Synthesis of Isotope Enriched (CN3H6)2[57Fe(CN)5NO] starting from 57Fe

A high‐yield, mmolar‐scale synthesis of pure guanidinium nitroprusside, (CN₃H₆)₂[⁽⁵⁷⁾Fe(CN)₅NO] (GNP) from iron metal is described. The iron metal contained pieces of 95.3% ⁵⁷Fe together with normal iron so that an isotope enrichment in ⁵⁷Fe of 25% was achieved. Single‐crystals of GNP could be grown in cubic shape and dimensions of about 3 × 4 × 4 mm³. The purity of the GNP product and the intermediates K₄[⁽⁵⁷⁾Fe(CN)₆] · 3 H₂O and Na₂[⁽⁵⁷⁾Fe(CN)₅NO] · 2 H₂O was ascertained by ⁵⁷Fe Mössbauer spectroscopy as well as ¹³C, ¹⁴N and ⁵⁷Fe NMR spectroscopy. The ⁵⁷Fe NMR chemical shift for [⁽⁵⁷⁾Fe(CN)₅NO]^2– in GNP was detected at +2004.0 ppm [vs Fe(CO)₅].     

Dinuclear complexes with a μ-cyano ligand. XII [1]. synthesis and characterization of cis-[(aa)2FCr–NC–Fe(CN)4NO] (aa = 1,3-propanediamine and 1,2-cyclohexanediamine) kinetics of the anation in the solid state

The new mixed complex salts trans-[CrF(aa)₂(H₂O)][Fe(CN)₅NO] · nH₂O (aa = ethylenediamine, 1,3-propanediamine, and 1,2-cyclohexanediamine) have been synthesized. From solid state heating of these complexes, the two new dinuclear compounds, cis-[(aa)₂FCr? NC? Fe(CN)₄NO] (aa = 1,3-propanediamine and 1,2-cyclohexanediamine) have also been synthesized. All the attempts to prepare the cis or trans-[(en)₂FCr? NC? Fe(CN)₄NO] failed. All the new complexes have been characterized by means of chemical analysis, electronic and infrared spectra, and TG measurements. The kinetics of the solid state dehydration-anation has been investigated in the case of trans-[CrF(chxn)₂(H₂O)][Fe(CN)₅(NO)] by means of isothermal thermogravimetry. From the Activation Energy found (ca. 40 kcal/mol) and by comparison with other data, a chemical mechanism for the dehydration reaction is proposed.     

μ‐Cyano‐1:2κ2C:N‐tetracyano‐1κ4C‐(5‐methyl‐5‐nitro‐3,7‐diazanonane‐1,9‐diamine‐2κ4N1,3,7,9)‐nitrosyl‐1κN‐copper(II)iron(II) dihydrate

The title binuclear complex, [CuFe(CN)₅(C₈H₂₁N₅O₂)(NO)]·2H₂O or [CuFe(nelin)(CN)₅(NO)]·2H₂O (nelin is 5‐methyl‐5‐nitro‐3,7‐di­aza­nonane‐1,9‐di­amine) consists of discrete binuclear mixed‐metal species, with a Cu centre linked to an Fe centre through a cyano bridge, and two water mol­ecules of crystallization. In the complex, the Cu^II ion is coordinated by five N atoms and has a distorted square‐pyramidal geometry. The Fe^II centre is in a distorted octahedral environment.     

Charakterisierung von Distorsionsisomeren der Anionen Pentacyano-oxo-molybdat(IV) sowie Tetracyano-oxo-aqua-molybdat(IV) im festen Zustand. Kristallstrukturen von [(C6H5)4P]3[MoO(CN)5] · 7 H2O(grün), [(C6H5)4As]2 [MoO(OH2)(CN)4] · 4 H2O (blau) und [(C6H5)4P]2[MoO(OH2)(CN)4] · 4 H2O (grün)

