Polynuclear metal complexes of ligands containing phenolic units

Separation Performance of Membranes Containing Ultrathin Surface Coating of Metal-Polyphenol Network

Metal-polyphenol networks (MPNs) are being used as versatile coatings for regulating membrane surface chemistry and for the formation of thin separation layers. The intrinsic nature of plant polyphenols and their coordination with transition metal ions provide a green synthesis procedure of thin films, which enhance membrane hydrophilicity and fouling resistance. MPNs have been used to fabricate tailorable coating layers for high-performance membranes desirable for a wide range of applications. Here, we present the recent progress of the use of MPNs in membrane materials and processes with a special focus on the important roles of tannic acid-metal ion (TA-Mⁿ⁺) coordination for thin film formation. This review introduces the most recent advances in the fabrication techniques and the application areas of TA-Mⁿ⁺ containing membranes. In addition, this paper outlines the latest research progress of the TA-metal ion containing membranes and summarizes the role of MPNs in membrane performance. The impact of fabrication parameters, as well as the stability of the synthesized films, is discussed. Finally, the remaining challenges that the field still faces and potential future opportunities are illustrated.

Impact of tannic acid on nisin encapsulation in chitosan particles

This study investigates the effect of addition of tannic acid on nisin encapsulated in chitosan matrices. Composite materials were prepared using a mild, environmentally friendly procedure, ionotropic gelation of chitosan by sodium tripolyphosphate in the presence of nisin (N) at different concentrations. In two parallel sets of preparations, tannic acid (TA) was added at 10:1 and 5:1 N:TA, respectively. The obtained particles were characterized by FTIR, SEM, size, zeta potential, encapsulation efficiency, loading capacity, and ratio of residual free amino groups. The kinetics of nisin release from the particles was studied to assess the role of TA as a potential modulator thereof. Its addition resulted in enhanced release, higher at lower N:TA ratio. An additional benefit was that TA, a strong antioxidant, imparted antioxidant activity to the composites. Antimicrobial turbidimetric tests were performed against one gram-positive bacterium (Staphylococcus aureus) and two gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), all relevant for the food, pharmaceutical, and cosmetic industries. All the composites showed synergistic effects against all the bacteria tested. The positive coaction was stronger against the gram-negative species. This is remarkable since nisin by itself has not known activity against them.

A New Family of Macrocyclic Polyamino Biphenolic Ligands: Acid-Base Study, Zn(II) Coordination and Glyphosate/AMPA Binding

In this study, the ligands 23,24-dihydroxy-3,6,9,12-tetraazatricyclo[17.3.1.1(14,18)]eicosatetra-1(23),14,16,18(24),19,21-hexaene, L1, and 26,27-dihidroxy-3,6,9,12,15-pentaazatricyclo[20.3.1.1(17,21)]eicosaepta-1(26),17,19,21(27),22,24-hexaene, L2, were synthesized: they represent a new class of molecules containing a biphenol unit inserted into a macrocyclic polyamine fragment. The previously synthesized L2 is obtained herein with a more advantageous procedure. The acid-base and Zn(II)-binding properties of L1 and L2 were investigated through potentiometric, UV-Vis, and fluorescence studies, revealing their possible use as chemosensors of H⁺ and Zn(II). The new peculiar design of L1 and L2 afforded the formation in an aqueous solution of stable Zn(II) mono (LogK 12.14 and 12.98 for L1 and L2, respectively) and dinuclear (LogK 10.16 for L2) complexes, which can be in turn exploited as metallo-receptors for the binding of external guests, such as the popular herbicide glyphosate (N-(phosphonomethyl)glycine, PMG) and its primary metabolite, the aminomethylphosphonic acid (AMPA). Potentiometric studies revealed that PMG forms more stable complexes than AMPA with both L1- and L2-Zn(II) complexes, moreover PMG showed higher affinity for L2 than for L1. Fluorescence studies showed instead that the L1-Zn(II) complex could signal the presence of AMPA through a partial quenching of the fluorescence emission. These studies unveiled therefore the utility of polyamino-phenolic ligands in the design of promising metallo-receptors for elusive environmental targets.

Tannic acid-based functional coating: surface engineering of membranes for oil-in-water emulsion separation

Recent progress in the tannic acid-based functional coating for surface engineering of membranes toward oil-in-water emulsion separation is summarized.

