Transition metal halide salts of 8-methylquinolinium: Synthesis and structures of (8-methylquinolinium)2 MX4·nH2O (M = Cu, Co, Zn; X = Cl, Br; n = 0, 1)

The reactions of metal(II) chlorides and bromides with 8-methylquinoline (8-mequin) in neutral and acidic solutions were investigated. The reaction with ZnCl₂, ZnBr₂, CoCl₂, CoBr₂, CuCl₂ or CuBr₂ with the appropriate HX in water or aqueous ethanol gave complexes of the formula (8-mequin)₂MX₄ (1, M = Cu, X = Cl; 2, M = Cu, X = Br; 3, M = Co, X = Cl; 4, M = Co, X = Br) or (8-mequin)₂ZnX₄·nH₂O (5, X = Cl, n = 0; 6, X = Br, n = 0; 7, X = Cl, n = 1; 8, X = Br, n = 1). Crystals of 1, 2 and 4-8 suitable for single crystal X-ray diffraction were obtained and the structures reported. Compounds 1 and 2 crystallize in the monoclinic space group C2/c, while 4-8 crystallize in the triclinic space group, . Variable temperature magnetic susceptibility data indicate very weak interactions for the copper compounds 1 and 2, while the magnetic behavior of 3 and 4 is dominated by single ion anisotropy, with weaker antiferromagnetic interactions.     

Zirconium and hafnium aqua complexes [(H2O)3M(P2W17O61)]: Synthesis, characterization and substitution of water by chiral ligand

The hydroxocomplexes [{(H₂O)M(μ₂-OH)(P₂W₁₇O₆₁)}₂]¹⁴⁻ (M = Zr, Hf) in HCl undergo cleavage of the hydroxo bridges with the formation of monomeric species [(H₂O)₃M(P₂W₁₇O₆₁)]⁶⁻. In the case of Hf single crystals of the composition (Me₂NH₂)_5.5(H)_1.5[(Hf(H₂O)₃)_0.9(WO)_0.1{P₂W₁₇O₆₁}]Cl·9.5H₂O (1), as the result of co-crystallization of [(H₂O)₃Hf(P₂W₁₇O₆₁)]⁶⁻ and [P₂W₁₈O₆₂]⁶⁻ salts, were isolated from these solutions and structurally characterized. Zr gives (Me₂NH₂)₂(H)₄[{(H₂O)₂ZrP₂W₁₇O₆₁}]·8.67H₂O (2), in whose structure chiral polymeric chains {[(H₂O)₂M(P₂W₁₇O₆₁)]}_n⁶ⁿ⁻ are present. Under hydrothermal conditions the water molecules in [(H₂O)₃M(P₂W₁₇O₆₁)]⁶⁻ are replaced by l-malic acid with the formation of stable chiral polyoxoanions, isolated as (NH₂Me₂)₈[M(L-ООССН(ОН)СН₂СОО)P₂W₁₇O₆₁]·7·9H₂O (M = Zr, 3; M = Hf, 4). The structures of 1, 2 and 3 were determined; 3 and 4 were found to be isostructural. The products were also characterized by elemental analysis, thermogravimetry and IR-spectroscopy.     

Mn(II) complexes of monoanionic bidentate chelators: X-ray crystal structures of Mn(dha)2(CH3OH)2 (Hdha = dehydroacetic acid) and [Mn(ema)2(H2O)]2 · 2H2O (Hema = 2-ethyl-3-hydroxy-4-pyrone)