Characterization of Distortional Isomers of the Anions Pentacyano-oxo-molybdate(IV) and of Tetracyano-aqua-oxo-molybdate(IV) in the Solid State. Crystal Structures of [(C₆H₅)₄P]₃[MoO(CN)₅] · 7 H₂O (green), [(C₆H₅)₄As]₂[MoO(OH₂)(CN)₄] · 4 H₂O (blue), and [(C₆H₅)₄P]₂[MoO(OH₂) (CN)₄] · 4 H₂O (green) Preparation of a series of salts containing the new pentacyano-oxo-molybdate(IV) anion is described: Cs₂H[MoO(CN)₅] (blue), [(CH₃)₄N]₂H[MoO(CN)₅] · 2 H₂O (blue) and [Cr(en)₃] [MoO(CN)₅] · 4 H₂O (green). The green [(C₆H₅)₄P]₃[MoO(CN)₅] · 7 H₂O crystallizes triclinic in the space group P1 . The molybdenum(IV) center is in an pseudo-octahedral environment of a terminal oxo-group (d(Mo?O); 1.705(4) Å), a CN^? group in the trans-position (d(Mo? C): 2.373(6) Å), and four equatorial CN^? groups (averaged d(Mo? C): 2.178 (Å). The blue and green salts exhibit v(Mo?O) stretching frequencies at 948 cm^?1 and 920 cm^?1, respectively. Blue and green salts containing the [MoO(OH₂)(CN)₄]^2? anion and [(C₆H₅)₄P]⁺ or [(C₆H₅)₄As]⁺ cations have been prepared and characterized by single crystal crystallography. [(C₆H₅)₄P]₂[MoO(OH₂)(CN)₄] · 4 H₂O (green) and [(C₆H₅)₄As]₂[MoO(OH₂)(CN)₄] · 4 H₂O (blue) crystallize monoclinic in the space group C—P2₁/n. They are considered to be distortional isomers of the complex anion: the green species has a Mo?O bond distance of 1.72(2) Å whereas for the blue species d(Mo?O) = 1.60(2) Å is found; the corresponding v(Mo?O) frequencies are at 920 cm^?1 and 980 cm^?1.     

Population dynamics of the two light induced metastable states in Na2[Fe(CN)5NO]·2H2O single crystals

The dependence of the population dynamics on intensity, time, wavelength and polarisation of the illuminating light and on the temperature of both metastable states in Na₂ [Fe(CN)₅NO]·2H₂O single crystals is investigated by differential scanning calorimetry. The population and depopulation behaviour can be described by exponential functions. The wavelength dependence shows the spectral range in which both states can be excited and the existence of a transfer process from state II into state I. Further, light of the near infrared region, transfers state I into state II.     

Synthesis,electrochemical and antimicrobial studies of mono and binuclear iron(III) and oxovanadium(IV) complexes of [ONO] donor tridentate Schiff-base ligands

Tridentate Schiff bases (H₂L¹ or H₂L²) were derived from condensation of acetylacetone and 2-aminophenol or 2-aminobenzoic acid. Binuclear square pyramidal complexes of the type [M₂(L¹)₂]?·?nH₂O (M?=?Fe–Cl, n?=?0; M?=?VO, n?=?1) were accessed from interaction of H₂L¹ with anhydrous FeCl₃ and VOSO₄?·?5H₂O, respectively. A similar reaction with H₂L², however, produced mononuclear complexes [ML²(H₂O) _x ]?·?nH₂O (M=Fe–Cl, x?=?0, n?=?0; M=VO, x?=?1, n?=?1). The compounds were characterized using elemental analysis, FT-IR, UV-Vis, and NMR (for ligand only), and mass spectroscopies and solution electrical conductivity studies. Magnetic susceptibility measurements suggest antiferromagnetic exchange in binuclear Fe(III) and VO(IV) complexes. Thermo gravimetric analysis (TGA) provided unambiguous evidence for the presence of coordinated as well as lattice water in [VOL²(H₂O)]?·?H₂O. Cyclic voltammetric studies showed well-defined redox processes corresponding to Fe(III)/Fe(II) and VO(V)/VO(IV). In vitro antimicrobial activities of the compounds were investigated against Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeroginosa, Escherichia coli, Bacillus subtilis, and Proteus vulgaris. H₂L¹ and its binuclear complexes exhibited pronounced activity against all the microorganisms tested.     