Syntheses, structures, and magnetic properties of a series of Mn-M-Mn trinuclear complexes with different spin configurations

A series of trinuclear complexes, [MnII2Y^III(L)₂(HL)₂(NO₃)₃][Y^III(NO₃)₅]·7H₂O (1'), [MnII2Gd^III(HL)₄(NO₃)₄]₂[MnII2Gd^III(L)(HL)₃(NO₃)₄][Gd^III(NO₃)₅]₄·2(o-Xy)·12H₂O (2') and [MnII3(L)(HL)₂(NO₃)₄](NO₃)·1.25(p-Xy) (3'), were synthesized using a β-diketone ligand HL (HL = 1,3-bis(pyridin-2-yl)propane-1,3-dione). X-ray structural analyses revealed that each complex has a trinuclear core with an Mn(II)-M-Mn(II) arrangement (M = Y^III (1), Gd^III (2), and Mn^II (3)). In 1' with a diamagnetic Y(III) ion, negligible antiferromagnetic interactions between terminal Mn(II) ions are operative. On the other hand, 2' shows ferromagnetic interactions between Mn(II) and Gd(III) ions, affording a spin ground state of S_T = 17/2. The homometallic Mn(II)₃ complex of 3' has an S_T = 5/2 spin ground state resulting from the antiferromagnetic interactions between neighboring Mn(II) ions. The maximum magnetic entropy change (-ΔS_m) of 1'-3' was estimated to be 12.3, 24.8, and 8.0 J kg^-1 K^-1, respectively.

Proton controlled synthesis of two dicopper(II) complexes and their magnetic and biomimetic catalytic studies together with probing the binding mode of the substrate to the metal center

This paper describes the synthesis, and structural and spectroscopic characterizations of two doubly bridged dicopper(II) complexes, [Cu₂(μ-H₂L)(μ-OMe)](ClO₄)₄·2H₂O (1) and [Cu₂(μ-L)(μ-OH)](ClO₄)₂ (2), with a binucleating ligand (HL) derived from the Schiff base condensation of DFMP and N,N-dimethyldipropylenetriamine, and their biomimetic catalytic activities were related to CAO and phenoxazinone synthase using 3,5-di-tert-butylcatechol and o-aminophenol (OAPH), respectively, as model substrates. Structural studies reveal that the major differences in these structures appear to be from the distinct roles of the tertiary amine groups of the ligands, which are protonated in 1, whereas it coordinates the metal centers in 2. Magnetic studies disclose that two copper(II) centers are strongly antiferromagnetically coupled with slightly different J values, which is further interpreted and discussed. They exhibited very different biomimetic catalytic activities; whereas 2 is an efficient catalyst, complex 1 showed somewhat lower substrate oxidation. The higher reactivity in 2 is rationalized by the strong involvement of the tertiary amine group of the Schiff base ligand, where the substrate oxidation is favored because of the transfer of protons from the substrate to the tertiary amine group, showing the importance of the functional groups in proximity to the bimetallic active site. Emphasis was also given to probing the binding mode of the substrate using an electronically deficient tetrabromomocatechol (Br₄CatH₂) and the isolated compound [Cu₆(μ-HL)₂(μ-OH)₂(Br₄Cat)₄](NO₃)₂·4H₂O (3) which suggests that monodentate asymmetric binding of 3,5-di-tert-butylcatechol and OAPH occurs during the course of the catalytic reaction.

A novel triple aqua-, phenoxo- and carboxylato-bridged dinickel(ii) complex, its magnetic properties, and comparative biomimetic catalytic studies with analogous dinickel(ii) complexes

A unique triply bridged dinickel(ii) complex and two doubly bridged dinickel(ii) complexes are reported, and their magnetic properties and comparative biomimetic catalytic performances are studied.

Applications of tannic acid in membrane technologies: A review

Today, membrane technologies play a big role in chemical industry, especially in separation engineering. Tannic acid, one of the most famous polyphenols, has attracted widespread interest in membrane society. In the past several years, researches on the applications of tannic acid in membrane technologies have grown rapidly. However, there has been lack of a comprehensive review for now. Here, we summarize the recent developments in this field for the first time. We comb the history of tannic acid and introduce the properties of tannic acid firstly, and then we turn our focus onto the applications of membrane surface modification, interlayers and selective layers construction and mixed matrix membrane development. In those previous works, tannic acid has been demonstrated to be capable of making a great contribution to the membrane science and technology. Especially in membrane surface/interface engineering (such as the construction of superhydrophilic and antifouling surfaces and polymer/nanoparticle interfaces with high compatibility) and development of thin film composite membranes with high permselectivity (such as developing thin film composite membranes with ultrahigh flux and high rejection), tannic acid can play a positive and great role. Despite this, there are still many critical challenges lying ahead. We believe that more exciting progress will be made in addressing these challenges in the future.