This report describes synthesis and characterization of bis-ligand Mn(II) complexes of bidentate chelators: maltol (3-hydroxy-2-methyl-4-pyrone), ethylmaltol (2-ethyl-3-hydroxy-4-pyrone), 1,2-dimethyl-3-hydroxy-4-pyridinone (DMHP) and dehydroacetic acid. All four Mn(II) complexes were characterized by elemental analysis, IR, UV/Vis, EPR, cyclic voltammetry, and X-ray crystallography in cases of Mn(dha)₂(CH₃OH)₂ and [Mn(ema)₂(H₂O)]₂ · 2H₂O. The bidentate chelator plays a significant role in the solid state structure of its Mn(II) complex. For example, dha forms the monomeric complex Mn(dha)₂(CH₃OH)₂ while ethylmaltol forms the dimeric complex [Mn(ema)₂(H₂O)]₂. Because of smaller size, maltol ligands in Mn(ma)₂ are able to bridge adjacent Mn(II) centers to give a polymeric structure in solid state. Despite of the difference in their solid state structures, both Mn(ema)₂ and Mn(ma)₂ exist in solution as monomeric Mn(II) species, Mn(ema)₂(H₂O)₂ and Mn(ma)₂(H₂O)₂. This assumption is supported by the similarity in their UV/Vis spectra, EPR data and electrochemical properties. Replacing maltol with DMHP results in a decrease (by ∼100 mV) in the redox potential for the Mn(II)/Mn(III) couple, suggesting that DMHP stabilizes Mn(III) better than maltol. Since Mn(DMHP)₂(H₂O)₂ is readily oxidized to form the more stable Mn(III) complex Mn(DMHP)₃, DMHP has the potential as a chelator for removal of excess Mn(II) from patients with chronic Mn toxicity.     

The structural definition of adducts of stoichiometry MX:dpex (2:3)(∞), M = Cu, Ag, X = simple anion, dpex = Ph2E(CH2)xEPh2, E = P, As

Single crystal X-ray structural characterizations are recorded for a number of adducts of MX:dpex (2:3) stoichiometry (MX = simple univalent copper or silver salt; dpex = Ph₂E(CH₂)_xEPh₂ (E = P, As)). CuX:dppe (2:3) (X = Cl, Br, I, CN) are binuclear [(dppe-P,P′)CuX(P-dppe-P′)CuX(P,P′-dppe)], all centrosymmetric. AgX:dpex (2:3) (dpex = ‘dpae’ (Ph₂As(CH₂)₂AsPh₂), X = Br, F₃CCO₂ (= ‘tfa’), F₃CSO₃ (≡ ‘tfs’); dpex = ‘dpape’ (Ph₂As(CH₂)₂PPh₂), X = CN, SCN, OClO₃) are one-dimensional polymers ?-E′)₁AgX(E-dpex-E′)₂-AgX(E-dpex-E′)₁AgX?, P, As sites scrambled in the latter. AgNO₃:dpam (2:3) is also a one-dimensional polymer, ?AgO·NO·OAg(As-dpam-As)AgO·NO·OAg? (‘dpam’ ≡ Ph₂As(CH₂)₂AsPh₂). AgX:dpae (2:3) (X = I, CN, ClO₄, NO₃) and AgX:dpape (2:3) (X = Br, I, NO₃) are two-dimensional polymers with large 30-membered macrocyclic rings; similar webs are found for dppx ligands in AgOH:dppb (2:3) and AgNCO, Agtfa:dpph (2:3) with 42- and 54-membered rings. Complexes AgX:dpape (1:3) (X = Cl, Br) are defined as mono-nuclear [XAg(Ph₂P(CH₂)₂AsPh₂)₃] arrays, the unidentate ligands predominantly P-bound. Synthetic procedures for the adducts are reported, selected compounds being characterized both in solution (¹H, ³¹P NMR, ESI MS) and in the solid state (IR).     

Synthesis and characterization of a polyoxotungstate-supported metal compound [{Cu(enMe)2(H2O)}{Cu(enMe)2}3P2W18O62] · nH2O

A new polyoxotungstate formed by Wells-Dawson clusters and copper(II) complexes, [{Cu(enMe)₂(H₂O)}{Cu(enMe)₂}₃P₂W₁₈O₆₂] · nH₂O (enMe = 1,2-diaminopropane, n = 0.81) has been synthesized under hydrothermal conditions. Single-crystal X-ray diffraction revealed that one terminal and three bridging oxygen atoms of the Wells-Dawson cluster in the title compound are coordinated to copper(II) atoms, and forming a unique tetrasupporting polyoxometalate structure. Its cyclic voltammetric behavior in aqueous electrolyte demonstrated that its modified carbon paste electrode has a good stability. It was exhibited that the compound has catalytic activity in epoxidation of maleic anhydride.     