Synthesis,spectral, thermal and crystallographic investigations on oxovanadium(IV) and manganese(III) complexes derived from heterocyclic β-diketone and 2-amino ethanol

Novel mononuclear oxovanadium(IV) and manganese(III) complexes [VO(L¹)₂·H₂O] (1); [VO(L²)₂·H₂O] (2); [VO(L³)₂·H₂O] (3); [Mn(L¹)₂]ClO₄·H₂O (4); [Mn(L²)₂] ClO₄·H₂O (5); [Mn(L³)₂]ClO₄·H₂O (6) were prepared by condensation of 1 mol of VOSO₄·5H₂O or Mn(OAc)₃· 2H₂O with 2 mol of ligand HL¹, HL² or HL³ (where HL¹ = 4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2- phenyl-2,4-dihydro-pyrazol-3-one; HL²=4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one; HL³=4-{4-[(2-hydroxy-ethyl-amino)-methyl]-3-methyl-5-oxo-4,5-dihydropyrazol-1-yl} benzene sulfonic acid). The resulting complexes were characterized by elemental analyses, molar conductance, magnetic and decomposition temperature measurements, electron spin resonance, FAB mass, IR and electronic spectral studies. From TGA, DTA and DSC, the thermal behaviour and degradation kinetic were studied. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of oxovanadium(IV) complexes and regular octahedral stereochemistry of manganese(III) complexes. Hamiltonian and bonding parameters found from ESR spectra indicate the metal ligand bonding is partial covalent. The X-ray single crystal determination of one of the representative ligand was carried out which suggests existence of amine-one tautomeric form in the solid state. The ¹H-NMR spectra support the existence of imine-ol form in solution state. The LC-MS studies sustain the¹H-NMR result. The electronic structure of the same representative ligand was optimized using 6-311G basis set at HF level ab initio studies to predict the coordinating atoms of the ligand.     

3d-Metal Nitroprusside–Thiosemicarbazide Complexes: Synthesis and Properties

The following complexes were synthesized from 3d-metal nitroprussides and thiosemicarbazide: [CrL₃][Fe(CN)₅H₂O] · 6H₂O, [FeL₃]₂[Fe(CN)₅NO]₃ · 14H₂O, [CoL₃]₂[Fe(CN)₅NO]₃ · 4H₂O, [NiL₂][Fe(CN)₅NO], [CuL₂][Fe(CN)₅NO] · 5H₂O, and [[ZnL₂][Fe(CN)₅NO], where L is thiosemicarbazide. Their structures and properties were studied by IR and diffuse reflection spectroscopies and DTA.     

Hydrate isomerism in [Cu(en)2(H2O)1.935]2[Fe(CN)6]·4H2O

The title compound, bis[di­aqua­bis­(ethyl­enedi­amine‐κ²N,N′)copper(II)­] hexa­cyano­iron(II) tetrahydrate, [Cu(C₂H₈N₂)₂(H₂O)_1.935]₂[Fe(CN)₆]·4H₂O, was crystallized from an aqueous reaction mixture initially containing CuSO₄, K₃[Fe(CN)₆] and ethyl­enedi­amine (en) in a 3:2:6 molar ratio. Its structure is ionic and is built up of two crystallographically different cations, viz. [Cu(en)₂(H₂O)₂]²⁺ and [Cu(en)₂(H₂O)_1.87]²⁺, there being a deficiency of aqua ligands in the latter, [Fe(CN)₆]⁴⁻ anions and disordered solvent water mol­ecules. All the metal atoms lie on centres of inversion. The Cu atom is octahedrally coordinated by two chelate‐bonded en mol­ecules [mean Cu—N = 2.016 (2) Å] in the equatorial plane, and by axial aqua ligands, showing very long distances due to the Jahn–Teller effect [mean Cu—O = 2.611 (2) Å]. In one of the cations, significant underoccupation of the O‐atom site is observed, correlated with the appearance of a non‐coordinated water mol­ecule. This is interpreted as the partial contribution of a hydrate isomer. The [Fe(CN)₆]⁴⁻ anions form quite regular octahedra, with a mean Fe—C distance of 1.913 (2) Å. The dominant intermolecular interactions are cation–anion O—H⋯N hydrogen bonds and these inter­actions form layers parallel to (001).     

Copper(II) cyanido-bridged bimetallic nitroprusside-based complexes: Syntheses, X-ray structures, magnetic properties, Fe Mössbauer spectroscopy and thermal studies

Three heterobimetallic cyanido-bridged copper(II) nitroprusside-based complexes of the compositions [Cu(tet)Fe(CN)₅NO]·H₂O (1), where tet=N,N′‐bis(3-aminopropyl)ethylenediamine, [Cu(hto)Fe(CN)₅NO]·2H₂O (2), where hto=1,3,6,9,11,14-hexaazatricyclo[12.2.1.1^6,9]octadecane and [Cu(nme)₂Fe(CN)₅NO]·H₂O (3), where nme=N-methylethylenediamine, were synthesized and characterized by elemental analyses, ⁵⁷Fe Mössbauer and FTIR spectroscopies, thermal analysis, magnetic measurements and single-crystal X-ray analysis. The products of thermal degradation processes of 2 and 3 were studied by XRD, ⁵⁷Fe Mössbauer spectroscopy, SEM and EDS, and they were identified as mixtures of CuFe₂O₄ and CuO.     