Chiral tetranuclear copper(ii) complexes: synthesis, optical and magnetic properties

The chiral tetranuclear Cu(ii) cubane complexes with the general molecular formula [Cu₄(R-L₁)₄] (R-1) and [Cu₄(S-L₁)₄] (S-1) exhibit ferromagnetic exchange coupling, which is in contrast to the literature reports. This is corroborated by theoretical calculations.

New thiosemicarbazide and dithiocarbazate based oxidovanadium(iv) and dioxidovanadium(v) complexes. Reactivity and catalytic potential

The new thiosemicarbazide and dithiocarbazate based vanadium complexes show remarkable catalytic potential for oxidation of alcohols and simple arenes.

New polyaminocarboxylate macrocycles containing phenolate binding units: synthesis, luminescent and relaxometric properties of their lanthanide complexes

The synthesis of two new polyaminocarboxylate macrocycles incorporating one or two intracyclic phenol units (H₄L¹ and H₈L², respectively) is described. The 12-membered H₄L¹ macrocycle leads to soluble and stable mononuclear Ln^III complexes of [(L¹)Ln(H₂O)₂]^- composition (Ln = Eu, Tb and Gd) in aqueous solutions. In Tris buffer (pH 7.4), the [(L¹)Tb(H₂O)₂]^- complex displays a suitable efficiency for sensitized emission (η_sens = 48%) and a high luminescence quantum yield (Φ = 22%), which is worthy of note for a bis-hydrated terbium complex. Besides, luminescence experiments show that bidentate endogenous anions (citrate, carbonate, and phosphate) do not displace the two inner-sphere water molecules of this complex. In contrast, the possible presence of LMCT states causes the europium complex to be weakly luminescent. The [(L¹)Gd(H₂O)₂]^- complex is characterized by high relaxivity (r = 7.2 s^-1 mM^-1 at 20 MHz) and a very short water residence time of the coordinated water molecules (τ = 9 ns), promising values for the realisation of macromolecular systems with high relaxivities. Thus, the Tb and Gd complexes of the H₄L¹ macrocycle exhibit several improvements in terms of luminescent (lower excitation energy, higher brightness) and relaxometric (shorter τ_M) properties compared to the corresponding LnPCTA complexes, where a phenol moiety substitutes a pyridine ring. On the other hand, the 24-membered H₈L² macrocycle including two phenol units in its structure leads to dinuclear complexes of [(L²)Ln₂]^2- composition. Its terbium complex shows a long luminescence lifetime (2 ms) and a high quantum yield (43%) in aqueous solutions, making this compound a new promising candidate for time-resolved applications.

Dinuclear metal(ii)-acetato complexes based on bicompartmental 4-chlorophenolate: syntheses, structures, magnetic properties, DNA interactions and phosphodiester hydrolysis

A series of dinuclear metal(ii)-acetato complexes: [Ni2(μ-L(Cl)O)(μ2-OAc)2](PF6)·3H2O (1), [Ni2(μ-L(Cl)O)(μ2-OAc)2](ClO4)·CH3COCH3 (2), [Cu2(μ-L(Cl)O)(μ2-OAc)(ClO4)](ClO4) (3), [Cu2(μ-L(Cl)O)(OAc)2](PF6)·H2O (4), [Zn2(μ-L(Cl)O)(μ2-OAc)2](PF6) (5) and [Mn2(L(Cl)-O)(μ2-OAc)2](ClO4)·H2O (6), where L(Cl)O(-) = 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenolate, were synthesized. The complexes were structurally characterized by spectroscopic techniques and single crystal X-ray crystallography. Six-coordinate geometries with doubly bridged acetato ligands were found in Ni(ii), Zn(ii) and Mn(ii) complexes 1, 2, 5 and 6, whereas with Cu(ii) complexes a five-coordinate species was obtained with 4, and mixed five- and six-coordinate geometries with a doubly bridged dimetal core were observed in 3. The magnetic properties of complexes 1-4 and 6 were studied at variable temperatures and revealed weak to very weak antiferromagnetic interactions in 1, 2, 4 and 6 (J = -0.55 to -9.4 cm(-1)) and ferromagnetic coupling in 3 (J = 15.4 cm(-1)). These results are consistent with DFT calculations performed at the B3LYP/def2-TZVP(-f) level of theory. Under physiological conditions, the interaction of the dinculear complexes 1-5 with supercoiled plasmid ds-DNA did not show any pronounced nuclease activity, but Ni(ii) complexes 1 and 2 revealed a strong ability to unwind the supercoiled conformation of ds-DNA. The mechanistic studies performed on the interaction of the Ni(ii) complexes with DNA demonstrated the important impact of the nickel(ii) ion in the unwinding process. In combination with the DNA study, the phosphatase activity of complexes 1, 3, and 5 was examined by the phosphodiester hydrolysis of bis(2,4-dinitrophenol)phosphate (BDNPP) in the pH range of 5.5-10.5 at 25 °C. The Michaelis-Menten kinetics performed at pH 7 and 10.7 showed that catalytic efficiencies kcat/KM (kcat = catalytic rate constant, KM = substrate binding constant) decrease in the order: Ni(ii), 1 > Zn(ii), 5 > Cu(ii), 3. A similar trend was also observed with the turnover numbers at pH = 7. The results are discussed in relation to the coordination geometry and nature of the metal center as well as the steric environment imposed by the compartmental phenoxido ligand.

