively by the metal-template condensation of formaldehyde with N-(2-aminoethyl)-1,3-propanediamine and ethylenediamine at room temperature. The complex reacts with nitroethane and formaldehyde to yield the pentaaza macrocyclic complex ( = 8-methyl-8-nitro-1,3,6,10,13-pentaazabicyclo[13.3.1]heptadecane) bearing one C- pendant arm. The reduction of by using Zn/HCl produces ( = 8-amino-8-methyl-1,3,6,10,13-pentaazabicyclo[13.3.1]heptadecane) bearing one coordinated C- pendant arm that is readily protonated in acid solutions. The hexaaza macrocyclic complex ( = 8-phenylmethyl-8-nitro-1,3,6,8,10,13-hexaazabicyclo[13.3.1]heptadecane) bearing one N- pendant arm has also been prepared by the reaction of with benzylamine and formaldehyde. The nickel(II) complexes of , , and have square-planar coordination geometry in the solid states and in nitromethane. However, they exist as equilibrium mixtures of the square-planar (L = , , or ) and octahedral species in various coordinating solvents (S); the proportion of the octahedral species is strongly influenced by the ligand structure and the nature of the solvent. Synthesis, spectra, and chemical properties of the nickel(II) complexes of are described.

Self‐Assembled Tetragonal Prismatic Molecular Cage Highly Selective for Anionic π Guests

The metal-directed supramolecular synthetic approach has paved the way for the development of functional nanosized molecules. In this work, we report the preparation of the new nanocapsule 3·(CF(3)SO(3))(8) with a A(4 B(2) tetragonal prismatic geometry, where A corresponds to the dipalladium hexaazamacrocyclic complex Pd-1, and B corresponds to the tetraanionic form of palladium 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (2). The large void space of the inner cavity and the supramolecular affinity for guest molecules towards porphyrin-based hosts converts this nanoscale molecular 3D structure into a good candidate for host-guest chemistry. The interaction between this nanocage and different guest molecules has been studied by means of NMR, UV/Vis, ESI-MS, and DOSY experiments, from which highly selective molecular recognition has been found for anionic, planar-shaped π guests with association constants (K(a)) higher than 10(9) M(-1) , in front of non-interacting aromatic neutral or cationic substrates. DFT theoretical calculations provided insights to further understand this strong interaction. Nanocage 3·(CF(3)SO(3))(8) can not only strongly host one single molecule of M(dithiolene)(2) complexes (M=Au, Pt, Pd, and Ni), but also can finely tune their optical and redox properties. The very simple synthesis of both the supramolecular cage and the building blocks represents a step forward for the development of polyfunctional supramolecular nanovessels, which offer multiple applications as sensors or nanoreactors.

Synthesis and Chiral Recognition of Nickel(II) Macrocyclic Complex with (R)‐Naphthylethyleneamine Pendant Groups and its Self‐Assembled Framework

A novel nickel(II) hexaaza macrocyclic complex, [Ni(L(R,R))](ClO(4))(2) (1), containing chiral pendant groups was synthesized by an efficient one-pot template condensation and characterized (L(R,R) ═1,8-di((R)-α-methylnaphthyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The crystal structure of compound 1 was determined by single-crystal X-ray analysis. The complex was found to have a square-planar coordination environment for the nickel(II) ion. Open framework [Ni(L(R,R))](3) [C(6)H(3)(COO)(3)](2) (2) was constructed from the self-assembly of compound 1 with deprotonated 1,3,5-benzenetricarboxylic acid, BTC(3-). Chiral discrimination of rac-1,1'-bi-2-naphthol and rac-2,2,2-trifluoro-1-(9-anthryl)ethanol was performed to determine the chiral recognition ability of the chiral complex (1) and its self-assembled framework (2). Binaphthol showed a good chiral discrimination on the framework (2). The optimum experimental conditions for the chiral discrimination were examined by changing the weight ratio between the macrocyclic complex 1 or self-assembled framework 2 and racemates. The detailed synthetic procedures, spectroscopic data including single-crystal X-ray analysis, and the results of the chiral recognition for the compounds are described.

A novel hexaaza macrocyclic complex [CuL](ClO4)2

A novel N4-planar Cu(II) macrocyclic fragment, namely, [CuL](ClO4)2 (I) (L = 4-methyl-1,3,6,8,11,14-hexaazatricyclo[12.2.1.18,11)octadecane has been prepared from a simple template condensation reaction and structurally characterized for the first time. The complex of I crystallizes in the monoclinic system of space group P21/c with unit cell parameters: a = 17.124(10), b = 9.255(5), c = 14.053(8) A and β = 111.262(7)°.