Raman and infrared spectroscopic and theoretical studies of dinuclear rhenium and osmium complexes, M2(O2CCH3)4X2 (M = Re, Os; X = Cl, Br)

Infrared, far-infrared and Raman spectra of Re₂(O₂CCH₃)₄X₂ (X = Cl, Br) and Re₂(O₂CCD₃)₄Cl₂ have been recorded. Assignments of the vibrational spectra of Os₂(O₂CCH₃)₄Cl₂ and its deuterated derivative have been completed together with the Re complexes on the basis of normal-coordinate analysis. Force constant calculation was made for the acetate ion as well as for a four-atomic unit (with the CH₃ and CD₃ groups considered as point masses) using optimized masses of 16.7, 17.8, 20.5 and 21.6 for ¹²CH₃, ¹³CH₃, ¹²CD₃ and ¹³CD₃ groups, respectively. The force constants of the acetate ion have been adopted to the starting force field of the M₂(O₂CCH₃)₄X₂ type complexes. The metal-halide (0.889, 0.997 and 1.286 N cm⁻¹) and metal-metal stretching (3.32, 3.34 and 3.57 N cm⁻¹) force constants were obtained for Re₂(O₂CCH₃)₄Cl₂Re₂(O₂CCH₃)₄Br₂ and Os₂(O₂CCH₃)₄Cl₂ complexes, respectively. It was shown that the so-called diatomic approximation in most cases overestimates the M-M stretching force constants by 30-40%. Much better correlation has been obtained to fit these force constants, which produced values very close to those obtained by full normal-coordinate calculations. The Re-Re stretching force constants showed a reasonable correlation with the Re-Re bond distances for 18 rhenium complexes.     

3D hydrogen bonded metal-organic frameworks constructed from [M(H2O)6][M′(dipicolinate)2] · mH2O (M/M′ = Zn/Ni or Ni/Ni). Identification of intercalated acyclic (H2O)6/(H2O)10 clusters

New heterodinuclear Zn^II/Ni^II (1) and homodinuclear Ni^II/Ni^II (2) water-soluble and air stable compounds of general formula [M(H₂O)₆][M′(dipic)₂] · mH₂O have been easily prepared by self-assembly of the corresponding metal(II) nitrates with dipicolinic acid (H₂dipic) in water solution at room temperature.  The compounds have been characterized by IR, UV/Vis and atomic absorption spectroscopies, elemental and X-ray single crystal diffraction (for 1 · 4H₂O and 2 · 5H₂O) analyses.  3D infinite polymeric networks are formed via extensive hydrogen bonding interactions involving all coordinated and crystallization water molecules, and all dipicolinate oxygens, thus contributing to additional stabilization of dimeric units, metal-organic chains and 2D layers.  In 1 · 4H₂O, the latter represent a rectangular-grid 2D framework with multiple channels if viewed along the c crystallographic axis, while in 2 · 5H₂O intercalated crystallization water molecules are associated to form acyclic nonplanar hexameric water clusters and water dimers which occupy voids in the host metal-organic matrix, with a structure stabilizing effect via host-guest interactions.  The hexameric cluster extends to the larger (H₂O)₁₀ one with an unusual geometry (acyclic helical octamer with two pendent water molecules) by taking into account the hydrogen bonds to water ligands in [Ni(H₂O)₆]²⁺.  The obtained Zn/Ni compound 1 relates to the recently reported family of heterodimetallic complexes [M(H₂O)₅M′(dipic)₂] · mH₂O (M/M′ = Cu/Co, Cu/Ni, Cu/Zn, Zn/Co, Ni/Co, m = 2, 3), what now allows to establish the orders of the metal affinity towards the formation of chelates with dipicolinic acid (Co^II > Ni^II > Zn^II > Cu^II) or aqua species (Co^II < Ni^II < Zn^II < Cu^II).     

Syntheses and structures of adducts of stoichiometry MX:dpex (2:1)(n), M = Cu, Ag, X = (pseudo-) halogen, dppx = Ph2E(CH2)xEPh2, E = P, As

Single crystal X-ray studies have defined the structures of a number of adducts of the form MX:dpex (2:1), M = univalent coinage metal (Cu, Ag), X = (pseudo-)halide, dpex = bis(diphenylpnicogeno)alkane, Ph₂E(CH₂)_xEPh₂, E = P, As, of diverse types, some novel. The adducts of AgCl,Br:dppm and AgNCO:dpem (x = 1) are tetranuclear as is the AgNO₃:dppp (x = 3) array, all derivative of the familiar ‘step’ structure while the combination CuCN:dppm yields a two-dimensional web of twenty-membered macro/metallacycles. Synthetic procedures for all adducts have been reported. All compounds have been characterized both in solution (¹H, ¹³C, ³¹P NMR, ESI MS) and in the solid state (IR).     