Crystal structure of bis-{μ2-2,2'-[(4,10-dimethyl-1,4,7,10-tetra-aza-cyclo-dodecane-1,7-di-yl)bis(meth-yl-ene)]bis-(4-oxo-4H-pyran-3-olato)}dicobalt-calcium bis-(perchlorate) 1.36-hydrate

The title compound, [CaCo2(C22H30N4O6)2](ClO4)2·1.36H2O or {Ca[Co(H-2L1)]2}·2ClO4·1.36H2O {where L1 is 4,10-bis-[(3-hy-droxy-4-pyron-2-yl)meth-yl]-1,7-dimethyl-1,4,7,10-tetra-aza-cyclo-dodecane}, is a trinuclear complex whose asymmetric unit comprises a quarter of the {Ca[Co(H-2L1)]2}2+ trinuclear complex, half of a perchlorate ion and 0.34-water mol-ecules. In the neutral [Co(H-2L1)] moiety, the cobalt ion is hexa-coordinated in a trigonal-prismatic fashion by the surrounding N4O2 donor set. A Ca2+ cation holds together two neutral [Co(H-2L1)] moieties and is octa-coordinated in a distorted trigonal-dodeca-hedral fashion by the surrounding O atoms belonging to the deprotonated oxide and carbonyl groups of two [Co(H-2L1)] units. The coordination of the CoII cation preorganizes L1 and an electron-rich area forms, which is able to host hard metal ions. The comparison between the present structure and the previously published ones suggests a high versatility of this ligand; indeed, hard metal ions with different nature and dimensions lead to complexes having different stoichiometry (mono- and dinuclear monomers and trinuclear dimers) or even a polymeric structure. The heterotrinuclear CoII-CaII-CoII complexes are connected in three dimensions via weak C-H⋯O hydrogen bonds, which are also responsible for the inter-actions with the perchlorate anions and the lattice water mol-ecules. The perchlorate anion is disordered about a twofold rotation axis and was refined giving the two positions a fixed occupancy factor of 0.5. The crystal studied was refined as a two-component inversion twin [BASF parameter = 0.14 (4)].

A Biphenol-Based Chemosensor for Zn(II) and Cd(II) Metal Ions: Synthesis, Potentiometric Studies, and Crystal Structures

We synthesized and characterized the ligand N,N'-bis[(2,2'-dihydroxybiphen-3-yl)methyl]-N,N'-dimethylethylenediamine (L), which contains two biphenol moieties linked as side arms to an N,N'-dimethylethylenediamine scaffold. The ligand is highly soluble in a 50/50 (v/v) water/ethanol mixture and, in its deprotonated form H-2L(2-), is able to coordinate transition-metal ions such as Ni(II), Zn(II), Cu(II), Cd(II), and Pd(II). The crystal structures of [Ni(H-2L)·2n-BuOH], [Ni(H-2L)·2MeOH], [Cd(H-2L)·2DMF], [Cu(H-2L)(DMF)], and [Pd(H-2L)(DMF)] were also determined and described. Potentiometric titrations were carried out in a mixed solvent with Zn(II), Cu(II), and Ni(II) metal ions to determine the acid-base and stability constants. L was highly fluorescent in the visible range (400 nm). Moreover, its emission intensity increased upon the addition of Zn(II) or Cd(II) ions in an ethanol/water solution and behaved as a chemosensor for the presence of these ions in the solution.