Fourteen membered hexaaza copper macrocycle: Synthesis, characterization, crystal structures and the consequence of anion coordination

Fourteen membered hexaaza macrocyclic complexes of the type [CuLX2] (where L = 3,10-bis(benzyl)1,3,5,8,10,12-hexaazacyclotetradecane and X=ClO4-, SCN−) and [CuL(CH3CN)2](PF6)2(CH3CN)2 have been synthesized by template assisted condensation reaction. They have been characterized by spectral and X-ray crystallographic techniques. It was of interest to investigate the effect of anions on the gross geometry and chemical properties of Cu(II) ion. The crystal structure of all the complexes show axially elongated octahedral geometry with weakly coordinated anions. The macrocyclic ring adopts the trans-III configuration with six- and five-membered chelate rings in chair and gauche conformation, respectively. The IR and other spectral properties are consistent with the result of X-ray diffraction. It was observed that in the solid state the arrangement of the coordination sphere is distorted octahedral whereas in solution, a square-planar structure is predominant. The molar conductivity of the complexes indicates that the axially bonded anions are almost entirely dissociated in acetonitrile solution. The EPR spectra of complexes 1–3 are axial and consistent with a dx2-y2 ground state.

A two-dimensional coordination polymer with a brick wall structure: Synthesis, crystal structure, and properties of a nickel(II) hexaazamacrocyclic complex with azido ligand

A 2D hexaazamacrocyclic complex trans-[Ni(hto)(N 3) 2] ( 2) (hto = 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1 6,9]octadecane) was synthesized from the mononuclear fragment [Ni(hto)]Cl 2·2H 2O ( 1) and sodium azido in methanol solution. The crystal structure of complex 2 is centrosymmetric and the nickel(II) atom has an axially elongated octahedral geometry with four nitrogen atoms from the hexaazamacrocycle and two nitrogen atoms from the azido ligands. Each trans-[Ni(hto)(N 3) 2] unit extends its structure to form a 2D brick wall network based on hydrogen bonding interactions between the nitrogen atoms of azido ligands and the secondary amine of the macrocycle in neighboring four units. Complex 2 exhibits blue fluorescent emission in the solid state at room temperature.

ChemInform Abstract: The Synthesis of New Binucleating Polyaza Macrocyclic and Macrobicyclic Ligands: Dioxygen Affinities of the Cobalt Complexes.

Abstract Six macrocyclic and five macrobicyclic Schiff bases have been synthesized by condensation of rigid dialdehydes with diethylenetriamine or tris (aminoethyl) amine, and have been reduced to the corresponding saturated hexaaza macrocyclic complexes or octaaza macrobicyclic complexes. Six of the dicobalt complexes of these new ligands were found to be oxygen carriers.

Synthesis and characterization of macrocyclic nickel(II) complexes with α-methylbenzyl groups as chiral pendants

Novel nickel(II) hexaaza macrocyclic complexes, [Ni(LR,R)](ClO4)2 (1) and [Ni(LS,S)](ClO4)2 (2), containing chiral pendant groups have been synthesized by an efficient one-pot template condensation and characterized (LR,R/S,S=1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. Each complex has a square-planar coordination environment for the nickel(II) ion, and is either an R or an S enantiomorph depending on the pendant groups. The circular dichroism spectrum of 1 showed a negative, positive and negative peak at 345, 440, and 492nm, respectively, and that of 2 exhibited an enantiomeric pattern.

Template synthesis and physicochemical studies of 14-membered hexaazmacrocyclic complexes with Co(II), Ni(II), Cu(II) and Zn(II): a comparative spectroscopic approach on DNA binding with Cu(II) and Ni(II) complexes

A new series of 14-membered pendant arm hexaazamacrocyclic complexes of the type [MLX2] · [M = Co(II), Ni(II), Cu(II) or Zn(II) for X = Cl; Co(II), Ni(II), Cu(II) or Zn(II) for X = NO3] has been synthesized by metal template condensation of 1,2-phenylenediamine and 1,4-phenylenediamine with formaldehyde in methanol. The mode of bonding and overall geometry of these complexes have been deduced by elemental analyses, molar conductance values, FT-IR, 1H-NMR, 13C-NMR, EPR, ESI-mass and UV–VIS along with magnetic measurement studies. The fluorescence and UV–VIS studies revealed a significant binding ability to DNA.

3,7,11,19,23,27-Hexaazatricyclo[27.3.1.113,17]tetratriaconta-1(32),13,15,17(34),29(33),30-hexaene hexachloride tetrahydrate

The title compound, C28H52N6 6+·6Cl−·4H2O, is a dinucleating 28-membered centrosymmetric hexa­azamacrocyclic complex. The macrocyclic ligand adopts a chair-like conformation, with the crystallographic inversion center located in the macrocyclic cavity. The six chloride ions and four water mol­ecules are situated symmetrically outside the macrocyclic cavity. The crystal structure is stabilized by N—H⋯Cl, N—H⋯O and O—H⋯Cl hydrogen bonds.

