Metal complexes of dipyridine hexaaza macrocycles. Structural differences between 18- and 20-membered macrocycles on complexation

Branco, Luı́s C.; Costa, Judite; Delgado, Rita; Drew, Michael G. B.; Félix, Vítor; Goodfellow, Brian J.

doi:10.1039/b204189h

Cited by 21 publications

(36 citation statements)

References 32 publications

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“…The 1 H-NMR spectra of both the binuclear Zn(II) macrocyclic complexes recorded in DMSO-d 6 show a sharp signal in the 1.81-1.83 ppm region corresponding to imine methyl (CH 3 C ¼ N; 12H) protons [34]. A broad signal observed in the 4.45-4.50 ppm region may be ascribed to the secondary amino protons (C-NH-N; 4H) of the condensed N,N¢-diacetylhydrazine moiety.…”

Section: H-nmr Spectramentioning

confidence: 99%

“…Among polyazamacrocycles, the tetraazacycloalkanes [3,4] are the most studied due to their applications in variety of catalytic, biochemical and industrial processes [5]. The hexaazamacrocycles are known to give several mononuclear and binuclear complexes [6]. However, less work has been reported for higher membered polyazamacrocyclic complexes.…”

Section: Introductionmentioning

confidence: 98%

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Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

Khan

Naseem

Azim

et al. 2007

Transition Met Chem

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A novel series of 16-membered binuclear complexes of octaazatetraimine ligand, ½M 2 LX 4 [M = Mn II , Co II , Ni II , Cu II and Zn II ; X = Cl or NO 3 ] have been synthesized by metal template condensation reactions of o-phenylenediamine with N,N¢-diacetylhydrazine in 1:1:1 molar ratio in methanol. The proposed stoichiometry and the bonding of the macrocyclic moiety to metal ions along with the overall stereochemistry have been derived from the results of elemental analyses, magnetic susceptibility, conductivity data and the spectral data revealed from FT-IR, 1 H-NMR , ESI mass, UV-visible studies. An octahedral geometry has been envisaged for Mn II , Co II , and Ni II complexes while a slight distortion in octahedral geometry has been noticed for Cu II complexes. The low conductivity data of all the complexes suggest their non-ionic nature.

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Section: H-nmr Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

Khan

Naseem

Azim

et al. 2007

Transition Met Chem

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“…The X-ray single-crystal structure of the dicopper complex with a related ligand [20]py 2 N 4 , having propyl spacers between the pyridine heads (see Scheme 1), showed that two water molecules are directly coordinated to each copper centre, [9] and the same species was confirmed in aqueous solution. [13] Each copper centre is located at each head of the macrocycle, displaying a distorted square-pyramidal coordination environment with the basal plane defined by three consecutive nitrogen donors and one water molecule and the apical position fulfilled with the other water molecule at a longer distance than the equatorial one. [9] Therefore the presence of [Cu 2 L(H 2 O) 4 ] 4+ confirmed in our solution results led us to assume that an iden-tical structure is adopted by the complex studied in the present work.…”

Section: Potentiometric Measurementsmentioning

confidence: 99%

Hexaazamacrocycle Containing Pyridine and Its Dicopper Complex as Receptors for Dicarboxylate Anions

Delgado

Félix

2005

Eur J Inorg Chem

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The host–guest binding interactions of the hexaazamacrocycle [26]py2N4, in its tetraprotonated form H4[26]py2N44+ as well as in its dicopper(II) complex [Cu2([26]py2N4)(H2O)4]4+, with dicarboxylate anions of different stereoelectronicrequirements, such as oxalate (ox2–), malonate (mal2–), succinate (suc2–), fumarate (fu2–) and maleate (ma2–), were evaluated. The association constants were determined using potentiometric methods in aqueous solution, at 298.0 K and 0.10 mol·dm–3 KCl. These values for the tetraprotonated ditopic receptor with the dicarboxylate anions revealed that the main species in solution corresponds to the formation of {H4[26]py2N4(A)}2+ (pH ≈ 4–9), A being the substrate anion. The values determined are not especially high, but the receptor exhibits selectivity for the malonate anion. The study of the cascade complexes revealed several species in solution, involving mononuclear and dinuclear complexes, mainly protonated and hydrolysed species, as well as the expected complexes [Cu2([26]py2N4)(A)(H2O)x]2+ or [Cu2([26]py2N4)(A)2(H2O)y]. Ox2– and mal2– form cascade complexes with only one anion, which will necessarily bridge the two copper atoms because of the symmetrical arrangement of the dinuclear complex. The two other studied anions, suc2– and ma2–, form species involving two substrate anions, although species with only one suc2– anion were also found. UV/Vis and EPR spectroscopy have shown that the dicopper complex can operate as a sensor to detect and quantitatively determine oxalate spectrophotometrically because of the red shift of the maximum of the visible band observed by addition of ox2– to an aqueous solution of the dinuclear copper complex. However the selectivity of [Cu2([26]py2N4)(H2O)4]4+ as a receptor for ox2– in the studied series is not sufficiently high to detect ox2– spectrophotometrically in the presence of the other anions. Molecular dynamics simulations indicated that the H4[26]py2N44+ receptor provides a large and flexible cavity to accommodate the studied anions. Molecular recognition is based in electrostatic interactions rather than in multiple hydrogen‐bonding interactions acting cooperatively. By contrast, the [Cu2([26]py2N4)]4+ receptor has a well‐shaped cavity with adequate size to uptake these anions as bridging ligands with formation of four Cu–O bonds. The ox2– anion is encapsulated within the cascade complex while the remaining anions are located above the N6 macrocyclic plane, suggesting a selective coordination behaviour of this receptor. In spite of our molecular simulation being carried out in gas phase, the modelling results are consistent with the solution studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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“…In the latter complex the copper adopts an octahedral geometry. 3 The crystal structure of the copper() complex with py 2 [14]pyN 3 is not available, but that of nickel exhibits an elongated cis-octahedral geometry. 25, 26 The electronic parameters also reveal that [Cu( [18]py 2 N 4 )] 2ϩ has a stronger ligand field than that of [Cu(Me 2 [28]py 2 N 6 )] 2ϩ , which is much closer to that of [Cu(py 2 [14]pyN 3 )] 2ϩ .…”

Section: Uv-vis Of the Nickel(ii) And Copper(ii) Complexes And Epr Sp...mentioning

confidence: 99%

“…The metals are encapsulated in hexa-co-ordinate environments, the macrocycles adopting a twisted helical topology. 3 In spite of the dimensions of both macrocycles their cavities are too small to incorporate two metal centres without the folding of the macrocycle. In fact, to the best of our knowledge, dinuclear complexes with [18]py 2 N 4 and [20]py 2 N 4 are not to be found in the Cambridge Structural Data Base (CSD).…”

Section: Introductionmentioning

confidence: 99%

Metal complexes of a dipyridine octaazamacrocycle: stability constants, structural and modelling studies

et al. 2003

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Metal complexes of dipyridine hexaaza macrocycles. Structural differences between 18- and 20-membered macrocycles on complexation

Cited by 21 publications

References 32 publications

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

Hexaazamacrocycle Containing Pyridine and Its Dicopper Complex as Receptors for Dicarboxylate Anions

Metal complexes of a dipyridine octaazamacrocycle: stability constants, structural and modelling studies

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