Dendrimers and Polyamino-Phenolic Ligands: Activity of New Molecules Against Legionella pneumophila Biofilms

Legionnaires’ disease is a potentially fatal pneumonia caused by Legionella pneumophila, an aquatic bacterium often found within the biofilm niche. In man-made water systems microbial biofilms increase the resistance of legionella to disinfection, posing a significant threat to public health. Disinfection methods currently used in water systems have been shown to be ineffective against legionella over the long-term, allowing recolonization by the biofilm-protected microorganisms. In this study, the anti-biofilm activity of previously fabricated polyamino-phenolic ligands and polyamidoamine dendrimers was investigated against legionella mono-species and multi-species biofilms formed by L. pneumophila in association with other bacteria that can be found in tap water (Aeromonas hydrophila, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae). Bacterial ability to form biofilms was verified using a crystal violet colorimetric assay and testing cell viability by real-time quantitative PCR and Plate Count assay. The concentration of the chemicals tested as anti-biofilm agents was chosen based on cytotoxicity assays: the highest non-cytotoxic chemical concentration was used for biofilm inhibition assays, with dendrimer concentration 10-fold higher than polyamino-phenolic ligands. While Macrophen and Double Macrophen were the most active substances among polyamino-phenolic ligands, dendrimers were overall twofold more effective than all other compounds with a reduction up to 85 and 73% of legionella and multi-species biofilms, respectively. Chemical interaction with matrix molecules is hypothesized, based on SEM images and considering the low or absent anti-microbial activity on planktonic bacteria showed by flow cytometry. These data suggest that the studied compounds, especially dendrimers, could be considered as novel molecules in the design of research projects aimed at the development of efficacious anti-biofilm disinfection treatments of water systems in order to minimize legionellosis outbreaks.

Syntheses, crystallographic, mass-spectroscopic determination and antioxidant studies of Co(II), Ni(II) and Cu(II) complexes of a new imidazol based Schiff base

A new imidazole-based Schiff base, 2-((1H-imidazol-4-yl)methyleneamino)benzylalcohol (HL) and corresponding analogous bis(2-((1H-imidazol-4-yl)methyleneimino)benzylalcohol)metal(II) perchlorates (M: Co(1), Ni(2), Cu(3)) have prepared and characterized by elemental analyses, ESI-MS, IR, UV-Vis spectroscopies and conductivity measurements. X-ray single crystal structures of 1 and 2 have been also determined. Elemental analyses, spectroscopic and conductance data of 3 demonstrated similar structural features with these of crystallographically characterized complexes and based upon this relevances, HL ligands are neutrally coordinated to metal(II) ions in tridentate mode and all complexes are isostructural, dicathionic, contain perchlorate anions as complementary ions and, are in octahedral geometry with the formulae of [M(HL)2](ClO4)2 (for 3) and [M(HL)2](ClO4)2·H2O (for 1 and 2). Radical scavenging activities of the complexes have been evaluated by using DPPH, DMPD(+), and ABTS(+) assays. SC50 values (μg/mL) of the complexes and standards on DPPH, DMPD(+), ABTS(+) follow the sequences, BHA (9.06±0.33)>CMPD3 (15.62±0.52)>CMPD2 (17.43±0.29)>Rutin (21.65±0.60)>CMPD1 (25.67±0.51)>Trolox (28.57±0.37), Rutin>BHA>CMPD3>CMPD2>Trolox>CMPD1, and Trolox>BHA>CMPD3>CMPD2>Rutin>CMPD1 respectively.

Oxidative DNA cleavage promoted by two phenolate-bridged binuclear copper(ii) complexes

Both the binuclear copper complexes 1 and 2 could efficiently cleave the supercoiled pUC19 plasmid DNA into its nicked and linear forms in the presence of excessive ascorbic acid (Vc) under nearly physiological conditions. The DNA binding ability and the DNA cleavage efficacy of 1 are superior to 2.

Magnetic and structural properties of dinuclear singly bridged-phenoxido metal(ii) complexes

Five new dinuclear bridged-phenoxido dichlorido-metal(ii) complexes [M₂(μ-L^ClO)(X)₂Cl₂]PF₆/ClO₄ complexes, where M(ii) = Co, Ni, Cu (1–4) and Zn (5); X = CH₃OH, H₂O or 0 were synthesized and structurally characterized. Complexes 1–4 revealed weak to moderate antiferromagnetic coupling.