Zinc complexes of 6-methyl-2-pyridinecarboxylic acid. Crystal structure of [Zn(MeC5H3NCOO)2(H2O)] · H2O

Reaction of Zn(AcO)₂ · 2H₂O with 6-methyl-2-pyridinecarboxylic acid (L) yielded a new compound [Zn(MeC₅H₃NCOO)₂(H₂O)] · H₂O. This complex was characterised by elemental analyses, conductivity measurements, infrared, ¹H and ¹³C{¹H} NMR spectroscopies and single-crystal X-ray diffraction. The crystal structure consists of discrete molecules involving a pentacoordinated Zn atom with a geometry intermediate between a trigonal bipyramid and a square pyramid and with the two N_py atoms occupying the apical sites. Treatment of the complex [Zn(MeC₅H₃NCOO)₂(H₂O)] · H₂O with 2,2^′-bipyridine (bpy) produced [Zn(MeC₅H₃NCOO)₂(bpy)]. The metallic atom in this complex displays a distorted octahedral geometry and is coordinated to two ligands (L) via the pyridine nitrogen and the carbonyl oxygen atoms and to one 2,2^′-bypyridine (bpy).     

BEDT-TTF salts of the unsymmetrical [M(tfadt)2] dithiolene complexes (M = Ni, Au; tfadt = S2C2(CN)(CF3))

Two closely related 1:1 salts are obtained upon electrocrystallization of BEDT-TTF (BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene) in the presence of the isosteric [M(tfadt)₂]⁻ dithiolene complexes (tfadt: 1-trifluoromethyl-2-cyano-1,2-dithiolato), which essentially differ by their spin state, S = 0 in [Au(tfadt)₂]⁻, S = 1/2 in [Ni(tfadt)₂]⁻. In both [BEDT-TTF][M(tfadt)₂] salts, the BEDT-TTF radical cations form chains with a strong lateral overlap and strong antiferromagnetic interactions while the paramagnetic anions in the nickel-containing salt [BEDT-TTF][Ni(tfadt)₂] are essentially non-interacting. The structural differences between the nickel and gold complexes are analyzed and discussed.     

Synthesis and characterization of deuterium-labelled (fulvene)M(CO)3 complexes (M = Cr, Mo)

The preparation and characterization of a series of deuterium-labelled (fulvene)M(CO)₃ (M = Cr, Mo) complexes is reported. (η⁵-6-Dimethylaminofulvene-d₂)Cr(CO)₃ and (η⁵-6-dimethylaminofulvene-d₂)Mo(CO)₃ were obtained in high yields by reacting the deuterated fulvene ligands with (MeCN)₃M(CO)₃ (M = Cr, Mo). In addition, syntheses of 6,6-diphenylfulvene-d₁₀ and 6,6-diphenyl-1,2-benzofulvene-d₁₀ as well as the corresponding tricarbonylchromium complexes are described.     

The cyanocarbanion (C[C(CN)2]3) as monodentate ligand: Synthesis, structure and magnetic properties of [Mn2(bpym)3(tcpd)2(H2O)2] (tcpd = (C[C(CN)2]3) and bpym = 2,2′-bipyrimidine)

One-pot reaction between MnCl₂·4H₂O, K₂tcpd (tcpd²⁻ = [C₁₀N₆]²⁻ = (C[C(CN)₂]₃)²⁻ = 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide anion) and 2,2′-bipyrimidine (bpym = C₈H₆N₄) in aqueous solution yields the new compound [Mn₂(bpym)₃(tcpd)₂(H₂O)₂] (1). The molecular structure of 1 consists of a centrosymmetrical binuclear complex which includes unprecedented unidentate tcpd ligands with two bidentate and a bis-chelate bpym units. Examination of the intermolecular distances reveals that the dinuclear units are held together by hydrogen bonds involving coordinated water molecules and two nitrile groups of the tcpd ligand, giving rise to a 2D structure overall. Variable-temperature magnetic susceptibility data show the occurrence of slight antiferromagnetic coupling (J = −0.58 cm⁻¹) between the Mn(II) ions through bridging bpym (the exchange Hamiltonian being defined as ).     