The HNO donor ability of hydroxamic acids upon oxidation with cyanoferrates(III)

The hydroxamic acids (RC(O)NHOH, HA) exhibit diverse biological activity, including hypotensive properties associated with formation of nitroxyl (HNO) or nitric oxide (NO). Oxidation of two HAs, benzohydroxamic and acetohydroxamic acids (BHA, AHA) by [Fe(CN)₅NH₃]^2? or [Fe(CN)₆]^3? was analyzed by spectroscopic, mass spectrometric techniques, and flow EPR measurements. Mixing BHA with both Fe(III) reactants at pH 11 allowed detecting the hydroxamate radical, (C₆H₅)C(O)NO˙^?, as a one-electron oxidation product, as well as N₂O as a final product. Successive UV–vis spectra of mixtures containing [Fe(CN)₅NH₃]^2? (though not [Fe(CN)₆]^3?) at pH 11 and 7 revealed an intermediate acylnitroso-complex, [Fe(CN)₅NOC(O)(C₆H₅)]^3? (λ_max, 465 nm, very stable at pH 7), formed through ligand interchange in the initially formed reduction product, [Fe(CN)₅NH₃]^3?, and characterized by FTIR spectra through the stretching vibrations ν_(CN), ν_(CO), and ν_(NO). Free acylnitroso derivatives, formed by alternative reaction paths of the hydroxamate radicals, hydrolyze forming RC(O)OH and HNO, postulated as precursor of N₂O. Minor quantities of NO are formed only with an excess of oxidant. The intermediacy of HNO was confirmed through its identification as [Fe(CN)₅(HNO)]^3? (λ_max, 445 nm) as a result of hydrolysis of [Fe(CN)₅(NOC(O)(C₆H₅)]^3? at pH 11. The results demonstrate that hydroxamic acids behave predominantly as HNO donors.     

Molecular modeling,spectral, and biological studies of 4-formylpyridine-4 N-(2-pyridyl) thiosemicarbazone (HFPTS) and its Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Cd(II), Hg(II), and UO2(II) complexes

The present work describes the preparation and characterization of some metal ion complexes derived from 4-formylpyridine-⁴ N-(2-pyridyl)thiosemicarbazone (HFPTS). The complexes have the formula; [Cd(HFPTS)₂H₂O]Cl₂, [CoCl₂(HPTS)]·H₂O, [Cu₂Cl₄(HPTS)]·H₂O, [Fe (HPTS)₂Cl₂]Cl·3H₂O, [Hg(HPTS)Cl₂]·4H₂O, [Mn(HPTS)Cl₂]·5H₂O, [Ni(HPTS)Cl₂]·2H₂O, [UO₂(FPTS)₂(H₂O)]·3H₂O. The complexes were characterized by elemental analysis, spectral (IR, ¹H-NMR and UV–Vis), thermal and magnetic moment measurements. The neutral bidentate coordination mode is major for the most investigated complexes. A mononegative bidentate for UO₂(II), and neutral tridentate for Cu(II). The tetrahedral arrangement is proposed for most investigated complexes. The biological investigation displays the toxic activity of Hg(II) and UO₂(II) complexes, whereas the ligand displays the lowest inhibition activity toward the most investigated microorganisms.     

5,7,7,12,14,14‐Hexamethyl‐4,11‐diaza‐1,8‐diazonia­cyclo­tetra­decane penta­cyano­nitroso­ferrate(II) dihydrate: a supramolecular compound constructed by hydrogen bonds

The title compound, (C₁₆H₃₈N₄)[Fe(CN)₅(NO)]·2H₂O, contains one [Fe(CN)₅(NO)]²⁻ dianion, two half [H₂teta]²⁺ dications (teta is 5,7,7,12,14,14‐hexa­methyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane), each lying about an independent inversion centre, and two solvent water mol­ecules, all of which are held together by hydrogen bonds to form a three‐dimensional supramolecular framework.     