Oxidative Dehydrogenation of Hexaaza Macrocyclic Nickel(II) Complexes Bearing Two N-Alkyl Pendant Arms: Preparation of New Complexes Containing Imidoylamidine Linkages

Metal-promoted reactions of coordinated organic compounds, such as oxidative dehydrogenation reactions, have attracted particular attention because of their potential applications in organic chemistry, catalysis, and biochemistry. The saturated tetraaza macrocyclic nickel(II) complex [NiL] is known to react with HNO3 to yield [NiL] containing four isolated imino groups. The reaction of [NiL] with HNO3 produces [NiL] and [NiL] containing only one or two imino groups in the six-membered chelate ring(s). On the other hand, [NiL] reacts with H2O2 to produce the dinuclear complex [Ni2L], in which two unsaturated macrocyclic units are linked together by a C=C bond. Literature up to date clearly shows that the number and position of the imino groups in the product is strongly influenced by the structural characteristics of the macrocycle. In this work, we attempted the oxidative dehydrogenation of the hexaaza macrocyclic complexes [NiL] and [NiL] bearing two N-alkyl groups and prepared [NiL] (L = 1,8dimethyl-1,3,6,8,10,13-hexaazacyclotetradeca-2,6,9,13-tetraene) and [NiL] (L = 1,8-dibenzyl-1,3,6,8,10,13-hexaazacyclotetradeca-2,6,9,13-tetraene) containing two imidoylamidine (–N=CH-N(R)-CH=N-) linkages. Interestingly, [NiL](ClO4)2 consists of two stable conformational isomers and forms a 2D supramolecular structure. Synthesis and chemical properties of [NiL] and [NiL] are reported. Imidoylamidines are widely used as precursors for the synthesis of various organic compounds and polymers, exhibiting useful properties. Recently, some nickel(II) complexes of imidoylamidines (HN=CR-NH-CR=NH; R = alkyl group) have been also prepared and characterized. However, [NiL] and [NiL] are rare examples of 14membered hexaaza macrocyclic complexes that contain two imidoylamidine linkages.

Synthesis, crystal structures and properties of two novel macrocyclic nickel(II) and copper(II) complexes

Two new 14-membered hexaaza macrocyclic complexes with the formulae [NiL](ClO 4) 2·CH 3COCH 3 ( 1) and [CuL](ClO 4) 2·CH 3COCH 3 ( 2), where L = 3,10-bis(2-thiophenemethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, have been synthesized and characterized by elemental analyses, single-crystal X-ray diffraction analyses, electronic spectra, IR and TG-DTA. In 1, the nickel(II) ion is four-coordinated with four nitrogen atoms from the macrocycle and forms a square-planar coordination geometry. In 2, the copper(II) ion is six-coordinated with four nitrogen atoms from the macrocyclic ligand in the equatorial plane and two oxygen atoms from the perchlorate anions in the axial position exhibiting an elongated octahedron coordination geometry. The two complexes present two different molecular arrangements in which the [ML] 2+ (M = Ni, Cu) cation arrays in the manner of M(1)M(2)M(1)… in sequence. The pendant thiophene groups of the neighboring macrocycles have no π⋯π interactions. All the ClO 4 - anions and acetone molecules are involved in hydrogen-bonding interactions with the macrocyclic ligand.

Synthesis and Characterization of New Hexaaza Macrotricyclic Copper(II) Complexes with a 5-6-6-6 Chelate Ring Sequence

The design and synthesis of new polyaza macrocyclic complexes have received much attention, since their chemical properties are strongly influenced by the structural characteristics of the ligands. Metal-directed condensation reactions of coordinated amines with formaldehyde are useful for the preparation of polyaza macrocyclic complexes containing N-CH2-N linkages. 4-13 For instance, the squareplanar complexes [ML] and [ML] (M = Cu(II) or Ni(II)) with a 5-6-5-6 chelate ring sequence have been prepared by the one-pot reaction of Eq. (1) or (2). Although numbers of polyaza macrocyclic complexes containing N-CH2-N linkages have been prepared and investigated, most of them contain 14-membered hexaaza macrocycles and have squareplanar coordination polyhedron with a 5-6-5-6 chelate ring sequence. Some 15-membered hexaaza macrocyclic complexes with a 5-6-5-5-4 chelate ring sequence, such as [NiL] (Eq. (3)), have been also investigated. As far as we know, however, the preparation of 15-membered hexaaza macrocyclic copper(II) or nickel(II) complexes with a 5-6-66 chelate ring sequence is not reported to date. Herein, we report new copper(II) complexes [CuL] and [CuL] with a 5-6-6-6 chelate ring sequence. They were prepared by the metal-directed reactions (Eqs. (4) and (5)) of appropriate amines with formaldehyde. Interestingly, [CuL] is considerably inert against decomposition even in concentrated acid solution, unlike [CuL] and other polyaza macrocyclic copper(II) complexes with a 5-6-6-6 chelate ring sequence. Synthesis and chemical properties of the copper(II) complexes are described.