New oligo-/poly-meric forms for MX:dpex (1:1) complexes (M = Cu, Ag; X = (pseudo-)halide; dpex = Ph2E(CH2)xEPh2, E = (P), As; x = 1, 2)

Single-crystal X-ray structural characterizations of MX:dpam (1:1) (‘dpam’ = Ph₂AsCH₂AsPh₂) are reported for MX = AgCl, Br; CuI, CN/Cl (all isomorphous) and AgI, AgSCN, CuSCN arrays, all being of the novel form [(μ-X){M(μ-X)(As-dpam-As′)₂M′}]_∞, essentially the familiar M(E-dpem-E′)₂M′ binuclear array with both ‘bridging’ and (linking) ‘terminal’ (pseudo-)halides involved in the polymer. A different arrangement of bridging and linking entities is found with AgX:dpae (1:1)_2(∞|∞), X = Br, NCO, ‘dpae’ = Ph₂As(CH₂)₂AsPh₂, now comprising [M(μ-X)₂(As-dpae-As)M] kernels linked by As-dpae-As′, while in the thiocyanate analogue units are linked by the dpae ligands into a two-dimensional web. Synthetic procedures for all adducts have been reported. All compounds have been characterized both in solution (¹H, ¹³C, ³¹P NMR, ESI MS) and in the solid state (IR).     

One-pot synthesis of the decaniobate salt [N(CH3)4]6[Nb10O28] · 6H2O from hydrous niobium oxide

A robust and easily reproducible one-pot synthetic method for the preparation of [N(CH₃)₄]₆[Nb₁₀O₂₈] · 6H₂O is introduced.     

A trinuclear copper(II) complex with 2,5-pyridine-dicarboxylato bridges - [Cu3(2,5-pydc)2(Me5dien)2(H2O)2(BF4)2] · H2O: Synthesis, crystal structure and magnetic properties

A trinuclear copper(II) complex, [Cu₃(2,5-pydc)₂(Me₅dien)₂(BF₄)₂(H₂O)₂] · H₂O 1, has been constructed from 2,5-pyridine-dicarboxylato bridges (2,5-pydc²⁻) and N,N,N′,N″,N″-pentamethyl-diethylenetriamine (Me₅dien) acting as a blocking ligand. The copper ions, within the centrosymmetric trinuclear cations, are connected by two 2,5-pydc²⁻ bridges, with an intramolecular Cu···Cu separation of 8.432 Å. The central copper ion exhibits an elongated octahedral geometry, with semicoordinated ions, while the terminal ones are pentacoordinated (distorted square-pyramidal geometry). The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the copper(II) ions (J = −5.9 cm⁻¹, H = −JS_Cu1S_Cu2 − JS_Cu2S_Cu1a).     

Investigation of the MSO4 · xH2O (M = Zn, x = 7; M = Cd, x = 8/3)/methyl 2-pyridyl ketone oxime reaction system: A novel Cd(II) coordination polymer versus mononuclear and dinuclear Zn(II) complexes

The reactions of methyl 2-pyridyl ketone oxime, (py)C(Me)NOH, with MSO₄ · xH₂O (M = Zn, x = 7; M = Cd, x = 8/3), in the absence of an external base, have been investigated. The synthetic study has led to the two new complexes [Zn(SO₄){(py)C(Me)NOH}(H₂O)₃] · H₂O (1 · H₂O) and [Zn₂(SO₄)₂{(py)C(Me)NOH}₄] · (py)C(Me)NOH [2 · (py)C(Me)NOH], and the coordination polymer [Cd(SO₄){(py)C(Me)NOH}(H₂O)]_n · [Cd(SO₄){(py)C(Me)NOH}(H₂O)₂]_n (3). In the three complexes the organic ligand chelates through its nitrogen atoms. The sulfate anion in 1 · H₂O is monodentate; the complex molecule is the mer isomer considering the positions of the aqua ligands. The Zn^II centers in 2 · (py)C(Me)NOH are bridged by two syn, anti η¹:η¹:μ₂ ligands; each metal ion has the cis-cis-trans disposition of the coordinated sulfate oxygen, pyridyl nitrogen and oxime nitrogens, respectively. The molecular structure of 3 is unique consisting of two different linear and ladder - type chains. π-π stacking interactions and/or hydrogen bonds lead to the formation of interesting supramolecular architectures in the three complexes. The thermal decomposition of complex 3 has been studied. Characteristic vibrational (IR, Raman) bands are discussed in terms of the nature of bonding and the structures of the three complexes.     