Limiting nuclearity in formation of polynuclear metal complexes through [2 + 3] cycloaddition: synthesis and magnetic properties of tri- and pentanuclear metal complexes

The cycloaddition reaction between [Ni(L)(N₃)] and different organonitriles afforded tetrazolate bridged tri- and pentanuclear nickel(ii) complexes.

Spectroscopic and mechanistic studies of dinuclear metallohydrolases and their biomimetic complexes

An enhanced understanding of the metal ion binding and active site structural features of phosphoesterases such as the glycerophosphodiesterase from Enterobacter aerogenes (GpdQ), and the organophosphate degrading agent from Agrobacterium radiobacter (OpdA) have important consequences for potential applications. Coupled with investigations of the metalloenzymes, programs of study to synthesise and characterise model complexes based on these metalloenzymes can add to our understanding of structure and function of the enzymes themselves. This review summarises some of our work and illustrates the significance and contributions of model studies to knowledge in the area.

Di-maltol-polyamine ligands to form heterotrinuclear metal complexes: solid state, aqueous solution and magnetic characterization

The binding properties of the two ligands (L) N,N'-bis[(3-hydroxy-4-pyron-2-yl)methyl]-N,N'-dimethylethylendiamine (Malten) and 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (Maltonis) towards M(II) transition metal ions (M(II) = Cu(II) for Malten and Co(II) for Maltonis, respectively), were investigated in aqueous solution. Each compound contains two 3-hydroxy-2-methyl-4-pyrone units (Maltol) symmetrically spaced by a different polyamine fragment. The formation of only mononuclear complexes was detected and the main species present in a wide range of pH is the neutral [M(II)(H-2L)] complex. This is able to stabilize one hard M(III) metal ion such as Gd(III) and Y(III), giving rise to the formation of new hetero-trinuclear complexes of M(II)-M(III)-M(II) sequence. The trinuclear species having the formula {M(III)[M(II)(H-2L)]2}(3+) (M(II) = Cu(II) and M(III) = Y(III) or Gd(III) for Malten and M(II) = Co(II) and M(III) = Gd(III) for Maltonis) are also formed in a wide range of pH, including pH = 7 and can be isolated in high yield as a perchlorate salt. The crystal structures of all the studied hetero-trinuclear species highlight that such systems are formed thanks to the synergy between the different stereochemical requirement of the transition metal (Cu(II) or Co(II)) and the different donor atoms set of the ligands which preorganize the maltol units for the binding of the hard M(III) metal, otherwise difficult to bind in water, through L/M(II)/M(III) self-assembling. The magnetic properties of the hetero-trinuclear spin systems were investigated; in the M(II)-Gd(III)-M(II) species, Gd(III) interacts with the two 3d ions of this class of compounds by similar coupling mechanism.

Preorganizing binding side-arms on a cyclen scaffold: the choice of a suitable metal ion

The binding properties of 4,10-bis[(3-hydroxy-4-pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L1) and 4,10-bis[(2-hydroxy-5-nitrophenyl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L2) towards Cu(II) and Co(II) transition metal ions in aqueous solution and in the solid state were studied and compared. Each system consists of a cyclen scaffold bearing two different side-arms; the role of the two transition metal ions to involve side-arms in coordination was investigated. Each metal ion is coordinated in a similar way by both ligands although a different side-arm arrangement occurs. The Me2Cyclen base is always involved in the coordination of the transition metal cation with the four amine functions; both side-arms bind Co(II) while only one of them binds Cu(II). As a consequence, Co(II) forms only mononuclear species with both ligands; the main [Co(H−2L)] species exhibits both side-arms on the same part with respect to the macrocyclic plane. In the case of L1, this allows the formation of an electron rich area, formed by the four converging oxygen atoms of the two maltol functions, able to lodge one hard metal ion such as sodium. On the other hand, L1 forms a dinuclear Cu(II)-species using the remaining unbound maltolic function which affords a Cu(II)-tetranuclear species in the solid state. This behavior is attributed to the different coordination requirements of the two metals, thus providing information for the choice of a suitable metal to preorganize side-arms on a polyamine macrocyclic scaffold. Potentiometric and UV-Vis solution studies as well as four crystal structures of metal-complexes support this conclusion.