Spektroskopische Untersuchungen an Eisen(II)-nitrosodicyan-methanid- und -nitrosocarbamoylcyanmethanid-Komplexen [Fe(NOC(CN)2)2(C5H5N)4] und [Fe(NOC(CN)C(O)NH2)2(C5H5N)2]

Spectroscopic Investigations of the Iron(II) Nitrosodicyanomethanide and Nitrosocarbamoylcyanomethanide Complexes [Fe(NOC(CN)₂)₂(C₅H₅N)₄] and [Fe(NOC(CN)C(O)NH₂)₂(C₅H₅N)₂] The syntheses of new iron(II) complexes of the nonlinear pseudohalides [NOC(CN)₂]^? and [NOC(CN)C(O)NH₂]^? is reported. The Structures of the compounds are discussed on the basis of IR, Mößbauer, ¹³C, and ¹⁴N NMR spectra as well as of the results of magnetic measurements.     

Spectroscopic Evidence of in situ Formation of a Novel Tetrakis(Tetrazolato)Iron Compound

In an attempt to synthesize the complex [Fe(CN)₅(N₂)]^3- by reaction of Na[Fe(CN)₅(NO)]·2H₂O with azide followed by treatment with NO[SbCl₆], a similar method to that used by Feltham to obtain trans-[RuCl(N₂)(das)₂]Cl₂ from trans-[RuCl(NO)(das)₂]Cl₂, we found spectroscopic evidence that excess azide reacts with the CN^- ligands to generate tetrazolato groups C-coordinated to Fe. Initial results suggest that the obtained compound is sodium azidotris(2H-tetrazolato)(5H-tetrazolato)iron(0). The spectroscopic evidence also indicates that these heterocycles are destroyed by reaction with NO[SbCl₆], and the CN^- groups are regenerated. Here we present the characterization of these complexes by IR, ¹³C NMR, conductivity measurements, elemental analysis and magnetic susceptibility.     

Physical and chemical properties of zinc Cyanoferrates(II)

Neutral zinc cyanoferrate(II) Zn₂Fe(CN)₆ · 2.5H₂O and its hydrogen form HZn_1.5Fe(CN)₆ · 4.5H₂O were synthesized and studied. X-ray diffraction, vibrational spectroscopy, and ¹H NMR showed that Zn₂Fe(CN)₆ · 2.5H₂O in aqueous solutions undergoes reversible hydrolysis. The hydrogen form of zinc cyanoferrate(II) is stable up to ≈200°C. The conductivity of HZn_1.5Fe(CN)₆ · 4.5H₂O in the temperature range 90–120°C is σ = 10^?3.3 S/cm, which is about three orders of magnitude higher than the conductivity of the neutral salt.     

Die Kristallstruktur der hydratisierten Cyanokomplexe NMe4MnII[(Mn, Cr)III(CN)6] · 3 H2O und NMe4Cd[MIII(CN)6] · 3 H2O (MIII = Fe,Co): Verwandte des Berliner Blaus

The Crystal Structure of the Hydrated Cyano Complexes NMe₄Mn^II[(Mn, Cr)^III(CN)₆] · 3 H₂O and NMe₄Cd[M^III(CN)₆] · 3 H₂O (M^III = Fe, Co): Compounds Related to Prussian Blue The crystal structures of the isotypic tetragonal compounds (space group I4, Z = 10) NMe₄Mn^II · [(Mn, Cr)^III(CN)₆] · 3 H₂O (a = 1653.2(4), c = 1728.8(6) pm), NMe₄Cd[Fe(CN)₆] · 3 H₂O (a = 1642.7(1), c = 1733.1(1) pm) and NMe₄Cd[Co(CN)₆] · 3 H₂O (a = 1632.1(2), c = 1722.4(3) pm) were determined by X‐rays. They exhibit ⊥ c cyanobridged layers of octahedra [M^III(CN)₆] and [M^IIN₄(OH₂)₂], which punctually are interconnected also || c to yield altogether a spaceous framework. The M^II atoms at the positions linking into the third dimension are only five‐coordinated and form square pyramids [M^IIN₅] with angles N–M^II–N near 104° and distances of Mn–N: 1 × 214, 4 × 219 pm; Cd–N: 1 × 220 resp. 222, 4 × 226 resp. 228 pm. Further details and structural relations within the family of Prussian Blue are reported and discussed.     