Long-range superexchanged magnetic interaction observed in heterometallic complex: {[Fe(Tpms)(CN)3][Mn(H2O)2(DMF)2]} · DMF

A new tri-cyanometalate building block for heterometallic complexes, [PPh₄]₂[Fe^II(Tpms)(CN)₃] (2) (PPh₄ = tetraphenylphosphonium; Tpms = tris(pyrazolyl) methanesulfonate), has been prepared. Using it as a building block, a one-dimensional chain compound, {[Fe^II(Tpms)(CN)₃][Mn^II(H₂O)₂( DMF)₂]} · DMF (3), has been synthesized and structurally characterized. The magnetic properties of 3 correspond to a ferromagnetic chain with weak long-range superexchanged magnetic interaction between the high-spin manganese(II) ions.     

Crystal structures of [M(NTf2)3(H2O)n] (M = Eu and Yb) and a template effect of linear molecules on the 3D hydrogen bonding network structure of [Eu(NTf2)3(H2O)3]

Lewis acid catalysts [Eu(NTf₂)₃] and [Yb(NTf₂)₃] can be easily crystallized from a p-xylene solution in the presence of carboxylic acids and a small amount of water to give a trihydrate and a pentahydrate, respectively. In the crystallization of [Eu(NTf₂)₃(H₂O)₃], linear molecules such as n-alkanes and n-alkanoic acids act as templates to form crystals belonging to the trigonal space group with a hexagonal cylindrical structure, which is constructed by 3D hydrogen bonding network. On the other hand, [Eu(NTf₂)₃(H₂O)₃] crystallized in the cubic space group P2₁3 in the presence of a bulkier carboxylic acid, cyclohexanecarboxylic acid. In both [Eu(NTf₂)₃(H₂O)₃] crystals, ligands act as bidentate ligands coordinating to the Eu atom through two oxygen atoms. [Yb(NTf₂)₃] crystallized as a pentahydrate in the monoclinic space group P2₁/n, in which ligands coordinated to the Yb atom with only one oxygen atom.     

The structural definition of adducts of stoichiometry MX:dppx (1:1) M = Cu, Ag, X = simple anion, dppx=Ph2P(CH2)xPPh2, x = 3-6

Single crystal X-ray structural characterizations are recorded for a wide range of adducts of the form MX:dppx (1:1)_(n), M = silver(I) (predominantly), copper(I), X = simple (pseudo-) halide or oxy-anion (the latter spanning, where accessible, perchlorate, nitrate, carboxylate - a range of increasing basicity), dppx=bis(diphenylphosphino)alkane, Ph₂P(CH₂)_xPPh₂, x = 3-6. Adducts are defined of two binuclear forms: (i) [LM(μ-X)₂L], with each ligand chelating a single metal atom, and (ii) [M(μ-X)₂(μ-(P-L-P′))₂M′] where both ligands L and halides bridge the two metal atoms; a few adducts are defined as polymers, the ligands connecting M(μ-X)₂M′ kernels, this motif persisting in all forms. Synthetic procedures for all adducts have been reported. All compounds have been characterized both in solution (¹H, ¹³C, ³¹P NMR, ESI MS) and in the solid state (IR).     

An unusual gadolinium ten-coordinated dimeric complex in the series of MRI contrast agents: Na[Gd(H2O)AAZTA] · 3H2O

The crystal structures of the ligand AAZTA (6-amino-6-methylperhydro-1,4-diazepine tetraacetic acid) and of its Gd complex Na[Gd(H₂O)AAZTA] · 3H₂O have been determined by single crystal X-ray diffraction. The AAZTA ligand crystallizes in a zwitterion form with two deprotonated carboxylic groups and two protonated tertiary nitrogen atoms. Two independent molecules of about a similar conformation and three water molecules as asymmetric units, are present in the crystal. In the solid state the gadolinium complex is a centrosymmetric dimer with a bicapped square antiprismatic coordination geometry around each metal ion. Two symmetric bridging carboxylate groups determine the dimer formation with Gd-O(2) and Gd-O(2)′ bond distances rather comparable of 2.526(4) and 2.548(4) Å, respectively, while the Gd-O(1) (inner sphere water) bond distance is 2.443(5) Å. A network of hydrogen bonds between the water of inner and outer spheres and the AAZTA carboxylic groups is present in the crystal structure.