Trigonal kristallisierende Metall(II)-hexacyanoferrate(II)M2II[Fe(CN)6]

Trigonal Crystallizing Metal(II) Hexacyanoferrates(II) M₂^II[Fe(CN)₆] According to X-ray powder diagrams, Ca₂[Fe(CN)₆], Cd₂[Fe(CN)₆], Zn₂[Fe(CN)₆] · 2 H₂O, Pb₂[Fe(CN)₆] and the firstly described compounds Zn₂[Fe(CN)₆] · 2 NH₃ and Sn₂[Fe(CN)₆] crystallize trigonal containing one formula unit in the unit cell. Ca₂[Fe(CN)₆] and Cd₂[Fe(CN)₆] are belonging to the space group D—P3 1m, the other compounds to D—P3 m1. The latters are described as coordination polymers with a coordination number 4 for Zn and 3 for Sn and Pb, respectively.     

Kinetics of the reaction of nitric oxide with polypyridylamine iron(II) complexes

The reactions of three polypyridylamine ferrous complexes, [Fe(TPEN)]²⁺, [Fe(TPPN)]²⁺, and [Fe(TPTN)]²⁺, with nitric oxide (NO) (where TPEN = N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine, TPPN = N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,2-propylenediamine, and TPTN = N,N,N′,N′-tetrakis(2-pyridylmethyl)trimethylenediamine) were investigated. The first two complexes, which are spin-crossover systems, presented second-order rate constants for complex formation reactions (k_f) of 8.4 × 10³ and 9.3 × 10³ M^?1 s^?1, respectively (pH 5.0, 25 °C, I = 0.1 M). In contrast, the [Fe(TPTN)]²⁺ complex, which is in low-spin ground state, did not show any detectable reaction with NO. k_f values are lower than those of high-spin Fe(II) complexes, such as [Fe(EDTA)]^2? (EDTA = ethylenediaminetetraacetate) and [Fe(H₂O)]²⁺, but higher than low-spin Fe(II) complexes, such as [Fe(CN)₅(H₂O)]^3? and [Fe(bipyridine)₃]²⁺. The release of NO from the [Fe(TPEN)NO]²⁺ and [Fe(TPPN)NO]²⁺ complexes were also studied, showing the values 15.6 and 17.7 s^?1, respectively, comparable to the high-spin aminocarboxylate analogs. A mechanism is proposed based on the spin-crossover behavior and the geometry of these complexes and is discussed in the context of previous publications.     

Second-Sphere Coordination of the Tris(5, 5′-diamino-2, 2′-bipyridine)iron Complex With Arene-Carboxylate Ligands Through N-H···O Hydrogen Bonding

The tris(5, 5′-diamino-2, 2′-bipyridine)iron(II) complex [Fe(DABP)₃]²⁺ can be engaged in hydrogen-bonding interactions from the amino groups to carboxylate-containing molecules as H-bond acceptors. This so-called second-sphere coordination of the metal complex is investigated here by using benzene-1, 4-dicarboxylate (terephthalate, L¹ ), benzene-1, 3-dicarboxylate (isophthalate, L² ), biphenyl-2, 2′-dicarboxylate ( L³ ), and benzene-1, 3, 5-tricarboxylate (trimesate, L⁴ ) anions for N-H···O bonding. The second-sphere coordination of [Fe(DABP)₃]²⁺ is further complemented by water molecules of crystallization in the isolated and structurally elucidated compounds of [Fe(DABP)₃]( L¹ )·5H₂O, [Fe(DABP)₃]( L² )·8H₂O, [Fe(DABP)₃]( L³ )·12.5H₂O, and [Fe(DABP)₃]₃( L⁴ )₂·20H₂O. The hydrogen-bonding between [Fe(DABP)₃]²⁺ and the dicarboxylate anions ( L¹-L³ ) decreases from a three-dimensional supramolecular network (with L¹ ) to discrete units (with L² and L³ ) with the increasing number of crystal water molecules. The tricarboxylate ligand L⁴ is capable of capping the triangular face formed by the three amino groups in [Fe(DABP)₃]²⁺. The solid-state structures of DABP·2H₂O and 5, 5′-bis(ethoxycarbonylamino)-2, 2′-bipyridine (BEBP) are reported.